Railway Seminar on P Way

NATIONAL TECHNICAL SEMINAR ON

Impact and Experience of Heavier Axle Loads on Indian Railways and Resultant Maintenance Strategies & Innovation in Design & Construction of Road Over Bridges and Road under Bridges on the Indian Railways

(VOLUME - I)

NATIONAL TECHNICAL SEMINAR ON Impact and Experience of Heavier Axle Loads on Indian Railways and Resultant Maintenance Strategies & Innovation in Design & Construction of Road Over Bridges and Road under Bridges on the Indian Railways

JANUARY : 21 st - 22nd , 2010 PUNE

TECHNICAL PAPERS Organised by INSTITUTION OF PERMANENT WAY ENGINEERS (INDIA)

Published by : Institution of Permanent Way, Engineers (India) Rail Bhavan, New Delhi

Compiled by : Technical Committee, Pune Centre, IRICEN Pune

Opinions expressed by authors in technical papers are not neccessarily the opinion of IPWE (I) C All rights reserved by Institution of Permanent Way Engineers (I) Printed by : Kalyani Corporation 1464, Sadashiv Peth, Pune - 411 030.

PREFACE Indian economy is growing annually at the rate of about 8% compounded for the last few years and Indian Railways is targeted to carry 1000 GMT by the end of the 11th Five Year Plan (March 2012). With the same trend continuing, Indian Railways has to increase the throughput by almost double in another decade. Increase of axle load from 20.3 tons to 25 tons on the existing corridors and 32.5 tons on DFC is a step towards meeting the demand of traffic. The studies conducted by UIC and other research organizations suggest that with the higher axle loads, deterioration of the track becomes much faster requiring much greater inputs. The topic of the seminar “Impact and experience of heavier loads on Indian Railways and resultant maintenance strategies” is a very apt subject to share the experience of the railway engineers, consolidate the same in the future maintenance strategy. Along with the increased throughputs, safety of operations is another very important aspect for all railwaymen. Accidents at level crossings have been an area of concern and the only permanent solution appears to be to have grade separation at the crossings. Presently construction of ROBs/RUBs take quite a long time due to the work to be done under traffic, accompanied with speed restrictions and traffic blocks. With a view to identify new technologies to construct ROBs/RUBs to be completed in the shortest possible time with least disturbance to traffic, the second topic of seminar “Innovation in design and construction of ROBS and RUBS on the Indian Railways” is expected to pave the way for expediting the process and construction of gradeseparated crossings. Four technical sessions on the above two topics have been planned in the seminar. These sessions will provide forum for discussion and exchange of views relating to the technological aspects of these issues. The technical papers to be presented during the seminar are brought out in two volumes.

Ashok Kumar Goel Chairman, IPWE(I) Pune Centre & Director/IRICEN

Governing Council of THE INSTITUTION OF PERMANENT WAY ENGINEERS ( INDIA ) President Shri Rakesh Chopra Member Engineering, Railway Board & Ex-officio Secretary, Government of India

Vice President Shri S.K. Malik Addl. Member, Civil Engineering, Railway Board Hony. General Secretary Shri A. K. Gupta, Principal Chief Engineer, Northern Railway Hony. Treasurer Shri V.K. Govil, Executive Director, CE/B&S, Railway Board

Chairmen of Zonal Centers 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.

Shri P. K. Saxena Shri V. Srihari Shri S.C. Jha Shri S.S. Narayanan Shri A.K. Gupta Shri D.D. Dewangan Shri Manoj Kumar Shri G.S.Tiwari Shri Laj Kumar Shri G. Narayanan Shri Pradeep Kumar Shri B.P. Khare Shri V. K. Sangal Shri D.G. Diwate Shri G.C. Agarwal Shri Pankaj Jain Shri A.K. Goel Shri Sonvir Singh

Pr. Chief Engineer, CR, Mumbai Pr. Chief Engineer, ER, Kolkata Pr. Chief Engineer, ECR, Hajipur Pr. Chief Engineer, ECoR, Bhubaneswar Pr. Chief Engineer, NR, New Delhi. Pr. Chief Engineer, NCR, Allahabad Pr. Chief Engineer, NER, Gorakhpur Pr. Chief Engineer, NFR, Guwahati Chief Engineer(Co-ordn), NWR, Jaipur Pr.Chief Engineer, SR, Chennai Pr.Chief Engineer, SCR, Secunderabad Pr. Chief Engineer, SER, Kolkata Pr. Chief Engineer, SECR, Bilaspur Pr. Chief Engineer, SWR, Hubli Pr. Chief Engineer, WR, Mumbai Pr. Chief Engineer, WCR, Jabalpur Director, IRICEN, Pune Executive Director (Track), RDSO, Lucknow.

Executive Director

Shri S.K. Jagdhari Executive Secretaries, IPWE

Shri P.K. Sharma

Shri S. D. Sharma

ORGANISING COMMITTEE 

Shri A.K. Goyal, Director, IRICEN, Pune & Chairman IPWE(I), Pune Centre



Shri Suresh Gupta, Dean & Secretary, IPWE(I), Pune Centre



Shri N.C. Sharda, Sr. Professor/Track-1



Shri Ajay Goyal, Sr. Professor/Bridges-1



Shri Naresh Lalwani, Sr. Professor/Bridges-2



Shri Pradeep Kumar Garg, Sr. Professor/Track-2



Shri A.K. Agrawal, Sr. Professor/Projects



Shri S.K. Garg, Sr. Professor/Works



Shri Manoj Arora, Professor/Tr.Mc. & Jt. Secretary, IPWE(I), Pune Centre



Shri V. B. Sood, Professor/Bridges



Shri Nilmani, Professor/Track

PROGRAMME & SEMINAR COMMITTEE 

Convenor Shri Suresh Gupta, Dean, IRICEN, Pune



Member Secretary Shri Pradeep Kumar Garg, Sr. Professor/Track-2 Shri Manoj Arora, Professor/Track Machine



Members Shri Nilmani, Professor/Track Shri V.B. Sood, Professor/Bridges Shri N.K. Khare, APW Shri Shyam Khoche, AXEN2

RECEPTION, ACCOMMODATION & TRANSPORT COMMITTEE 

Convenor Shri N.C. Sharda, SPT1



Member Secretary Shri Ajay Goyal, SPB1 (Transport) Shri S.K. Garg, SPW (Accommodation)



Members Shri V.S. Wadekar, Dy. CE/C/Pune Shri N.R. Kale, AXEN1 Shri R.L. Wasnik, ADFM

PRESS & PUBLICATIONS 

Convener

-

Shri Suresh Gupta



Member Secretary

-

Shri Manoj Arora, PTM



Member

-

Shri Y.K. Singh, PRO/CR/PA

TECHNICAL & SOUVENIR COMMITTEE 

Convenor

-



Member Secretary -

Shri Pradeep Kumar Garg, SPT2



Members

Shri Shyam Khoche, AXEN2

-

Shri Naresh Lalwani, SPB2

EXHIBITION, HOSPITALITY INCLUDING CATERING & CULTURAL PROGRAMME COMMITTEE 

Convenor

-

Shri A.K. Agrawal, SPP



Member Secretary

-

Shri V.B. Sood, PB (Exhibition)

-

Shri A. Chandolikar, AP (Hospitality)

-

Shri N.R. Kale, AXEN1



Members

TABLE OF CONTENTS TECHNICAL PAPERS Technical Session 1 Impact of Heavier Axle Loads on Track and Maintenance Strategies 1.

Effects of Increased Loading on Track Structure S.K. Sharma 1.1 - 1.14

2.

Challenges Faced in Running Iron Ore Rake on SWR Including Severe Ghat Section K. J. S. Naidu 1.15 - 1.30

3.

Impact and Experience of Heavier Axle Loads on Indian Railways and Resultant Maintenance Strategies Hemendra Choudhary 1.31 - 1.42

4.

Experience of Running Heavier Axle Loads on KTEBIN Section and Resultant Maintenance Strategies Rajesh Arora & Vijay Pandey 1.43 - 1.56

5.

Experience of Heavier Axle Loads Operations & Maintenance Strategy Adopted by SWR for CC+8+2 Axle Load Operations D.G.Diwate, Vijay Agrawal & P.S. Basha 1.57- 1.71

6.

Effect of Enhanced Loading (CC+8+2) on the Track & Rolling Stock on Chennai Division a Managerial Perspective for RU-AJJ-MAS Section S.K.Kulshrestha 1.72 - 1.84

7.

Heavier Axle Load – Effect on P. Way & Reorganizing Track Maintenance Strategies Amit Agrawal, Rajiv Kumar Tanwar & 1.85 - 1.102 M.Jayaprakash Reddy

8.

Overcoming the Challenges of Weak Formation for Heavier Axle Loads - Formation Rehabilitation by Mechanised Blanketing Munna Kumar, Manohar Reddy & 1.103 - 1.122 L. N. Reddy

9.

Impact and Experience of Heavier Axle Loads on Indian Railway - M.R.Srinivasan 1.123 - 1.132

Technical Session 2 Impact of Heavier Axle Loads on Bridges and Experience of Running Heavier Axle Loads on other Railways 1.

Experience of World Railway Systems for Running of Heavier Axle Loads with Special Reference to Indian Railways M.M. Agarwal & K.K. Miglani 2.1 - 2.25

2.

Effect of Higher Axle Loads on Bridges in South Western Railway R.S. Dubey, Ramesh Kambli & 2.26 - 2.54 T.A. Nandakumar,

3.

Strengthening of Bridges on Feeder Routes to Eastern and Western Dedicated Freight Corridors V.K.Govil, S.N. Singh & Ashish Agarwal 2.55 - 2.63

4.

Formation Design and Specification for Heavier Axle Loads on Indian Railways J. C. Parihar, J.S. Sondhi & 2.64 - 2.89 Rajesh Agarwal

5.

Impact of Increasing Axle Load on Fatigue Life of Standard Steel Girder Bridges – A Study Based on Revised Fatigue Provisions R. K. Goel & H.O. Narayan 2.90 - 2.107

Technical Session 3

Running of Heavier Axle Loads – The Road Ahead 1.

A Total Rail Maintenance Strategy for Heavier Axle Load Railways Joseph W. Palese & Allan M. Zarembski 3.1 - 3.22

2.

Strategy for Rail Grinding for Running Heavier Axle Loads on Indian Railways 3.23 - 3.36 Pradeep Kumar Garg, Sanjeev Agarwal & Tushar Pandey

3.

Effects of Heavier Axle Loads and Strategic Mitigation Measures Parmeshwar Funkwal 3.37 - 3.51

4.

Improved Track Structure and Efficient Track Maintenance System for Heavier Haul Routes 3.52 - 3.75 J. S. Mundrey

5.

Running of Higher Axle Loads : Challenges, Limitations & Maintenance Strategies Bansh Narain Singh & Ajit Kumar Mishra 3.76 - 3.102

6.

Track Management System for Indian Railways 3.103 - 3.111 S.K. Malik & R. Dhankher

Technical Session 4

Innovation in Design & Construction of ROBs & RUBs on Indian Railways 1.

Innovation in Design and Construction of ROBs/RUBs on Indian Railways V. K. J.Rane 4.1 - 4.7

2.

Adoption of Innovative Design for ROB and RUB Construction Subodh Jain & Raju Bhadke 4.8 - 4.14

3.

Innovation in Construction of ROBs – Strategy for Mitigating Difficulties & Pitfalls H. P. Tripathi & A. K. Tiwari 4.15 - 4.26

4.

Enhancing Safety of Subways in Low Embankment Level Crossings N. K Garg 4.27 - 4.31

5.

Methods of Launching of Railway Span in Road Over Bridges: Comparison, Evaluation & Improvisation Ajit Kumar Mishra, Jawaid Akhtar & 4.32 - 4.54 G. B. Nagendra

6.

Innovative Concepts for ROBs over Cuttings in New Line Projects Neeraj Jain & Debasis Konar 4.55 - 4.63

7.

Construction of RUB by Box Pushing Method at Bishwas Nagar Delhi Vinay Singh & S.K.Mishra 4.64 - 4.73

8.

Launching of Precast PSC Girders by High Capacity Road Cranes for Construction of ROB at Rohatak in Northern Railway Vinay Singh & S.K.Mishra 4.74 - 4.82

Effects of Increased Loading on Track Structure S.K.Sharma*

Synopsis: Increased loading density affects track structure in many ways. It may be in the form of higher stresses, higher rate of wear, faster degradation of rail, ballast and formation. Moreover the maintenance inputs have shorter life under higher load. The fatigue life is consumed at a faster rate and fatigue signs appear too fast to be ignored only at the cost of serious safety repercussions. An attempt has been made here to assess the effect of increased axle loading/ Carrying capacity on Rail stresses. 1.0 Introduction: In 2004, Indian Railways took a historic step which can be called revolutionary in many ways. The carrying capacity of goods 8 wheeler wagon was increased by 8 tonnes (CC+6+2) and 10 tonnes (CC+8+2) on selective routes first and later on CC+6+2 loading was universalised on many other routes. Here it is mentioned that 2 tonnes was mentioned as loading tolerances. Two arguments were floated at that time; 

World over higher loading density has been adopted and therefore it will be possible on Indian Railways also.



In any case overloading is continuing sometimes in connivance of Railway staff, therefore let us legalise it.

These arguments may look to be flawed even to the common sense and that too without any detailed calculations. The theoretical knowledge was given go by and also the differences between construction and maintenance technologies beside so many other social and economic issues involved was overlooked. If theoretical knowledge is deficient then it may be because of our lack/gap of understanding or even after that if the knowledge is still not passing the test of time, it is the right time to give a quantum change in it. Even if we presume that the present theory level is not adequate, * CAO (C)/ South Central Railway

1.1

then also we may expect an error margin of 20-30% which is sufficient at least for making a good estimate. Also citing this error margin, the theoretical knowledge cannot be thrown in trash bin. At least we could have taken a conscious decision knowing fully well its repercussions. Here maximum increase of 10 tonnes (CC+8+2) in BOXN only shall be discussed. 2.0 Increase in Axle Load : The tare weight of BOXN wagon is 25 tonnes approximately. For a carrying capacity of 55 tonnes (Total load of 80 tonnes) this increase of 10 tonnes , the % increase constitute of about 18.18 %. Thus the total weight of wagon will be thus 90 tonnes approximately i,e 12.5 % increase in Wagon load. The similar increase will be there in axle load and wheel load also. 3.0 Existing Knowledge Level : The bending moment of the rail is calculated from the equation developed by Zimmerman in 19th century which is as follows; M=0.25 Pe**(-x/l) (Sin x/l - Cos x/l). Therefore if all other track parameters are assumed as constant, then as per this formula, the bending moment is directly proportional to wheel load P. Thus M shall increase by 12.50 %. Since the rail stresses are calculated by dividing the M by Rail sectional modulus, therefore the Rail stresses shall also increase by 12.5 %. 4.0 Effect of Vehicle Characteristic : The dynamic augment as per IR practice is calculated as per following formula. Speed Factor = (4.5 V**2/100000)- (1.5 V**3/10000000), where V is the speed in kmph. From this equation, at stationary position or at a low speed, the speed factor is zero. Also the dynamic augment or speed factor is a function of speed only neglecting the effects of vehicle characteristics. This situation is difficult to digest and not amenable to any analytical tools. At stationery or at low speed also, the vehicle characteristics assumes importance as widely varying from two stage suspension passenger vehicle to single stage secondary suspension freight bogies. Here the effect of decorative piece of primary level pads at crown level can be neglected. Therefore the dynamic loading at 1.2

stationery or at low speeds also assumes importance where at present no guidance is available, the vehicle properties should be taken into account. The K value of BOXN wagon is around 800-1000 Kg/mm. Higher is the K value and at higher damping ratio the effect is more pronounced even at low speed at small wave length track perturbations. At stiffness of 800 kg/mm and damping ratio of 20%, the Speed Factor may vary from 1.1 to 1.2. Therefore the Dynamic augment at a very low speed may be taken as 1.15. The net result is that the 12.50 % increase in Rail stresses shall be further enhanced to 14.37 % 5.0 Dynamic Effects at High Speeds. A. Indian Railways Practices : The dynamic effects on track is calculated by Dynamic augment formula as adopted on Indian Railways as given above. If we consider the maximum speed of 60 kmph of CC+8+2 rakes, then the Dynamic Augment shall be 0.15. Therefore the Rail Stresses shall increase to a level of 16.53 %. B. World Scenarios :Whatever practice we are adopting, can at best be called poor man dynamic analysis which is flawed at various levels. The dynamic rail stresses are a function of speed, vehicle parameters and track conditions. Essentially the dynamic effects may be characterised as follows: 1. Vehicle-Load both sprung and unsprung, Damping ratio. 2. Track-Imposed frequency Let us analyse here the BOXN wagon only. There are three modes viz, Bouncing, Pitching and Rolling. For wheel loading effects, the Bouncing mode is the most important therefore here only Bouncing effects only shall be discussed. 5.1 Natural Frequency of BOXN (Hz) : The natural frequency have been measured as under; Tare (25 tonnes)— 4.1 CC+6+2 (88 tonnes)—4.16 CC+8+2 (90 tonnes) – 2.5 Since these are measured values therefore let us assume that the minimum error will be present in measurements of natural frequency 1.3

in tare conditions. Therefore the natural frequency level of 4.1 is assumed correct and let us adopt it as base value. Since the natural frequency varies in inverse square root proportion of total weight, therefore at CC+6+2 level it is calculated as 2.29 Hz and at CC+8+2 level it is calculated as 2.161 Hz. The variation of natural frequency as measured and as calculated is shown as under; Natural Frequency (Hz)

BOXN Natural Frequencies 4.5 4 3.5 3 2.5

As Measured

2

As Caculated

1.5 1 0.5 0 0

20

40

60

80

100

Total weight of wagon tonnes

Fig 1 Natural frequency v/s Total weight of a wagon. The natural frequency as measured and as calculated are very close at CC+8+2 level, therefore the calculated values bear more semblance and can be taken as correct values. It also shows that at CC+6+2 level, the measured value of 4.16 can not be trusted which means lot of error in the measurements at CC+6+2 level. Therefore the natural frequency of 2.5 Hz at 80 tonnes level and 2.161 Hz at CC+8+2 level can be considered for further discussions. In design itself, the damping is provided by inclined wedges only. During service, the wedges get jammed due to loss , corrosion, dirt and ultimately jamming. Therefore a value of 5-10% damping is very much probabilistic. If we take up welding defects at 13 m interval then, at the speed of 60 kmph, the imposed frequency shall be about 1.28 Hz. The frequency ratio thus comes to 0.512 for 80 tonnes (Up to CC only) and 0.60 for 90 tonnes (CC+8+2). 5.2 The Dynamic Effects will be as Follows : For normal loading (CC) for a frequency ratio of 0.512 and damping ratio of 7.5%, the dynamic factor comes to about 1.35 i,e 35 % increase in loading.For increased loading (CC+8+2) for a frequency ratio of 0.60 and damping factor of 7.5%, the dynamic factor comes to about 1.55 i,e 55 % in loading. 1.4

5.3 Comparison with Indian Railway Practice. By Indian Railway practice, the dynamic augment comes to 15 % while taking in to account of Wagon features, the dynamic effect comes to 35 % . Therefore on Indian Railways, there is gross underestimation of 20 % in general in loading and consequently on Rail stresses. Similarly in CC+8+2 loadings, the dynamic augment comes to 55 %. Therefore the net effect of increased loading is follows: No. 1.

Sub Nominal Wagon Load (tonnes)

CC 80.00

CC+8+2 90.00

2.

Small Wavelength effects

92.00

103.50

3.

Dynamic effect as per Wagon (tonnes) 108.00

139.50

4.

Dynamic effect taking into accounts Small Wavelength effects

124.20

160.42

5.

Dynamic effect as per IR practice (tonnes)

92.00

103.50

Thus if we increase the carrying capacity by 10 tonnes, the Rail stresses shall increase by: 1. 12.5 %. if we take into account the static load only. 2. 30 % if we take into account the small wavelength effects. 3. 51.6 % if we compare IR practice on CC and Wagon features on CC+8+2 loading. 4. 30 % if we take into account Wagon features on CC and CC+8+2 loadings. 5. 74.36 % if we compare IR practice on CC and Wagon features (Including small wave length effects) on CC+8+2 loading. The net result is that the Rail stresses shall increase by about 74 % by adopting 10 tonnes increase in Carrying capacity. 6.0 Transverse and Longitudinal Stresses The stress model in these two modes has not been standardized so far except some very loosely defined formulas. The height of ignorance can be judged from the fact that the joint effects of these three modal stresses are still an enigma for Indian Railways. At lease there is dynamic augment formula for vertical direction, the similar formula is absent in other two directions. Simply we assume that there is no 1.5

dynamics involved in Transverse and longitudinal directions. 7.0 Contact Stresses The contact between rail and wheel flange should be theoretically a point. In practice the elastic deformation under high axle load results in deformation of steel of wheel and the rail creating an elliptical contact area. Contact stresses are determined by the normal force on the contact area, while the ratio of the ellipse axes a and b depends on the main curvatures of the wheel and rail profiles. Inside the contact area a pressure distribution develops which is semi-elliptical in shape with highest contact pressure occurring at centre.

Fig 2 Shear stress distribution at railhead The concentrated load between wheel and rail causes a shear stress distribution in rail head as shown in figure above. The contact problem is most serious in case of high wheel loads or relatively small diameters. Eisemam devised a simplified formula to calculate the maximum shear stress in railhead, which is as follows; max= 4.13

(Q/R)

max = maximum shear stress in railhead.(Kg/mm2)

Where Q

= Wheel load + load due on loading due to curves. (kgs)

R

= Wheel radius (mm).

Maximum Contact shear stress occurs at a depth of 5-7mm below the rail surface.

1.6

The Contact stress varies in direct square root proportion of wheel load. Therefore a variation of 74 % excess of axle load causes a straight increase of 32 % of Contact Stresses. For 90 tonnes wagon gross load and at 813 mm wheel diameter (Worn), the Contact stresses comes to about 21.91 kg/mm2. As per IR practice the max permissible Contact stress should be 30 % of Rail UTS. This approach is OK as far as segmental approach is concerned. What is the overall view when it is combined with bending stresses (Bending Moment is the first derivative of Shear force) is totally a Black hole from which nothing comes back. 7.0 Wheel and Axle Imperfections The views given above is OK for perfect wheel axle sets. On an average the conditions of majority of wheel sets, the conditions are far from perfect. The wheel axle imperfections generally are : Wheel flats, Oblong wheels, Bent axles, Worn wheels, Jammed bearings All these imperfections cause extra rail stresses. For example if we try to analyse the wheel flats alone, the extra load on rail depends on: Flat size, Train Speed, Wheel radius and Wheel load Effects of Wheel Flats : ORE 161.1/RP 3 reports of the tests carried out on flat tyres measuring the effects of speed, size, sleeper type and axle loads. The results reveal: i) The forces at frequencies above 500 Hz referred to as P1 forces increases continuously with speed, while the forces at frequencies below 100 Hz, referred to P2 forces are more or less independent of speeds. The P1 forces have bearing on wheel rail contact stresses. This force, which causes most of damage to rails and concrete ties, increases with increase in speeds. Effects of Speed on Wheel Force:

1.7



The P1 force is largely responsible for Track stresses.



The P1 force increases from 500 KN to 600 KN if the speed is increased from 30 kmph to 60 kmph i.e, 20 % increase. The 80 tonne total load will become 96 tonne at 60 kmph. It also shows how far we from this figure vis a vis the value of load from our dynamic augment formula specially at higher speeds.

Effect of Wheel Flat Size on Wheel Force.



The relationship between the flat size and force is almost linear.



The increase in Dynamic wheel force is more for concrete sleepers than for wooden sleepers.



Let us compare case nos 1 and 3 having concrete sleepers and in winter conditions of 22.5 t and 20 t axle loads. The wheel force jumps from 28 t to 33 tonnes i.e, 18 % increase at 30 kmph.



Therefore if we take into account the speed also, then at 60 kmph, the total load shall increase from 96 t to 132 tonnes i.e, 37.5 % robust increase.

Studies have also revealed that movement of wheels with flats can generate dynamic forces, as high as six times the normal static load, in extreme situations. The Dynamic forces increase with increase in speed and axle loads. On Indian Railways, the effect of rail/ wheel defects and vehicle suspension, on static wheel load, is represented by a speed factor which can assume a maximum value 1.8

of 1.75 for locomotives and 1.65 for wagons. Such occasional high loads may result in higher rail stresses reducing the fatigue life of rails and causing fracture of rail/ welds in extreme cases. The problem assumes alarming proportions incase of thermit welds (which have the impact strength of 50-60% of parent rail) in LWR territories, during winter season, when the full tensile stresses are present in rail section. According to UIC leaflet 510-2, flats on wheel with diameter of 1000630 mm should be restricted to a length of 60 mm and a depth of 0.91.4 mm. Other Wheel Axle and Bogie Imperfections. Track stresses are also related to other imperfections of rolling stocks;  Oblong wheels.  Bent axles.  Worn wheels.  Jammed bearings.  Difference in wheel diameters on the same axle or on the same bogie.  Ineffective/jammed damping system.  Spring characteristics change.  Condition of couplings. Even these factors cause greater level of stresses more than sometime wheel flats, no efforts have been made to determine the stress level increase due to these factors. Does our ignorance leads us to a situation where we claim that these factors are not important. 8.0 Combination of Rail Stresses : Although algorithms have been developed to determine the effects of vertical, longitudinal and lateral loadings individually but the various combinations are yet to be understood on IR system. All the parts of rail section profile has to be analysed from various combination point of view duly supported by practical test data. From this analyses, the mysteries behind rail fractures and weld failures which we have made so assiduously shall start unfolding. And possibly then we can take remedial measures. 9.0 Seriousness- a Big Question : Hoe serious we are is clear from half hearted approach which we 1.9

have adopted to stop overloading. Firstly no proper mechanism to install and maintain the weigh bridges. Secondly when we talk about wheel impact load device, we are told that its technology is not fully proven therefore we cannot adopt it. Thirdly when we talk to post the C&W staff to check the overloading , Wagon imperfections and consequently detachment at entry to Railway system, there is huge uproar and opposition from one particular department. 10.0 Penultimate Scenario : There is 74% increase in Rail Stress level and 37.5 % increase in Rail Contact stresses in case we increase the Carrying Capacity by 10 tonnes.. However no studies are available whether these two types of stresses are having any linkages or not. After all the bending stresses give rise to shear stress and Contact stresses also in shear mode only. If these are directly additive then the increase in shear stresses shall be 112 %. This increase is in relation to actual stress level in Carrying Capacity scenario only. What is this stress level in rails?. Well it is a million dollar question. On Indian Railways this rail stress level under actual field conditions is still a mystery. This mystery is yet to be unfolded since we are not in a position to state the actual Rail stress level under dynamic field conditions with carrying capacity load of BOXN wagon with any amount of certainty. If we are not aware and agree on basic stress level under a given load in dynamic field conditions, any amount of analysis shall not yield useful result and we shall not lead to any conclusion, leave alone the remedial measures to contain Rail fractures and weld failures. 11. Result of this Profligacy The result of this profligacy and freedom with track has been disastrous. An analysis was made on NCR in 2009. The results are explained here; 11.1 Over the last few months it has been noticed that the incidence of rail fractures have increased. A detailed analysis of Rail and weld failure was done to establish the proper cause and implement the remedies. On analysis of the fracture data it was observed that the rate and pattern of rail failure has changed in a major way from May 2006 onwards. In May 2006 heavier axle load of CC+6+2T were introduced over the main line section of NCR. Therefore in order to analyze properly the effect of heavier axle load 1.10

on the failure pattern of Rails in terms of Rail fracture and weld failure, a detailed analysis of the rail failure pattern, as discussed in this report, has been done for the main line sections of all the three NCR divisions. 11.2 Period of Analysis : The heavier axle load has been introduced over NCR in two stages. The loading of CC+6+2T has been introduced over the main line sections of NCR i.e. MGS-GZB section of ALD division and BINA –PWL section of Jhansi and Agra Divisions in May 2006. Later on even further heavier loading of CC+8+2T was introduced in Nov ’07 over the MGS-GZB section of ALD division and in April ’08 over the BINA-AGC section of JHS division. In ALD div UP direction is the loaded direction while in remaining two divisions DN direction is loaded direction. To arrive at a comparative position, a total period of 04 years i.e. from May 04 to May08 is taken for analysis so that rail failure figures of corresponding periods of before and after heavier loading introduction is taken and compared. Detailed analysis was done between the fracture patterns for 02 years period before and after of CC+6+2T introduction i.e. from May 04 to May 06 (before introduction period) and May 06 to May 08(after introduction period). However it is difficult to compare the rail failure figures resulting after the introduction of CC+8+2T loading, as there is no corresponding base figures available, since prior to introduction of CC+8+2T loading the loading of CC+6+2T was continuing at all the Main line sections. 11.3 Methodology Adopted: However while doing the above analysis for judging the effect of heavier loading on rail failure behaviour it is noticed that failure data taken for the complete sections is not strictly comparable. This is because lot of input has been given in the track in terms of CTR/TRR during the last 04 years in these main line sections of MGS-GZB and BINA –PWL. These considerable inputs given in terms of new and heavier track structure compensates to a large extent the negative impact of heavier loading on rail failure. Hence while comparing the overall failure figures of complete sections, true picture of negative impact of heavier loading is not reflected. 1.11

Therefore to single out the effect of heavier loading on the available track structure, rail failure analysis of only those sections is meaningful where no major input in terms of CTR/TRR etc is given over the time period of comparative study. Accordingly such sections of NCR were identified and the detailed rail failure analysis of these sections is done before and after the introduction of heavier loading. The corresponding data and the comparative rail failure position is given below; 11.4 Data Sheet: Section wise fracture details Enclosed as Annexure 1 11.5 Results Obtained: Although there are some aberrations in the trend/pattern but that may be due to local field conditions/other temporary reasons of the sections. The results obtained from this analysis can be summarized as follows:

The rail failures have increased by almost 75% subsequent to the introduction of CC+6+2T over the sections where track has not been renewed.



The weld failures have increased by almost 85% subsequent to the introduction of CC+6+2T over the sections where track has not been renewed.

This clearly shows that the negative impact of heavier loading on rail failure is considerable and it increases the rail failure to a very high rate compared to earlier failure rates. Although it is difficult to quantify but it can be safely concluded that the cumulative effect of this increased loading over the passage of time will further accelerate the incremental failure rate even beyond 85% that has been observed in the first two years of increased loading. The effect of CC+8+2T loading on rail failure will obviously be much harsher and more steep than that resulted by the introduction of CC+6+2T. Therefore it is proved that the heavier loading, which is now CC+8+2T for the last 18 months over the mainline sections, has been a major cause of increased number of Rail and weld failures of NCR. Though considerable inputs and efforts are being given in terms of 1.12

USFD inspections, improved weld quality and other safety measures to contain the fracture menace but to reduce the rates of failure considerably, will take some time till the system stabilizes with the impact of heavier loading. 12.0 Conclusions : The 74 % increase in Rail stress level should have been sufficient to ring the bell. First there is strong need to develop analytical methods to calculate the stress level in Rails duly supported by actual field measurements. After calculating the stress level under increases axle load, if it is considered essential to increase the axle load after techno economic analysis, we should certainly we should increase. Had this decision been a techno-economic decision, there would not have been any problem. Was it a conscious decision, keeping in view the stress level increase, increased cost of maintenance, rail replacement costs and safety costs in case of undetected Rail Fractures and Rail Failures. Unfortunately this was not the case and the decision was taken without carrying out any detailed analysis and weighting against the economics behind replacement and maintenance of permanent way.

1.13

Annexure 1 : S. No.

Section

Lenght Total Time Period (Km) (before & After )

1.

GHER58.28 AGC DN

Total period-May 04 to May 08 Before Period May 04 to May 06, After May 06 to May 08

0

4

5

16

2.

BLNRHET DN

49.3

Do

9

16

12

24

3.

KQRDDA DN

6

Do

2

11

0

3

4.

KRQ-SLV 63.63 Up

Do

5

2

4

20

5.

STLI11.28 BLNR UP

Do

2

5

2

10

6.

BTSRAJH UP

Do

0

0

1

3

7.

MTJ3 BTSR DN

Do

12

18

6

8

8.

ALJNMWUE UP

Total Period Nov.04 to Nov. 07 Before Period Nov. 04 to May. 06;After Period May. 06 to Nov. 07

4

3

1

7

9.

MTI-CMR 16.14 UP

Do

0

0

5

0

10.

MWUEMIU UP

95

Do

2

4

32

35

Total

321.91

36

63

68

126

15.2

4.08

***

1.14

Rail Facture & weld Failure details for the section Where no major input (CTR/TRR etc) is given

Challenges Faced in Running Iron ORE Rakes on South Western Railway Including Severe Ghat Section K.J.S. Naidu* Synopsis: This paper deals with Challenges faced in the Maintenance of Track including Points & Crossings, Bridges in heavily worked Iron Ore Route in South Western Railway including severe Ghat Section of 1 in 37 continuous grade, compounded by 7 to 8 deg. Curves. Solutions found to mitigate this problem and their implementation. 1.0 Introduction Bellary-Vasco, Bellary-Hasssan-Mangalore are two important iron ore routes on S.W.Railway. Bellary area is full of iron ore mines, large scale iron ore is being exploited since long years. From Bellary iron ore used to be sent to Chennai port through Bellary-Guntakal-Renigunta-Chennai route. Before large scale GC works, Bellary-Guntakal was operated as a goods line in this route. During this period, Bellary-Vasco was on MG route, small quantities of iron ore might have been going to Vasco, being MG. on Bellary-Vasco (MG) route trains had to cross severe ghat section of Castle rock-Kulem where gradient 1 in 37 existed. During 1990s, large scale GC works were carried out on indian railways. During this period the line between Bellary-Vasco was also converted into BG. After conversion of this line into BG between Bellary-Vasco, large no. of iron ore rakes started going to Vasco, being the nearest Port. Neither the Staff of Hubli Division nor the Track provided during GC was able to cater to the High Density of Iron Ore traffic on this Route, particularly so in the Ghat Section between Dharwad to Vasco (145 Kms), more particularly in severe Ghat Section of Braganza Ghat from Castle Rock-Kulem (26.23 Kms). In this Ghat gradient of 1 in 37 continuous compounded by 7 deg. to * CRS/Southern Circle, Bangalore

1.15

8 deg. curves continuously, are available. This paper deals with Problems faced, Remedial actions proposed with status of remedial measures. This route became the route identified for CC+8+2 in the first lot of routes identified by the Railway Board for plying CC+8+2 Rakes during May 2005. 2.0 Trend of Traffic on Bellary-Vasco : 2.1 Fig.1 indicates the increase of Iron Ore Traffic in GMT, the increase is tremendous from almost Nil to 30 GMT in 5 to 6 years time. Fig. 1 Comparative Figure of Iron One Traffic 35

30

25

20

15

10

5

0 2000-01 2001-02 2002-03 2003-04 2004-05 2005-06 2006-07 2007-08 2008-09

The Route between Hubli-Londa is common route for both BellaryVasco and Bangalore-Miraj-Mumbai besides Bangalore-Vasco, hence Hubli-Londa assumes high importance. This Section carries maximum Traffic in S.W.Railway which includes Iron Ore also. Besides this, Dharwar-Londa is a semi-Ghat section having 1 in 80 grades (though on paper it is 1 in 100, actually it is 1 in 80) with large no. of 5 deg. to 6 deg. Curves. Hence, this Route between DharwarKulem can be compared to KK Line, the length of this Section is 96.57 Kms. Dharwar-Kulem assumes higher importance as the traffic from Vasco Port towards Hubli, Bellary i.e. Coal, Fertilizer etc is also very high. The Section between Dharwar-Kulem is having Loaded Traffic from both sides, because of this fact this route is more heavily worked than KK Line. Added to all these factors another important item is running of Express Trains along with Minerals and Fertilizer loaded Trains. For these facts brought out above, importance of strengthening the Route between Bellary-Vasco was given highest 1.16

priority in particular to Castle Rock-Kulem and Dharwar-Londa being heavily worked having Mixed Traffic of both Goods (Mineral) & Passenger Traffic. Railway Board introduced CC+8+2 loaded Rakes in May 2005 in this Route. By the time higher axle load was officially permitted in May 2005, the problem of this critical section was already studied and solutions were thought of and started implementing. 2.2 Problems Faced in the Section: a) 90R Rails available during MG work were retained during GC works by Construction Organisation resulted in large scale Rail/Weld Failures. Rail top table damage with both vertical and side wear in Ghat Section of Castle Rock – Kulem section where 1 in 37 Grades compounded by 7 to 8 deg. Curves exist. b)

Formation Problems: Between Bellary-Hubli-Londa there were several locations having Formation Problems. In this Section, Track passes through BC Soil area more predominantly between Bellary-Hubli, due to this fact there are several stretches having Formation problems. The list of location of Formation Problems as in Table below. Though such problems existed in MG period also, Construction Organisation chose not to treat the Soil in the Formation during Gauge Conversion Works. Similar problem existed between Hubli-Londa as indicated in the list referred above (refer Table 1 below): Table 1: List of KMs having Formation Treatment

P.Way Section Hubli

Dharwar

Location Km. From 489/500

To 490/000

0.50

490/800

491/400

0.6

492/500

493/200

0.7

496/400

498/100

1.5

500/800

501/300

0.5

504/400

506/000

1.6

509/600

510/100

0.5

1.17

Length

Bijapur

511/200 515/000 519/000 520/200 521/400 522/400 523/300 524/900 169/000 178/000 201/000

511/800 516/000 519/800 520/800 522/000 522/600 523/600 525/500 171/000 182/50 202/500

95/000 165/000 62/000

101/000 169/000 98/000

612/000 5 19

625/10 7 29

Total Bijapur

Total Belgaum Hubli Total c)

0.6 1 0.8 0.6 0.6 0.2 0.3 0.6 2 4.5 1.5 8.00 6.00 14.4 20.4 13.0 2.0 10.0 12.0

Points and Crossings on Wooden Layouts and Wooden Sleepers on Girder Bridges: Throughout the length of this Section between Bellary to Vasco, Points and Crossings were laid using Wooden Sleepers to cater to the Track circuit needs of Signalling. No Wooden Sleepers were available for replacement. The deterioration of Wooden Sleepers both in Points & Crossings and Bridges was very high in this heavily worked Section.

d)

Failure of PSC Sleepers in Ghat Section: PSC Sleepers in Ghat Section between Castle Rock-Kulem where the Gradient is 1 in 37 continuous, compounded by 7 deg. to 8 deg. Curves, the percentage of broken Sleepers (see Table blow) had reached upto 48% in some Kms. 1.18

Table 2 Sleeper Damage (Ordinary, PSC- RDSO T.2496 & 135-B-1979) Km. No. of

Percentage of Damage

Km.

Sleepers

No. of Percentage Sleepers of Damage

25

158

10.26

38

182

11.82

26

98

3.36

39

742

48.18

27

139

9.03

40

597

38.77

28

81

5.26

41

453

29.42

29

70

4.55

42

443

28.77

30

90

5.84

43

443

28.77

31

199

12.92

44

361

23.44

32

72

4.68

45

216

14.03

33

178

11.56

46

214

15.65

34

57

3.70

47

200

12.99

35

121

7.86

48

131

8.51

36

134

8.70

49

95

6.17

37

222

14.42

Total

5723

14.87

The type of Failures noticed in the PSC Sleepers are as below: i) Longitudinal Cracks (along the length of Sleepers)

Photo 1: Longitudinal Cracks in PSC Sleepers. 1.19

ii) Transverse Cracks (along the Circumference of Sleepers)

Photo 2: Traverse Cracks in PSC Sleepers iii) Cracks emanating from the ferule fixed locally by drilling holes into the PSC Sleepers to fix checkrails in Curves, during laying of PSC Sleepers by Construction Organisation. Looks like while drilling holes, the prestressing tendons have got disturbed, this triggered the Cracks from this hole to start with. During the course of Service period these Cracks further developed and propagated along the length of Sleepers, Cracks also widened.

Photo 3: Damage started from Ferrule fixed for fixing Checkrail. 1.20

e)

Rail Damage: The top table of Rail i.e. contact surface of wheel and Rail on Rail top table and Gauge face were damaged extensively, particularly so in Ghat Section between Castle Rock-Kulem. On top table of rail tear of surface was seen which must have been due to very high contact stresses at Rail – Wheel contact surface. Along with Rail table damage, abnormally high lateral and vertical wear were also observed. As the Traffic level in Ghat Section kept increasing, the life of rail was found to be around 3 to 4 years, or even less.

Photo 4 : Top Table Damage f)

Points & Crossings laid on 7 deg. Curves in Station Yards of Ghat Section between Castle Rock-Kulem Points & Crossings have been laid on 7 deg to 8 deg Curves in the yards located in Ghat Section. Due to this, wear on Tongue Rails were abnormally high. This problem is compounded by the layout available on the Ghat Section Yards due to nonavailability of Catch Siding, the Trains have to necessarily take Turnouts. Due to this arrangement, 100% of Trains have to take Turnout without fail hence wear of tongue rail used to be very high, along with faster deterioration of Wooden Sleepers and hence increasing ineffectiveness of Fittings was noticed.

g)

Bridge Problems Generally in Bridges problems were not noticed except in one of the Bridges of Ghat Section of Castle Rock-Kulem (the problem was not with the Bridge but due to unstable slopes on Downstream Side). Because of excellent alignment chosen during construction, not many bridges are there in Ghat Section. 1.21

Even in available Bridges most of them are functioning well. Only one Bridge which is of 1 of 18.3 m. + 1 of 12.29 m.. Girder just before the Tunnel 1, actually at the mouth of Tunnel i.e. Bridge 69 at Km. 27/3-4 in Castle Rock-Kulem Section had serious problem of stability of Downstream Side Slope of hills, as it was getting de-stabilised. The Slope of the Hill is slightly steeper than 45 deg. Every rainy season the width of disturbance was increasing. During the year 2002, M/s Macefere gave a solution of providing Gabbions at three levels, these Gabbions by themselves rest on a mat supported on 150 mm Micro piles at close intervals. As already brought out, over a period, due to disturbance to slopes during every monsoon the pile cap of these Micropiles on which Gabbions were founded got disturbed. Though the Gabbion by itself slightly tilted, no failure had taken place. But the situation indicated that these Gabbions may fail during the course of time. As M/s Macafere did not carry out detailed analysis to identify the cause of the problem of destabilization of Slopes on Downstream Side of this Bridge, Analysis of this problem was found important. This study was entrusted to Geological Survey of India, Bangalore, who agreed to study and suggest remedial measures. But unfortunately, they could not continue the Study beyond a certain time limit due to Logistic problem in Forest area of this Ghat Section. Later the problem has been entrusted to M/s Stup, Bombay, who are studying to find a solution. A Paper has been published by Author along with Shri A.V. Mittal the then Dy.CE/Bridge of S.W.Railway in the Journal of Indian Railway Institute of P.Way Engineers published during October 2008 in Vol.8 No.4, this may be referred to if more details on this is sought. h)

Tunnels There are 16 nos. of Tunnels in the Ghat Section of Castle Rock-Kulem through 26 Kms length. The Tunnels are in Hard Rock. As all the Tunnels are hard rock Tunnels, due to inadequate Ballast Cushion, Track is sitting on Rock. To provide 300 mm Ballast Cushion in these Tunnels, poses problems of Clearance both vertical and lateral. To assess the problem in each Tunnel, the Laser Profile Measuring Equipment available with RDSO was used. We were the first to use this Equipment. After obtaining profile of Tunnels it was found that in four Nos. of Tunnels it would not be possible to provide Cushion of 300 mm. 1.22

2.3 Solutions Implemented in the Section Carrying Iron ORE: This can be split into two Components. a) In Ghat Section, and b) In other than Ghat Section. 2.3.1Solutions in Ghat Section : As already brought out in Ghat Section main problems were: i) Sleeper Damages ii) Rail Damages iii) Maintenance of Points & Crossings laid on Curves of 7 deg. iv) Maintenance of Track inside Tunnels. (i) Sleeper Damages A survey of Sleepers used in other Ghat Sections of Indian Railways was undertaken particularly in K.K Line of E.Co. Railway, Lonavala-Karzat Section of Central Railway. Following Table 3 indicates comparison of Sleepers used in these Ghat Sections: Comparison of Sleepers used in other Similar Ghat SectionsLength of Ghat

Ruling Max. Rails Gradient Curature

Sleepers

Sleeper Density per KM

CLR-Kulem 25 km

1 In 37

80

60 kg Normal PSC 1540 90 UTS T-2496 & 135B-1979 THOSTI BBRV System (Equivalent to normal sleepers)

KK Line

60 km

1 IN 60

80

60 kg HH

KarjatLonavala

28km

1 IN 37

5.50 (No Check rail)

60kg Normal & Slack 1660 HH gauge 60 Kg 90 UTS

PSC-Slack gauge T-4183-86

1818

From this it can be seen that K.K.Line had designed a Special Sleeper for Heavier Loads to be used in Ghat Section. The properties are as 1.23

given below in the Table 4. Table 4 : Properties of Normal PSC Sleepres as compared to heavier Slack Gauge Sleepers DEFFERENCE BETWEEN NORMAL SLEEPERS AND WIDE BASED SLACK GAUGE SLEEPER RDSO T- 418-4186 Normal PSC sleeper

Slack Gauge Sleeper

Drawing No.

T-2496

T-4183 to T-4186

Gauge

1673 (G-3)

S-11675mm (G-1) S-1677mm (G+1) S-1679mm (G+3) S-1682mm (G+6)

Shape (Under Rail Seat)

154 mm

150 mm 210 mm

217 mm

249 mm

284.2

HTS Wires

3 ply-18 Nos (3mm)

3 ply-18 Nos (3mm)

Insert (Drg.No.)

T-381 (1.55kg)

T-3705

Pre-tension force

486 KN

486 KN

Centre top

60 KN

50 KN

Centre bottom

52.50 KN

60 KN

Rail seat

220 KN

250 KN

Moment of Failure

370 KN

480 KN

Loads for Load test :

From the above Table 4 it can be seen that Slack Gauge Sleepers to Drawing NO. T. 4183 to 4186 is heavier, having higher Moment of Resistance, Trials were carried out at Hospet Sleeper Factory of S.W.Railway by manufacturing Sleepers to these Drawings. During Trials the Sleepers failed to satisfy the Bending Test loads prescribed. RDSO suggested slight modifications to reinforcements when approached with this problem. After few trials, as suggested by RDSO, the trials were successful in all tests. Meanwhile, Railway 1.24

Board was approached for premature CTR of 26 KMs in Ghat Section of Castle Rock-Kulem with increased sleeper density of 1660 Sleeper per Km. The then ME visited Ghat Section,. On observing the condition existing agreed for premature renewal during 2006, the Work was sanctioned in the year 2006-2007. From the experience, it was also found that Sleeper life gets affected due to inadequate Ballast Cushion besides sleeper density. Ballasting was also programmed, Ballasting posed problem in Tunnels dealt in subsequent Paras. (ii) Rail Damages Due to 1 in 37 continuous grade for 26 Kms, the loaded Trains going down the Ghat used to brake continuously. Initially, Triple Loco consist of WDG3A were used to take loaded rakes down the Ghat. Lately, coupled WDG4 are being used. Up the Ghat also, Trains loaded with Coal, Fertilizer are plying in this Ghat Section. Rail damages due to these loaded Trains were very high. These Trains of 58 Boxes were hauled by 7 nos. of Locos of WDG3A in total (total Tractive Effort of 7 Locos was 283.5 Tonnes), three Locos in front, three locos in the middle and one loco at the end. The total force was very high. With the adoption of WDG4 Locos, Five nos. of Locos are being used as Tractive Effort of each loco is around 50 Tonnes, the distribution of these Locos in the Train is two in front, two in middle and one at the end. Due to very high Tractive Effort/Braking Force, contact surface of wheel and Rail develops very high stresses. Due to these high contact stresses, top table of rail surface was tearing.Rail damage was abnormal, Rail Wear was very high. Hence it was felt that Head hardened Rails is a must in this situation. In CTR proposals HH Rails were proposed. ME also was shown about Rail damage, he also agreed and sanctioned HH Rail for renewal. Here it is brought out that fractures were not there in this Section as the Rail was getting worn out faster, the fatigued surface of rail was getting removed due to higher wear before cracks from fatigued portion of rail could propagate and result in fracture. But the side wear was abnormal besides Top table wear. The extent of wear was so high in this Section that the frequency of Rail Renewal reduces to 3 to 4 years time. This 3 to 4 years time is not enough to cater to the cycle of time required to get the Renewals sanctioned following the present 1.25

procedures. Railways need to take appropriate action before it goes out of hands. (iii) Points & Crossings: As already brought out above, Points & Crossings have been laid on 7 deg. Curves during Gauge Conversion of the Section posing serious problems in maintenance. RDSO was approached to advise Sleeper Spacing to cater to 7 deg. Curves to lay Fanshaped PSC turnout Sleepers as the present design of Fanshaped Turnouts are designed for laying upto 2 deg. Curves only. Meanwhile, proposals for shifting of Points to straight was also studied. But loop lengths were becoming more than 1 Km. Traffic Department also wanted to increase the loop lengths. Hence shifting of Points to straights was taken up and Wooden layouts were replaced by PSC Fanshaped layouts in Straights eliminating Points on Curves. (iv) Ballasting to Provide 300 mm Ballast Cushion: During Gauge Conversion proper ballast Cushion was not ensured. For providing ballast cushion of 300 mm, main problem was posed by Tunnels. There are 16 nos. of Tunnels in total in the Section. Tunnel profile was to be measured accurately, as existing, to know the problem. A new Laser based Profile Measuring Equipment was available with RDSO which was not used anywhere. It was obtained and Tunnel profile was measured using the Equipment. This equipment uses laser beams to measure the profile. The laser beam emitter rotates 360 deg. so that at each location tunnel profile could be measured accurately. Sample results are given in following fig. and Tables 5 & 6. The Photo 5 below indicates the Laser based Profile Measuring Equipment.

Photo 5 : Laser based Profile Measurement Equipment 1.26

Fig.2 : Sample profile of Tunnel obtained from Profile Measuring Equipment Table 5

1.27

Table 6

2.3.2 Solutions In other than Ghat Sections: In other than severe Ghat Sections, following action was taken: a)

Renewal of 90R Rails : About 100 Kms of 90R Rails were available on this Iron route with not only Speed Restriction of 30 Kmph for Iron Ore rakes, but also large no. of Weld Failures and Rail fractures, the Fig. below indicates the extent. These Rails were replaced on priority with 10 rail panels further welded as LWR/CWR. The weld failures and Rail fracture were contained as could be seen from the Fig. 3 600 500 400

Statistics of RF-WF No. of Failure WF

300

Statistics of RF-WF No. of Failure RF

200 100 0 2003- 200404 05

200506

200607

200708

2008- 200909 10

Fig. 3 : Rail/Weld Failures on Hubli Division. b)

Replacement of all Wooden Sleeper Turnout Sleepers: A programme was drawn to replace all the Wooden Sleeper Turnouts. The balance no. of Wooden Sleeper Turnouts available

1.28

on S.W.Railway were around 1550 nos. Materials required like Turnout Sleeper for Fanshaped Turnouts, Rail points and Crossings required along with Fittings were assessed and a detailed programme was drawn up to eliminate all Wooden Sleeper Turnouts in a phased manner in 3 years time. In this, priority was assigned to Bellary-Vasco, in about 18 months time on this route since 2005, the completion was achieved. c)

Replacement of Bridge Timbers: Programme was already available to replace the Wooden Timbers on Bridges, this also was accelerated and completed.

d)

In some sections broken PSC sleepers were noticed in plane section but not to the extent as found in Ghat Section. These were also programmed for replacement.

e)

Formation Problems: Though Formation Problems were available in the section as already brought out, there were no stretches under Speed Restrictions, priority was given for Turnout, Bridge Timber replacements. Later work of Geogrid strengthening at some stretches have been carried out, results have to be watched.

2.4 Scabbing of Rails Scabbing of Rails in other than Ghat sections was very severe, the problem was not so much on Ghat section though present to small extant. The then CME/S.W.Railway took appropriate steps and brought about very high discipline in ensuring Sanding Gear working in all the Locos with availability of dry sand at all locations, so that Loco Pilots could easily take dry sand from any station on Platform itself. This ensured total stoppage of Scabing of Rails needing Renewal of Rail prematurely, a very costly asset of Railways, besides saving Loco which would be getting damaged due to stalling with added advantage of avoiding hindrance to Traffic Movement. 3. 0 Conclusions i)

Railways while carrying out any work particularly Construction Organization shall carry out survey in case of critical sections like Ghat Section and provide appropriate Track structure.

ii)

Maintenance Engineers also to keep vigil, compare notes with other Railways particularly in Heavily Worked Routes further

1.29

compounded by Steep gradients, sharp curves for long stretches. If Problems are identified, Solutions could be found. This has to happen at all levels. iii)

Needs high quality of Materials that are being used in such heavily worked Sections.

iv)

Needs high quality in execution of Works

v)

Needs close and appropriate monitoring at all levels.

***

1.30

Impact and Experience of Heavier Axle Loads on Indian Railways and Resultant Maintenance Strategies Hemendra Choudhary *

Synopsis : SER system is extensively covered by routes identified for CC+8+2 or CC+6+2 trains. Here predominant traffic is iron ore.This paper presents the experience gained on CNI-ANR (CC+8+2) route. This section is under Adra Division of SER. The paper seeks to cover the problems being faced & offers some remedies for those problems.

1.0 Introduction : The running of CC+8+2 load BOXN wagons was introduced by Railway Board in certain identified routes of S.E.Railway since 15.05.05, subsequently other routes were also added. The running of CC+6+2 Ton load BOXN/BOBRN wagons was introduced in certain routes of this Railway since Feb’06 & other routes were added later on. Now heavy axle loads are in operation in about 90% routes of SER. 2.0 Higher Axle Load Operation : On SER heavier axle loads are primarily being operated for iron ore rakes in electrified routes. The loading of iron ore is being done at 16 loading points in Chakardharpur Division, both for domestic steel plants & for export. Most of the iron ore loading is being done GUA-BARAJAMDANOAMUNDI-BANSAPANI sector for feeding the steel plants of TISCO at Tata Nagar, IISCO at Burnpur and DSP at Durgapur and in Barsuan/ Kiriburu sector for feeding the steel plants at Rourkela & Bokaro. CNI-BURN section is basically feeding IISCO at Burnpur & DSP at Durgapur along with small iron factories at Bhaga, Radhanagar, Chowrasi etc.This section is having a traffic of 59.6 GMT. DEN(Central) Adra Divn, SER

1.31

3.0 Impact of Heavier Axle Load on the Basis of the Field Experience : Based upon the experience gained so far, particularly in respect of weak spots such as points and crossings, SEJs, glued joints, approaches of level crossings, curves, rubber pads of steel channel sleepers on bridges, AT welds and considering various maintenance problems, additional inputs are very much required for the maintenance of the track those carrying heavier axle load with high GMT. 4.0 USFD Testing in Chandil – Anara DN Line Section & the Results : It is a well known fact that due to heavy axle load running over the track, the rails are subjected to more stress and fatigue and resulting into earlier failure in the form of fractures. It is also a well known fact that in the sections where heavy load is running, the magnitude of alertness is high and when deterioration of rails is detected then need based renewal is also approved by the head quarter. By such early renewals and timely actions , sometimes it is understood that there is not much effect of heavy load over the track because number of fractures are not increasing much in recent time due to timely attention by the Permanent Way Engineers. The detailed study of USFD results of CNI-ANR DN line section considering the age of the rails, GMT carried ,and new defects noticed during recent testing is being presented. Comparative Study of USFD Rail/Weld Testing Work Between ANR-CNI DN Line S. No.

Item

2004-05

2005-06

2006-07

39.39

41.66

Rail=4 Round/ Yr. ATW= Every 3Yrs.

Rail=6 Round/Yr. ATW= Every 3Yrs.

1

Sectional GMT

28.98

2

Rail TestingFrequency Rail=4 Round/ Yr. ATW= Every 4Yrs.

3

Total Length of the Track laid with

52Kg=12.5 Km, 60Kg =69.4Km

52Kg=8.5 Km, 60Kg =71.4Km

52Kg=3.5 52Kg=3.5 52Kg=2.7 Km, 60Kg Km,60Kg Km, 60Kg =74.4Km =74.4Km =75.2Km

4

A IMR(Rail)

5

4

5

1

5

B IMR(weld)ATW&FBW 2

3

28

2

15

1.32

2007-08 55.35 Rail=6 Round/Yr. ATW= Every 2Yrs .

2008-09 59.60 Rail=6 Round/Yr. ATW= Every 2Yrs.

5.

WELD DEFECTS

RAIL DEFECTS

C OBS Rail

209

165

118

D OBS(weld) ATW&FBW 183

255

59

63

65

277

E Defects in centralportion 445

275

193

72

90

F Defects in GF & NGF

Data 68 notavailable

114

305

G Total No. of defects 445

275

261

186

395

H No. of Rail fracture

7

2

NIL

1

1

I ATW Population

9485

9130

8440

8502

8657

Data notavailable

98

J Tested During the year 4657

4828

617

1579

7712

K No. of DFW defected 88

63

17

185

355

L % Increase or Decrease -

0.60%

1.50%

1.70%

2.90%

M No. of weld failure

8

2

2

3

3

N Defects %

1.90%

1.30%

2.80%

1.70%

4.60%

Note: Rails: Due to on going rail renewal programme, the No. of defects in 52Kg Rails is decreased substantially apparently it looks that the No. of defects in rails are in decreasing trend but the fact is that the No. of newly generated GF/NGF defects especially in AT Welds are increasing rapidly. The systematic & efficient USFD testing work accompanied with the prompt action taken by the maintenance staff (i.e. Sectional PWI) minimizes the occurrence of Rails & Welds failure in the section. Welds : Due to increase in GMT by almost 38% along with Heavy Axle Load, the No. of DFW defects is increasing at a rapid rate of 3% which may consider as quick deterioration of AT Welds in the section. The Details of USFD Testing of Rails During Period From 08/08/2009 to 22/08/09 Between ANR-CNR Dn Line S. N0.

1 2

Rail Section / Year

52 Kg before 1997 60 Kg/ 1996

No. of defects

Approx GMT Carried till date

Defects detected

Defects Position

Defects in

Defects gradient

Mid AT Mid AT Cen- GF/ W W tral NGF

St

Curye

L

Up/ Slow Fa Very Dn st Fast

New

Defects propa gation rate

Old

3

600

-

2

-

1

1

2

2

1

1

2

1

-

-

2

600

-

-

-

2

-

2

2

-

-

2

2

-

-

1.33

3

60 Kg/ 1997

21

560

-

6

-

15 -

20

19

1

3

17

8

4

2

4

60 Kg/ 1998

1

520

-

-

-

1

-

1

1

-

-

1

1

-

-

5

60 Kg/ 1999

11

480

-

7

3

1

1

9

10

-

1

9

6

1

2

6

60 Kg/ 2000

2

440

-

2

-

-

1

1

2

-

1

1

-

-

-

7

60 Kg/ 2001

14

400

-

2

1

11

1

12

12

1

3

10

8

1

1

8

60 Kg/ 2002

7

360

-

1

-

6

-

7

6

1

-

7

5

1

-

9

60 Kg/ 2003

-

320

-

-

-

-

-

-

-

-

-

-

10

60 Kg/ 2004

1

280

-

-

1

1

-

1

-

-

11

60 Kg/ 2005

2

240

-

1

-

2

1

2

1

-

12

60 Kg/ 2006

1

200

-

-

-

1

-

1

-

13

60 Kg/ 2007

1

160

-

-

-

1

-

1

1

-

-

-

21 5

57

7

12

51

33

9

5

66

-

40 4

57

Detailed Study Report of Rail Defects Between CNI-ANR DN Line (km - 395/20-364/0) During 08/08/2009 to 22/08/09 SI. Rail Section/Year Total No. Length (km)

Approx Total GMT No. of carried till defects testing

Defects No. of Track New Kilodefects metre

New defects Track Kilometre

1

52 Kg/Before2000 2.7

600

3

1.11

2

0.74

2

60 Kg/1996&1997 22.7

600

23

1.004

6

0.26

3

60 Kg/1998&1999 10.3

520

12

1.16

7

0.68

4

60 Kg/2000&2001 13.8

440

16

1.15

4

0.29

5

60 Kg/2002&2003 8.3

360

7

0.84

1

0.12

6

60 Kg/2004&2005 8.8

280

3

0.34

1

0.11

7*** 60 Kg/2006&2007 1.4

150

2

1.43

Nil

------

Remark: Due to very small amount of length i.e. 1.4 Kms, SI. No. 7 is not taken in to account during the time of this analysis. Though it is quiet clear that the defect generation rate is directly proportional 1.34

to the age of the rail, that is GMT carried by that particular rail section, but there is slightly variation noticed against SI No.2 due to existence of a small patch of Head hardened rail in that particular section. GMT Carried

1.35

From above graphs based on the detailed study of defects in (CNIANR) DN LINE, it is clear that total defects are on rise trend with the age of the rails.Here the effect of heavy axle load could be understood by the new defects. The rate of the defects is increasing after introduction of heavy axle load. Further it is to be noted by USFD testing that the size of the defect in the Rail section is increasing with the time on such routes those are carrying heavy axle load. 5.0 Problems Being Faced in Maintaining the Track due to Running of Heavier Axle load: 5.1 Rails: i)

CORROSION: It has been noted that due to falling of iron ore, rate of corrosion has become faster on rail, MS liner & contact area. SOLUTION: To over come this problem new rails are being painted with red lead on side before laying. 1.36

Also in service rails are painted with anti- corrosive paint along with sealing of liner contact area on gauge face side using grease graphite to prevent development of corrosion pits on rail foot. This requires additional manpower & expenditure. ii)

SCABBING/WHEEL BURNT CASES: Due to stalling of trains/sudden breaking, there is increasing trend of rails getting damaged on account of scabbing/wheel burns. SOLUTION: Rails need to be changed on such spots. The experience of relaxing such spots by Micro flow thermal spray (using flow alloys) technique has not been good for main line. So, it is better to change the rails. The scabbed rails/wheel burnt rails can be used in the yard/sidings after welding by this technique of the affected area.

5.2 Fittings: GR Rubber Pads: The crushing of GR pads is very fast requiring frequent renewals (once in 02-03 years). Now, we should think about the use of 10 mm GR pads with improved materials in place of existing 6 mm GR Pads. Further, the main problem of rubber pads getting crushed rapidly is under CMS X-ings. The rubber pads under crossings are found to be getting crushed within a period of 09 to 12 months. Rubber pads under crossing with more thickness 10-12mm & with better material should be used. It needs a review by RDSO. 5.3 Insert Liner, etc: The design of the inserts & ERCs should be reviewed to suit 10 mm thick rubber pads. Similar is the case with rubber pads used under channel sleepers. The thickness of the rubber pads to be used under the channel sleepers may be upto 20 mm. 5.4 Points & Crossings: i)

With the introduction of heavier axle load, the rate of wear on crossings has increased, thereby need to carry out reconditioning more frequently.

ii)

Replacement of crossings also to be required within a period of 4 – 5 years (200 GMT).

1.37

iii)

The GR sole pad under the crossings are getting crushed at a very faster rate & remedial action is only to replace them frequently. There is need to develop new vendors for supplying Rubber pads or augmentation of capacity of the existing vendors to cater the need.

iv)

The thickness of Rubber pads under CMS crossing should be increased upto 10-12mm & also the design of inserts & ERCs are to be modified accordingly. It is required because CMS X-ing works as a monolithic structure & there are no chances of bending of CMS crossing like rails, so all the vertical force goes to sleepers & from sleepers to ballast & from ballast to formation. Rubber pad acts as a resilient media between Rail & sleepers. So, it should be thick & adequate.

v)

The heavy wear on tongue rails:Introduction of thick web switches essential for the routes subjected to heavier axle load. Provision of short check rails ahead of switches located on curves has given considerable relief in Chandil , Biramdih and Urma yard.

vi)

Frequent changing of pandrol clips is needed (09-12 months) in CMS X-ing due to its monolithic structure.Although recently provided GJ clips have been a better relief.

5.5 Bridges: i)

No major problem in maintenance of bridge has been felt due to heavier axle loads in this section. However, Instrumentation tests have been conducted for substructure & super structures of two important bridges (Br.No. 414 5X100’+1X80’ & Br.No. 520-22X100’).

ii)

Frequency of attention for tightening of channel sleepers fittings have been increased from once in six months to two/ three months. SOLUTION : To prevent frequent loosening of nuts on channel sleepers, the design of nut should be modified & the castle nut may be used.

1.38

A castle nut has 06 number grooves on one side of simple nut & a pin is passed through the grooves of the nut into the bolt.

iii)

Free rail joints are also weak structure & they are difficult to maintain due to severe impact of heavier load & efforts are to be made to eliminate rail joints wherever possible. SOLUTION: As per provisions of LWR Manual, LWRs are not permitted through deck bridges so one metre long fishplates are being used to reduce the impact on such joints. Alternative solution may be to permit continuing LWR through deck bridges with permanent speed restrictions in the interest of better maintainability and also to prevent damages to bridge structures. RDSO may go for investigating into this concept.

5.6 Rail Welding Welded joints in rails are the weak links. Thermit welds are weaker than flash butt welds by 40%. It is important that population of thermit welds vis-à-vis flash butt welds is controlled. The solution lies in using 10 Rail panels & 20 Rail panels in the present & future renewals.Quality of AT welding, needs to be improved. It is also a known fact that AT welds are weaker links on rail track & there are guidelines to replace the AT welds when it attains the half of the life of the rail but many times AT welds have failed at earlier than the 50% of the fatigue life of the rails. 1.39

In a long run, we should think in the direction of movable flash Butt Welding plant, so that field weldings can be done as Flash Butt. 6.0 Infrastructural Improvement Required to Maintain Track Subjected to Heavier Axle Load. i)

To improve the life of CMS crossings and also to reduce the incidences of breakage, deep screening of points & crossings has to be carried out by deploying machine, as manual deep screening is not of much use. Each zone should be provided with exclusively two BCMs for deep screening of Points and crossings along with UNIMAT & DTS.

ii)

Despite monitoring, instances of overloading continues. Clear policy directives are required to be issued from Railway Board to handle such rakes on detection of overloadings.

iii)

There is immediate need to create a “Small Track Machine Organization” for effective handling & utilization of small track machines.

iv)

Discipline in loading upto the prescribed limits is the need of the day. The existing penal charges for overloading are not sufficient deterrent & other punitive measures including control on indents are also required.

v)

Increased axle loads generate high contract stresses between rail and wheel, specially where rail table profile has degenerated. Preventive rail re-profiling by rail grinding at committed intervals to reduce contact stresses between rail and wheel may have to be introduced.

vi)

Regular re-profiling of wheels and rails to a conformal condition to specifically avoid high stress contacts may have to be introduced.

vii) The actual gradient in some sections do not match with those mentioned in the load table of the working time table. It is necessary to identify such difficult sections & provide adequate power for hauling of the trains in such sections to prevent stalling and wheel burns.

1.40

viii) In stretches where wheel burn & wheel scabbing is prevalent, premature track renewal may be permitted. ix) As the presence of small defects in track parameters get magnified quickly on heavy axle load routes, the standard of track maintenance has to be improved. Better track machines, lower track tolerances and the system of corridor blocks are to be ensured. x)

Friction management protects the rail gauge face and wheel flange while ensuring good traction on running surface for which way side lubrication is recommended.

xi) While the rail removals have increased, the actual rail fractures have not increased to the same extent because of increased alertness and timely renewals. This has been possible only because of extensive patrolling being done virtually around the year. This is leading to a significant loss in manpower, which needs urgent recoupment. xii) Gate keeper, Keyman & patrolman should be put in the separate categories & they should be provided with extra allowance for their tough duties. It will be better if these three categories are put together & called tough duty trackmen & they are recruited through RRB directly with better pay & allowance and promotional aspects. xiii) Wheel Impact Load Detectors are to be installed at convenient locations, not only to detect the axle load of the loaded wagons but also to detect wheel flats, if any. xiv) Frequent USFD testing of complete rail head by new technology (e.g. walking stick of M/s Sperry) is to be insisted upon. xvi) We have to ensure better quality and frequent renewal of rubber pads and providing weldable CMS crossings & thick web switches to reduce the wear of their fittings. xvi) We have to mechanise all the P.Way activities in phases. This technical paper is based on my experiences gained of heavy axle load in CNI-BURN section. Heavy axle load is the need of the

1.41

day, so now it is our responsibility to find the ways of better maintenance of our assets & I hope my this Paper will Contribute something, May be little, to find the ways for better maintenance of the track.

***

1.42

Experience of Running Heavier Axle Load on KTEBIN Section and Resultant Maintenance Strategies

Rajesh Arora * Vijay Pandey ** Synopsis : Axle load on track is increasing continuously. Developing newer ways of track maintenance is the need of the hour. In this paper the authors have presented case study of KTE-BIN section of West Central Railways. The effects on track due to running of higher axle load in KTE-BIN section have been studied in detail and better maintenance practices have been suggested to minimise the ill effects. This paper will serve as a guideline to the PWay engineers involved in the maintenance of high axle load routes. 1.0 Introduction : Heavy axle load has the same effect on track that heavy physical stress has on humans. It takes time to notice the ill effects in both the cases. Initially the track may be able to bear the higher load and to some, it may appear perfectly normal. However, the stresses keep on building inside the rail and may collapse on a later date. Therefore, it is high time that we study the effects of higher axle load on track in different sections all across the Indian railways to conclude the ill effects of higher axle load and then, arrive upon a common maintenance strategy to combat the same. Indian railways are a commercially social organisation. While it has the responsibility of carrying passengers from and to all corners of the country, it also has to care for its economic health and earn revenue. It is already known to all that major chunk of railways revenue comes from freight services. And with the ever increasing prices of fuel, the pressure of not increasing the freight rates and the constraint of most of the sections running to full capacity, the only way for railways to keep them into business is by making the same goods rake earn some extra revenue, obviously, by carrying some extra load. This means that increase in axle load is an irreversible process *CTE/West Central Railway *Sr. DEN/West/Jabalpur.

1.43

and the higher loading is here to stay, infact, grow further. A typical axle running over the track looks like as under:

The load gets transferred from the axle of the rolling stock in following manner: Rail

GR Pad

Sleeper

Ballast

Formation 2.0 Brief about BIN-KTE Section To conduct the study and find out the effect of higher axle load, first and the foremost requirement is a defined section. Precise and detailed 1.44

study can only be done when the area of interest is well defined and of manageable length. For the purpose of this study, the authors have selected Bina-Katni (hereafter called BIN-KTE) section of West Central Railway. The section is 260 km in length and falls under Dspl route category. Heavily loaded with freight trains, the annual GMT of this section in loaded direction (UP road) is 63.23. CC+8+2T loads have been plying in this section since May’2005. The chief transport commodity of the section is coal and the common rolling stock is BOXN wagon. Loaded BOXN rakes of coal do ply on DN road also but they are lesser in number and the annual GMT on DN road is 26.99. The ruling gradient on UP and DN road is 1 in 200 and 1 in 100 respectively while the sectional speed is 100kmph. 3.0 Period of Study CC+8+2T loads started plying in this section from May’2005. The period of study had to be decided keeping two aspects in mind: i. Equal representation is given to data of pre and post CC+8+2T loading. ii. Availability of reliable recorded data. Based on the above two aspects, a study period from year 2003-04 to year 2008-09 was arrived upon. Much older records were not maintained properly and therefore not considered for study.

1.45

4.0 Effect on Rail The effect of higher axle load on rail is most visible and best recorded. Rail is also the most important part of the track structure and the effect of higher loading is more damaging on it than on any other part. The rail can also be called as first line of defence of the track against the incumbent load. It directly bears the brunt of the load which is reflected in the form of scabbing, battering of joints, side wear and fractures. The effect of higher loading on rail was studied for following parameters: i.

Rail fractures and weld failures

ii.

USFD results

iii.

Wheel scabbing

iv.

Flattening of inner rail on curves

v.

Side wear of outer rail on curves

vi.

Effect on glued joints

vii.

Wear and tear on turnouts

4.1 Rail fractures and weld failures The most difficult task in the study of rail/weld failures is the availability of correct data. In this respect, following approach has been adopted. In sub-division/Division unit record of USFD testing along with number of IMR/OBS/DFW detected and removed during the month is maintained regularly. While there is no discrepancy in records of IMR/ OBS/DFW, large discrepancy is observed in reporting of occurrence of Rail/Weld failure. Main plea behind the discrepancy is stated to be that “There are number of rail/weld failures, which do not effect the train operation, termed as rail crack/weld crack and being replaced without reporting to traffic. The discrepancy in date due to above reason gives a totally different picture than the actual and would have defeated the very purpose of the project. In order to obtain correct picture, field data maintained in the form of “Section register of PWI”, correspondence between PWI/ AEN/Division and progress reflected through PCDO was collected and scrutinized. Scrutiny of basic field record gives the true picture of actual occurrence of rail/weld failures during last 5 years for BINKTE section (5 PWI units). 1.46

For the comparision of rail/weld failures, locations where rail renewal or deep screening, TSR, etc has been done, were not considered. This is because, the rail/weld failures not only depend on the rail itself, but also on other factors like quality of packing, destressing, shifting of liner seat, etc. The year wise rail/weld failure detail for BIN-KTE section including the effects of higher axle loads is given as under: Total RF/WF on BIN-KTE section. (Excluding track renewal locations) Type of fracture

2003-04

2004-05

2005-06

2006-07

2007-08 2008-09

RF

3

7

4

6

7

8

WF

97

106

135

172

208

221

Total

100

113

139

178

215

229

Total RF/WF on KTE-BIN section

Fractures

250 200 150

RF

100

WF

50 0 2003-04

2004-05

2005-06 2006-07 Year

2007-08

2008-09

The analysis clearly shows that the failures are increasing every year. However, this increase is mainly due to the weld failures. This means that, while the rail is able to bear the increased loading quite satisfactorily, it is the AT welds that is ringing the alarm bell. The impact of increased loading coupled with passing of occasional minor flat tyres is causing more and more welds to fail. This may be primarily due to rapid loss in the strength of weld under the impact load of CC+8+2T loading. As a good maintenance practice, we should increase the frequency of weld testing through USFD. This will help in protecting the welds which are likely to fail. Moreover, the limiting 1.47

value of flat tyre should also be revised for higher axle loading routes. 4.2 USFD Results : Year wise compilation of USFD flaw generation has been studied. During the period of the study, through rail replacement was done at some locations and therefore, for a meaningful study, year wise USFD flaw generation has been compiled only for those locations where rail continued to be the same. Description

2003-04

2004-05 2005-06 2006-07 2007-08 2008-09

UP DN UP DN UP DN UP DN UP DN UP DN IMR (Rail) OBS (Rail) IMR (Weld) OBS (Weld) DFW

16 116 5 215 538

13 68 1 148 144

22 43 5 134 422

10 56 5 148 289

7 91 8 521 663

1 111 6 481 361

27 135 2 299 470

14 159 2 514 746

21 194 6 682 466

6 123 7 538 453

12 164 1 639 349

5 74 0 381 165

GFC testing was started in the year 2006 and therefore, comparison of GFC flaws cannot be done for pre and post CC+8+2T period. This is the reason why GFC flaws are not appearing in the above table. From the table it is very clear that number of new flaws getting generated in rails/welds every year is much higher after 2005-06. This is primarily due to the running of CC+8+2T loads since May’2005. 4.3 Wheel Scabbing : Wheel scabbing occurs when the hauling loco is not able to pull the trailing load. Preceded by wheel stalling, this phenomenon normally occurs on a gradient or on the approach of some stop signal where the effective trailing load increases. The wheel stalling and rail scabbing data of BIN-KTE section during the study period is tabulated as under:

1.48

NO. OF CASES

Description Length of rails replaced (m)

2003-04 2004-05 2005-06 2006-07 2007-08 2008-09 57

54

191

253

289

719

The data clearly shows that the problem of rail scabbing is increasing ever since the introduction of CC+8+2T loading. All the wheel stalling and consequent rail scabbing cases have occurred on rising gradients. The problem is more acute on DN road due to steeper gradients. Now, there are three governing factors in this case: i.

The steep gradient

ii.

The trailing load

iii.

The power of the hauling loco

Of the above three, gradient is a permanent feature. This clearly means that if the trailing load is to increase due to the increase in loading, it must be supported with similar increase in the power of hauling loco to negotiate the gradient of track. And this is exactly what is not happening in BIN-KTE section. Even when the trailing load has increased substantially (approx 500T per rake) the hauling power continues to be the same. As a result, the wheel stalling as well as rail scabbing cases are on a continuous increase. The remedy to the problem lies in providing adequate hauling power or a banker to the loaded rake. 1.49

4.4 Flattening of Inner Rail of Curve When a loaded rake runs at a speed slower than the design speed, it causes flattening of inner rail of curve. 26 curves were selected for the study. Vertical wear of inner rail of these curves has been measured since the start of CC+8+2T loading. Increase in average vertical wear of these curves with time is tabulated as under:

Year

2005-06

Average vertical wear in mm 2.08

06-07

07-08

08-09

3.21

4.67

5.81

The data shows that the flattening of inner rail of curve is increasing at an average rate of 1.25mm per year. A rail, will therefore, be due for renewal in a period of around 10 years. Thus, the life of rail is getting reduced. 4.5 Side Wear of Outer Rail of Curve The cant deficiency of a curve is responsible for the side wear of outer rail of curve. However, the increased axle load causes further increase in side wear by increasing the force. The study was conducted over a set of 33 curves, the side wear of which were being measured since the start of CC+8+2T loading. Increase in average side wear of these curves with time is tabulated as under:

1.50

Year

2005-06

06-07

07-08

08-09

Average side wear in mm

1.86

4.19

5.84

6.60

The data shows that the side wear of outer rail of curve is increasing at an average rate of 1.58mm per year. A rail, will therefore, be due for renewal in a period of around 6-7 years. Thus, the life of rail is getting reduced. As a good maintenance practice, frequency of greasing of outer rail of curve should be increased. 4.6 Wear and Tear on Turnouts The wear and tear on various turnouts over the years is explained in the following table: Description

2003-04 2004-05 2005-06 2006-07 2007-08 2008-09

No. of tongue rails reconditioned

36

51

126

114

119

119

No. of tongue rails replaced

32

39

99

76

80

68

No. of crossings reconditioned

48

87

132

155

155

185

No. of crossings replaced

42

53

50

63

73

73

The tongue rail of a turnout wears out due to the inherent curvature. As a preventive measure, all main line turnouts of BIN-KTE section were provided with check rails near the SRJ during July to Sept 2007. The idea was to reduce the wear in the first two meter length of the tongue rail. The results have been encouraging. The cases of reconditioning or replacement of tongue rail have reduced after the provision of check rails. However, as a measure of system improvement, we must only provide thick web switches on CC+8+2T routes. The crossing of a turnout wears out due to the impact load as a result of the wheel jumping from the throat of crossing to the nose of crossing. The cases of reconditioning or replacement of crossings have been increasing every year. This means that the impact load is continuously increasing. The life of crossing may be increased if, through some means, this impact load may either be decreased or 1.51

dissipated. Increasing the elasticity of track at crossing portion may be a good idea. Some of the ways of reducing the impact load are: 

Use of thick rubber pads.



Improving the ballast cushion.



Providing gapless frozen joints.



Eliminating the vertical and lateral misalignment at crossings.

4.7 Effect on GR Pad : GR pad serves as an elastic medium which reduces the impact on the sleeper. It absorbs the energy by getting deformed under the wheel load. Besides, it also has a role to play in providing correct toe load on the rail. However, due to increased loading, the deformation of the pad increases. The life of rubber pad gets reduced due to this phenomenon. A sample study done in BIN-KTE section showed that 30 to 40% of the rubber pads are crushed at locations where CTR was done in the year 2006. However, the GR pads were found all intact at locations where TFR has been recently after the year 2008. The life of the rubber pad gets further reduced if they are not centrally seated over the sleeper. This is because when the pad gets dislocated, the effective bearing area gets reduced and the compressive stress increases. Therefore, as a matter of good practice, care should be taken while placing a new rubber pad over the sleeper. The dislocation of rubber pad can also be avoided by pasting the pad on the sleeper with epoxy or similar glue. RDSO may also like to design sturdier rubber pads for such routes. 4.8 Effect on Sleeper : No noticeable effect has been seen on sleepers, other than that on level crossings, due to the running of CC+8+2T loads. This is because the effect of axle load on sleeper largely depends upon the condition of rail, rubber pad and ballast cushion. Casual renewal of sleepers is done routinely at isolated locations which are mostly due to either rounding off of sleeper bottom or breakage of CI insert. This is more of a maintenance problem and therefore cannot be attributed to higher axle loading. However, on level crossings due to caking of ballast, the impact on sleeper increases and hence groove formation takes place at the rail 1.52

seat. During the overhauling of level crossings, more and more cases of unserviceable sleepers are being noticed. The details are tabulated as under: YEAR No. of sleepers replaced at LCs on BIN-KTE UP road

2003-04 2004-05 2005-06 2006-07 2007-08 2008-09 50

37

33

77

129

260

To reduce the groove formation on sleeper rail seat at LCs, following may be done: 

Track at level crossings should be deep screened at a reduced interval



Spacing of sleepers at LCs should be reduced

4.9 Effect on Ballast : Higher impact loading damages the ballast by crushing it. This causes an increase in the proportion of fines ( 35T

5.0 Monitoring Health of The Bridges : With the introduction of CC+8+2t operations, bridges are being inspected and their health is being monitored closely through regular quarterly inspections. The details are given below. 1.67

5.1 No of Bridge Identified for Inspection : i.

Important

-

1

ii.

Major

-

44

iii.

Arch

-

4

iv. Others 597 5.2 Details of Major Deficiency Noticed: (i) In bearings

-

NIL

(ii) In super structures

-

NIL

(iii) In substructures

-

NIL

(iv ) Any other

-

NIL

5.3 Status of Instrumentation of Bridges: i)

In Phase I :

Sl.No Bridge No.

Bridge Details

1.

Span 2x18.29 + 4 x 7.62 m. (Arch.)

Name of

Scope of work

Current status

2.

3.

4.

5.

Span 20, UBL-HPT 5 x 9.14m Section @ km. Arch type 46/15-47/1 139 A, BAYGAD section, HPT yard.

Span 1x30.48 m (Open Web Grider)

Span 3, TNGL-BNHT 2x 19.4 m section, @ Km. (through 1/0-1 Grider) Span 2x27.43 m. 102, LD-VSG section, @ km. (Through Plate 34/14-15. Girder)

Indian Institute of science, Banglore

Agency 128, LD -VSG Section, @km 39/5-6

It includes instrumentation of selected Railway bridges for assessing their static/Dynamic behaviour, development of computational models to assess the current condition and to develop the tools for system identification and residual life assessment due to enhanced axle loads and longitudinal loads on the bridges.

Instrumentation in all the bridges has been completed. Report of all the five bridges have been received which indicates that all bridges are safe for 25 T axle load. Final report of all bridges sent to RDSO Lucknow.

ii) In Phase II : Five bridges have been identified for instrumentation in phase II over SWR as below:

1.68

Bridge Details

47 LD - VSG in UBL Division

5 x 12.2 Arch Bridge

2.

293 HAS MAQ in MYS Division

2x30.5 Under Slung

3.

184 HPT- BAY in UBL Division

1x12.2 Composite

4.

497 HAS MAQ in MYS Division

4x45.7 + 8 x 4.4 OWG & PG

5.

47 GDJ - SMLI 3x12.2 in UBL Division PG

1.

Name

Scope of work

Current status

of Agency

M/S Sharma & Associates INC, Ahmedabad

Sl.No Bridge No.

It includes instrumentation of selected Railway Bridges for assessing their static / Dynamic behavior, development of computational models to assess the current condition and to develop the tools for system identification and residual life assessment due to enhanced axle loads and longitudinal loads on the bridge

1) First round of instrumentation of all bridges have been completed in April / May – 09. 2) The report of all five bridges have been received and under study at HQ. 3) Second round of instrumentation has been conducted in Nov & Dec 09.

5.4 Restriction of Tractive Effort to 30t for Running of WDG4MU on Bridges. Further in this route the following bridges are having restriction of tractive effort to 30t per loco for running of WDG4MU with CC+8+2 rakes. These bridges are also inspected regularly every quarter and so far no adverse effect has been noticed. Sl.No 1 2 3 4 5 6 7 8 9 10

Bridge No. 3 39 47 157 184 200 204 206 240 243

Location 1/1-2 19/10-11 24/7-25/1 153/8-9 167/9-168/0 174/0-1 174/10-11 177/13-14 194/8-9 197/6-7

1.69

Between station TNGL-RNJP GDJ-SMLI GDJ-SMLI HPT-BAY HPT-BAY HPT-BAY HPT-BAY HPT-BAY HPT-BAY HPT-BAY

6.0 Stalling / Scabbing Cases : Number of stalling cases has almost been brought down to zero by ensuring proper powering after conducting number of trials on higher axle load route. The details of stalling cases vis-à-vis no. of trains loaded with CC+8+2 t are given below. YEAR

No of trains Run with CC+8+2

Stalling cases

2005-06

4627

3

2006-07

6080

0

2007-08

5934

0

2008-09

4813

2

2009-10

3030

8

The stalling cases have been brought down to negligible percentage by powering the trains judiciously and counseling the driver’s suitably. However, the rise in stalling cases during the current year has been attributed to extended monsoon on SW railway and the reiteration of guide lines to loco driver to ask for banker to avoid wheel burns and scabbing of rails. 7.0 Conclusion: With the experience gained in running higher axle loads and the increased demand of freight transport, it is possible to optimize utilization of existing assets. However, higher axle load operations demand  Real time reaction of field engineers in monitoring the health of the P.Way and intelligent deployment of the track machines.  Elimination of thermit welds as much as possible.  Ultrasonic flaw detection need to be further improved so as to accurately predict the asset performance.  Close monitoring of maintenance inputs by introducing TMS on identified routes in addition to Pilot divisions will be very essential.  Use of In-motion Weigh Bridges to detect over loading.

1.70

 Use of Wheel Impact Load Detector (WILD) to prevent passage of flat tyres and unevenly loaded wagons.  Elimination/Reduction of rail joints on bridges to reduce dynamic impact of bridges.  Preventing over speeding of goods trains.  Planning for need based renewals instead of GMT based renewals.  Introduction of strict discipline in checking over loading and action on results of WILD.  Correct powering of trains loaded up to CC+8+2 and improved enginemanship. It is time to look forward for introducing 25 T and higher axle loads by suitably strengthening the bridges and inducting rolling stock with better suspension.

***

1.71

Effects of Enhanced Loading (CC+8+2) on the Track & Rolling Stock on Chennai Division A Managerial Perspective for RU-AJJ-MAS Section

- S. K. Kulshrestha*

Synopsis: The progressive adoption of enhanced loading of Indian Railways warrants analysis of the issues of maintenance, operation and the policies, the optimum utilization of the assets enhancing the scope for earning the revenue without undue stress. In the present paper, a managerial approach to the failures in RU-AJJMAS section suggests changes in the policies to suit the local need.

1.0 Introduction: 1.1 The upward revision of loading targets by Railways require optimum utilization of rolling stock, path, etc. This requires fine tuned coordination between various departments as with enormity of the issues, the results may not be forthcoming beyond certain limits. The policy of bulk loading, end to end running, running of CC rakes and incremental loading have been adopted by Railway Board apart from procurement of additional rolling stock and new lines. Each change in policy brings in a new change for the maintenance engineers. 1.2 The revival of Railway, reported recently, is due to the incremental loading. This decision has helped in achieving the targets with ease. However, they have cut the safety margins for maintenance and are likely to threaten the safety and viability of the system. To analyse the impact of the incremental loading and the perils of few of the decisions which have manifested as failures a torough analysis was done to suggest the course of action. The CC+8+2 routes have been analysed as it has the critical impact on the system. * DRM/MAS/Southern Railway

1.72

1.3 The Ports in and around Chennai are the links for the export of iron ore and for receiving coal, fertilizers, etc. The linkages for the Port are to the power house and major industries. Railways handles about 50% of the commodities transacted at Port. The nonmovement of the remaining traffic is attributed to space availability and poor progress of mechanizing, reduced maintenance of the rail assets within the HOM area and the practices of HOM. The cost of movement by road is more than the Railways but due to ease and convenience road ways has a considerable share of the same. Enhancing the share of Railways in moving the goods from Port provides scope for additional revenue. With the overheads remaining the same, profits rise up and can be used for the maintenance. The enhanced loading has the effect of increase in carrying and thereby improving the operating ratio. The extensive damages to Rolling Stock as well as Track can cost dearly in incremental loading thus proving counter productive. 1.4 The damages to Rolling Stock makes it unfit for loading and damaged wagons are moved as empty along with loaded wagon reducing the earning and enhancing the expenditure. 1.5 The carrying capacity of BOXN wagon is 55 tons, the enhanced load is 8 tons per wagon which is a 14.5% increase. If the wagons running as empty in a rake of 59 exceeds 8, the benefits of incremental loading will be completely nullified. In certain cases due to exigencies, these wagons also gets detached and composition of rake gets reduced. Running trains with short of compo/empty wagon subject Rolling Stock and Track to higher stress without extra revenue but with extra expenditure on empty haulage and repairs. The details of various types of wagons are tabulated below: S. No

Type

Axle Load

Tare

CC

Whether upgraded

1

BOXN

20.32

23.2

58.08

Yes

2

BOXN HS

22.82

23.2

68.08

Yes

3

BOXN HA

22.1

23.17

65.23

Yes

4

BOXN HL

22.9

20.6

71

Yes

5

BOXN EL

25

23.1

76.9

Yes

6

BOXN LW

20.3

18.26

63.02

-

1.73

1.6 The policy of Railway Board communicated in their Commercial Circular has commodity specific monsoon period to be adopted throughout India. During monsoon period, the loading is restricted to CC+6+2. The monsoon over India varies from region to region. In certain regions particularly southern India, it can so happen that there will be a loss of revenue due to reduced loading in a season where there are no rains. This in turn enhances the damage to Rolling Stock as well as Track with the continuing of enhanced loading even during rain. The part of the CC+8+2 route from HOM to RU, running via South Western Railway and South Central Railway upto Hospet, is a best representative for analysis. Routes CC+8+2

Vasco-HPT-RU-AJJ-VPY-HOM VPY-AIP,AIP-EPLS

CC+6+2

All other routes of Southern Railway

1.7 In the present paper, an earnest attempt is made to analyse various aspects of maintenance and practices adopted for enhanced loading in a section with the effect on asset failures, to find the remedial measures. The loading being as under. Originating Loading in tonnes (in ‘000s) Period 2008-09 2009-10 (upto October ’09)

Target 17,358 9,926

Actual 16,923 9,749

2.0 Track 2.1 The track structure in RU-AJJ-MAS Upline was with 1540 sleeper density with 52Kg rails and 1660 sleeper density with 60 Kg rails during 2006-07. Subsequently, except 10 Km all the stretches have been converted into 1660 sleeper density with 60 Kg rails. 2.2 CC+8+2 Routes In Chennai Division Southern Railway has 631 Km under CC+8+2 Route. (i)

Renigunta (RU)-Arakkonam(AJJ)-Vysarpadi(VPY)-Attipattu (AIP) (For Ennore Port) and Chennai Beach (For Chennai Harbour- HOM)-154 Km (134+20) 1.74

(ii) Gudur (GDR) – Chennai Central (MAS) – 136 Km (iii) Arakkonam (AJJ)-Mettur Dam (MDTM) and Jolarpettai (JTJ) – Somanayakanpatti (SKPT) – 317 Km (294 +23 ). This route has been recently nominated for CC+8+2 route, vide Rly. Boards’ Lr.No.2008/CE-II/TS/2 Dated 31-8-2009. (iv) TOK-PNMB (Tokkur to Panambur) 24 Km Out of total 631 Km in Southern Railway, Chennai Division alone has CC+8+2 route of 436 Km . The route (ii) and (iii) are recently included in CC+8+2. However, the route (i) RU-AJJ-VPY-AIP-HOM has been nominated for CC+8+2 as a Pilot Project since July’2006. 2.3 Monitoring Mechanism: To monitor the Permanent way assets due to the running of CC+8+2 iron ore rakes, the Quarterly Inspection Report of ADENs is to be submitted to HQrs through Division. The report involves the following parameters: (i)

No. of CC+8+2 trains run during that Quarter

(ii) Safety – derailment of CC+8+2 train with cause (iii) Track – Status of 90R rails ( Balance if any to be removed) (iv) Track – Status of Rail / weld failure (v)

Track – Status of USFD testing involving no. of IMR and GFC (Gauge Face Corner) defects

(vi) Track – scabbing and wheel burn on rails (vii) Track – Effects on turnouts involving wear on CMS Xings & crushing of rubber pads (viii) Track – Effects on curves of more than 3 degree involving lateral wear (ix) Bridges – Important Bridges, Typical arch bridges and certain no. of minor bridges have been selected and the inspection being done every 3 months to ascertain the behaviour of bearings, superstructures and substructures 2.4 Impact on Track Assets: After the pilot study was introduced the following observations have been made with regard to the track on the section. 1.75

(i)

2 locations scabbing of rails /wheel burn on rails have occurred within the very First year of running of CC+8+2 trains, i.e, from July’06 to Sep’06.

(ii) The wear on curve outer rails is more in CC+8+2. Upto 2mm vertical wear is found on 3 degree curve within 2 years (The rail was laid during July’07; the measurement was taken on April’09). (iii) It is observed that wear at the crossings is more and G.R. Sole plates at CMS crossing requiring renewal once in six months. At the same time the CMS crossing requires frequent renewal (iv) Wear is more on built up crossing requiring renewal once in six months. (v)

Wear on outer tongue rails has increased

(vi) No. of OMS lateral peaks increased (vii) Rubber pads are getting crushed frequently warranting renewal within 2 years. (viii) Iron ore powder falls on shoulder contaminating the ballast warranting shoulder ballast cleaning. Iron ore falling on rail table and getting crushed is causing pitted rail top. (ix) The glued joints get severely battered due to Heavy axle loads and requires frequent attention and renewal. (x) No. of Points and Crossings require frequent tamping. (xi) However, there are no adverse effects on bridges in this route. (xii) More USFD defects like OBS(W) and IMR were noticed in the old rails in the section. Even after renewing with 60 Kg new rails, this problem is continuing. This can be seen from the table below:

1.76

Abstract Of USFD Defects Yearwise In AJJ-MAS Up Line Between Km.4/0-68/0 YEAR

OBS

OBS(W)

IMR

IMR(W)

Total No. of Defects

2004-05

18

46

0

0

64

2005-06

8

59

2

0

69

2006-07

16

77

0

2

95

2007-08

9

67

2

0

78

2008-09

3

62

0

0

65

2009-10 (upto Nov. 2009)

20

45

5

2

72

1. CC+8+2 was introduced in July 2006. 2. Interchanging of rails have been done during 2007-2008 that resulted in lesser USFD defects. 3. It is evident from the data shown above that the defect rate is in increasing trend after introduction of CC+8+2. Abstract Of USFD Defects Yearwise In AJJ-MAS Up Line Between Km.68/0-134/780 YEAR

OBS

OBS(W)

IMR

IMR(W)

2004-05

20

25

0

0

45

2005-06

10

28

1

1

40

2006-07

20

58

0

0

78

2007-08

15

67

0

0

82

2008-09

10

60

0

0

70

2009-10 (upto Nov. 2009)

19

44

1

1

65

1.77

Total No. of Defects

1. CC+8+2 was introduced in July 2006. 2. Interchanging of rails have been done during 2007-2008 that resulted in lesser USFD defects. 3. It is evident from the data shown above that the defect rate is in increasing trend after introduction of CC+8+2. (xiii) The details of renewals done is given below: KM Engine Run MAS-TRL AJJ-RU AJJ-RU AJJ-RU AJJ-RU AJJ-RU AJJ-RU AJJ-RU MAS-AJJ MAS-AJJ MAS-AJJ

Line FROM 4/0 69/450 82/250 82/900 87/500 88/840 103/475 125/0 8/100 8/600 10/40

UP UP UP UP UP UP UP UP UP UP UP

TO 5/0 71/450 82/700 87/500 88/740 95/240 125/0 133/600 8/600 9/940 11/600

Total Rail UTS KM Section 1.000 52 90 2.000 60 90 0.450 60 90 4.600 60 90 1.240 60 90 6.400 60 90 23.525 60 90 8.600 60 90 0.500 60 90 1.340 60 90 1.200 60 90

Laid Year 2008-09 2008-09 2007-08 2007-08 2007-08 2007-08 2007-08 2008-09 2006-07 2007-08 2007-08

Works done CTR TRR CTR CTR CTR CTR CTR CTR CTR CTR CTR

TOTAL 50.855 KM (xiv) It can be seen from the following table that RF/WF have increased during the initial stages of introduction of CC+8+2, i.e, during 2006-07; subsequently failures have reduced due to large scale renewal works, ie., about 51 Km of CTR works done in this Section. RU-AJJ Year 2003-04 2004-05 2005-06

RF 52 31 20

WF 68 82 91

AJJ-MAS RF 63 29 16

WF 60 34 23 1.78

TOTAL RF 115 60 36

WF 128 116 114

Remarks

2006-07

25

108

16

21

41

129

2007-08 2008-09 2009-10 (upto Nov /09)

9 8 3

49 48 23

11 11 16

36 27 17

20 19 19

85 75 40

*CC+8+2 introduced $ Reduction in failure due to track renewals

Note * CC+8+2 is having more impact on Weld failures. $ Reduction in failure is due to track renewals. (xv) The TGI value is found to be deteriorating as can be seen from the following table: In MAS-AJJ Section, the TGI value is decreasing due to CC+8+2 route as only 4.040 Km of CTR has been done in this Section. However, in AJJ-RU Section, the TGI value is increasing due to large scale CTR works done. Comparative TGI Values for 7 years in CC+8+2 routes

YEAR

MAS-AJJ

AJJ-RU

2003-04

86.51

94.32

2004-05

90.82

83.91

2005-06

91.92

82.75

2006-07

96.81

87.96

2007-08

92.51

90.53

2008-09

96.45

98.27

2009-2010

95.53

98.11

1.79

2008-09

3.0 Availability and Damages to Wagon The enhanced loading increases the stress on structural members, couplers and suspension. This has increased the pace of deterioration requiring earlier attention than the scheduled attention. The number of vehicle maturing for attention increased more than ten fold with repairs such as body, CBC defects, wheel defects, spring renewal, elastomeric pad renewal, etc. Apart from increased duration for attention, the wagons awaiting attention have also increased. The average wagons marked sick post-incremental loading have increased considerably. The data pertaining to JTJ and TNPM depots is enclosed. Taking cognizance of such detention, Railway Board went to the extent of directing Shops to give priority for unloadable repairs over the POH of wagons at Workshops and encouraged outsourcing of unloadable repairs to augment repair capacity. The increased repairs and detention have caused reduced availability of the wagon. The severity of this has damaged only the BOXN wagons. The reduced availability of BOXN wagons coupled with the increased loading targets have made the Railway to view seriously the damages caused by unloading agencies and defer the maintenance schedules. While deferring the maintenance schedules will increase failure such as hot axles, enhanced repair per wagon at Shops, etc will lead to reduced availability of wagons. The Railway will be in a vicious circle 1.80

giving a reduced output unless augmented by procurement of more wagons involving extra expenditure. 4.0 Speed of Trains: The speed of the goods trains have also undergone a downward revision with the introduction of CC+8+2 loading. The speed potential of the train have been revised as below : Type of Stock

Speed for Normal loading

Speed for Enhanced loading

BOXN

75

60

BOXN HS

100

60

4.1 The reduction of speed has reduced the kinetic energy available to the train while hitting the gradient. Therefore, the need to maintain the higher tractive effort while negotiating a gradient on account of higher load has increased to maintain the constant speed. This has the potential to increase stress on the track giving scope for failures of the track. 5.0 Policy on Monsoon Season The Railway Board in their various circulars have assumed a commodity specific uniform monsoon period for CC+8+2 rakes. The loading of gypsum during 1st June to 31st August is restricted to CC+6 even in the CC+8 loads and loading of E, F and G grade coal is restricted to CC+6 from 1st July to 15th August whereas the monsoon in the Chennai Division is during October and extends upto middle of January. Therefore, during the period where restriction is imposed by Board, the Southern Railway can actually run trains to CC+8+2 loading. Therefore, there is a loss of revenue for forgoing the loading due to instructions from Railway Board. The loss is quantified as under In terms of Wagons

Jul-Aug 2009

Coal

Steel coal

Coke Total

1722

6484

3201

Total enhanced weight by 2 tons

11457 22914 tons

1.81

5.1 Similarly, during the monsoon at Chennai Division, the loading is continued, with 751 number of CC+8+2 trains during Oct-Dec 2008. These trains have potential to cause damages to track. The lacunae in the policy can therefore cause enhanced damages to track on one hand and also result in loss of revenue on the other hand. The wagon defects such as flat tyre, defective suspension, etc have capability to transfer higher impact load to the track. It is required to quantify the impact load to isolate the wagons which have potential to cause damage. Total No. of Trains run with CC+8+2 in MAS Division Period

No. of Trains

Period

No. of Trains

April-June 2009

783

April-June 2008

809

July-Sept 2009

916

July-Sept 2008

622

Oct-Dec 2008

751

Jan-Mar 2009

1089

6.0 Equipments to Pre-warn Damages to Track The Railway Board has made provision of Wheel Impact Load Detectors in the CC+8+2 routes. One such impact load detector is in the section from RU to AJJ near AJJ. This Wheel Impact Load Detector (WILD) has identified 5 number of wagons since its inception and helped to detect the culprit wagons capable of causing damages to track. If the Wheel Impact Load Detector is placed closer to RU, the damages caused by running wagons from RU to AJJ can be avoided. Therefore, it is required to relocate the WILD to RU. Similarly, the WILD is an improvised weighbridge with additional sensors and logic. If all the weighbridges are converted into WILD, apart from making the weighment, it will also help in detecting the defects in wagon suspension and wheel which will eliminate the defects. The cost of WILD and In-motion Weighbridges is as below : Description

Procurement

Cost

In Motion Weighbridge

2009

Rs.14,96,000/-

Wheel Impact Load Detector

2007

Rs.75,68,910/-

1.82

6.1 The location of the WILD can be rationalized such that the exposure of the track to the defective wagons is minimized. 7.0 Unloading Time The total load on the train has increased by 14.5%. The length of the train has also increased by a wagon or two. Yet the timing allowed for unloading and loading have remained the same. Due to paucity of time, the wagons are generally seen with uneven loading and extensive damages due to mechanized unloading. This is furthering the damages to wagons and consequential damages to track. 8.0 Conclusion & Recommendations 8.1 The policy of enhanced loading has provided a scenario where the loads in the wagons have increased by 14.5% and the maximum speeds of the trains have come down by 20%. The wagon defects directly attributable to increased loading have risen tenfold in most of the crucial parameters. The availability of wagon has come down due to extensive detention and detachment of wagons awaiting repairs forcing Railways to augment capacity for attention by outsourcing. This has resulted in shortage of wagons. Therefore, Railways have resorted to postponing maintenance schedules of wagons. Now, instructions have been received for postponing the POH of BOXN as well as BCN wagons. As we need to continue with the CC+8+2 loading, it is suggested that to contain the damage to the minimum by directed improvements in the rolling stock the policies should be made conducive to enhanced loading. The following are suggested with regard to rolling stock: (i)

Outsourcing of on rake attention of damaged wagons.

(ii) Providing WILD for detecting wagon defects (iii) Running of train with engine at both ends to avoid excessive coupler force and removing the brake van so Guard can travel in the loco in the rear. (iv) Making a policy for rainy season or providing a temporary cover for wagon (v) Provision of additional spring on wagon. 8.2 During the past Two and Half years, with the experience of dealing with CC+8+2, it is understood that various track elements like Points and crossings, glued joints, rails on sharp curves have been badly 1.83

affected. At the same time, the existing bridges withstand CC+8+2 traffic without much maintenance problems. In fact, some of the Bridges in this route (1 major bridge with PSC girders with span of 14 Nos. x 20.5m and another major bridge with steel girders with a span of 13 Nos. x 12.19m) have been tested with CC+8+2 rakes and Instrumentation was done with the help of IIT/Madras. It is found that the stresses are well within the permissible limits. Hence, the following recommendations are made with respect to track maintenance in CC+8+2 routes: a)

CMS Crossings may crack under heavy impact load and hence the GR pads need to be renewed within 2 years.

b)

Greasing of outer rail curves having more than 3 degree curvature to be done frequently to avoid wear.

c)

Level crossings to be maintained with clear cushion to avoid rail/weld failure

d)

Points and Crossings to be deep screened and tamped with a frequency of one and half year.

e)

Rubber pads and glued joints to be renewed frequently.

f)

Shoulder ballast cleaning to be done to improve the drainage.

g)

If old rail exists, frequent USFD testing of rails and welds to be done.

h)

Built up crossings in CC+8+2 route to be eliminated.

***

1.84

Heavier Axle Load – Effect on P.Way & Reorganising Track Maintenance Strategies. Amit Agarwal * Rajiv Kumar Tanwar** M.Jayaprakash Reddy***

Synopsis: Indian Railways in an effort to increase its transport capacity have taken a bold decision to run trains with higher axle load on iron routes and some other specified routes. Such a decision no doubt has made a financial gain for Indian Railways but it has introduced a lot of implications, which requires to be studied and addressed. The paper deals about the effects of running higher axle loads on track based on experience of running CC+8+2T load on Guntakal & Guntur division for last 4 years and the sensitive issue of management and mechanized track maintenance which are the main issues if Indian Railways have to maintain the track efficiently and economically to run heavier axle load trains.

1.0 Recent Development of Adopting Heavy Axle Loads on Indian Railways : The beginning has been made in the year 2005-06 by taking up the pilot project wherein axle load upto 22.82 ton against existing 20.3 ton have been permitted on existing BOXN wagons and on designated routes (22 routes over seven Railways). With the experience gained from this pilot project for one year ( 15th May 2005 to 14th May 2006), the running of 22.82 ton axle load has been universalized in most of the freight intensive routes of Indian Railways. Now Indian Railways is gearing up to move one step further in this direction i.e., running of trains with axle load of 25 ton in near future on selected routes.

*Sr.DEN/South/GTL/SCR **DEN/Bridges/GTL/SCR ***DEN/West/GNT/SCR

1.85

2.0 World Scenario of Heavy Axle Loads: Railways

Axle Load

BHP Biliton, Australia

38.0

Canadian Pacific Railways

33.0

Russian Railways

23.5

Norfolk Southern Railways( USA)

33 – 36

Chinese Railways

25

IHHA recommendations

30 – 34

It is evident that heavy axle loads ranging from 30 to 40 tonnes are running in America, Australia and other advanced railways. But there is major difference in scenario prevailing on Indian Railways unlike world railways, where heavy freight trains runs on dedicated routes. the same infrastructure has to carry both freight and passenger traffic on Indian Railways. 3.0 Heavy Axle Loads on Guntakal & Guntur Divison of SCR: Railway Board has permitted operation of BOX’N’ wagons loads up to CC+8+2 on identified iron ore routes as pilot project vide Railway Board lr No.2003/CE-II/TS/5/Vol I dt 02/05/2005. Guntakal Division being the fore most routes in transporting iron ores on this Railway, the stretch between Bellary-Guntakal (SL) and Guntakal-Renigunta (UP/SL) was identified for the pilot project and from 15/05/05 the heavy axle load vehicles were introduced with a speed restriction of 60 Kmph. The higher axle loads of CC+8+2 were also permitted between Guntakal-Dhone-Nandyal stretch on GTL division and Nandyal-Guntur section on GNT division, and trains started running with higher loads from Feb’06 onwards. In JAN’08 it was further extended to PDL-GY-DMM section. At the same time all other routes of GTL Division were universalized for CC+6+2 loading.

1.86

4.0 Track Response Under Heavy Axle Load As heavy load moves over a rail, the track is compressed temporarily or deflects and then rejoins after the load has been removed. This vertical deflection is the best indicator of the track strength, life and quality. Excessive deflection results in differential movement and wear of track components. Research and guidelines of Railways through out the world reveals maximum deflection of 6mm for heavy track with firm sub-grade. Track which deflects more than 10mm will deteriorate quickly under axle loads. The track structure must simultaneously satisfy requirement for stiffness ( i.e. resistance to deflection and flexibility). Track quality is measured by track modules, which is a overall measure of support underneath rail. Track modules affected by ballast depth and quality and subgrade characteristics in which PSC sleepers and elastic fastenings are vital component to be maintained properly. 5.0 Experience of Running CC+8+2T Loads (22.82T) Axle Load Since May 2005 on Guntakal & Guntur Division i.e. BellaryGuntakal - Renigunta and Guntakal –Nandyal-Guntur Section. 5.1 Ballast and Screening: The support beneath the rails is critical factor for effective transfer of loads. The function of ballast is to transfer and distribute the load from sleeper to larger area of formation, to provide elasticity and resilience etc., to track. Increasing axle load will require increased depth of ballast cushion. The existing ballast cushion on these route is ranging from 200mm to 300mm. Efforts have been taken to complete the deep screening of track as per norms and ballast has been dumped into the track as required. The deep screening of GTL –NDL section had completed in 2007-08 and 2008-09 duly using 2 BCM’S and at present there is no overdue location on these routes. However, due to constant dropping of iron-ore particles which were loaded beyond the door level and due to improper closure of wagon doors, the ballast gets contaminated and is becoming solid bed like rock duly affecting drainage and running quality. This have been noticed especially at the approaches of major yards like Dhone, Gooty, Nandlure,and Renigunta. The problem is more acute in yards where loading is also being done. In Hagri which is iron ore loading point

1.87

the problem of poor drainage is noticed during rainy season. With the result of this, it is necessary to carryout shoulder ballast cleaning once in 2 years and deep screening once in 7 years. 5.2 Effects on Sleeper and Fittings: (i) Deficient packing at joggled fish plated location It is observed that after running of CC+8+2T load, the increased generation of USFD defects due to OBS/Cupped Welds has resulted in increased population of joggled fish plated welds. The present fittings in use at these joggled fish plated joints ( i.e. ERC mark.III in reverse condition/J clip) makes the sleeper vulnerable to more impact because of lesser toe load and propensity of development of gap between rail bottom and sleeper. In fact, this has further deteriorated the situation due to crushing of rubber pads on welded joint locations. (ii) Extra stress on sleeper fastenings near weld locations Due to inappropriate dimensional tolerances formed during initial welding stage and during process of maintenance (formation of cupped welds), the rubber pad gets crushed near the weld locations require frequent renewals. In fact in this railway a practice is made to keep 2 rubber pads at each such welded joints, the frequency of renewals at these locations approximately once in 2 years against the normal renewals. (iii) Effect due to iron ore droppings (a) Due to falling of iron ore particles on the flanges of rails, liners and ERCs, the rails and fittings are getting more corrosion compared to earlier resulting in greasing to ERCs and painting of rails to be done at increased frequency as that of corrosion prone area. (b) Due to continuous iron ore droppings in some of the stretches the ballast is becoming caked up and therefore affecting the drainage as well as quality of tamping. This in long run will result in more frequent shallow screening/ deep screening. Consequently, as a result of reduced resilience the additional stresses are likely on sleeper/fittings. The life of fittings is getting reduced in such location. (iv) Reduced life of rubber pads in general The experience of last 4 years has shown that other than the locations discussed vide i, ii & iii above, the available design of elastic fastenings are surviving without abnormal deterioration except rubber 1.88

pads. In fact, at several TFR locations ( other than corrosion prone area), it is noticed that lot of metal liners and ERCs are found to have further residual life whereas the condition of rubber pad are deteriorated. With the increase in loading patterns, this phenomena of crushing of rubber pads will be more and require their frequent renewal. To meet the variations in life cycle of the different fittings, it is required to adopt thick/improved rubber pads. Further, it is recommended that Through Pad Renewals on such heavier axle routes in between TFR cycle for maintaining the track parameters may be required. 5.3 Rails: Due to dropping of iron-ore particles on flanges of rails, the corrosion in 90UTS rails are increasing compared to earlier, necessitating painting of rails at increased frequency as that of corrosion prone area, though the stretch is in non-corrosive area. Formation of small spots on top of rail head: Due to iron ore lumps dropping on top of the rail and getting crushed under moving wheel, formation of small spots upto 2mm size noticed which are affecting the running qualities of track at a later stage. (i) Rail/Weld Failures: The comparative statement of Rail/Weld failure for section running CC+8+2 loads for last four years are as under: Rail/weld Failure in CC + 8 + 2 route BAY - GTL (DN), GTL-RU (UP/SL) & GTL - NDL (SL) & NDL - GNT (Sl) S Section No.

2006-07

2007-08

RAIL

WELD

RAIL

2008-09

WELD RAIL

2009-10 (upto Sep.09)

WELD RAIL

WELD

1.

BAY-GTL (DN)

2

31

1

11

-

5

-

1

2.

GTL-RU (UP/SL)

2

109

1

66

-

43

-

10

3.

GTL-NDL (SL)

1

19

1

36

3

67

1

43

4.

NDL-GNT (SL)

1

130

0

232

0

279

1

24

TOTAL

6

289

3

345

3

400

2

78

1.89

•

In BAY - GTL Section :There was weld failure in 2005-06 mainly on account of old 52 kg72 UTS rails which were already carried enough GMT. The same had come down considerably in 07-08 and further in 2008-09 on completion of 40 KM deep screening by BCM and renewal of old track with CTR(P) 60 Kg.

•

In GTL-RU section, there is a phased reduction in rail/weld failures in GTL- RU section mainly due to CTR/TRR of about 100 Kms with 60 kg rail and deep screening of about 60kms PSC track which was overdue. The track works like deep screening and TFR have lot of impact on reducing of weld failures which can be noticed in km.233 between MMPL and VNM where 7 failures have taken place in 06-07 and only one failure in 07-08 after deep screening and TFR.

•

In GTL-NDL & NDL-GNT section, the failures have increased in this section from 151 in 06-07, 269 in 07-08 to 349 in 08-09. Even in this current year also there are 69 failures till SEP’09. This section is having 52 kg rails of 1996-97 laid during gauge conversion. The population of skv welds are more since free rails were welded and made LWR.

•

This section opened with 4 GMT traffic in 1997 and now GMT is 32, therefore the more weld failures may be due to increase GMT also. However efforts are being made to reduce it by carrying out TFR and Destrssing during last 2 months, and there is considerable reduction in Weld failures in last one month in GTLNDL section.

(ii) Curves: Wear on outer rails in curves have increased, necessitating greasing of curves once in a week/twice a week depending upon the sharpness. The wear on sharper curves in GTLNDL section has considerably increased in the last 2 years of running of CC+8+2 in block section PNM- BMH of GTL-NDL Sction, which is having 1in 83 rising gradient with 12 curves having maximum degree up to 6, both lateral and vertical wear crossed the permissible limits. Here 14.5 KM of CTR got sanctioned on that account in 2007-08 and 2008-09. further 11 KM CTR(P) is proposed in PWP-2010-11 for MYLDHNE section on wear account. Similarly in GNT division on a 5.7 degree curve laid with 52kg 90 UTS rail on PSC 5 sleepers at Km.217/4-218/0 and at Km.171/8 – 172/2

1.90

with fairly uniform versine throughout its length, lateral wear on outer rail has reached 10mm and rails renewed on 3/2009 despite of provision of check rail and hand greasing of gauge face of the rail twice a week. The wear was 3mm during 6/2005 and the cumulative GMT carried by the rail is just 35% of estimated 525 GMT. The spurt of wear attributable to positive angle of attack of wheel flange aggravated by higher axle load in turn higher flange force. However efforts are being made to do regular curve greasing to reduce wear. Use of automatic greasing machine may help in reducing the manpower and provides uniform application of grease. Manual system of greasing besides being irregular and non uniform, involves safety risk to trackmen deployed for greasing on sharp curves due to visibility problems. There is need to evolve an efficient automatic greasing system. Available systems were tried but not found to be successful on long term basis. Providing wear resistant rails on curves or reducing the frequency of replacement of outer rails of curve to 150 GMT for 52 kg 90 UTS rails may also provide relief. (iii) Stalling : On steep rising gradients, more number of stalling cases is noticed, especially in rainy season where the axle load is getting increased due to water content. The comparative details of stalling are given below: Section

06-07

07-08

08-09

09-10 (Up to SEP’09)

BAY-GTL

0

1

0

0

GTL-RU

9

3

0

0

GTL-DHNE-NDL

3

4

0

0

Due to strict vigilance on over loading and right powering, stalling has been reduced. This can be fully avoided if additional tractive power is provided between HX-NRE stations especially during rainy season. (iv) Scabbing : Scabbing is mostly found on rising gradient, signal approaches and where trains speed is restricted due to caution order or other reasons. The comparative details of scabbing are given below:

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Section

06-07

07-08

08-09

09-10 (Up to SEP’09)

BAY-GTL

0

0

1

0

GTL-RU

3

1

1

0

GTL-DHNE-NDL

13

3

0

4

In GTL-RU section the scabbing mostly has occurred in rising grade and in combination with insufficient tractive power at signal approaches and at caution order spots where driver could not regulate the speed in time. As regards GTL-NDL section they have mostly occurred in Ghat section where continuous rising gradient exists in uncompensated sharp curves in between PNM-KEF and in raising gradient between GTL-MKR stations. This can also be avoided by having sufficient tractive power and good engineman ship. 5.4 Points and Crossings: This being the weakest link, requires frequent attention. Due to increased hammering at all free joints including crossing joints, the packing gets badly disturbed and alignment defects noticed, the fittings getting crushed/worn out/ dropped, also running quality getting deteriorated, necessitating packing with Unimat mandatory once in 6 months. Picking up slacks is being attended with off-track tampers as and when necessary. The GR pads of complete turnout are to be changed once in 4 years & under points and crossings once in a year with 10mm GR pads with horns. GFN liners are to be changed once in 3 yrs and especially outer liners on outer rails once in a year where side wear takes place and GFN liners are getting ejected. Due to heavier axle load, the trains while negotiating turn out induce more stresses on outer rail due to which outer side bearing plates, rail screws are getting wornout frequently specially at sleeper no 14,15,16 in 1 in 8.5 turnout plate screws are bending/shearing. At other locations life of plate screw is 5 years but at these 3 sleepers location because of more thrust due to heavy axle load trains from turnout side, life of plate screws are getting reduced to 2 years only. The design of these sleeper fitting requires some improvement in the form of provision of MCI insert and ERC at the end of slide chairs to provide more lateral stability as available at sleeper no 3,4,5.

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5.4.1 Wear of Turn Out Side Tongue Rails: • On fan shaped lay outs laid during 1995-96 during gauge conversion between GID-NDL, turn out side tongue rails were taken up for reconditioning on account of knife edge formation as 1st occasion during 09/2005 after a initial service of 10 years and majority of the tongue rails again reconditioned during 11/2006 within a short span of about 1 year for the same reason. • Reconditioned Tongue rails of 52kg 1 in 12 (Point No.28B, 25B, 24B/NDL) found to sustain only for a period of 7 or 8 months effectively i.e. for a life of 15 GMT as against anticipated life of 30 GMT. 5.4.2 Chipping of CMS Crossings Nose: Due to wheels jumping from wing rail to crossing and vice versa, the wear of crossing nose & wing rail have considerably increased with chipping/breakage of crossing noses, specially at locations where re-conditioning have been done number of times and where resilience is not available due to hard bed. Comparative statement showing crossing nose chipped off is given below: Section

06-07

07-08

08-09

09-10 (up to SEP,09)

BAY-GTL

10

4

4

2

GTL-RU

16

5

6

3

GTL-DHNE-NDL

27

10

10

5

As regards to GTL-NDL section the increase in crossing nose chipped off is mainly due to initial stage of introduction. Further heavy goods traffic started running only from Feb-06 onwards. All the points and crossings were laid in 1997 during gauge conversion and since mostly passenger traffic were running they were not reconditioned. The Goods trains coming from GNT side are not being weighed any where and loading particulars were not available for detailed analysis. Hence, over loading beyond CC+8+2 can not be ruled out as one of the possible reason. As this stretch is in ghat section with continuous gradient (condoned) slight over loading also causes heavy damage to track components specially points and crossings. All effort like deep screening, packing, ensuring fittings are being done now to ensure safety. 1.93

5.4.3 Wear of CMS Crossings: Newly laid 52kg CMS crossings is fast wearing to an extent of 45mm (6-2mm) on Nose and 3mm on wing rails within a period of 12 to 18 months. 5.4.3.1 Details of Laying and Wear of CMS Crossings is as under:

-

Similarly reconditioned CMS crossings attain wear of 6mm in 6 months i.e. on passage of 12 to 13 GMT.

-

On many occasions reconditioned CMS crossings are getting chipped off quickly and are not serving for more than 3 to 4 months after their insertion.

-

Increased frequency of reconditioning of switches and on passage of every 60 GMT is recommended.

-

GR pads get crushed at a faster rate as compared to other than heavier axle load routes. The problem is acute beneath crossing portion of turn outs.

-

To sustain the maintainability provision of Rubber Pads made out of Nylon Conveyer Belt 10mm thick is tried and the results are encouraging. 1.94

5.5 On loop lines Wherever the axle counters are provided the sleeper spacing will normally more than 60 cm and hence at such locations heavier axle load will cause more rail seat stresses and crushing of rubber pads etc. 5.6 On Glued joints At the glued joint location, the existing system of fittings i.e, GRSP/ J clip is causing lesser toe load and hence the more impact forces will be likely under heavier axle load. For better riding and durability of Glued Joints, it is necessary to adopt new glued joints clips quickly. 5.7 Bridges No abnormalities were noticed on bridge structures after introduction of CC+8+2 in physical inspection. It has to be watched further for coming to any conclusion on the effect of CC+8+2 on bridges. The track parameters on girder bridges are getting disturbed at frequent interval. Alignment on girder bridges and approaches are getting frequently disturbed. The experience of Bridge No.292 ( 33 x 12.2 + 1 x 9.15 spans ) with channel sleepers has shown that rubber pads and elastromatic pads are getting wornout/crushed resulting in creep. The fittings of channel sleepers also getting loosened frequently and need to be tightened more often. Similarily 40% of GR pads (T5199) of newly laid channel sleepers during 7/2007 on bridge No.427 Km.93/1-4 (GNT division) (11x18.29m span) are badly crushed/cut and worked out from its position at free joints as well as at mid rail within 5 month period, similar is the situation at Bridge No.408 which was laid during 11/2006. Prolonged continuation of this situation will lead to dent in rail foot and sleeper seat and ultimately rail fracture. Remedial Measures suggested: i)

Frequent tightening of fittings will have to be ensured to avoid play between bottom of Rail and GR pad.

ii)

Replacement of fittings with castle nut arrangement or GFN topi nut which prevents loosening of fittings.

iii)

Replacement of normal GR pads below channel sleeper with 25mm single piece elastromatic pads with holes drilled at sight to suite the rivet location. 1.95

iv)

Use of H. Beam sleepers in place of channel sleepers is recommended as the H.Beam sleepers are having less fittings, and also provided with Elastic Rail Clips and all the above problems can be totally eliminated.

v)

Replacement of smaller span upto 9.15 m with PSC.

6.0 Infrastructural Requirements to Sustain the Track Structure for Running of Higher Axle Loads: With above discussion it is understood that track inputs in the form of men and machinery have to be increased to sustain the maintenance of P.Way for running of heavier axle loads. At present the P.Way staff position in Group C and D category up sep-09 in Guntakal division shows that there are total 1394 vacancies available which includes 887 trackmen vacancies. Hence the manpower problem is going to become most critical area in time to come. Due to depletion of gang strength and also growing age of available trackmen, the existing pattern of maintenance may not be workable in future. So there is a requirement of realistic assessment and reorganization of existing maintenance units duly adopting more mechanized maintenance pratices. There are various railways in world which are even carrying more loads than CC+8+2, so what are their practices? 7.0 International Maintenance Practices :International Practice for High speed as well as Heavy-haul traffic routes is fully mechanized system for their track maintenance. Manual is only for the operation and maintenance of machines, co-ordination of machine working and attention to assets failures. The systems deploy a convoy of machines(ballasting, grading, tamping, and dynamic stabilizing) which after a round of maintenance render the track fit for full speed with retentivity of up to 4-5 years. Preventive as well as corrective rail grinding are an essential component of maintenance of tracks, to keep the rail profiles for optimum rail wheel interaction to prolong the life of rails and wheels. No railway system is adopting various patrolling as is being done by IR. 8.0 IRPWM Provision for Mechanized Maintenance:Present system of track maintenance: As laid down in Indian Railways P.Way Manual, three tiers system of track maintenance is being

1.96

adopted on I.R for sectors nominated for mechanized maintenance. This has been adopted mostly on concrete sleeper track as under (i) On track machines (OMU) (ii) Mobile Maintenance Units (MMU) (iii) Section Gangs (SG) Tier-1: On track machines unit(OMU) : The work of systematic mechanized maintenance of track will be done with help of heavy on track machines which include tie-tamping machines for plain track and turnouts, shoulder ballast cleaning machines, ballast cleaning machines, ballast regulating machines and dynamic track stabilizers. These machines shall be deployed to carry out the following jobs: (a) Systematic intermediate tamping of plain track as well as turnouts; (b) Shoulder ballast cleaning, ballast profiling/redistribution, track stabilization, periodical deep screening. (c) Renewal of PQRS & TRT machines (d) Welding by Mobile Flash Butt Welding machines. Tier-2: Mobile Maintenance Unit (MMU) : The work of picking up of slacks and other related works will be done with the help of MMU-I & MMU-II and their functions will be as follows: (a) MMU-1 (Rail bound vehicles based). One with each PWI in charge with a jurisdiction of 40-50 Kms double line or 90-10 Kms single line. 459 (i) Need based spot tamping: (ii) Casual renewal and repairs except planned renewals: In Situ rail welding. (iii) Overhauling of Level Xing’s. (iv) Replacement of glued joints; Rail Cutting/drilling and chamfering (v) Permanent repairs to fractures (vi) Creep or gap adjustments involving use of machines; Distressing of LWR/CWR. (vii) Loading/Unloading of materials & other misc.functions assigned. 1.97

(b) MMU-II (Road Vehicle Based). One with each sub-division. (i)

Reconditioning of turnouts

(ii)

Minor repairs to the equipments of MMU

List of equipments for MMUs: (i) Mobile Maintenance Unit-I (MMU-1) Spot tamping machines like track tampers and lifting jack, rail cutting and drilling equipment; Rail welding equipments; Distressing equipments such as Rail tensors etc; gas cutting equipments; material handling equipments; safety & protection equipments; inspection gadgets & communication equipments. (ii) Mobile Maintenance Unit-II (MMU-II) Points and Crossing reconditioning equipments such as Welding Generator; Arc welding equipment; Hand held rail grinder; Equipments for minor repairs such as spanner & gadgets. Tier-3: Section Gangs: It will perform the following functions: (i) Patrolling of track viz keyman’s daily patrol, Hot/cold weather patrolling; Monsoon patrolling; Watching vulnerable locations. (ii) Attention of emergencies viz temporary repairs of fractures. (iii) Need-based attention to bridges, turnouts, SEJs and approaches of level crossings. 9.0 Ground Realities :There is an annual programme of maintaining the concrete sleeper track where works have been nominated for pre-monsoon, monsoon and post monsoon period. Though theoretically there is three tier system of maintenance, but the ground realities are quire different. Some of the important issues are as given below: (i) Working of On-Track machine(OMU) Unit: No doubt heavy track machines are being used for tamping the track, but their output is limited because of non-availability of regular traffic blocks. Even with the introduction of corridor blocks, the availability remained only to the tune of 50%. Many of the pre-tamping & post-tamping works as

1.98

well as works like deep screening of ballast, and ballast profiling etc are also being done manually. (ii) Works of Mobile Maintenance Units (MMU): Other attention to track except for tamping like casual renewal and repairs etc is mostly being done by manual labour. Few small track machines are available with PWIs/AENs, but in the absence of proper repair/maintenance system as well as their transport arrangements use is very limited. At some places AMC is in place. There are hardly any Rail-cumRoad vehicles and the transport to site of small machines is quite difficult. (iii) The work load & pressure is very heavy on grass-root level of track maintenance staff particularly on PWIs (Section Engineer) leaving very little time for effectively maintaining the track. (iv) a)

Small Track Machines: Poor availability of latest small track machines; some of the machines are old & outdated. All machines run on their own engines making them heavy and difficult to handle. 461

b)

No proper arrangement and expertise for repairs/maintenance of these small track machines.

c)

There are no rail-cum-road vehicles and the transportation of small machines is an upheaval task.

(v) Gang men for maintenance jobs a)

Large number vacancies of gang men (About 15 to 25%).

b)

Most of gangmen are illiterate.

c)

Gagmen have to carry out strenuous job. The age group of gangmen is quite high about 50% gagmen in some of the beats in age group of 45-50 years. This is affecting the quality of work. (iv) Non functional work done by gangmen like security patrolling etc is very heavy (10 to 15%). 10.0 Suggestions to improve man management for track maintenance:It has been observed that maintenance inputs have gone up on heavy haul sections. To meet the increasing maintenance needs due to

1.99

running of high axle loads in present time and still higher Axle load in the near future, this is the time to act in improving the man management for track maintenance. 1 Better Training to P.Way Staff a) Faculty member of training institutions (Trainers) to be competent persons who are interested in this type of job. Proper incentives to be planned for them. Faculty member can be got trained by foreign leading training institutes. b) Intensive training for mechanization of track of modern track to be given to gangmen, P.Way Mistries & PWIs so that they can maintain track efficiently and economically. 2 Better quality & availability of small track machines a) Small track machines selected should be of latest type giving good output and least maintenance. b) In each DEN/Sr.DEN’s jurisdiction there should be repair workshop for repair and overhauling of these machines or at least at divisional level. The track machines sent for repairs should be repaired immediately & in intervening period, a service machine should be given which can replace the existing machine. 3

Rethinking about inspection schedule of track inspection With introduction of concrete sleeper & track machines the focus on items which can be attended such as excessive wear on crossing, loose bolts & fittings etc.The inspections schedule is also required to be modified to suit the modern track.

4

Better Social environments: The Hqr. Of AENs/PWIs should be revised based on the requirement of education medical attention to these officials & their families. Suitable changes can be made without affecting the duties/responsibility of P.Way staff.

5

The gangmen as well as sectional engineers which are safety categories staff should be given time bound grades, so that they have adequate incentives to carry out the work.

6

The cadre & recruitment of gangmen should be so planned that at least 25% Gangmen will be ITI qualified so that they can handle the requirement of modern track & track machines.

7

Outsourcing more number of gang activities:- In view of the large 1.100

gang men vacancies and absenteeism, already some activities like pre tamping and post tamping operations, cleaning of drains, cess repairs, attention to cuttings & trolley refuges are being outsourced. Some more activities like shallow screening, over hauling of Level Crossings, curve greasing, ERC greasing along with sealing of liner contact area etc can be outsourced to off load the pressure on gangs. 11.0 Steps to be taken to introduce 100% mechanization : 1) Provide computer to all the SSE/P.Ways’ and AENs duly linked and having facility of broadband connection ( Net working) 2)

Set up workshop for repairs and supply of small track machines,

3)

Provide Rail cum Road Vehicle with each PWI

4)

Provide a road vehicle with each AEN

5)

Withdraw all the tools and plants being used for manual

6)

Withdraw all present inspection registers and provide new inspection

7)

Replace existing tools and plants of key men and provided with only those tools required for mechanized maintenance like Clip Applicator etc

8)

Provide Automatic Track Parameters and Feature Recording Machine with each PWI

9)

Rail Grinding machine: Mixed traffic routes by and large need more frequent maintenance activities to restore geometric standards than structural adequacy related maintenance works. In heavy haul operations rail/wheel interaction plays a very important part in the performance of rails and wheels particularly on curves. Excessive rail wear, rail corrugation, rail surface defects, gauge corner fatigue defects are problems generally faced. Therefore, for heavy haul systems Rail Grinding as major maintenance activity combined with Rail lubrication to enhance the rail life and cost savings associated with it and to prevent premature rail failures affecting train running.

1.101

12.0 Conclusion From the experience gained so far in Guntakal & Guntur Division, it can be concluded that by CC+8+2 loading, early deterioration is noticed in some track components like CMS xing, rubber pads at some location, tongue rails, rails on ghat sections. In order to meet the requirement of Heavier Axle Loads, it is the need of hour to strive for introduction of 100% mechanized track maintenance, deployment of rail grinding machine, improving quality of welding, sustained efforts to eliminate AT welds and automatic rail lubricators. This is in addition of efforts to be made for reorganizing existing track maintenance strategies at field staff level. For this, there are various aspects which is to be ensured like better training to P.Way staff, better quality and availability of small track machine, better social environment for SSE/P.Ways, JE/P.Ways etc and offer career planning of P.Way staff.

***

1.102

Overcoming the Challenges of Weak Formation for Heavier Axle Load - Formation Rehabilitation By Mechanised Blanketing Munna Kumar* Manohar Reddy** L. Narender Reddy***

SYNOPSIS : Rehabilitation of bad formation has been a challenge to Railway Engineers for quite some time and so far the search for a credible method which can be implemented without much traffic disruption and which gives reasonable rate of progress is still on. There are solutions available. But a feasible solution which takes into account the traffic requirement, the availability of material and ease of implementation ensuring reasonable progress simultaneously has not been in sight so far. Hyderabad Division has successfully tried a method for formation rehabilitation in which full width blanketing is done by track dismantling method which takes into account the traffic requirement as well as reasonable progress of work duly considering the technical requirements for formation rehabilitation.

1.0 Extent of Formation Problem on Indian Railways On Indian Railways 700 km of track is under permanent speed restriction and approximately 2000 km of track requires imposition of temporary speed restriction because of weak formation. Due to weak formation track components like rails, sleepers and fittings are put to additional stress which results in their premature failure. For running the traffic safely, weak formation requires much more attention than the normal track; hence the maintenance resources are unnecessarily put to severe strain. This leads to extra cost of maintenance and additional lifecycle cost of replacement. Needless

Sr. DEN/Co-ord/HYB/SCR DEN/Lines/HYB/SCR ADEN/NZB/SCR

1.103

to say that temporary and permanent speed restriction put severe squeeze on system throughput which results in loss of potential revenue as well as increased operating cost. To sum up weak formation is too costly for the Railways to be ignored and left unattended. Further running of higher axle load is going to aggravate the existing problem and may result in surfacing of problems at some of those locations where the problem has not been observed so far. Hence a strategy has to be developed to get rid of weak formation not only for present operational requirement and axle load but also keeping in view future scenarios. 2.0 Importance of Formation: Track consists of sub-structure and super structure. Formation as we all know is part of sub-structure and in any structure no component/link can be allowed to be kept weak as it nullifies all the gains which we are supposed to make out of other stronger components. Hence, the formation has to be equally strong as rails, sleepers, fittings etc. In fact in permanent way nothing is permanent except formation. Rails, sleepers, fittings and ballast get renewed and also get upgraded from time to time, but formation is supposed to serve for the whole life of track and it is not supposed to be replaced in normal course (as a life cycle), until and unless there is a problem. Whenever such problems are identified then also formation is to be treated/rehabilitated but is not to be replaced completely. Hence, it becomes still more important that formation is strong enough to take care of all future requirements of loading, traffic density etc. Major hitch in rehabilitation of formation is to get the work done with minimum traffic disruption and to achieve desired compaction in the short span of whatever traffic block is given, duly ensuring that reasonable progress is achieved. 3.0 Formation Failures – Symptoms and Causes: The failure of formation takes place in different forms and common symptoms and causes are listed below: 3.1 Heaving of Base Beyond Toe of Bank. This happens because of sub-base failure. Whenever natural ground on which formation has been laid is too weak to support the load coming over it, the soil of the natural ground fails under the load and results in heaving up of ground beyond toe of the bank. 1.104

3.2 Slope Failure or Excessive Deformation of Banks Slopes This failure takes place because of poor subgrade or fill material used while making the formation. This failure may also take place because of inadequate slope of the bank.

3.3 Heaving of Cess, Ballast Benetration, Mud Pumping, Crack in the Formation. These are the most common symptoms encountered at the site having formation problem. The reason for all the above causes is that the top layer of formation is not strong enough to take care of the concentrated load coming through ballast. 4.0 Why Top Layer to be Different? The top layer of formation directly supports the ballast. These ballasts are hard angular particles which do not transfer the load uniformly on the formation. The sharp edges of ballast result in stress concentration on formation. Further, the angular shape of the ballast results in the vertical loads getting modified as partly vertical and partly horizontal load resulting in tensile stress over the top surface of the formation. If top layer of formation is not well compacted and strong enough to take this horizontal component of load, the ballast

1.105

penetrates into the formation resulting in disturbance of the geometry of the track. Other layers of formation except top layer are subjected to uniform vertical stress all along the surface and hence there is no horizontal component of load transfer at these layers. This is the reason why the top layer of the formation has to be much more stronger than the bottom layer of the formation. Keeping this in mind RDSO has issued guidelines from time to time regarding the quality requirement for the top layer as well as for the other layers of the formation.

Puncture of ballast - Loading pattern on top of formation

Loading pattern at other than top layer

5.0 Guidelines For Blanketing On Indian Railways The first guidelines for earth work were issued in August 1978 by RDSO. As per this guideline blanketing has to be done for a thickness of 30 cms while making the formation for normal soils. In case the soil is weak the thickness of this balanket layer should be increased to 60 cms. In 1987 RDSO issued new guidelines. As per this guideline the blanketing layer in all cases has to be 1 meter. This was decided taking into account future growth of traffic, increase in axle load etc. These guidelines were further modified in 1991 and it was stated that the thickness of blanketing layer will be decided by the Chief Engineer concerned subject to a minimum of 30 cms. RDSO report in June ’93, suggested that blanketing of 1 meter thickness must be provided in all cases of new line and doublings. In 2003 a comprehensive guideline was issued by RDSO which for the first time stated that different thickness of blanketing should be done ie., 45 cms, 60 cms and 100 cms, depending on the quality of subgrade of the soil. It was further decided that this blanketing layer is sufficient for 22.5 tonnes of axle load. 1.106

6.0 Blanketing Practices World Over The blanketing practices world over are listed below: 6.1 UIC – It recommends blanketing thickness of 15 to 75 cms depending on subgrade of the soil. It also recommends use of geotextiles depending on subgrade soil. The quality of subgrade and blanketing layer is determined by its CBR value instead of the sieve analyses. 6.2 Japanese Railways – It recommends 5 cms of bituminous concrete as the top layer of the formation below which 25 to 75 cms mechanically stabilized crushed stone are provided. Below this layer atleast 3 metres of good soil is provided depending on the height of the bank. 6.3 American Railways – They recommend 30 cms of sub ballast over good quality of soil which is used in formation. The plasticity of the soil used in formation must be more than 12. 6.4 Australian Railways – They recommend 15 cms of blanketing over 50 cms of subgrade of CBR above 8 or 100 cms of sub grade of CBR between 3 and 8. 7.0 Evaluation of Various Methods of Formation Rehabilitation on Indian Railways – RDSO report No.GE 39 of 2003 RDSO has published a report duly evaluating various methods adopted for formation rehabilitation on Indian Railways and a study has been published in the form of the above report. The efficacy of various methods as brought out in the report is reproduced below: 7.1 Lime Slurry Pressure Induction (LSPI) – This method was used for bearing capacity failure and for the formation where excessive swelling/shrinkage was reported. LSPI aimed to change the chemical composition of the soil so that swelling and shrinkage of the soil is kept within limit. It was found that it does not change the soil composition. Further lime is leached out due to rain. This method is not being recommended. This method was used in patches in Panskura-Haldia section of SER. 7.2 Ballast Piling – In this method vertical hole is drilled and ballast is filled up which acts as support as well as drain for the water to seep out. It was found that in the hole, lot of water gets collected which had no passage resulting in further weakening of formation.

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7.3 Cement Grouting – This method is similar to LSPI. It was found that only localized lumps were formed without any resultant change in soil characteristics. This method was used in BapatlaSundur section of SCRly in 1977. No permanent improvement in formation has been observed at this location. 7.4 Cross Drain – In this method coarse material are filled by providing cross drains. However, these coarse material get washed away. This causes more damage to the bank than being useful. This method was used in Barahia – Mankatha section of East Central Railway in 1992. 7.5 Polyethene or Similar Impervious Sheet – The sheet is provided in the formation to arrest the water from further entering into the formation. However, it leads to increase in moisture content below the sheet which results in reduction of soil strength. This method was used in Rajkharsawan – Sini section of SER. 7.6 Geo Textiles – Geo textiles have been used below ballast at many places. However, this alone does not help. It has to be used alongwith blanketing. It was done in Sandila-Lucknow section of NR. 7.7 Partial Blanketing – In this method blanketing material is used to increase the cess width as well as the slopes which results in increase of counter weight on the formation from sides. This method works only when the ballast penetration has stopped. 7.8 Widening of Bank – This also has the effect of increasing the counter weight on slope of the bank which results in extra confinement of load bearing strata of the formation. This also works only when ballast penetration has stopped. 7.9 Full Width Blanketing – This method involves replacement/ addition of blanket material on the top layer of the formation. This is the only method universally accepted by world Railways world over. Unstable formations have already been eliminated by this method. Some of the Railways use this method in combination with geo textiles. Apart from this, S C railway has tried the formation rehabilitation by sand treatment method in which sand is fed into the track in stages and track is vibrated with DGS. This leads to penetration of sand into the formation filling the cracks resulting in stabilization of formation. 1.108

The short term results are satisfactory and very encouraging; However long term improvements needs to be still evaluated. 8.0 Experience Over Indian Railways With Blanketing – RDSO Report No.GESR.0017/2008 RDSO has published the above report which lists out ballast penetration into the formation in the section where blanketing has been done and those sections where blanketing has not been done. The details of ballast penetration are given below: Ballast penetration details without blanket S.No Section

GMT Penetration (cm)

01

Colonelganj-Jarwal Road

73

0 to 100

02

Allahabad - Kanpur

300

0 to 26

03

Bareilly – Moradabad

180

2 to 35

04

Bareilly – Moradabad

230

5 to 70

05

Bareilly – Moradabad

216

1 to 15

06

Bareilly – Moradabad

230

0 to 20

07

Bareilly - Moradabad

230

2 to 26

08

Ujjain-Bhopal

64

38 to 50

09

Moradabad- Ghaziabad

25

2 to 17

10

Secunderabad-wadi

130

0 to 12

11

Secunderabad-wadi

130

5 to 13

12

Itarsi-Dularia

71

79 to 125

Ballast penetration detail with blanket. S.No Section

Thickness

GMT Penetration

(cm)

(cm)

01

Jarwal Road - Burthwal

60

24

Nil

02

Bilaspur-Dagori

100

81

Nil

1.109

03

Cuttack - Paradeep

100

156

Nil

04

Cuttak - Paradeep

100

35

Nil

05

Korba-Gevra Road

80 to 100

61

Nil

06

Sarona - Bhilai

80 to 100

113

Nil

07

Gurap - Sakthigarh

55 to 65

10

Nil

08

Dharamvaram - Penikonda 95 to 105

19

Nil

09

Shoranoor - Mangalore

90 to 95

31

3 to 22

10

Rajathgarh - Talchar

24 to 30

393

1 to 6

The report also discusses about the sections where blanketing has not resulted in much reduction of ballast penetration. Mostly the reasons were poor quality of blanketing material being used in these sections. 9.0 Various Methods Tried in the Past for Full Blanketing of Formation Under Traffic 9.1 Alluminium Alloy Girder Method -In this method a light weight girder is used as a relieving girder below which formation is dug and blanketing material is filled up. The compaction is done with portable compactors of low capacity. The blanketing by this method was done in Wadi – Nalwar section of SCR. It was also done in Sholapur and Delhi division. In SCR there were initial problems because of inadequate compaction. However, track got consolidated under traffic and the problem due to bad formation was eliminated. The only problem with this method is that it is very slow (progress 15 mts/ day) and desired compaction of blanketing material is difficult to achieve immediately. 9.2 Manually Operated Portals - This method was developed by SER. In this method manually operated portal crane similar to PQRS cranes are used with auxiliary track to dismantle existing track and blanketing is done. After blanketing track is put back with the help of the same crane. Because of auxiliary track the problem of compaction remains there in this method also.

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9.3 CC Crib/Rail Cluster Method - In this method rail cluster supported on CC crib is used to support the track. Below the rail cluster formation is dug up and blanketing material is filled up. As the work progresses rail cluster and CC cribs are shifted forward. In this method blanketing of 50 cms thickness is possible. The requirement of block is only for shifting of rail cluster and crib which is about 45 minutes. This work was done in Kamptee yard near NGP of SER. The compaction in this method is also achieved under passage of traffic hence caution order of very long duration is required to be imposed.

9.4 Lifting of Track with Deep Screening - In this method track is lifted on banketing material by first removing the ballast and compaction is allowed under traffic. Track is further lifted on ballast. In this method also long duration of caution order is required for compaction. However, little or no traffic block is required for carrying out the work. This method is labour intensive. This method was used in Sirpur town-Vempally, Manikgarh-Garchandoor sections of SCR, Chennai-Arakonam section of SR and Cuttak – Paradeep section of East Coast Railway. 9.5 Blanketing by Track Dismantling – Although blanketing by track dismantling method has been tried earlier, but it was found that there is lot of scope for improvement in working by mechanising the dismantling of track as well as removing of ballast, spreading of blanketing material and rolling. 10.0 Method Developed by Hyderabad Division - Mechanised Blanketing by Track Dismantling The method has been evolved over time and at present Hyderabad Division has developed a scheme by which entire blanketing operation including track work is mostly mechanized resulting in good progress of work. 1.111

Removing of Rail Panel from Track

Conversion into free rail

Removing of Ballast

Spreading of Blanketing material

Rolling by Vibratory Roller

Ballast Spreding

10.1 Description of the Method : First the existing rails (LWR converted to 10 Rail Panel) are removed and replaced with single rail panel of service rails. Ballast is also removed to some extent before the block. Blanketing material is stacked on the cess from the toe of the bank where it had been stacked earlier. During block single rail panels are removed from track by crawler mounted heavy duty cranes which are operated along the bank. 2 nos. of such cranes were utilized for the reason of expediting the progress as well as to take care of any eventuality of

1.112

breakdown of one of the cranes. This is followed by removal of ballast which is done with the help of excavators. The track ballast is removed and kept on either side of cess. The naked top of the formation is rolled lightly and the blanket material is spread over it with the help of excavators. These spread material is compacted using heavy duty vibratory rollers giving approximately 15 pass for each layer. The ballast is spread over this compacted layer with the help of excavating machines. This ballast layer is also rolled and dismantled track panels are put back with the help of crawler mounted crane and track linking is completed. Further lifting of track on ballast is done manually and after doing TRR and track consolidation, caution orders are relaxed. The work is being done duly taking block of 4 hours in which a progress of 200 meters is achieved. So far 20 kms of length has been completed by this method in SC-MUE section of Hyderabad division. The blanket layer thickness of 30 cms has been provided in this stretch. Further, Division is making efforts to increase this thickness of banket layer to about 60 cms by duly cutting into the formation if required.

Rolling of Ballast

Keeping back Track Panels

Connecting the Track

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Passing the Train

10.2 Resources Deployed in this Method: 1. 2 crawler mounted cranes of 40 ton capacity 2. 3 Ex-200 excavator machines. 3. 1 Vibro Max roller 4. 80 labourers for doing TRR, lifting of track and working with machines 5. 1 Water tanker for spreading water during rolling 6. Blanket material required is about 4000 cum/km 7. Ballast required is about 500 cum /km 8. The total cost per km is about 25 lakhs 10.3 Advantages of this Method: 1. Any blanketing thickness is possible by cutting the formation to the desired depth. 2. Compaction is done with heavy duty vibratory rollers. Hence long duration caution order is avoided. 3. The speed of work is reasonably good and it can be increased further by deploying multiple set of machines in the same block. 4. The method is suitable for providing geo grid as well as for different kinds of blanketing material. 11.0 Comparative Study of Track Parameter before and after Blanketing • • •

Block Section – BLSA – KEK KM - 407 to 408 Month - Mar’09

11.1 Tamping Done before Rehabilitation Year 2007 – 21.01.07 & 06.08.07 Year 2008 – Caution order imposed between April 2008 to July 2008 for want of Tamping. - Tamped on 29.07.08 1.114

11.2 Manual Attention: • •

Year 2007 – 22.01.07, 19.03.07, 11.04.07, 05.05.07, 05.06.07 Year 2008- 14.01.08, 06.05.08, 17.06.08, 10.09.08, 17.10.08. Comparison of TGI values (Km 407 to 408)

Date of TRC run

TGI Value

25.08.2007

52

15.05.2008

39

25.02.2009

65

After Rehabilitation

-

Remarks

TRC run not done after Rehabilitation work

OMS Peak Details (Km 407 – 408) Month

KM.

0.20 to

0.25 to 0.24 g

0.30g TO 0.29 g

TOTAL No. ABOVE

V

V

V

V

of Peaks L

L

L

Apr’08

NIL (caution order of 50 kmph)

May’08

NIL (caution order of 50 kmph)

June’08

407

4

July’08

0

0

0

0

6

0

NIL (caution order of 50 kmph)

Aug’08 Sep’08

2

NIL (CSM tamped) 407

1

0

0

0

Oct’08

Nil

Nov’08

Nil

Dec’08

Nil

0

0

1

0

Jan-09

408

1

0

0

0

0

0

1

0

Feb-09

408

1

0

0

0

0

0

1

0

Apr. to Aug’09

Nil

1.115

12.0 Drawbacks of the work done so far: 1. The blanketing thickness being done so far is 30 cms only. There can be a doubt about the effectiveness of thickness of blanketing layer of 30 cms. However, as discussed earlier the blanketing thickness can be increased by duly cutting the formation to suitable depth. Further as per the revised guidelines of RDSO even 30 cms of blanketing will be suitable enough for present day loading. 2. There can be a problem in electrified sections in operating cranes for removal of panels etc. However, by selecting suitable crane or by using Ameca T-28 crane the problem can be solved. Further in RE area cutting into formation will be a must as the level of track cannot be raised for blanketing. 13.0 RDSO Guidelines of 2008 for Blanketing: RDSO has issued guidelines for blanketing of formation duly taking the requirement of different axle loads and also taking into account the subgrade material of the formation. Further, it has issued guidelines for soil classification based on CBR value instead of particle size distribution. These new guidelines are in line with UIC guidelines for blanketing and are much more scientific. The guidelines also say that the blanketing thickness prescribed earlier were on very high side, blanket thickness recommended now is as low as 150 mm which will be very easy to be provided in the field in running traffic condition. The salient features of the guidelines are as under:

BLANKET LAYER

OPTIONAL GEOTEXTILE

PREPARED SUB-GRADE SUB-GRADE

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Type of Formation Layer

Minimum Required CBR Value

Blanket / Sub-ballast Layer

50 %

Prapared Sub-grade/ Top Layer of Formation

8%

Sub-grade/Embankment Fill

5%

Explanatory Notes : 1. Categories of soil Quality : Sl.

Soil Quality

Description w.r.t. FineParticles (size less than 75 micron)

IS Classifiacation to Referred Soil Quality (Suggestive)

1.

SQ 1

Soils containing fines > 50 %

CL, ML, CL,ML,CI,MI

2.

SQ2 **

Soils containing fines from 12 % to 50 %

GM, GC, SM, SC

3.

SQ3***

Soils containing fines < 12 %

GW, GP, SW, GWGM, GW-GC, SWSM, GP-Gm, GP-GC, SP-SM, Sp-SC, etc.

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Proposed Two Layers System Of Blanketing On Track Formation For Adoption On Indian Railways (Reference Calculations based on UIC practices in terms of UIC Code 719R-1994) SL Soil Quality Category in Sub grade need in embankment

Top Layer of Formation (prepared Subgrade)

Recommended Thickness lareal of Blanket for lute leads

Quality Thick-

20 T 22.9T 25 T (CC+ 8+2)

Remarks

30T

32.5 T (For D.F.C.)

1

SQI

SQ1

-

300

350

400

600

750

Geo-synthetiks to be used

2

SQ1

SQ2

500

150

200

250

450

600

Geo-synthetiks to be used

3

SQ1

S03

5OO

150

150

200

350

500

Goo-synthetics is optional

4

SQ2

SQ2

-

150

200

250

450

600

Geo-synthetiks to be used

5

SQ2

SQ3

350

150

150

200

350

500

Geo-synthetics is optional

SQ3

SQ3

-

150

150

200

350

500

Goo-synthetics is optional

6

Particle Size Distribution : Material shall be well graded with typical particle size distribution as follows :

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IS Sieve

Percentage Passing Nominal Size (20mm)

53 mm

100

37.5 mm

100

26.5 mm

100

19.0 mm

95-100

9.5 mm

-

4.75 mm

-

2.36 mm

30-80

0.075 mm

6-10

Atterberg Limits : •

Liquid Limit

:

Maximum 30 (35 for and areas)

•

Plastic Limit

:

Maximum 20

•

Plasticity Index

:

2 -10 (2 -IS for and areas)

•

Linear Shrinkage

:

Maximum 3%

Maximum Dry Density : Minimum 2.0 t/cum Soaked CBR : Minimum 50%, determined on material compacted to 95% (min.) of Maximum Dry Density General Soil Type

USC Soil Type GW GP GM GC Coarse-grained soils SW SP SM SC ML CL LL < 50 % OL Fine grained soils MH CH LL > 50 % OH 1.119

CBR Range 40 - 80 30 - 60 20 - 60 20 - 40 20 - 40 10 - 40 10 - 40 5 - 20 15 or Less 15 or Less 5 or Less 10 or Less 15 or Less 5 or Less

14.0 Conclusion: •

The problem of formation failure is going to gain much importance in view of increased axle load, demand for increasing line capacity by reducing PSR and TSR, and need to bring economy in operation as well as to bring down asset life cycle cost.

•

Formation even made of soil with sufficient bearing capacity may fail in punching and will need blanket cover.

•

Blanketing is the only reliable method for formation rehabilitation having symptoms of ballast penetration.

•

Depending on the traffic pattern selection of blanketing method can be done.

•

It is possible to lay any thickness of blanketing layer.

•

With reduced blanket thickness requirement and with use of geo grid reasonable progress can be achieved even in busy routes.

•

Use of Ameca crane can be tried in RE area.

•

Multiple working units is going to increase the progress in the same block.

•

Apart from strengthening the top layer, widening of bank/provision of sub-bank will address the problem of sub grade weakness.

15.0 Recommendations: 1. The present specification for blanketing material is stricter than the previous specification. As per present specification blanketing material should have CBR of 50 and above with MDD of 2.0 ton per cum. It is very difficult to get a naturally occurring material of this specification. In fact only well graded gravel will meet the above specification. The guidelines issued by RDSO do not specify the method by which a blanketing material of above specification can be obtained. It will be useful to the field staff if RDSO comes with the blending proportions of different materials like quarry dust and gravel of different sizes up to 20 mm which are to be mixed to achieve the above specification. 2. In field blanketing of new formation during construction of new lines or doubling is much easier than blanketing of formation of running

1.120

track. The RDSO guidelines has not specified if any relaxation can be given wherever rehabilitation of formation is to be done for running track due to difficult circumstances at the field level in carrying out the work. These relaxations can be in the form of thickness of blanketing material etc. It is recommended that based on the studies, the minimum thickness of blanketing for rehabilitation of track may be advised separately. 3. It will be also useful if guidelines are issued as done for bridges regarding rehabilitation of formation whereby the horizon axle load is prescribed based on the future traffic for different routes for rehabilitation of formation. 4. The rehabilitation/renewal of formation should be treated as track renewal and wherever rehabilitation is to be done it should be considered as overdue track renewal arrear. These track renewal arrear should be wiped out in a time bound programme as it was done for TRR, TSR etc. duly making rout wise plan and fixing targets. 5. For running heavier axle load a strategy for preventive rehabilitation should be made even for those stretches where there is no PSR/ TSR at present, based on present track parameters, frequency of track attention, ballast penetration, type of sub grade soil etc in a particular stretch. Based on these parameters works of formation rehabilitation should be taken up for catering to future axle load.

***

1.121

Impact & Experience of Heavier Axle Load on Indian Railways

M. R.Srinivasan *

Synopsis : Indian railways run about 11000 trains every day, carrying 5725 million passengers & 833 million tonnes of goods traffic in a year. Every year the traffic carried out is increasing due to industrial growth and increase in population.

1.0 Introduction To meet out the demand, of increasing traffic the railway has to improve their operation efficiency and performance with new technology.Operation efficiency means improving performance with the available resources. The operation efficiency may be improved by increasing the carrying capacity of coaches / wagons and reducing the idle time of the coach / wagons with optimum utilisation of line capacity of the track. The figures shows the freight load carried by IR’s Year

Freight Load Carried in Million Tonne

2004-05 2005-06 2006-07 2007 -08 2008-09 2009-10( Proposed)

626 682 725 778 833 882 ( proposed)

The freight load proposed to carry during 2009-10 is 40% higher than that of during 2004-05. How we could achieve this target, theoretically speaking it is possible only by adding 40 % additional line & wagons. *SE/PW/USFD/MDU/SR

1.122

But due to the constraint in resources railways have to meet out the target by improving their technology instead of simply multiplying its wagons. Figure shows the operation performance of IR’s with other Railways Railways

Japanese Railway Indian Railways French National Railways German Federal Railways Italian State Railways

Wagon Km per wagon per day

NTKms NTKms per wagon per tonne per day per wagon

Net tonnage carried per wagon

258.4 211 73.4 70.6 53.4

3481 2723 1600 1115 962

13.47 12.9 21.79 15.79 18.01

36713 42237 11681 9139 8006

The carrying capacity of IR’s is less, eventhough its wagon utilisation is high when compared to other railways. To improve this, we have to increase the carrying capacity of wagons i.e. by increasing the axle load of the wagons. 2.0 Axle Load & Loading Standard of IR : Axle load is the maximum weight of a train per pair of wheels allowable for a given section of track. The maximum axle load is related to the strength of the track, which is determined by weight of rails, density of sleepers and fixtures, train speed , amount of ballast and strength of bridges. IR’s Bridge Loading Standard Bridge Loading Standard

Wagon Load

Bridge Loading

Axle load

Wagon carrying

Axle load

standard BGML

22.9 t

capacity BOXN CC+6+2

22.32 t

RBG

22.5 t

BOXN CC+8+2

22.82 t

MBG

25 t

BOXN CC+10+2

23.32 t

1.123

3.0 Impact Due to Heavy Axle Load : Due to heavy Axle load, the track stresses and design of various track components will be affected such as , 1. Increase in track stress 2. Design of rail section 3. Design of sleeper 4. Change in LWR cold and hot temp 5. Gradient & hauling capacity of loco 6. Design of bridges. 7. Improvements in fastenings 8. Man power req due to fast deteriation of track 9. Increase in fatique failure of track 10.Formation problems 4.0 Increase in Track Stresses: Calculation of Track stress, consists of working out of Maximum Bending moment at any point in the track. The Bending moment can be calculated by considering the track as inverted continuous beam and support reaction as wheel loads at a span of wheel distances, considering the sleeper support as multiple point loads acting at a distance equal to sleeper spacing. Then the section of Rail req can be computed using M=f * z But the above calculation getting complicated since rail is subjected to dynamic loads and due to uncertanities in various parameters like subsoil modulus, climate condition, curvature effect etc , the wheel load is amplified with various factor called dynamic factor, Speed factor, lateral thrust, irregularities of track, inertia load etc. The net load obtained after such modifications is called virtual wheel loads. but this virtual wheel load is reduced again what is termed as relief of stresses. Based on the American professor A.N.Talbot the relief stress is due to continuity of the track below the wheels. The elastic deformation of the adjoining spans is to a certain extent counter balanced due to continuity of the span. Therefore let’s assume that the multipling factor of wheel load and reduction of wheel load due to continuity of track may balance each other and take the wheel load as it is for calculation purpose.

1.124

The BM can be computed using the formula ( Prof A.N.Talbot) M max = 0.319 W x x = 42.33 4 √I/μ Where M= Max BM in tonne -cm x = Distance from the load to the point of contraflexture in cm I= Moment of Inertia in cm4 W=lsolated wheel load in tonnes

μ = Subgrade modulus in kg/cm2 Based on the formula the 8M and Longitudinal stress found for various combination is tabulated below. μ for various type of soil

Moment

f(Long Temp Section stresses stress for Total modulus due to 30 deg stress N/mm 2 bending) N/mm 2 N/mm 2

30 (Soft 3055 clay) (for 60 kg)

536.19

335.50 ( for 60 159.81 kQ)

90

249.8

12.5

500 (for 3055 dense (for sand) 60 kg)

265.37

335.50 ( for 60 79.09 kg)

90

169.1

12.5

450000 ( for rock)

48.43

335.50 ( for 60 14.432 kg)

90

104.4

Load type

Wheel load in tonnes

MBG

12.5

MBG

MBG

I

3055 (for 60 kg)

permissible longitudinal stress=

220 to 250 N/mm2

For the worst combination of loading and formation, the total stress is less than the permissible long stress. If axle load increased more than MBG standard then we have to go for higher UTS rails.

1.125

5.0 Design of Rail Section Based on the experiment, the Axle load carrying capacity of rails is 512.06 times of weight of the rail section. The existing 60 kg rail section having the carrying capacity of 60.34*512.06 = 30.89 t which is more than the MBG load. 60 kg rail is having the capacity to carry axle load upto 30 tonne. 6.0 Design of Sleeper 6.1 Factor Influencing The Design of Sleeper: 1. Static and dynamic loads imposed on the rail seats depends upon the type of track ( straight or curved) , its construction and standard of maintenance, the axle load and axle spacing, the running characteristics, speed and standard of maintenance of vehicle. 2. The ballast reaction of the sleeper is based on the shape of sleeper, its flexibility and spacing, the unit weight of the rail, the standard of maintenance of track and characteristics of ballast. The static wheel load of 11 tonne ( Axle load 22 tonne) at the rail head was found to cause a vertical sleeper reaction of 6 tonne on straight track. To allow for dynamic effect, the design load adopted is 15 tonne at each rail seat based on static load 6 t which is multiplied by a dynamic factor of 150% under different condition of loading and spacing of sleeper. The figure shows the BMD & loading pattern PSC sleeper of T2495 under different condition The T2495 sleeper having the capacity to carry BM at rail seat of 12.77 KNm and 13.37 KNm at the centre of sleeper. Study from German Railways says that the percentage of failure due to cracking of sleeper is in the order of 1 % when sleeper having BM capacity of more than 10 KNm at centre, . Hence IR design of T2495 having BM capacity more than 10 KNm at centre to safeguard against the adverse effect of formation due to black cotton soil .

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1.127

Even by increasing the axle load, the capacity of the sleeper can be improved by reducing the spacing of the sleeper. Rail section Kg/m

Axle load tonne

Sleeper density

57

28

M+6

50

25

M+5

45

22.5

M+4

7.0 Change in the Criteria of LWR Cold and Hot Weather Patrolling The additional tensile stress in the track when temperature reduces to 30 degree is 90 N/mm2 . The limit of td-30 has been fixed by considering the total stress due to temp as well as stress due to load. If Axle load increases, the track stresses due to load will increase and it will ultimately lead to revising the permissible value of td-30 As far as Hot weather is concerned the increase in axle load may not affect the limit of td+20 . But some extra precaution to be taken on curve. Normally for goods trains, this will be subjected to only cant excess in the curve due to lower speed. Hence the extra axle load may not affect the Hot weather patrolling criteria when compared to cold weather patrolling. The destressing temperature ( stress free temp) also affected. In foreign railways majority of track are track circuited and there the destressing temp are kept in higher side since rail failure can be easily detectable due to track circuiting, but buckling may happen with out any prewarning . Hence it is always safe to keep stress free temp in higher side of the limit in the track circuited track. 8.0 Gradient & Hauling Capacity of Loco Due to increase in axle load, the loaded weight of the train formation will increase and the loco should have sufficient hauling capacity under the worst combination of gradient and climate condition. The worst combination is when the loco met with the gradient of 1 in 100 and greasy/oily rail condition. The figure shows the hauling capacity and load of the formation under different combination of the loads,

1.128

Calculation of Formation loadinQ (in tonnes) Wagon

Nos of Tare wagons

CC

C C+

Gross weight

Loaded weight with one BV

BOXN C C+6

59

22.5

58.81

64.81

87.31

5165

BOXN C C+8

59

22.5

58.81

66.81

89.31

5283

BOXN CC+10

59

22.5

58.81

68.81

91.31

5401

8.1 Loco Starting Hauling Capacity ( in tonnes) Loco class

WAG5

WAG7

WAG9

Gradient

Dry rail condition

Level 1/500 1/200 1/150 1/100 Level 1/500 1/200 1/150 1/100 Level 1/500 1/200 1/150 1/100

6000 5775 3810 3198 2407 10815 7169 4738 3997 3002 11550 7656 5060 4250 3205

Wet rail condition condition 4694 4518 3125 2660 2041 7317 4850 3360 2860 2200 7814 5180 3588 3041 2349

Oily / Greasy rail 3600 3465 2286 1919 1444 6489 4301 2843 2398 1801 6930 4594 3036 2550 1923

Hence special precaution to be taken while stopping the formation at the section having heavy gradient specially in rainy season and suitable

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additional banker loco or multiple loco may be used to improve the hauling capacity. Before increasing the axle load the section having maximum gradient may be checked with hauling capacity, if possible regrading of track may be proposed to improve the hauling capacity and to avoid the damage of rails due to wheel slipping. 9.0 Design of Bridges Before introducing the heavier axle load the loading standard of the Bridge designed is to be checked and in addition to that if the older bridge is designed with lesser axle load than the proposed one, the strength of the bridge may be improved by using suitable methods based on the type of the bridge. 10.0 Improvement in Fastenings The existing mark III ERC is having the Toe load carrying capacity of 850-1150 Kg . The mark IV ERC which is under development having the Toe load capacity of 1100-1300 kg . GRP should be designed to give more resilience due to heavier axle load. 11.0 Man Power Req. Due to Fast Deterioration of Track : Gang strength formula N=0.95 M K L U (1 +A+B+C) N=No of men req IKm K= Correction factor due to modernisation of track M=Manpower factor L= Length of track U=Traffic density factor A= Formation factor B=Alignment factor C= Rainfall factor U= Traffic density factor based on GMT 20-25 25-35 U

1.4

1.5

35-45

45-55

1.6

1.7

Increase U by 0.1 when BOXN Wagon PLY >5 per day Increase U by 0.1 when speed >110 kmph Hence increase in axle load will req additional manpower of 10% 1.130

12.0 Increase in Fatigue Failure of Track : If the load is applied gradually, the specimen fails at the ultimate load. In the case of specimen is loaded and unloaded large number of times, then the specimen fails at smaller load. The phenomena of decrease of resistance due to repeated stress is known as fatigue . The growth of defect will be faster when it is subjected to heavier axle load. Hence suitable precaution to be taken to detect the defect before its reaching premature stage. Rail joint should be avoided, since the hammering effect is more in free joint. 13.0 Formation Problem : The moment carrying capacity of the rails and sleeper is based on the dynamic modulus of the formation. The fig shows the dynamic modulus of various type of soil Type of the soil

Dynamic modulus (KN/m2)

Very soft clay

350-2800

Medium clay

4200-8400

Loose sand

10000-24500

Dense sand

100000-200000

Rock granite

25 to 45*106

Hence if the formation consist of weak soil suitable blanketing to be given to improve the bearing capacity of the soil. 14.0 Conclusion: By considering the various effect due to increase of axle load. The increase of axle load play a vital role in goods traffic only, since passenger traffic are fully based on speed. Hence instead of increasing the axle load in the existing track and running mixed traffic it is better to have a separate track for goods and passanger traffic. The passanger line may be designed as high speed track with low axle load and goods line may be designed for heavy axle load. This will improve the safety standard of the track as well as reduce the maintenace cost due to lesser cant excess, cant deficiency & less corrosion in the goods line.

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References: 1. Foundation Engineering - Dr K.J.Kasmalkar 2. Railway Engineering - Rangwala 3. Prestressed concrete - N. Krishna Raju 4. WTT of Palakkad division. 5. Technical diary - Inst of PW Engineers 6. Objective Railway Engineering - M.M.Agarwal 7. Analysis of structures - S.Ramamirthum 8. IRPWM

***

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Experience of World Railway Systems for Running of Heavier Axle Loads with Special Reference to Indian Railways M.M. Agarwal* K.K. Miglani** Synopsis : The phrase ‘Heavy Haul operation’ came into prominence with the first Heavy Haul Conference held in Perth in Western Australia in 1978. Starting from that beginning, a large number Heavy Haul Trains are being operated now in various countries in the world, in America, Australia, Africa, Europe, Brazil, Scandinavia and UK for last 3 to 4 decades. Fortescue Railway in Western Australia is possibly the world’s latest, newest and outstanding heavy haul line which has been opened on April 6, 2008. This line already got in prominence during 9th Heavy Haul Conference held in 2009 in Shanghai.

The authors have critically examined the problems faced by some of the important heavy haul systems in the world railways in construction as well as in operation, with special reference to Indian Railways. The main problems which require to be specially addressed for operation of the Heavy Haul trains have been highlighted in the paper along with remedial measures. It is felt that experience gained from these railways can be of utmost use for introduction of heavy axle trains on Indian Railways. 1.0 Introduction The phrase “Heavy Haul” (HH) operation probably came into prominence with the first Heavy Haul Conference, held in Perth, Western Australia in 1978. Heavy Haul (HH) trains operate in some of the world’s most difficult conditions of terrain and climate, with rail temperatures up to 75 degrees C in North West Australia, down to minus 50 degrees C in Canada, and with annual ranges of up to 80 degrees C. Trains can be of 250 vehicles giving a trailing weight of some 30,000 tonnes and train lengths of more than 3 kms., with track curvature of 220m and grades of 2%. * Former Chief Engineer/Northern Railway ** Deputy Chief Engineer/TP/Northern Railway

2. 1

As back as in 1975-1980 , Heavy Haul trains were being operated in Africa, Australia, Brazil, North America, Europe and Scandinavian countries. Growth has been phenomenal in Heavy Haul Operations since then and in most of the developed nations, these Heavy Haul Trains are running as part of economical necessity. It is proposed to take case studies of few typical railways and discuss the various troubles faced by them as well as remedial measures in construction as well as operation/maintenance of these railways. It may be brought out that some studies of Heavy Haul trains relate to earlier years. Though there has been lot of technical developments since then, yet some of the problems brought out in earlier days are still relevant in present day context. The case studies discussed in the paper for running of Heavy Haul trains in different countries of the world not only relate to construction and maintenance of the track but also of some specific issues concerning the track. The case studies discussed in the paper are: (i)

Burlington Railways of North America for maintenance of Heavy Haul Railway lines.

(ii) Harmersley Railways of North West Australia for maintenance of Heavy Haul Railway lines. (iii) Fortescue Railways of Western Australia for construction of Heavy Haul Railway Line. (iv) Economics of running Heavy axle load & longer trains in Sweden (Europe) (v)

Maintenance of Heavy Haul Corridor of Union Pacific Railway.

(vi) American Railways: Track Transition solutions for Heavy axle load service (vii) American Railways: Effect of Heavy axle load on Bonded Insulation Joints. It is felt that experience gained by different Railway systems of the world may be of immense help to Indian Railways specially for running of 25 tonnes axle load on nominated sections of Indian Railway as well as for Dedicated Freight Corridor. Details of the various case studies are discussed in subsequent paras along with conclusion.

2. 2

2.0 Burlington Railways of North America 2.1 Introduction Burlington Railways of North America is one of the oldest Heavy Haul operated railway, constructed in the decade 1970-1980. Traffic carried in the railway was mostly coal and mixed traffic with an axle load of 30 Tonnes and maximum speed of 75 km per hour. The annual tonnage was 50 HGT. The gauge adopted was standard gauge of 1435mm. 2.2 Track Structure The track consisted of 68 Kg per metre rail & with mostly wooden sleepers with cut spikes and also mono block concrete sleepers with special clips; maximum curvature was 220 metres radius. 2.3 Problems Faced for Running of Heavy Axle Loads: A study carried out indicated the following problems with the track on account of Heavy Axle loads : (i)

Rails: Rapid rail wear, Rail end batter and dipped joints, Cracked Rails, Corrugation of rails.

(ii)

Sleepers: (a) Wooden Sleepers - By far the most common wooden sleeper fastener used was cut spike and rail anchor. The problem faced was sleeper degradation causing deformation of track geometry, lesser sleeper life. (b) Concrete Sleeper – The concrete sleeper fasteners embody is housing forming an integral part of the sleeper, and a self-tensioning spring clip located in the housing In case of concrete sleeper there was no problem of any type except fastenings.

(iii) Fastenings – Different problems existed on different type of fastenings a)

Wooden Sleeper : Problems experienced were lifting and lateral movement of the spikes giving poor gauge.

b)

Concrete Sleeper : The problem faced were of low clamping force (toe load) and low rail creep resistance values. Also the rubber pads suffered from abrasion, cutting and permanent set.

2. 3

2.4 Conclusion It may be brought out that subsequent, up gradation of track structure and deployment of new technology has sorted out many of these initial problems caused during Heavy Haul operation. 3.0 Hamersley Railway of North Western Australia 3.1 Introduction Hamersley Railway of North Western Australia used to transport iron ore over a standard (1435 mm) gauge single track of 388 kms joining mines at Tom Price and Paraburdoo with two ship loading points. Trains consisted of three 2700kw diesel electric locomotives and up to 210 cars with a 30t axle load. Train length was over 2kms, and gross weight about 26,000 tonnes. On the 100km adverse grade of 0.4% existed between Paraburdoo and Tom Price. 3.2 Problem faced (i) Embankments: These were constructed quickly in a short span of about one year without proper consolidation and as such gave problems of settlement, slippage and even failure. (ii)

Track: Degradation resulting in poor track geometry, fastening became loose, wide gauge and effecting cross levels and other track parameters.

(iii) General  The constantly heavy axle loads, rising tonnage and train frequency had two important effects: increasing track degradation and decreasing time for repairs. 

By the mid 70’s, with tonnage at 55MGT/year and expected to go on increasing, it seemed that track maintenance would limit the capacity of the system.

3.3 Remedial Measure Addressed (i) Up gradation of track continuing of Rail of 68kg/m, proper consolidation of embankment. Improving quality of ballast and higher ballast cushion; use of Malaysian treated sleepers and better quality of fasteners. (ii)

Rail Profiling by proper rail grinding machine.

(iii) Monitoring of Track tolerances: Laying standard track tolerances and proper monitoring of the same. (iv) Better track management system.

2. 4

3.4 Conclusions The up gradation of the track technology and better track management system gave dramatic improvement in wear rates, lesser input for maintenance, lesser use of man hours, lesser rail failure and improvement in track geometry. 4.0 Fortescue Railway of Western Australia 4.1 Introduction Fortescue railways of Western Australia is the world’s newest HeavyHaul, railway which was competed in April 2008. 4.2 Historical Background Fortescue Mining Group was set up in Australia in 2003 to challenge the dominance of the big multi-national mining companies. Fortescue’s subsidiary, The Pilbara Infrastructure (TPI), signed an agreement in December 2004 with the state of Western Australia to build and operate a 288km railway from Fortescue’s first mine from Cloud Break to Port Hedland and provide port facilities there. 4.3 Construction of the Project The railways project started in November 2006, construction of the formation could not start until July 2007 as a cyclone destroyed the recently-built construction camps which had to be replaced. This forced Fortescue to complete the railway in less than nine months to meet the target date. Fortescue Railway opened on April 6 2008. It is designed to operate four 2.8km-long 240-wagon trains a day to enable it to carry 55 million tones a year initially. Trains are handled by two locomotives, with banking units for the first part of the trip. 4.4 Key Design Objectives There were four key design objectives for the new railway: 

Minimize the impact on the environment



Keep the overall track length to a minimum



Minimize adverse gradients, although this was not entirely possible as banking locomotives are needed to push the trains out of the mine, and



Achieve maintenance excellence and efficiency.

2. 5

4.5 Track Structure (i) Formation was mostly on embankments using local earth but duly treated. (ii) Rails were imported rails from China having 68 kg per meter with a tensile strength of 1100 Mpa (iii) Turnout – Two types of turnout are installed on the railway: 1:20 swing-nose tangential mainline turnouts designed for 70km/h operation, and 1:12 rail cast manganese tangential 40km/h turnouts for use in yards and sidings. (iv) Sleepers & Ballast – Pre-stressed monoblock sleepers were laid at intervals of 675mm. The ballast was initially laid to a depth of 150mm and then work-hardened and super-lifted to 250mm. 4.6 Problems in Construction of Fortescue Railway (i) Formation: Fortescue faced a number of construction challenges. It was difficult to produce a good formation on some parts of the railway. There was also a lack of a suitable formation capping material. Therefore, 1% cement-stabilised sand had to be used in some areas. The formation capping is a minimum of 200mm with 97% compaction. (ii)

Ballast: Quality of ballast also faced problems. The ballast had to be work hardened and depth increased from 150mm to 250mm.

(iii) Rails & Turnout : Special rails had to be imported from China with 68 kg per meter weight. Modern turnouts were used so that speed could go upto 70 km/h (iv) General : A key factor in designing the railway was to minimize operating and maintenance costs. Driver-only operation is the norm with train control situated in Perth, 1600km from the Pilbara. 4.7 Conclusion Fortescue railway has set a new benchmark in heavy-haul railway operation, and no doubt other heavy-haul railways will be keeping a close eye on Fortescue to see how 40-tonne axle load operation works in the long term.

2. 6

5.0 Economics of Running Heavier Axle Loads & Longer Trains in Sweden (Europe) 5.1 Background This is basically a study on the Economics of running heavier axle load and longer trains in Sweden in Europe. Under increasing international competition, the movement of iron ore from mines in Northern Sweden to ports in Norway and Sweden, was looking for ways to reduce transportation costs and increase competitiveness. As European railways came under increasing pressure to reduce operating costs, and to even show a profit in their freight (goods) operations, it was only natural that they look at the costs and benefits associated with heavier axle loads and see if the benefits experienced elsewhere can also be realized in the European environment. 5.2 Results of Study The analysis showed the following results a)

Operation of 68-wagon trains with 100 tonne load capacity (30 Tonne axle load) produced a reduction of approximately 30% in direct operating costs over the base case (52 wagons of 80 tonne capacity), taking into account the expected increase in track maintenance costs as a consequence of the increase in axle loads.

b)

Assuming a “worst case” increase in track costs, savings remained in the range of 27%.

c)

The increase to 30 tonne axle loads reduces costs by about 50% more than simply increasing train length, without increasing axle loads.

d)

The increase in axle loads also reduces the number of trains that must be operated to carry the current and future volumes of iron ore, freeing up line capacity for other traffic and allowing the more efficient scheduling of maintenance work.

5.3 Conclusions  Based on the results of this study, the decision was made to purchase new heavier axle load equipment, with 100 Tonne capacity (30 Tonne axle load) and radial bogies. 

Prototype orders were also placed, with 68 trainsets of 68

2. 7

wagons each, to be ordered upon completion of acceptance tests. 6.0 Maintenance of Heavy Haul Corridor of Union Pacific Railway 6.1 Introduction A study was undertaken by AREMA of four important Heavy Haul routes of Union Pacific Railway sometimes in 2003. Out of four corridors, one corridor of Heavy coal route had 80% traffic having 34 to 37 tonnes axle load. The weight of these Heavy Haul trains have been increasing year by year and in the year 2003, there were about 35 HAL trains and each train was carrying about 15,000 tones. 6.2 Track Structure: - UPRR HAL Standard Track Section Track Structure consisted of (i) 141# Rail Section (ii) Concrete Ties (iii) 12" Ballast under Concrete Ties (iv) 18" Shoulder Ballast (v) Concrete Bridges (vi) Concrete Crossings (vii) Concrete Turnouts (viii) Moveable Point Frogs 6.3 Track Maintenance (i)

The track was being maintained mechanically with the help of Heavy Track Machines consisting of Plasser 09-3X Tamper, Track Finishing Machine, Primary Surfacing Unit, Plasser RM80 Undercutter, Loaram Rail Grinder, Harsco Switch Grinder

(ii)

The rail joints were mostly welded by Plasser Flash Butt Welder and only at few locations the welding at site was done by Thermit Welding

(iii) Ultrasonic inspection of Track was done with the help of Mobile Rail Testing Trolley. (iv)

Rail detection was done with the help of Rail Testing Cars.

(v)

Trench Drains – Special Ballast filled Trench Drains were provided as shown in the Picture. (See Figure 6.1)

2. 8

Fig. 6.1 Ballast Filled Trench drains

The benefits of the Trench Drains were (i) Removes Water From Subgrade (ii) Opportunity to Observe Subgrade (iii) Minimal Interruptions to Train Operation 6.4 Problems of Heavy Axle Load Track and Remedial Measures. (i)

Failure of Glued Bonded Joint : The problem arises because either the insulation gets broken or there is failure of glue which bonds the joint.

(ii)

Failure of Concrete Tie Plate : The tie plate gets damaged or even broken particularly on receiving end. This happens because of the heavier loading conditions. The solution lies in providing second generation TIE, which gives about 25% less stress on the plates (Fig 6.2)

Fig. 2 Second Generation Tie Plate

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(iii) Failure of Concrete Ties on Bridges : The concrete ties got damaged due to Heavy Axle Loads. Cracks developed on the Ties particularly on bridges as seen in the picture. (Fig. 6.3)

Fig. 3 Cracked Concrete Ties on concrete bridge for HAL line

The remedial measure lies on providing the following: 

100-ft. Long, 8" Hot Mix Asphalt (HMA) Underlayment



100-ft. Long, 8" Geocell Subballast Reinforcement.



Cement Stabilized Backfill, 6.75 ft. Deep, 10 ft. Long with a 2:1 Taper, Upward



Standard Track Construction (12" ballast on compacted embankment)

(iv) Failure of rubber pads (Fig. 6.4) : There is also the possibility of rubber pads failure as shown in the picture.

Fig. 6.4 Damage of Rubber Pads

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The solution lies in providing ‘New Three Part Pad’ (Fig. 6.5)

Fig. 6.5 New Three Part Pad

(v) Spalling on Rails: The spalling on rails takes place particularly on curves (Fig. 6.6)

Fig. 6.6 Spalling on Rails

The solution lies in providing premium quality steel for rails having superior wear characteristics. 7.0 American Rail Roads – Track Transition Solutions for Heavy Axle Loads Service 7.1 Introduction: Track transition areas such as bridge approaches, level crossings, and special track work can become significant maintenance problems under heavy axle load traffic and can generate impacts that contribute to accelerated degradation and shortened component life.

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The Transportation Technology Center, Inc. (TTCI), Pueblo, Colorado, a subsidiary of the Association of American Railroads (AAR), made a study and evaluated the effectiveness of currently accepted track transition designs. Some of the important findings of this study are discussed in subsequent pages. 7.2 Main Problems in Track Transition Areas One important problem in mainline track is the performance of track transition such as those found at bridge approaches, level crossings, and special trackwork. In these locations, the track structure, and often the load environment, changes significantly over a very short distance. This can result in increased dynamic loading and needed track maintenance. Problems at a track transition are can be divided into three categories: (i)

Differential Settlement: Differential settlement is where two segments of track settle at different rates, such as the bridge to bridge approach track transition. Railroad bridges are built on deep foundations and are relatively immune to subgrade settlement. In contrast, the approach consists of fill and has a large amount of settlement compared with the bridge structure. The running surface deviation that develops in this situation can contribute to high dynamic loads as high as three times the static wheel load.

(ii) Track Stiffness Case : The track stiffness case is the abrupt stiffness change that occurs in the track transition. One typical case is of a concrete span ballasted deck bridge with concrete ties can have a very high track modulus compared with the surrounding track. The abrupt stiffness change by itself does not contribute to higher dynamic loads, but coupled with a running surface deviation can induce high impact loads. (iii) Track Damping Case: The track damping case addresses energy dissipation of high dynamic loads. Track damping differs between different track structures at a track transition. For example, on a bridge approach energy is dissipated through the track structure, subgrade, and surrounding ground. On a bridge structure, some energy is dissipated in the ballast layer, but much of the energy can reach the bridge structure. It is important

2. 12

to understand the types of impacts and design damping into the track structure to alleviate potential damage. Two types of impacts viz. wheel dynamic impact & wheel balance are generated at track transition with running surface defects, wheel impact and wheel bounce. 7.3 Research Studies Research studies are being done for all three Parameters viz. settlement, stiffness, and dampening track transition cases mentioned earlier. Apart from theoretical work, predictive tools are being developed to aid in designing effective track transitions. Field evaluations are being conducted to monitor the effectiveness of track transitions in place. As far as theoretical work is concerned, parametric studies have been done using NUCARS™ and Geotrack™ software to look at the effects of track damping and stiffness. A differential settlement model has been developed to help predict settlement for different track structures. The research studies have been done under the following main topics (i) Geotrack™ study (ii) NUCARS™ study (iii) Differential settlement model (iv) Laboratory & field testing (v) Fast & revenue service testing for bridge approach transitions (vi) Study for special track work transitions 7.4 Conclusions (i) Theoretical work suggests there are opportunities to improve performance of track transition areas. NUCARS™ modeling suggests that adding damping to a track structure can improve impact attenuation by up to 30 percent. Different ways to add damping to the track are being investigated. Rail seat pads, tie plate pads, ballast mats, and subgrade treatments are all potential solutions. Some typical damping pads are given in (fig. 7.7) (ii) The parametric study using Geotrack™ suggests the best method for raising approach track stiffness is subgrade treatment. The study also suggests the best method of reducing bridge track stiffness is to alter tie to pad properties. (iii) Field testing indicated that different tie materials can provide effective ways to improve the track stiffness transition. Plastic ties installed on bridges in concrete tie territory have been successful in eliminating the stiffness differential for the first 240 MGT.

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Rail Seat Pad

Ballast Mat

The Plate Pad

Under Tie Pad

Fig. 7.7 Various Type of Damping Tools

Concrete ties with rubber pads also helped in lowering the modulus below that of the approach and increasing the damping properties of the bridge structure. Thus, this method appears capable of addressing both track stiffness and damping issues and is a promising solution because the desired properties can be designed into the pads. (iv) A good number of predictive tools is being developed to provide a way to design effective track transitions to address stiffness, damping, and differential settlement. Field testing has proved that these are effective ways to address each of these issues. 8.0 Effect of Heavy Axle Load on Bonded Insulation JointResearch Study by TTCI (American Rail Board) 8.1 Introduction Heavy Axle Load (HAL) coal traffic, with higher speeds and higher traffic densities, places a significant performance demand on bonded insulated rail joints (bonded IJs) (Fig. 8.8)

Fig. 8.8 Typical main line bonded Insulation joint

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While bonded Insulated Joint (IJ) are essential as an operational need they also introduce weak points in the track which cause increased maintenance and service disruptions. Bonded IJs are also a potential safety risk. These thing get further aggravated when Heavy Axle Load pass on these joints. It may be brought out that Bonded IJ performance on heavy haul coal routes has significantly declined as the load environment has become more servere. Today, bonded IJ service life may be as short as 200 MGT. This short service life is lower than virtually all other running surface components including turnout frogs and switch points. On high tonnage routes, bonded IJs may be replaced within as little as 12 to 18 months with direct costs of thousands of dollars (Rupees) per mile per year. Indirect costs such as crew labor and schedule disruption due to train delay can be higher, especially on lines with full capacity. With such short service lives, the economics of developing a longer lived bonded IJ are compelling and is a technical requirement. In order to critically examine the design of existing bonded insulation joints, their failure modes, recent design evaluation, a research study was done by the Transportation Technology Centre, Inc., (TTCI), Pueblo, Colorado, a wholly owned subsidiary of the Association of American Railroads (AAR) in collaboration with some other organization. 8.2 Service Life of Bonded Insulation Joints The research studies taken on specific projects brought out that following important factors adversely affect service life of these joints due to Heavy Axle Loads.  Higher average wheel loads from larger capacity cars  Higher dynamic loads from higher speeds and a stiffer track structure.  Higher longitudinal forces from elimination of other rail joints and better rail anchoring.  Higher traffic density which reduces opportunities to perform bonded IJ maintenance activities such a surfacing and running surface flow grinding The service life of a bonded Insulated Joints classified differently from many other track components because it can deteriorate and fail rapidly.

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8.3 Effect of Axle Load, Dynamic Load, and Traffic Volumes The effects of static load (axle load), dynamic load, and traffic rates are interwoven in evaluating bonded IJ performance on HAL routes. As the railways have increased car capacity, they have also Increased traffic rates, Raised train speeds, Increased track stiffness, Increased the tensile stress in the rail. With these conditions in mind, it was perceived that the heavier loads and higher speeds were generating more mechanical component defects. The effect of all three factors (static load, dynamic load, and traffic rates) have been significant in raising the severity of the service environment experienced by track components such as bonded IJs. 8.4 Failure Mode Analysis In order to better understand failure mechanisms, a sample of 20 IJs removed from revenue service was collected and examined by TTCI. The joints were from lines that carry coal traffic predominantly in 286 Kip cars. Some of the important results which were arrived after examination of the sample were : (i)

Many joints have more than one defect.

(ii) There are several common modes that limit service life for bonded IJs in HAL service. Some of these are related to quality control issues in components and assembly. There are also service life-reducing aspects related to the design and capacity of the joint. These occur with structural aspects of the joint or components within the joint. These situations begin with the joint becoming a running surface discontinuity. This discontinuity generates dynamic loads at the joint which damage the foundation. Due to lower stiffness of joint, the deflection becomes significantly larger than deflections typically found in surrounding track. (iii) Cause of the poor foundation condition in this case is the dynamic loading generated by the running surface discontinuity of the IJ. The combination of high dynamic forces and larger deflections at the IJ cause the foundation to fail here before it does in open track. The foundation condition causes cracking in the glue or epoxy at the top-centre of the joint bar to rail interface.

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(iv) The weakened epoxy bond allows moisture intrusion and larger deflections. Due to this, the situation become of a disassembled bonded IJ with glue debonding and water intrusion. As the glue debonds, the joints becomes subjected to “pull-apart” because of the longitudinal forces in the rails. “Pull-apart” damages insulating components such as thimbles and end posts as well as mechanical joint components such as bars and bolts. (Fig. 8.9)

Fig. 8.9 Typical failure of Glued bonded joint

8.5 Conclusions (i)

Improving Performance of Insulated Joints (a) Improving the performance of bonded IJs can be accomplished by improving any of the weaknesses in current designs, maintenance and operations. The efforts to improve the design is based on the following points: (i) Reducing deflections (ii) Reducing component relative movement (iii) Increasing the strength of failure prone components. (b) Reducing Deflections Several methods have proven to be effective at reducing maximum bonded IJ deflections. These include: (i) Supported bonded IJs (ii) Multiple tie plates

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(iii) Longer Joint bars (iv) Larger (cross section) joint bars. (ii) Performance Requirements of Bonded Insulation Joints The research studies have suggested draft performance requirement of Insulated Joints. These requirements are a first draft based on the observed problems with existing bonded IJS in HAL service and the service environment measurements made. These have been tentatively laid down by American Rail-Roads. (iii) Advanced Design for Bonded Insulation Joint Based on the research studies, a design has been developed based on observation of current designs, analysis and modeling work, and the requirements of the draft performance guidelines. This design will have the following features: 

Reduce bonded IJ-caused dynamic loads with less running surface and more damping running surface design from AAR Frog Longitudinal Profile



More damping: Mitigates effects of dynamic loads



Lower Deflections: by having Foundation with larger bearing area on ties and ballast, Continuous support,



Components: having Stronger insulator and more environmentally stable epoxy



Assembly with Improved rail and bar surface preparation: to eliminate surface contamination.

9.0 Summary and Conclusions 9.1 Track Defects on Account of Heavy Axle Loads (i)  

Formation Problem of settlement, slippage and even failure. Special problems in yielding formation & bad quality soil.

(ii) Rails 13Defects develop in rail; cracked Rails Develops high contact stresses between rail & wheel causing wheel burn, wheel scabbing.  Rapid rail wear; Excessive wear of rail on curves.  

2. 18



Scabbing of rail is more prominent particularly on steep gradients.

(iii) Sleepers Wooden Sleepers: Fast deterioration causing poor track geometry; lesser sleeper life. Concrete Sleepers: Generally satisfactory but gets damaged, cracked or even broken in special locations like bridge approaches, on bridges and such other locations. (iv) Ballast  Ballast not of desirable quality; lesser ballast cushion. 

Pulverization of ballast & clogging of shoulder ballast on account of heavier axle loads & dropping from the wagons.

(v) Fittings & Fastenings  Fastening get loose very fast and thereby effecting track geometry. 

Rubber pads get damaged early. Heavy crushing of rubber pads.



Glued Insulated Joint start failing because either insulation gets broken or failure of glue which bonds the joints.



Short Service life of bonded Insulation joint which is sometimes as short as 12 to 18 months; This is almost the lowest than possibly all other surface components.

(vi) Points & Crossing  Quick wear, frequent renewal necessary. 

Breakage of CMS crossing at few locations.



Lesser speed effecting adversely the traffic output.

vii) Track Maintenance 

Track geometry gets deteriorated very early due to heavy loads.



Existing maintenance system may not be able to cope up with the increase in work load due to heavy axle load & allied problems.



Increase in weld failures specially of thermit welded joints.

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(viii) Bridges  Signs of distress on some of the bridges resulting in cracks & deterioration of other bridge components. Sleepers get cracked on bridges in some cases. (ix) Track Transition areas (Bridge approaches, Level Crossings & Special Track Works)  Due to differential settlement, extra track stiffness and differential damping Track Components gets damaged quite early. 

Increased dynamic loading & need for extra track maintenance.

9.2 Conclusion & Suggested Remedial Measures (i) General  The operation of heavy axle load trains is a economic and technical necessity & as such Heavy Haul trains today exist in most of the developed Railways of the World. (ii) Formation Soil stabilization by proper mechanical means during construction.





In case soil is not good, soil treatment of top capping soil should be done. Refer case of Fortescue Railway of NorthWest Australia where 1% cement stabilization was done of top 200 mm soil and with 97% compaction.



Special treatment of formation/back fill to be done on bridges.



Yielding formation & poor quality of soil require special treatment. In some situations, even provision of Ballast filled Trench drains may help as done in case of Union Pacific Railway (See Figure 6.1)

(iii) Rails Up to 25 tones axle load, 60 kg 90 UTS rails sufficient; For higher axle loads, special heavy rails to be procured.





It may be brought out that as per survey carried by JRP-2 initiated by UIC there is certain relationship between rail section & axle load (See Fig.10.10) 60 kg rail section would suffice for an axle load up to 25 tonnes.

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Survey of current practices, carried out by JRP-2, intiated by World Executive Council of UIC indicates the following relationship between Rail Section and Axle Load :



Rail Grinding Machine: Reprofiling to be done by Rail Grinding machine for prolonging rail life as well to prevent defects in rail head.



Mechanised USFD Testing of rails: Use improved and mechanized USFD technology (Spurt cars etc.) for testing of rails.



Roll longer rails to reduce welds and also to improve performance.

(iv) Sleepers Mono block PRC sleepers quite satisfactory in ordinary situations.

 

At special locations provide Special sleepers like “Second Generation Tie” to reduce stress on plates as done on Union Pacific Railway (See Fig 6.2).

(v) Ballast Better quality of ballast with full ballast cushion of 25 cm to 30 cm. If necessary, work hardening of ballast to be done to improve quality of ballast.





More frequent deep screening of ballast to be done by mechanized methods.

2. 21

(vi) Fittings & Fastenings Quality of fitting & fastening and rubber pads to be improved.





Develop better design of rail pads like ‘Three Point Pad’ as done by Union Pacific Railway (See Fig 6.5)



Bonded Insulated Joints are worst effected & their design to be further improved by looking after the problems in current design, maintenance & operation. The bonded insulation joint should be designed based on standard. ‘Performance Requirement’ for HAL Service and particularly ensuring reduced dynamic loads, lower defectors & stronger insulator & other components.

(vii) Points & Crossing To be modernized to cater for higher speeds of 75 kmph to 100 kmph. Refer Swing Nose Turnouts 1:20 designed for 70 kmph for Fortescue Railways of Western Australia.



(viii) Track Maintenance Complete Track mechanization of track maintenance & track renewal works.





Fixing proper tolerance for HAL trains & better Monitoring of track tolerances.

(ix) Bridges Bridges should be designed for heavier loading. Quality of bridge construction require to be improved.





As cracks develop sometimes in concrete ties on bridges, it is necessary that sub-base of bridge require to be strengthened by making it compacted embankment. The sub-base can be upgraded by providing hot mix as under layment, Geocell sub-ballast Reinforcement, cement stabilized back fill & 12" ballast

(x) Special Case for Track Transition Areas : (Bridge Approaches, Level Crossings & Spl. Track work)  Improving Track structure for track transition area such as Bridge approaches, level crossing & special track works. 

The studies suggest that proper damping devices on track can improve track impact by 30%. Provide special damping devices like Rail seat pads, Tie Plate pads Ballast pads

2. 22

etc to improve track performance. (See Fig 7.7) 

Development of Predictive tools to provide a way to design effective Track Transitions to address stiffness, damping & differential settlement.



Installation of Plastic ties bridges in concrete Tie Territory can be successful in eliminating the stiffness differential.



Concrete Ties with rubber pads can help in lowering track stiffers & damping issues and as such improve track performance.

(xi) Track Management cum Information System To introduce better track management cum information system so that monitoring of track maintenance & other aspects of track management can be supervised/ controlled. 10.0 Use of Experience of World Railways by Indian Railways System to Run Heavy Axle Load Trains 10.1 Introduction: Indian Railway took a bold decision in the year 2001-02 to run heavier axle load than existing axle load of 20.32 tonnes in an effort to enhance the traffic capacity of Railways to handle the increased traffic as well as to increase its financial viability A pilot project of (CC+8+2) with an axle load of 22.9 tonnes was implemented on the 20 routes initially and later on 14 more routes added after the positive feed back from the different railways, the major routes are in the South Eastern Railway, East Coast Railway, SEC Railway and Eastern Railway. Presently CC+6+2T is in operation nearly on 26000 route kms and CC+8+2T on 5000 kms. The experience gained by IR in a short span of few years was almost on similar lines as experience gained by other railway system of the world. Heavy wear & tear of rails, cracked rails, more frequent renewal of fittings & fastenings such as Pandrol clips, Insulation joints, Rubber pads, poor track geometry due to axle loads, problems on bridges are some of the typical examples. 10.2 Remedial Measures Suggested: The remedial measures suggested to mitigate the effect of heavier axle load based on experience gained by different Railways have been brought out in para 9.2

2. 23

These remedial measures are quite detailed & some of them very special and these can be of immense use to Indian Railways for running of heavier axle loads. Indian Railways have already nominated some lines for running of heavier axle load of 25 tonnes (called feeder routes). Dedicated freight corridor with an axle load of 30 tonnes have been planned on the golden quadrilateral out of which two corridors (Mumbai & Howrah corridors) are already sanctioned. The work on these projects is likely to be started shortly. 10.3 Concluding Remarks It is felt that experience of more than 3 decades gained by different railway system of the world may be of immense use to Indian Railways for running of heavy axle loads. 11.0 Bibliography 1.

Rail Road Track mechanics & Technology by Amold D. Kher, PERGAMON Press, New Delhi (1984 )

2.

Track Technology- Proceedings of a conference organized by Institution of civil engineers held at University of Notingham (1984)

3.

Indian Railway Track by M.M. Agarwal - Prabha & Co., New Delhi (2009)

4.

The impact of Track technology on Heavy Haul operations-WR …. Lecture in conference by I.C.E. held at University of Notingham (2006)

5.

Proceedings of Ist International Heavy Haul conference held in Western Australian (1978)

6.

Proceedings of 9th International Heavy Haul Conference held in Shanghai (2008).

7.

Turnround of Indian Railway by increasing axle load-A joint study by IIM Ahmedabad & Railway Staff College, Vadodra (July 2006)

8.

Heavy Axle load maintenance on Union Pacific Railway-A report by AREMA (2004)

9.

Fortescue New Line raises the bar for Heavy Haul-International Railway Journal Volume 49, issue of (September 2009)

10. Wheel-rail interface-Transnet gets to grips with wheel wear dataNew system transformation wheel–rail Interface –International Railway Journal-Volume 49, Issue of September 2009. 11. Introduction of Heavy axle load in Europe- The economics of 30 Tonne axle load operations in the main stress by Allan M.Zarembskir

2. 24

of ZETA-TECH of USA & Bjorm Paulsson Banverket Bortange, Sweden (2006) 12. Introduction of ‘Heavy axle load on IR-Paper by Rakesh Chopra & H.L. Suthar (2007) 13. Review of works involved for running of 25 Tone axle load on IR by Mahavir Singh Dy CECTS WR & K.L. Meena, DyCE/NWR (IRICEN Pune) 14. Technical paper on increase of Axle load on IR-Track Design concepts-RDSO Lucknow. 15. Bonded Insulated joint performance in main line track by D. DavidTechnology Digest TD04-006, TTCI, Pubelo, Colorado-May-2004. 16. Concrete Tie design for heavy axle load application-by G. GemeinerAREMA Annual Conference 2004.

***

2. 25

Effect of Higher Axle Load on Bridges in South Western Railway R.S.Dubey* Ramesh Kambli** T.A. Nandakumar***

Synopsis: To enhance the throughput to meet traffic demands of the nation, Railway Board permitted operation of CC+8+2 (Axle Load 22.82 t) and CC+6+2 (Axle load 22.32 t). As a pilot project it was introduced in S.W. Railway on identified routes. This paper deals with the experience of higher axle load on Bridges on S.W. Railway. 1.0 Introduction In developing economy, growing demands of transportation is one of the most important features. Railway being the bulk and Largest transporter, is playing important role in this. To meet this challenge, Railway had following options. 1) Increase the number of trains 2) Increase the number of wagons in train formation 3) Increase load carrying capacity of existing rolling stocks/ wagons 4) Increase number of lines 5) A separate freight corridor To begin with Indian Railways decided to permit heaver axle load on the existing system. In line with above objectives and routes were identified where heavier axle loads such as CC+6+2 and CC+8+2 could be run. Pilot projects were accordingly sanctioned by Railway Board to monitor the performance of rolling stock, track and bridges. 2.0 Higher Axle Load Train Operation On SWR South Western Railway consists of 3 divisions viz, Hubli, Bangalore and Mysore divisions. Total No of bridges available on these divisions * CBE/South Western Raillway **Dy.CE/Bridge/South Western Raillway ***ADEN/Bridge/South Western Raillway

2.26

including minor, major and important bridges are listed as below. Division

Total No. of bridges available

Bangalore

2681

Mysore

2249

Hubli

1900

Total

6830

Total No. of bridges available on the identified routes are listed below S. Route nominated for No. of No. of No.of No. of Total N. Higher axle load arch steel concrete Miscell- Number of operation bridges bridges (RCC/PSC) aneous bridges bridges bridges 1 Bellary-HospetHubli-LondaVasco-Da-Gama

132

93

387

299

911

2 ToranagalluRanajitpura

0

7

25

13

45

3 Hospet-Gunda Road-Swamihalli

1

2

107

29

139

4 Gunda Road-Kotturu

0

5

107

6

118

5 Bellary-Raydurga -Chikjajur

4

13

152

126

295

6 AmmasandraArasikere-BirurChikjajur-HariharHubli

201

32

113

89

435

7 ArasikereHassan-Mangalore

13

120

178

441

752

351

272

1069

1003

2695

TOTAL

2.27

RDSO vide letter No. CBS/Golden/Q/Strength dtd. 20/3/2007 has issued guidelines for running of CC+6+2T (22.32 T) and CC+8+2T (22.82 T) axle load operation. i. RDSO has checked the superstructure of standard spans (6.1m, 9.15m, 12.2m, 18.3m, 24.4m, 30.5m, 45.7m, 61.0m and 76.2m - all clear spans) of bridges for 60 Kmph speed for CC+6+2T and CC+8+2 T axle load and found that superstructure of all standard spans designed to BGML loading standard , RBG loading standard and MBG loading standard are fit for 60 Kmph speed (suitability of superstructure of standard spans has been checked for height of C.G. of wagon from rail level not exceeding 1830 mm). ii. RDSO has checked the bearings of standard spans of bridges for CC+6+2 T and CC+8+2 T axle load and observations are as below:a) Bearings of standard spans designed for MBG loadings are fit for running of CC+6+2 T and CC+8+2 T axle load BOXN wagon with coupled WDG 4 and coupled WAG 9 locomotives. b) In case, the bearings designed for BGML/RBG loading standards have been replaced in accordance with RDSO letter of even no. dtd. 30-12-2004 summarized in Annex-6, then bearings are fit for running of CC+6+2 T and CC+8+2 T axle load BOXN wagon. c) In case, the bearings designed for BGML/RBG loading standards have not been replaced in accordance with RDSO letter of even no. dtd. 30-12-2004 summarized in Annex-6, then Zonal Railways should either replace existing bearings as indicated above or strengthen the bearings as per Annex-6 for restricted speed of 60 Kmph. iii. Zonal Railways are required to check the suitability of bridges for CC+6+2T and CC+8+2T axle load, as below:a) Superstructure of non-standard spans including Arch Bridges etc. b) Bearings of non-standard spans and Substructures of all the bridges. Longitudinal forces are to be taken as given in Annex-2 of 4 (depending on the electric or diesel traction). These longitudinal forces are without considering dispersion. As per correction slip 32 to IRS Bridge Rules issued vide RDSO letter No. CBS/PBR

2.28

dt. 21/23-06-05 (copy enclosed as Annex-7), dispersion of longitudinal forces should also be considered while checking suitability of existing bridges. However while considering the dispersions of longitudinal forces the conditions given as per clause no. 2.8.3 2 of IRS Bridge Rules should be met with. If found unsafe, then details of longitudinal forces with limiting the tractive effort to 30 T per loco, as given in Annex-3 or 5 (depending on the electric or diesel traction) may be used and accordingly position should be prepared. c) One time inspection of all bearings apart from schedule inspection for their proper functioning and bed block for their soundness should be done. d) Following locations/members are to be monitored as being critical from fatigue considerations.  Connection of cross girder with stringer.  Outstanding leg of the top compression flange of the strings at its junction with web rivet.  Rivets of splice joints of bottom flange in plate girders. e) Physical conditions of bridges are to be certified by Zonal Railways. f) Sample bridges (representing type and span of those available on the routes) and vulnerable bridges, shall be selected for instrumentation for monitoring the effects of increased longitudinal forces and higher axle loads on the bridge components i.e. foundations, piers and abutments, bearings and superstructure. Instrumentation shall be with respect to measurement of settlement of foundations, tilting of piers/abutments, loads on bearings, deflections and stresses at critical points. Change in dynamic parameters may be monitored for quick evaluation. (Ref: Rly. Bd’s letter No. 2005/CE-II/TS/7 Pt dtd. 09-05-06). Accordingly, following action was taken by S.W. Railway – I. Checking the suitability of bridges for CC+6+2T and CC+8+2T axle load, the superstructure of non-standard spans including Arch Bridges. a) Superstructure of nonstandard spans

2.29

Following is the list of non-standard bridges in the section (BAY – UBL – LD – VSG section) Number of Non-standard Span Bridges Section UBL-LD LD-VSG UBL-BAY HPT-SMLI TNGL-RNGP

Major 0 13

Minor 19 44

6 2 1

12 27 2

Total 19 57 18 29 3

b) Arch Bridges In the BAY – VSG route the distribution of Arch Bridge is given below:Section UBL - LD LD - VSG

Total No. of Arch Bridges 21 66

UBL - GDG GDG - HPT GDG - SMLI Total

4 6 1 98

All the Arch Bridges, both major and minor were examined by Ring 1.5 software.This software has been developed by Sheffield University UK. It provides very useful tool for first level assessment of arch bridge. It is used as on aid to decision making regarding identifying critical bridges, frequency of inspections and strengthening required. II Bearings of non-standard spans and substructure of all the bridges. a)

The bearings of all non standard spans were checked and the bearings of the following bridge is strengthened by providing two additional anchor bolts.

2.30

Sl. Br. No. No. 1

Location

Between Span stations

Type of Type of bridge Sub structure

139A HPT yard BAY–GDG 1x30.48m Girder

RCC

b) On checking the sub-structure of all the bridges, the tractive effort had to be restricted to 30 T for the following bridges:Sl. No. 1 2 3

Br.

Location stations 47 Km 24/7-25/1 139A HPT yard 3 Km 1/0-1

4 5 6

39 Km 19/10-11 GDJ - SMLI 157 Km 153/8-9 BAY - HPT 184 Km 167/9-168/0 BAY - HPT

Span bridge 3x12.20m 1x30.48m 2x19.40m+ 1x12.19m 3x12.20m 1x12.20m 1x12.20m

7 8 9 10 11

200 204 206 240 243

8x12.20m 1x12.20m 4x12.20m 2x12.20m 3x12.20m

Km 174/0-1 Km 176/10-11 Km 177/13-14 Km 194/8-9 Km 197/6-7

Between SMLI - HPT BAY - GDG TNGL- NHT

BAY - HPT BAY - HPT BAY - HPT BAY - HPT BAY - HPT

Type of Type ofNo. Sub structure Girder Stone Masonry Girder RCC Through Granite Girder Masonry Girder Stone Masonry Girder Stone Masonry Composite Stone Masonry Girder Girder Stone Masonry Girder Stone Masonry Girder Stone Masonry Girder Stone Masonry Girder Stone Masonry

These bridges were proposed in the Works Programme 2007-08 and got sanctioned for strengthening. Out of 11 bridges, strengthening of 10 bridges is completed and work is in progress for Br. No. 200. Inspection of all the bearings from scheduled inspections for their proper functioning and bed block for their soundness. Apart from the scheduled inspections, all the bearings are inspected for their proper functioning every quarters and bed block for their soundness. So far no adverse effect has been noticed.

2.31

c) Problems in the Bed blocks of bridges in Sakleshpur-Subramanya road (HASSAN- MANGALORE SECTION) Sakleshpur-Subramanya road (HASSAN- MANGALORE SECTION) is a critical ghat section of Mysore Division where cracks in piers and pier bed blocks have been notices in some of the bridges. The section was opened after Gauge conversion for Goods traffic on and for passenger traffic on. The goods traffic consists of iron ore rakes of CC, CC+4 capacity Salient Features of SKLR - SBHR Ghat Section: •

Section length of 55 km passing through Western Ghats

•

There are total 241 bridges in this section, out of which 84 nos. are girder bridges

•

Number of tunnels are 57. Total length of tunnels is 10970m.

•

Number of block stations is 4.

•

The ruling gradient is 1 in 50.

•

Maximum degree of curve is 8o, total length of curves in Ghat section is 33.98 km i.e. 62%.

During the inspection February 2008 of bridges, it was noticed that there are some bed blocks in the SKLR- SBHR ghat section which have been crushed. The photos of some crushed bed blocks are as below:

BR 184 at KM 56/300-400 Pier No.1 span 1 LH SBHR end 2

BR 184 at KM 56/300-400 Pier No.1 span 1 LH SBHR end

2.32

BR 190 at KM 57/00-100 Pier No.1 span 2 LH SKLR end

BR 190 at KM 57/00-100 Pier No.1 span 2 RH SKLR end

Br 255 at KM 71/ 900-72/100 Pier No.2 span 2 LH S BHR end

Br 255 at KM 71/900 -72/100 Pier No.2 span 2 RH SBHR end

The bed blocks of following bridges have been crushed. Bridge

Location

Span

Superstructure Bed blocks location

No. 184

190

56/300-400 12.20 x 1+ Rivetted Plate 18.30 x 1+

Girder

12.20 x 1

(RIVTPG)

57/0-100 12.20 x 1+

RIVTPG

9.15 x 1+

P1 (LHS & RHS) P2 (LHS & RHS) P1 (LHS & RHS) P2 (LHS & RHS)

18.30 x 1 248

70/200-300 12.20 x 1+

RIVTPG

24.40 x 1+

P1 (LHS & RHS) P2 (LHS & RHS)

12.20 x 1

2.33

255

71/900-72/000 12.20 x 2+

RIVTPG

18.30 x 2+

P2 (LHS & RHS) P4 (LHS)

12.20 x 1 273

76/300-400 12.20 x 1+

RIVTPG

P1(RHS)

RIVTPG

P1(RHS)

18.30 x 1+ 12.20 x 1 165

52/0-100

12.20 x 1+ 18.30 x 3+ 12.20 x 1

227

66/500-600 12.20 x 1+

RIVTPG

9.15 x 1+

P1(LHS) P2 (LHS & RHS)

12.20 x 2 247

70/0-100

12.20 x 1+

RIVTPG

P2(LHS & RHS)

18.30 x 1+ 12.20 x 1 III Causes for Crushing of Bed Blocks After examination it is seen that the stepped bed blocks only crushed. The stepped bed blocks have been provided during construction on the piers, where different types spans are existing on both sides of the pier. The cracks have developed below the bed plate from the point of holding down bolts anchored into the bed blocks which are having more height and due to running traffic - the bed blocks have been crushed and bed plate have been bent. Further, it is noticed that these crushing of bed blocks has been observed only where the bed plates are provided at the edge of the bed blocks of high depth. These cracked bed blocks were attended by SIKA epoxy grout which is standing well without any problem. IV Special Instructions Special instructions were issued to check the following locations/ members which are critical from fatigue considerations during quarterly inspection 

Connection of cross girder with stringer.



Outstanding leg of the top compression flange of the stringer at its junction with web rivet.

2.34



Rivets connecting bottom flange angle of the stringer with web at mid span.



Vertical members at connection with top chords.



Rivets connecting bottom flange of cross girders with web at mid span.



Rivets of splice joints of bottom flange in plate girders.

V Monitoring of Bridges by Instrumentation Even though there is no any visible symptoms noticed in the bridges, it can not be taken granted that the bridges are safe for running higher axle loads based on the theoretical calculations and visual observations. In order to get a true assessment of adequacy of the strength of existing bridges and to forecast their behaviour for enhanced loading in the coming years, it was decided to monitor the health of some selected bridges, which were critical from theoretical considerations, by means of instrumentation. Initially to begin with following 5 different types of bridges were selected for instrumentation SL

BR. No. Location

Section

Span

TYPE

1 x 30.48

OWG

No. I

139A

II.

3

144 / 0-1 Gadag-Bellary 1/ 0-1

Toranagallu-

2 x 19.4 + 1 x 12.19 Plate Girder

Ranjitpura III.

102

IV.

28

V.

20

34 / 14-15 Londa-Vasco

2 x 27.43

Plate Girder

Londa-Vasco

2 x 18.29

Arch

46/15 - 47/1 Hubli - Hospet

5 X 9.14

Arch

39 / 5-6

In order to have a better involvement in the work, S.W. Railway approached to Indian Institute of Science (IISc), Bangalore which is a reputed technical institute, for carrying out the work of instrumentation for above 5 bridges and they had come forward to take up this work as a project work. Several meetings were conducted and preliminary investigationsre wmade to assess the efficacy of the modus operandi to be adapted for instrumentation of bridges. Subsequently, the requirement of various types of sensors and their

2.35

suitability and modus operandi was finalised by IISc, Bangalore and SWR officials. A) Scheme of Instrumentation Methodology / scheme of instrumentation is same for all type of bridges. Instrumentation was carried out to know/measure the deflection at various locations, stiffness of the girders, to draw the Influence line diagram, Dynamic augmentation factor at various speeds, maximum and minimum stresses developed, Max. tractive effort and braking forces applied as well as transferred to the bridge approaches, bearings and at bed block level. Following field trials/tests were conducted at each bridge location (1)

Static load test

(2)

Speed test

(3)

Influence line diagram for BM and SF

(4)

Measurement of longitudinal forces (with out brake binding)

(5)

Measurement of Tractive effort (with brake binding)

(6)

Coupling test

Following combination of test train was used for instrumentation (1) For conducting speed trials, static load test and influence line diagram 2 WDG 4 (Multi Loco) + 2 BRN loaded with 200 PSC sleepers each + 2 BOXNEL wagons loaded to 25 T axle load with Iron ore. (2) For measuring longitudinal forces (Tractive effort and Braking forces) 2 WDG 4 Locos (Multi) + 58 BOXN wagons loaded with Iron ore + 2 WDG 4 Loco (Multi) In order to have a better idea, instrumentation done at bridge No. 128 is explained in detail below.

2.36

 Salient Features of Arch Bridge No. 128 1.

Bridge No.

128

2.

Location

Km 39/1 & 2

3.

Section

Londa – Vasco (Ghat Section)

4.

Year of construction

1886

5.

Gradient on bridge

1 in 37

6.

No. of spans

2 x 17.7

7.

Type of Arch

Parabolic

8.

Type of foundation

open foundation

9.

Type of sub-soil

Hard rock

10.

Type of Masonry

Brick masonry

11.

Arch thickness

93 cm

12.

No. of arch rings

8

13.

Rise

4.5 mtr

14.

Abutments and piers

Brick masonry

15.

Width of pier at top

3400mm

16.

Height of pier

3900mm

17.

Bridge width

6850mm

18.

Alignment

In curve

19.

Depth of cushion

1.0 meter

 Track Structure Over Bridge: Rails

60 kg.

Sleepers

PSC 60 Kg.

Ballast cushion

Adequate

 Types of Sensors Used: The objective of the study was to understand the behaviour of the Arch and to determine the safety limits of the existing bridge from the point of view of the proposed increase in axle load (25 T). For this

2.37

purpose the bridge was instrumented with various types of sensors as given below.  STRAIN GAUGES, (to measure the strains for working out the induced stresses)  ACCELORAMETERS (to measure the accelerations)  LVDTs (to measure the deflection)  TILT METER (to measure the relative movement)  TEMPARATURE GAUGES (to measure the variation in temperature during the course of test and to verify the temperature effect)  SEISMOGRAPH (to measure the vibrations) In addition to above, acoustic emission test was also conducted using 8 sensors to measure the events that occurred during the course of testing. (For sound of crack or similar events). Location of Sensors : Following type of sensors were fixed on arch, pier, abutment and rails Type of Sensors

Span No. 1 Span No.2 Total

Strain Gauge (Electronic type)

8

4

12

Vibrating Wire Strain Gauge

3

2

5

Cross-Bow Accelerometer

4

-

4

B & K Accelerometer

4

-

4

LVDT (For deflection)

3

3

6

Cross-Bow Tri-axial Accelerometer

1

-

1

Tri-axial Diathrone Accelerometer

1

-

1

Tilt meter

1

-

1

Seismograph (Vibration)

1

-

1

Temperature gauge

1

-

1

27

9

36

(Mechanical type)

Total

2.38

Test train over arch bridge No. 128

Location of Sensors :

LVDTs mounted at springing level

LVDT at Crown level

Electrical strain gages at crown Electrical strain gages at rail web over arch

2.39

Test train over arch bridge No. 128 B) Testing and discussions of results 1. Static Load Test This test was conducted to study the value of stresses induced and the deflection at crown & at springing level so as to up date the model for numerical analysis. The results obtained from this test are co-related with the model study results and accordingly model was up dated.

Finite element model of Masonry Arch Bridge

Deflections measured during static test Load (no. of sleepers)

168+168 184+184 200+200

Springing Horizontal Deflections Crown vertical deflection Span 1 Span 2 CLR Kulem CLR Kulem CLR side Kulem side side side side side (mm) (mm) (mm) (mm) (mm) (mm) 0.2 0.05 0.04 0.05 0.49 0.3 0.0 0.21 0.0 0.29 0.55 0.6 0.1 0.17 0.01 0.18 0.57 0.6

2.40

Values of strains measured during static test

Fig 1

Fig 2

The tangential strains in span 1 along the center line of the track are shown in Figure 1. The strains are minimum and almost zero near the crown and maximum near the right springing position. Figure 2 shows the tangential strains along the width of the arch at the crown position. It may be mentioned here that one micro strain corresponds to approximately 0.0018 MPa (0.018 kg/mm2) of stress in the masonry. It is seen that the strains are largest near the eccentric position (far end of the barrel of the arch) when compared to the centre line of rail location. Figure 3 shows the transverse strains along the crown for different magnitude of loading. It is seen that all the transverse strains are tensile in nature. The maximum value of

2.41

transverse tensile strain is about 17 micro strains which corresponds to a tensile stress of about 0.00306 kg/mm2. This value is less than the codal permissible value of 0.011 kg/mm2 in tension. Values of stresses measured and computed in the Static Load Test (200 sleepers loaded on two BFR’s = 20.25tons/axle). Sl. DescriN. ption

1

2

3

4

5

Actual stresses measured (kg/mm2)

Type of stresses

Speed of train

Stress Permissible Remarks calculated stresses from as per numerical design (kg/mm2) 0.00136 0.05375 Within (Ten.) (Comp.) permissible 0.011 (Ten.) limits 0.00501 0.05375 Within (Comp.) (Comp.) permissible limits

Soffit of 0.000144 arch-Span 1-Crown Soffit of 0.002214 arch Span 11/4th SpanCR side Soffit of 0.002700 arch-Span13/4th spanK side Springing 0.004500 levelSpan 1CR side Springing 0.001116 level-Span 1, K side

Comp.

Static

Comp.

Static

Comp

Static

0.003615 (Comp.)

0.05375 (Comp.)

Within permissible limits

Comp.

Static

0.002443 (Comp.)

0.05375 (Comp.)

Within permissible limits

Comp.

Static

0.003574 (Comp.)

0.05375 (Comp.)

Within permissible limits

2. Results of the Speed Test Speed tests were conducted using both formations as mentioned at the beginning. The formations were made to move from Castle Rock to Kulem and Kulem to Castle Rock ends with different speeds. The speed test using formation 2 are part of the longitudinal load tests. The objective of the speed test is to estimate the dynamic magnification factor and to assess the dynamic characteristics of the bridge structure. Table 2 shows the max.values of the tangential stresses measured at different locations of the arch across all speed cases using formation 1. It is seen that the stresses are within the codal permissible levels.

2.42

Maximum values of Tangential Stresses Measured in theSpeed Test Sl. DescriN. ption

Actual Type Speed Permissible Details of Remarks stresses of of stresses as deflection measured stresses train per design (mm) (kmph) (kg/mm2) (kg/mm2)

1 Soffit of 0.00132 arch-Span 0.00207 1 - Crown

Ten. Comp.

30 KC 0.011 (Ten.) 20 KC 0.05375 (Comp.) 40 KC

Stresses Within permissible limits -0.1464

2 Soffit of 0.00449 arch-Span 1 - 1/4th Span

Comp.

40 KC

0.05375 (Comp.)

Not Stresses measured Within permissible limits

3 Soffit of 0.00387 arch-Span 1 - 3/4th Span

Comp.

20 KC

0.05375 (Comp.)

Not Stresses measured Within permissible limits

4 Springing 0.00037 level Span1-CR 0.0038 side

Ten.

20 CK

Comp.

20 KC

0.011 (Ten.) 0.05375 (Comp.)

Stresses Within permissible limits

Ten.

5 CK

Comp.

QS

0.011 (Ten.) 0.05375 (Comp.)

Stresses Within permissible limits

Comp.

10 CK

0.05375 (Comp.)

Stresses Within permissible limits

5 Springing 0.0034 level-Span 1 - K side 0.00160 0.0119 6 Soffit of arch-Span 2 - 1/4th and 3/4th Span

2.43

Measured response during speed test using formation 1; the results of quasi-static moving load test are also shown; x-axis is normalized to show the location of the leading wheel; CK: movement from Castle Rock to Kulem.

Measured response during speed test using formation 2; x-axis is normalized to show the location of the leading wheel; movement from Castle Rock to Kulem.

2.44

3. Influence Line Test Results Deflections measured during influence line test Following table gives the maximum values of deflections measured at crown as well as at springing levels across all episodes of testing. Springing Horizontal Deflections (in mm) Span 1 CR Kulem side side 0.10 0.17

Span 2 CR

Kulem

side side -1.42 0.01 & 1.21

Crown vertical deflection ( in mm)

Permissible value Both ends Span 1 Span 2 0.2

0.88

0.7

Permissible value 1.2

From the above table it may be seen that the horizontal displacement of the central pier at springing level is more than the limited values. This result may be due to de-lamination different types of materials i.e. masonry pier is jacketed with RCC. This is not to be considered as change of span.

Maximum strains measured on the two spans of the arch bridge in the Influence line load test Table below gives the maximum values of stresses measured across all episodes of testing in BM & SF test

2.45

Sl. Description

Actual

Type

Speed

Permissible

stresses measured (kg/mm2)

of stresses

of train

stresses as per design (kg/mm2)

Soffit of arch -Span 1 -

0.00123

Comp.

Quasi Static

0.05375 (Comp.)

Crown

0.00102

Ten.

(QS)

0.011 (Ten.)

Soffit of arch - Span 1 1/4th Span

0.00446

Comp.

Quasi Static

0.05375 (Comp.)

Within permissible limits

3

Soffit of arch 0.00172 -Span 1 - 3/ 0.00606 4th span (K)

Comp. Tensile

Quasi Static

0.05375 (Comp.) 0.011(Ten.)

Within permissible limits

4

Springing level - Span 1-CR

0.00282

Comp.

Quasi Static

0.05375 (Comp.)

Within permissible limits

5

Springing level Span 1, (K)

0.00161 0.00006

Comp. Ten.

Quasi Static

0.05375 (Comp.) 0.011 (Ten.)

Within permissible limits

6

Soffit of arch 0.011 -Span 2 -3/ 0.00033 4th span (K)

Comp. Ten.

Quasi Static

0.05375 (Comp.) 0.011(Ten.)

Within permissible limits

N.

1

2

Remarks

Within permissible limits

(CR)

4. Results of the Longitudinal Force Tests The main objective of this test is to determine the stability of the structure when subjected to extreme horizontal loads such as due to braking on the bridge or accelerating from rest on the bridge

2.46

Figure above shows the maximum strains measured at different points on the arch surface when the design train (formation 2) passed from Kulem to Castle Rock at maximum speed of 36 kmph. The force in tons (as high as 34 t) acting on the rails at different points is also shown. Figure below shows the maximum strains measured at different points on the arch surface when the design train (formation - 2) passed from Castle Rock to Kulem at maximum speed of 20 kmph with dynamic brake applied in the active WDG4s with the first axle of the leading WDG4 in the middle of span 1.

2.47

Following table gives the values of Horizontal Forces transferred to the Rails in Longitudinal Load Test Test Type

Tractive Force Force at Force transferred to rails (T) Remarks applied by Loco. Coupler as On rails in On rails (As shown in the measured Approach over Bridge loco screen of (Tons) (2 Rails) WDG4) (T)

Coupler Test 52.4T X 3=156* Design train - first axle of third WDG4 at right springing (CR) of span 1 and accelerating with full tractive effort

94.12

35.56

Maximum values reported are at different time

Design Train from 53.2 X 3 = 159.6 *Not Kulem to CR at measured 36 kmp

109.36

46.99

instances and should

Design Train, third 52.4 X 3 = 157.2 *Not WDG4 first axle at measured K-side springing of Span 2 and accelerating at full tractive effort

138.44

134.76

not be algebraically added

Design Train, third 52.6 X 3 = 157.8 *Not WDG4 first axle at measured mid-span of Span 1 and accelerating at full tractive effort

95.08

32.35

Design Train from 25.6 X 3 = 76.8 *Not CR to Kulem at measured 20kmph with dynamic brake

123.3

44.06

Design Train from 53.6 X 3 = 160.8 *Not K to CR at 20 measured kmph with service brake

95.79

40.09

Brake-binding Test

45.61

30.3

53.2 X 3 = 159.6

89.06

Not measured

2.48

Similarly following table gives the maximum values of measured tangential stresses and displacements in the Longitudinal Test Sl. Description N. 1

2

3

3

4

5

Soffit of arch -Span 1 Crown Soffit of arch Span 1 1/4th Span (CR side) Soffit of arch Span 1-3/4th Span (K side) Springing level-Span 1 (CR side) Springing level-Span 1 (K side) Soffit of arch Span 2 3/4th Span (K side)

Actual stresses (kg/mm2) 0.00199 0.00308 0.00568 0.00395 0.00310 0.0038 0.0034 0.00439 0.0304 0.0099 0.0123 0.0102

Type Speed Permissible of of train stresses stresses (kmph) (kg/mm2) Ten 20 0.011 (Ten.) Comp. 5 0.053 (Comp.) Comp. 5 0.053 (Comp.) Ten. Accele0.011 ration (Ten.) Comp. 20 0.053 (Comp.) Ten. Acceleration 0.011 (Ten.) Ten. Accele0.011 ration (Ten.) Comp. 36 0.053 (Comp.) Ten. Brake 0.011 binding (Ten.) Comp. Brake 0.053 binding (Comp.) Comp. 30 CK 0.053 (Comp.) Ten. Accele0.011 ration (Ten.)

Remarks

Within permissible limits Within permissible limits Within permissible limits Within permissible limits Codal clause violated in tension Within permissible limits

C) Comparision of instrumentation results with ring 1.5 software results : Analysis of the arch bridge was carried out using RING 1.5 software. Loading considered as MBG-1987 and also 2 WDG4 loco with 2 Nos BOXNEL loaded to 25 T axle load. Critical load factor is achieved as 2.76 when the compressive strength is restricted to 20 N/mm2 against the observed compressive strength of the masonry as 40 N/mm2.

2.49

The mean normal stresses calculated as per the software comes to 5.4 N/ mm2 and 0.536 N/ mm2 in the arch soffit and in the pier at foundation level respectively. These stresses are much lower than the allowable compressive strength of 40 N/mm2. This means that failure in the arch is not due to failure of masonry but due to function of mechanism. In addition to the above bridge, all the Arch bridges available over S W Railway have been analyzed in detail using the ring 1.5 software. The summery of the result is tabulated as below. Division

Total No. of arch No. of bridges No. of bridges for bridges available analyzed which F S less than 1.5

Bangalore

148

148

01

Mysore

293

293

57

Hubli

167

135

8

Total

608

576

66

D) Finite Element Analysis The masonry arch bridge with a soil infill has been idealized as composed of two isotropic homogeneous materials, namely, masonry and filler. A two dimensional plane stress model of the bridge has been used in this study. The finite element package ATENA encompasses many material model formulations for quasi-brittle concrete like materials, such as a bi-axial failure surface with different tension and compression thresholds, post crack strain softening based on exponential and multi-linear softening, specific fracture energy of the material, compression softening in cracked concrete and other fracture based parameters, such as crack interface shear transfer. A two-dimensional plane stress finite element model for the masonry arch bridge is shown in Figure. The brick masonry has been assumed to have a modulus of 1800 MPa and a Poisson’s ratio of 0.2. The soil infill has been idealized to have modulus of 800 MPa with a Poisson’s ratio of 0.18. A relatively small tensile strength of 0.3 MPa has been assumed for the masonry with a similar value of 0.3 MPa for the infill. These values are obtained through an iterative process of model calibration using the field measurements of the static load – deflection and quasi-static moving load studies. The boundary condition on the

2.50

vertical face of the abutment (Kulem end) is restrained in the longitudinal traffic direction and the base of the abutments and central pier have been constrained in the vertical direction. The boundary at the Castle Rock side abutment has been elastically constrained for longitudinal movement using linear springs

Finite element model with boundary conditions

Loads on the finite element model

Contours of displacement in y-direction (in m) under self weight

2.51

Displacement mm LVDT6

Displacement mm LVDT2

Contours of stress component σxx in Pa due to self-weight

Comparison of FEM predictions with measurements during speed test using formation 1. the formation moves from Castle Rocck to Kulem at 30 kmph. Based on the dynamic analysis, the first four natural frequencies are in the range of 5 - 11 Hz as observed from the field measurements.

2.52

E) Residual life of the Bridges The stress based computation estimates the factor of safety to be 1.5 for one million cycles. Here, each cycle corresponds to the passage of one train (CC+8+2), assuming ten trains passing on the bridge per day. Sl.No Br. No.

Type of bridge

1 2

Arch bridge Arch bridge

66 86

O W G Bridge Plate Girder Bridge Plate Girder Bridge

520 411 411

323 34 45

128 20

139 A 3 102

Stress Based Fatigue Life (In years)

Remarks

Time required for an initial crack of 0.1 mm to develop 10 mm

F) Results of Instrumentation The preliminary analysis carried out based on the field data are matching with the theoretical values and codal provisions. 

Load factor is coming as almost 2.5 by instrumentation. So, all existing arch bridges in good condition are fit for heavy haul of 25 T or more axle load. This value is nearly equal to the value obtained by arch ring 1.5 and modified MIXIE method



Dispersion of longitudinal force in approaches is considerable and more than 25%.



A static and slow moving axle load is more critical than fast moving axle load. So over bridges in good condition, no speed restriction should be normally imposed for carrying heavy axle load



All bridges appears to be safe based on the study report except for dynamic amplification factor which exceeds the codal provisions.

2.53

Conclusions Introduction of higher axle loads in actual field started in the year 2006. Since then a close watch has been kept on all the bridges, to observe any abnormal behaviour of the structure and any symptoms of cracking, bending, bulging due to over stressing of the members. With the experience so far has been: (a) Behaviour of both sub structure and super structure of the bridges is satisfactory under higher axle load trains (CC+8+2). (b) No adverse effect or distress is noticed in the bearings and in the superstructure. The isolated cases of bed block failures were reported in SKLR-SBHR section but these were not found to be related to higher axle loads. (c) All the arch bridges are being kept under close watch. So far none of the Arch bridges have showed any signs of distress. (d) There are 11 bridges where tractive effort had to be restricted to 30T for WDG4 MU operation. There bridges were provided boards at their approach to caution the drivers and Locos are provided with tractive effort limiting switch. The system has worked satisfactorily and no adverse effect has been noticed on these bridges. In the meantime, the strengthening works have also been completed. (e) Result of the instrumentation indicates that existing bridges are safe under higher axle load train operation.

***

2.54

Strengthening of Bridges on Feeder Routes to Eastern and Western Dedicated Freight Corridors

V. K. Govil* S.N. Singh** Ashish Agarwal*** Synopsis : Certain routes on IR have been identified as feeder routes to Eastern and Western Dedicated Freight Corridors. These feeder routes are required to be strengthened as per loading prescribed for that. IR has bridges built to various loading standards. Bridge Rules came in 1892, while there are bridges constructed prior to that. It is necessary to understand the comparison of various loadings to precisely assess their effect on super-structures and sub-structures. This paper analyses the various issues involved and strengthening

required. 1.0 Introduction 1.1 Various feeder routes identified to Eastern and Western Dedicated Freight Corridors are as below:1.1.1 Eastern Feeder Routes S. No.

Section

((i) (ii) (iii) (iv)

Sonnagar-Garwa Road-Barkakana Patratu –Gomoh including PD Branch Line Sonnagar – Gaya – Gomoh Gomoh-Pradhakhunta (39 kms.) including Kusunda Tetulmari (4.5 kms.), Katarasgarh – Nichitpur, Pradhankhunta – Pathardih links (24 kms.) Chandrapura – Dhanbad Gomoh – Chandrapura in Gomoh – Chandrapura – Kokar – Muri – Chandil – Sini section

(v) (vi)

**EDCE/B&S, Railway Board **CBE, Western Railway ***XEN/Design, Western Railway

2.55

Approx. Length (kms.) 311 128 249

67.5 36 216.34

(vii)

Dhanbad – kartrasgarh – Jamuniatar – Chandrapura

35.6

(viii)

Pradhankhunta-Asansol-Andal including coal branch lines

75

(ix)

Andal-Sainthia

151

(x)

Dankuni – Andul in Dankuni – Andul – Panskura – Haldia section

144.57

Dankuni – Dumduam Jn. – Ballugunj Jn. – Diamond Harbour – Baliganj Jn. – Budge Budge

101

(xii)

Bhojidih – Mohuda - Gomoh

36

(xiii)

Tatanagar - Chandil

—

(xiv)

Chandil – Bhojidih – Mohuda - Gomoh

—

(xv)

Andul – Panskura – Haldia in Dankuni – Andul – Panskura – Haldia section

—

(xi)

(xvi)

Aligarh – Hardua ganj

15

(xvii)

Kanpur - Paricha

219

(xviii) Mugalsarai – Unchahar via Janghai, Phaphamau

205

(xix)

Varanasi – Sultanpur – Ulratia – Rosa

558

(xx)

Zafrabad – Tanda

99

(xxi)

Ludhiana – Beas – Govindwal Sahib

112

(xxii)

Rajpura – Dhuri – Bhatinda (Lehra Mohabbat)_

173

(xxiii) Hissar – Bhatinda – Suratgarh — Biradhwal 1.1.2

320

Western Feeder Routes

S. No.

Section

Approx. Lenght (kms.)

(i)

Pipavav — Surendranagar – Viram — Mehsana

395

(ii)

Kandla Port – Gandhidham – Samakhiali — Palanpur

312

(iii)

Mundra Port – Gandhidham

66

(iv)

Viramgram — Samakhiali

182

(v)

Hazira – Surat

40

(vi)

Ludhiana – Hisar – Rewari

348

(vii)

Mumbai Port – Wadala – Kurla – connectivity with DFC

36

2.56

1.2 Approximately 4500 kms. of feeder routes is involved on eight zonal railways viz., CR, ER, ECR, NR, NWR, NCR, SER and WR. 2.0 Loading Standard for DFC Feeder Routes (i) Bridges being rebuilt of DFC feeder routes should have the substructure rebuilt on DFC loading (32.5t axle load) provided in IRS Bridge Rules vide correction slip No.39. Super structure of these bridges would be rebuilt to 25t loading – 2008 provided in IRS Bridge Rules vide correction slip No.38. (ii) Other bridges on DFC feeder routes requiring rehabilitation/ strengthening should have required works carried out for 25t loading – 2008 provided in IRS Bridge Rules. 3.0 Comparison of 25t Loading -2008 with BGML, RBG and MBG Loadings 3.1 Comparison of EUDL for Bending moment (BM) Comparison of EUDL for bending moment alongwith CDA for 25t loading -2008 with BGML, RBG and MBG loadings for various spans is as below:Comparison Of EUDL For Bending Moment With CDA S . Clear Effective B G M L span span (m) (m)

RBG

MBG

1

91.6

100

1.83

2.21

91.6

2

3.05

3.45

104.8

102.1

3

6.10

6.91

184.18

167.11

4

9.15

10.00

221.83

189.93

5

12.20

13.10

256.79

6

18.30

19.40

7

24.40

8

30.50

9

45.70

25t % % % LOADING- VARIA- VARIA VARIA 2008 TION TION TION OF 25t OF 25t OF 25t loading- loading- loading2008 2008 2008 w.r.t. w.r.t. w.r.t. BGML RGB MBG 100

+8.40

+8.40

0.00

104.8

107.83

163.26

170.61

+2.81

+5.30

+2.83

-7.95

+2.05

+4.31

185.30

184.80

-20.04

-2.78

-0.27

226.51

237.29

237.25

-8.24

+4.52

-0.02

315.64

275.38

286.49

300.63

-4.99

+8.40

+4.71

25.60 31.90

370.39

328.94

343.52

363.02

-2.03

+9.39

+5.37

422.33

379.54

397.78

423.26

+0.22

+10.33

+6.02

47.24

554.41

500.41

535.32

573.09

+3.26

+12.68

+6.59

2.57

Above comparison of EUDL for BM+ CDA indicates as below:(i)

EUDL for BM+CDA for 25t loading-2008 is on higher side for smaller span sizes such as 1.83m, 3.05m and 6.10m in comparison to BGML loading. Thereafter values for BM+CDA for 25t loading is on lower side for span up to 24.4m in comparison to BGML loading and thereafter it increases again for higher spans.

(ii) EUDL for BM+CDA for 25t loading-2008 is generally on higher side in comparison to RBG loading, except for 9.15m span. (iii) EUDL for BM with CDA for 25t loading-2008 is almost within variation of 5% up to 18.3m span in comparison to MBG loading. It increases consistently beyond span 18.3m for 25t loading2008 in comparison to MBG loading.

2.58

3.2 Comparison of EUDL for Shear Force Comparison of EUDL for Shear Force with CDA S . Clear span (m)

OVER ALL SPAN (M)

BGML

RBG

MBG

25t % % % LOADING- VARIA- VARIA VARIA 2008 TION TION TION OF 25t OF 25t OF 25t loading- loading- loading2008 2008 2008 w.r.t. w.r.t. w.r.t. BGML RGB MBG

1

1.83

2.58

90.6

90.32

91.5

94.5

+4.13

+4.42

+3.17

2

3.05

3.9

118.2

108.03

118.95

120.94

+2.27

+10.68

+1.65

3

6.10

7.09

173

152.09

164

166.17

-4.11

+8.48

+1.31

4

9.15

10.2

210.9

189.42

210.6

210.6

-0.14

+10.06

0.00

5 12.20

13.3

249.3

220.56 255.75

258.75

+3.65

+14.76

+1.16

6 18.30

19.65

329.3

294.03

329.25

0.00

+10.70

+0.68

7 24.40

26.05

406.5

365.18 408.75

432

+5.90

+15.47

+5.38

8 30.50

32.45

486

440.61 489.24

522

+6.90

+15.59

+6.28

327

EUDL for shear force with CDA for 25t loading-2008 is generally more than that for BGML, RBG & MBG loadings. 3.3 Comparison of Longitudinal Forces Longitudinal forces for 25t loading-2008 vis-à-vis BGML, RBG and MBG Loadings is as under: Comparison of Longitudinal Force with Dispersion S . Clear Loaded span Lenght (m) SPAN (M)

BGML

RBG

MBG

25t % % % LOADING- VARIA- VARIA VARIA 2008 TION TION TION OF 25t OF 25t OF 25t loading- loading- loading2008 2008 2008 w.r.t. w.r.t. w.r.t. BGML RGB MBG

1

1.83

2.58

1.89

0.00

0.70

5.00

+62.26 +100.00 +86.00

2

3.05

3.90

5.49

6.50

9.00

15.50

+64.58

+58.06

+41.94

3

6.10

7.09

16.84

6.50

17.30

17.32

+2.77

+62.47

+0.12

4

9.15

10.20

20.97

11.50

34.00

33.98

+38.29

+66.16

-0.06

2.59

5 12.20

13.30

24.51

21.50

34.00

47.00

+47.86

+54.26

+27.66

6 18.30

19.65

29.65

34.00

56.25

56.22

+47.26

+39.52

-0.05

7 24.40

26.05

32.59

44.00

62.48

63.00

+48.27

+30.16

+0.83

8 30.50

32.45

38.60

52.50

75.00

74.97

+48.51

+29.97

-0.04

On comparison of longitudinal forces along with dispersion for 25t loading-2008 with BGML and MBG Loading the observations are as under: (i)

Longitudinal force (LF) in bridges of MBG, RBG and BGML loadings of span lesser then 6.1 m even after dispersion is more in 25t loading-2008. For span lesser than 6.1 m there is a possibility of substructure built in MBG, RBG and BGML loading getting failed due to 25 t loading-2008.

(ii) LF in bridges of MBG loading of span up to 30.5m is almost same as for 25t loading- 2008 except for span 12.2m. Substructures built in MBG loading requires checking for 12.2 m span and for span higher than 30.5 m. (iii) F in bridges of BGML standard is lower than 25t loading-2008 except it is almost same for 6.1m span. There is a higher possibility of substructures except 6.1m span built up in BGML loading getting failed in 25t loading-2008 and requires checking. 2.60

(iv) LF in bridges of MBG loading of span up to 30.5m is almost same as for 25t loading- 2008 except for span 12.2m. Substructures built in MBG loading requires checking for 12.2 m span and for span higher than 30.5 m. 4.0 Issues Related to Checking of Existing Bridges to Loadings Standard of Feeder Routes 4.1 Existing bridges are required to be checked for their suitability for loading requirements of DFC feeder routes brought out in para 2.0. While doing so, it has to be kept in view that on IR bridges are conforming to various loading standards, viz. (a) Bridge rules came in 1892. (b) Prior to 1892, bridges were built according to the Britain Board of Trade Rules, which did not specify the longitudinal loads. (c) Provision of longitudinal forces first appeared in bridge rules in 1923. (d) Detailed provisions on longitudinal forces were made in Bridge Rules – 1926. (e) BGML-1926 – prescribed train load of 7.67t/m with maximum TE of 47.6t for two loads. (f) RBG – 1975 – prescribed train load of 7.67t/m with maximum TE of 75t for two loads. (g) MBG – 1987 – prescribed train load of 8.25t/m with maximum TE of 100t for two loads. 4.2 Besides the issue of bridges built to various loading standards, it is also important to consider that on IR, there are two types of super-structures, viz. standard spans to RDSO drawings and nonstandard spans to zonal railway drawings. For standard spans, RDSO has issued various drawings for steel and RCC/PSC super-structures. For non-standard spans and even in some cases for standard spans, drawings have been developed by railways. For sub-structure bridge drawings, by and large, railways have their own designs/drawings. 4.3 Checking of non-standard super structures and all sub-structures has to be done by the railways. However, suitability of RDSO’s standard steel and RCC/RSC super structure drawings designed to various loading standards for 25t loading – 2008 have been checked

2.61

and advised to zonal railways by RDSO and briefly the same is as below:4.3.1 RDSO standard steel super structure (a) All steel standard spans are fit for 75 kmph speed, except 76.2m open web girders to RBG loading, which is fit for 50 kmph. (b) Bearings strengthening works required for bridges 24.4m span and above. 4.3.2 RDSO standard RCC/PSC super structure (a) RCC box to MBG loading are safe. (b) RCC slabs of span 0.61m, 0.915m, 1.22m, 1.83m, 2.44m of RBG and MBG loadings are fit for 75 kmph. (c) Pre-tensioned PSC slabs for spans 3.05m. 3.66m, 4.57m, 6.10m and 9.15m of MBG loading are safe for 75 kmph. 4.4 Though it is apparent that many of standard steel and RCC/PSC super-structures are coming safe for 25t loading-2008 with restricted speeds after doing bearing works, sub-structure would be critical primarily from considerations of increase in longitudinal forces. Therefore, though major works in super-structures may not be necessary, except on condition basis etc., major works of strengthening of sub-structure would be required. 4.5 Arch bridges : These should be checked by Ring 1.5 and Ring 2.0 provided physical conditions are satisfactory. Considerations be made for adequate barrel length, drainage, cushion, physical condition, performance of repairs undertaken, etc. 5.0 Recommendations While deciding strengthening works required, have considerations for following:

Design loading standard of the bridge.



BGSL (BGML+BGBL) came in 1926 – Bridges constructed earlier require special scrutiny.



Existing load running pattern on the routes – CC+8+2/CC+6+2 and response of the bridges to same.



Compare theoretical stresses under design load, load actually running and 25t loading – 2008. 2.62



CDAs given in Bridge Rules para 3.3.1 are for 125 kmph speed.



As per clause 2.8.3.1 and 2.8.3.4 of Bridge Rules – dispersion of longitudinal force not be taken for design of new bridges but upto 25% of longitudinal force can be dispersed while checking existing bridges.



Attention also invited to CS No.23 of IRS bridge sub-structure in code which reads as below:

“Whenever it is not possible to carry out theoretical checks, or wherever the results of theoretical checks are found to be inconsistent with the physically sound condition of an existing bridge, running of locomotives and rolling stock with heavier tractive force / braking force may be permitted subject to physical condition being certified and bridges being kept under close observation, as considered necessary by the Chief Engineer. In such cases, the increase of tractive and/or braking forces shall not be more than 20% over bridges above the level of tractive and braking forces running over the bridges for the past one year or so.” 

For standard spans, suitability of super-structure for 25t loading -2008 issued by RDSO be referred.



As longitudinal forces are more in 25t loading- 2008, suitability of sub-structure needs to be adequately evaluated from various considerations brought out above.

***

2.63

Formation Design and Specification for Heavy Axle Load on Indian Railways J. C. Parihar* J. S. Sondhi** Rajesh Agarwal*** Synopsis : Indian Railways have entered the era of heavy axle loads by running of CC+6+2 & CC+8+2 loadings and have also started construction of ‘Dedicated Freight Corridors’. Provision of blanket layer on top of formation is essential to construct stable formation, suitable for running heavy axle loads. Design of formation layers including blanket has been be re-looked into for catering heavy axle load train operation.

The present paper discusses & suggests the specifications & thickness of blanket layer For IR, suitable for heavy axle load train operations for different axle loads with incorporation of new features like, two layered concept of blanket layer & layer of prepared subgrade, which also covers additional Filter Criteria & Los Angles Abrasion Value for blanket material. Similar to highways & some other railway systems, CBR value of soil & blanket material have been recommended for material selection & formation design. 1.0 Introduction Over the years, increase in traffic and speeds have placed a greater structural demand on conventional track, constructed initially to cater for much lighter traffic. Gradual improvement to track support system however, remained confined to track superstructure, i.e. rails, sleepers, fastening etc. The sub-structure below sleeper level remained practically unchanged. Provision of blanket on top of formation has become a necessity. Due to non-provision of blanket, large stretches of track on Indian Railways are having speed restrictions, uneconomical maintenance practices as well as have become an impediment in the introduction of higher speed and higher axle loads viz. CC+8+2 loading & 25 T. *Sr. Executive Director/Geo-technical Engineering/RDSO **Divisional Railway Manager/Lucknow/Northern Railway, ***Director/Geo-technical Engineering/RDSO

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Traditionally, blanket layer of single specified material, as thick as 1 meter or more, was recommended, which becomes very costly & difficult to provide. Under the circumstances, multi-layered system of formation layers for use in top portion of formation has been evolved & recommended from strength as well as economic considerations. 2.0 Historical Developments on Blanket Layer 2.1 Provision of blanket layer on Indian Railways was stipulated in August-1978 for the first time in the ‘Guidelines for Earthwork in Embankments & Cuttings of New Construction, Doubling & Conversion Projects’, for a thickness about 30cm in ordinary clayey soil & 60cm, if formation soil is weak. Subsequently, in “Guidelines for Earthwork in Railway Projects” May 1987, one metre thick blanket layer was recommended for all new constructions, keeping the future growth of traffic densities and axle loads as well as the experience with already existing troublesome formations. 2.2 Later, Railway Board, vide their letter no. 90/CEII/SF/9, dated 12.4.1991, and modified provisions of “Guidelines for Earthwork–1987 to provide blanket (not be less than 30cm) duly taking into account the type of soil, rainfall and density of traffic and other factors relevant to the site conditions. It further stipulated that Sub-ballast of 15cm depth below the ballast layer, comprising of locally available coarse material so as to serve as an effective medium between the formation earth and ballast stone may be provided, if decided by Chief Engineer (Const.) in-charge of the project”. The instructions regarding thickness of blanket were again modified in terms of Railway Board’s letter no. 94/CE-II/MB/2, dated 10.12.98 recommending blanket thickness based on axle load, GMT & speed. 2.3 In August 2001, committee of four SAG officers recommended provision of blanket thickness based on various soil types, which has subsequently been adopted in RDSO’s revised ‘Guidelines For Earthwork in Railway Projects : July 2003’. 3.0 Functions of Blanket Layer 3.1 Blanket is a layer of coarse grained material between ballast and sub-grade, spread over entire width. On some other railway systems of the world, this layer is also called as sub-ballast. Provision of blanket layer helps in :

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1.

Improving the bearing capacity by modifying the stiffness and achieving a better distribution of transmitted loads on the subgrade soil, thus preventing ballast penetration into the formation.

2.

Reduction of induced stresses on the top of sub-grade to a tolerable level.

3.

To prevent mud pumping and fouling of ballast by upward migration of fine particles from the sub-grade.

4.

To prevent damage of sub-grade by ballast.

5.

Shedding surface water from the ballast and help drain it away from the sub-grade.

6.

Protection of sub-grade against erosion and climatic variations.

Thus, blanket layer serves Stress Reduction Function as a Primary Function and Separation Function, Drainage Function & Prevention of Mud Pumping, as Secondary Functions. These functions are fulfilled effectively, if specifications of blanket material are such that : i) The material is coarse grained, hard and well-graded and ii) Maximum percentage of fines (particle size less than 75 microns) present in blanket material is limited to 10% to 12%. Allowing more fines in blanket material leads to plastic behaviour of blanket material but a minimum percentage of fines are required to give binding property to the blanket material. 4.0 World Railway Practices –Blanketting Benchmarking 4.1 European Railways (UIC) : As per UIC code 719 R, 2008, minimum thickness (e) of track bed layers is given by the formula; e = E + a + b + c + d + f as per figure 1.

Fig. 1. Components of Formation in UIC

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where, e = Total depth of ballast & blanket E = Factor depending upon quality class of soil used in prepared subgrade a = Factor depending on UIC groups based on GMT b = Factor depending on type & length of sleeper c = Factor depending on different working conditions on existing lines d = Factor depending on axle load of hauled vehicle f = Factor depending on inclusion of geo-textile based on quality class of prepared sub-grade. The values of above factors, as given in the UIC-719R, 2008 code are as under: E = 0.70 m For QS1 soils used as prepared sub-grade E = 0.55 m For QS2 soils used as prepared sub-grade E = 0.45 m For QS3 soils used as prepared sub-grade (Thickness of prepared sub-grade varies from 35 cm to 50 cm) a=0

For UIC groups 1-4

a = -0.10m

For UIC groups 5 & 6

b=0

For wooden sleepers of length 2.60m

b = (2.50-L) / 2

For concrete sleepers of length L (b in m, L in m, if L > 2.50m)

c=0

For usual dimensions

c = -0.05 m

For difficult working conditions on existing lines

d=0

For 200 kN axle load

d = 0.05 m

For 225 kN axle load

d = 0.12 m

For 250 kN axle load

f = + Track bed must include a geo-textile for soil of QS1 or QS2 class

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Soil Quality Classes QS0, QS1, QS2 & QS3 are defined in UIC Code are as under : Soil Type (Geo-technical Classification) Organic soils Soft soils containing more than 15% fines (1) with high moisture content: therefore unsuitable for compaction.Thixotropic soils (2) (e.g. quick clay) Soils containing soluble material (e.g. rock salt or gypsum)Contaminated ground (e.g. industrial waste) Mixed material/organic soils (2) Soft soils containing more than 40% of fines (1) (except for soils classified under 0.2)Rocks which are very susceptible to weathering, e.g. Chalk with ρd 40

QS1 (3)

Soils containing from 5% to 15% of fines (1) Uniform soil containing less than 5% of fines (1) (Cu d” 6)Moderate hard rock, e.g. : If 25 12 for a depth within 4 feet below sub-ballast should be avoided, if possible. 4.2.1 AREMA Specifications for Sub-ballast : i) Material to be used is similar to highway bases and sub-bases such as crushed stone, natural or crushed gravel, natural or manufactured sands, crushed slag etc. ii)

Sub-ballast shall be granular material so graded as to prevent penetration into sub-grade and penetration of ballast into subballast zone.

iii)

Filter principles should be used in drainage to the grading of sub-grade.

iv)

Maximum size of sub-ballast should not exceed maximum size of ballast.

v)

Not more than 5% of the sub-ballast should pass the no. 200 sieve (60 micron).

4.2.2 Filter Criteria Requirement : The two separation gradation for drainage filter criteria are : i) D15 (filter blanket) < 5 x D85 (sub-grade) ii)

D50 (filter blanket) < 25 x D50 (sub-grade) (Ratio of D50 in range of 9 to 30)

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Criteria ensures blocking the upward movement of particles at the coarsest end of protected soil (D85). iii)

Additional criteria to ensure adequate permeability to drain subgrade D15 (filter) < 20 x D15 (sub-grade) (Ratio of D15 in range of 6 to 18)

4.3 Blanket/Capping Layer In Australian Railways : Australian Railway Track Corporation provides 15 cm blanket/capping material over 0.5 m of sub-grade having CBR values more than 8 or over 1 m of sub-grade if its CBR is in range of 3 to 8 as shown in Figure 2 below :

Fig.2 Formation Details in Australian Railways

4.3.1 General Requirements of Blanket Material in Australian Railway : Material proposed for capping shall be a well graded natural or artificially blended gravel/soil. It shall have sufficient fines to permit it to be compacted to high densities by static or vibratory steel-tyred rollers or by ballasted pneumatic-tyred rollers. Materials such as natural ridge gravel, free from vegetable matter, ripped sandstones with low clay content and crushed and blended tough durable rock or slag, have been found to meet material properties of this specification. Natural gravels may be combined to provide material which conforms to this specification. Crushed rock shall include such added material as necessary for the combined material to satisfy the requirements of this specification.

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4.3.2 Particle Size Distribution : Material shall be well graded with typical particle size distribution as follows : Table 1 AS Sieve

Percentage Passing Nominal Size (20mm)

53 mm

100

37.5 mm

100

26.5 mm

100

19.0 mm

95-100

9.5 mm

-

4.75 mm

-

2.36 mm

30-80

0.075 mm

6-10

4.3.3 Atterberg Limits : 

Liquid Limit

:

Maximum 30 (35 for arid areas)



Plastic Limit

:

Maximum 20



Plasticity Index

:

2 -10 (2 -15 for arid areas)



Linear Shrinkage :

Maximum 3%

4.3.4 Maximum Dry Density : Minimum .2.0 t/cum 4.3.5 Soaked CBR : Min. 50%, determined on material compacted to 95% of MDD. 4.3.6 Granular Layer Thickness based on ORE D117 Report and on Various Railways The relation between granular layer thickness versus sub-grade modulus according to ORE D117 for various Railways is reflected in the adjoining Figure. (Ev2) or CBR values or soil types are correlated to the granular layer thickness required. As can be seen, the required thickness e= (ballast + sub-ballast), for given sub-grade properties, differs on various Railways.

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Fig. 3 Ballast + Sub-ballast thickness versus sub-grade CBR/ Modulus (based: ORE D117, Design Handbook RP28)

5.0 World Railway Practices –Earthwork Benchmarking Various design methods of formation, particularly for blanket thickness, are in use in different railway systems. These are based on different properties of soil used in embankment construction which govern the behaviour of soil viz. percentage of fines (size less than 75 microns) present in the soil, CBR value of soil, undrained shear strength Cu of soil etc. These methods have been described briefly as under : 5.1 UIC method (Based upon fines in soil) : Basis of the design is mainly governed by the percentage of fines present in the subgrade soil. The different soils have been grouped in three soil groups viz. QS1, QS2 & QS3 based mainly on percentage of fines in the soil. The blanket thickness for a soil of a particular group has been determined for different axle load, speed, GMT and other parameters. This method has already been described briefly in para 6.1 which is based on UIC Code 719 R, 1994 and ORE report No. D - 117 RP 28. 5.2 British Railway Method (Based on Threshold Stress of soil) This method developed by British Railways in 1970s, deals with selecting the granular layer thickness based on threshold strength of the subgrade soil. The objective is to limit the stress on the subgrade soils to less than a threshold stress in order to protect against subgrade failure by excessive plastic deformation, more pertinent in case of cohesive soils.

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The threshold stress is determined from repeated load tests in which the cumulative strain of the soil layer is noted as a function of the number of loading cycles applied. For such (clay) subgrade soils, there exist a value of the stress below which soil will experience terminating deformation but if subjected to the stress value higher than that, the soil show non-terminating deformation ( i.e. the rate of cumulative plastic deformation is extremely rapid) and ultimately fails in shear. Such limiting value of the stress has been termed as threshold stress. Such soils subjected to repetitive triaxial tests in laboratory would fail before certain nos. of cycle ( typically 3000) application of test loads causing stress above the threshold stress levels. Design procedure involves determination of stress at top of subgrade due to design axle load including dynamic augment. Threshold stress is determined by conducting cyclic triaxial tests on soils. Blanket thickness is determined such that stress at top of subgrade due to moving axle load is less than threshold strength of the subgrade. In absence of cyclic triaxial tests, threshold strength of subgrade can be approximated as 45% of Unconfined compressive strength of (clayey) subgrade. Design curves for the subgrade giving the depth of granular layer (ballast & blanket) have been developed for different axle loads and threshold strength of soil, and given in ORE Report No. D-71 RP 12. 5.3 Association of American Railroads (AAR) Method ( by Li and Selig ) : The AAR method is based on the Li & Selig (1998) design approach developed for design of sub-grade, and adopted on American Railways System. Li & Selig (1998) based on detailed experimental observations, presented a rational design method and considered two failure criteria: (i)

Progressive shear failure

(ii)

Excessive plastic deformation

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Fig 4 . Sub-grade progressive shear failure

Fig. 5 : Excessive Sub grade Plastic Deformation (Ballast Pocket)

Design Criteria: The two criteria used to design the granular layer (ballast + sub-ballast) thickness on top of formation, for preventing subgrade failures, are based on: (i) limiting cumulative plastic strain at the subgrade surface, intended to prevent subgrade progressive shear failure, and (ii) criterion to prevent excessive sub grade plastic deformation. Both criteria need to be evaluated to determine the one that gives the larger granular layer thickness in each case. Design Procedure 1 - This design procedure is used for determining granular layer thickness based on criterion of limiting cumulative plastic strain at the subgrade surface. The design procedure consists of the following 3 steps: 1. Prepare the information required for the design, including:

Traffic conditions: Dynamic wheel load must be determined using eq. (i) or based on actual measurements, and the number of load repetitions for the design period must be determined using eq. (ii)

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(i)

(Pdi )= (1+ 0.0052V/D) Psi

(ii)

Ni = T / (8 Psi )

Where, Pdi - dynamic wheel load in kN, Psi

- static wheel load in kN,

V

– speed in kmph

D

– Wheel Diameter in meter,

Ni

– Number of load repetitions in the design period

T

– Total traffic tonnage for the design period

εpa - allowable cumulative plastic strain at sub grade top Allowable strain: 1. The magnitude of the allowable cumulative plastic strain at the sub grade surface εpa must be determined for a certain number of load repetitions (i.e. for the design period) Sub grade characteristics: The sub grade soil type, soil compressive strength σs and the soil resilient modulus Es must be determined. Granular material: The resilient modulus Es for the granular material must be specified. 2. Determine the allowable deviator stress at the sub grade surface. This can be done using the charts in Appendix A of AAR Report No. R-898. This is completely based on the information obtained from step 1, i.e. soil type, the allowable cumulative plastic strain at the sub grade surface for the design period, and the soil compressive strength. However as an alternative to the allowable strain determined from the first step, the allowable deviator stress at the sub grade surface may be selected directly at this step. 3. Select the required granular thickness to prevent the sub grade progressive shear failure as follows: 

Calculate the strain influence factor Ie by the equation, Ie= σda A/ Pdi Where σda = allowable deviator stress at the sub grade surface determined from step 2; Pdi = design dynamic wheel load

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determined from step 1; and A = area factor used to make the strain influence factor dimensionless. The area factor A is 0.645 m2 (1000 in2). 

Determine the value of H/L (H – Granular Layer Thickness & L – Length Factor) corresponding to the strain influence factor Ie using a design chart A2 in Appendix A of AAR Report No. R-898 (Li & Selig October 1996), for the values of granular layer resilient modulus Eb and the sub grade resilient modulus Es.



Multiply H/L by the length factor L to get the required granular layer thickness H. Length factor is used to make the design charts dimensionless. The L is equal to 0.152m (6 in).

Design Procedure 2 : This procedure is based on the criterion which limits total plastic deformation of the subgrade layer. The granular thickness design consists of the following 3 steps: 1. In addition to the information required in design procedure 1, design procedure requires knowledge of the thickness of the deformable sub grade layer T. The allowable cumulative plastic strain at the sub grade surface for design procedure 1 is replaced by the allowable total plastic deformation of the sub grade layer for design procedure 2. 2. Calculate the deformation influence factor Ip by the following equation (Li and Selig 1998): Ip =

ρa /L ——————— a (Pd /σs A)m Nb

x 100

Where: ρa = allowable total sub grade plastic deformation for the design period N = total equivalent number of load repetitions during the design period Pdi = design dynamic wheel load σs = soil compressive strength a, b, m = material (soil) parameters and A, L = area and length factors.

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3. Select the required granular layer thickness to prevent excessive sub grade plastic deformation as follows: 

Select the design chart as given in Appendix B that the best corresponds to the existing soil type, sub grade resilient modulus, and granular layer resilient modulus.



Calculate T/L (where T is thickness of deformable subgrade layer from bottom of granular layer to top of rigid layer) and locate the point in design chart as given in Appendix B corresponding to Ip and T/L. Obtain the value of H/L for that point, and multiply H/L by the length factor L to get granular layer thickness H.

6.0 Design Of Formation For 25, 30 & 32.5 T Axle Load On The Basis Of Different Methods : Calculations of blanket thickness requirement have been done based on above methods for 25T, 30T & 32.5T axle loads. These are as under : 6.1 UIC Method (Based on fines in Soil) :Recommendations have been made in UIC Code 719 for axle loads in range of 20 to 25 tonne. Since formation design is to be done for 30 T & 32.5 T axle loads, extrapolation has been done for 30 tonne and 32.5 tonne axle loads from UIC provisions. Keeping in view the other relevant factors, Speed, GMT, Sleeper Length suitable for Indian Railways, detail calculations of blanket thickness for various soils, based on UIC practices have been carried out. Calculated Thickness of blanket material & prepared sub-grade and type of sub-grade alongwith soil types as per IS Classification belonging to various ‘Soil Category SQ’ have been given in Table-2. Soil Categories SQ1, SQ1 & SQ3 have been modified slightly from UIC practices to suit Indian conditions & BIS Classification system. 1.

Thickness of blanket material has been worked out with the provision of 300mm ballast.

2.

Recommended blanket thickness is suitable for GMT >=25 & Speed < 160 kmph.

3.

Geo-textile should be provided below blanket layer, if prepared subgrade is of SQ2 soil.

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Table 2 - UIC Based Two Layers System of Blanketing On Track Formation (Ref : Calculations based on UIC practices in terms of UIC Code 719R-1994) Soil Quality Category in Sub-grade SQ1 SQ1 SQ2 SQ2 SQ3

Top Soil of Formation (prepared Subgrade) Quality Thickness (mm) SQ2 SQ3 SQ2 SQ3 SQ3

500 500 350 -

Recommended Thickness (mm) of Blanket for Axle Loads 25 T 30T 32.5 T 250 150 250 150 150

450 350 450 350 350

600 500 600 500 500

Soil Quality Class SQ1, SQ2 & SQ3 has been given in Table 3 below. Table 3 - Description of Soil Quality Class Soil Quality

Description w.r.t. FineParticles (size less than 75 micron)

Soils as per IS Classification Conforming to Referred Soil Quality

SQ1

Soils containing fines > 50 %

CL, ML, CL-ML, CI, MI, CH, MH

SQ2

Soils containing fines from 12% to 50%

GM, GC, SM, SC

SQ3

Soils containing fines < 12%

GW, GP, SW, SP, GW-GM, GW-GC,SW-SM, GP-GM, GP-GC, SP-SM, SP-SC

6.2 AAR Design (Selig Method) – Based on Cumulative Strain & Plastic Deformation Criteria Based on AAR method, as described in para 6.3 above, calculations have been done for 25, 30 & 32.5 T for different values of Compressive Strength, σs of soils. The results of

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calculated blanket thickness are given in Table 4 below. Table 4 - Calculation of Blanket Thickness (in cm) For different Axle loads & CBR of soil CBR (%) (Indic -ative value)

Subgrade Axle Load 25 T Axle Load 30 T Axle Load 32.5 T Compr essive From From MaxiFrom From MaxiFrom From MaxiStrength Cumulat- Cumulat- mum of Cumulat- Cumulat- mum of Cumulat- Cumulat- mum of ive Strain ive Defor two ive Strain ive Defor two ive Strain ive Defor two σs (kPa) Criterion mation Criterion Criterion mation Criterion Criterion mation Criterion Criterion Criterion Criterion

2

60

3

90

4

120

5

150

6

180

120

120

-

-

-

70

85

85

120

120

120

-

-

-

30

25

30

55

50

55

75

75

75

15

Nil

15

25

15

25

35

40

40

Nil

Nil

Nil

15

Nil

15

20

Nil

20

120

-

-

-

Note : 1. Value of T (here T is assumed as 2m), the depth of deformable layer is site specific. Hence, actual design may vary from site to site. 2.

AAR method is based on the approach that stress on subgrade is less than permissible strength such that plastic cumulative deformation does not take place over the design period.

3.

Calculations for granular layer thickness have been done using soil parameter & chart of CH type of soil assuming worst soil conditions.

The design calculations have been done with following assumptions of typical values or empirical relations :  Soil Compressive Strength, (in kPa) , σs = 30 x CBR  Elastic Modulus of ballast, Eb has been assumed to be 140 MPa.  Elastic Modulus of Soil, Es =10 x CBR (For CBR 5) (Ref : Page no 53 of IRC Guidelines for the Earth design of flexible pavements, IRC:372001)  Values of a, b & m for soil & Curves for Soil have used for CH type soil..

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Depth of deformable subgrade,T has been assumed as 2.0 m.



GMT is 30 and design period is 5 year. ( i.e. Total Design GMT is 150)



Permissible cumulative plastic strain, εpa at the end of design period is 2%.



Permissible cumulative plastic deformation at the end of design period is 25 mm.



Ballast Thickness is 30 cm.

7.0 Multi-layers System of Formation Design 7.1 From the observations of provisions of various World Railway Systems, it is evident that there is requirement & practice of not allowing poor soils in top one metre thickness of sub-grade and strengthening of about top 1 metre of formation is necessary with material of superior quality like blanket material. From the perusal of practices adopted in other leading railway systems, it is evident that multi-layer formation system – layers with adequate strength and stiffness to be adopted. Layers comprise of blanket layer, prepared subgrade/top layer of formation etc. is preferred in place of single layer blanket system. The specifications and thickness of various formation layers specified are in line with practices of UIC, AAR and other World Railways. 7.2 As on date, one metre blanket layer is being provided for 20.32T axle load train operation on Indian Railways with single type of material having superior specifications, which many a times is available at very high cost; thus it proves to be uneconomical. Also, dispensation to its provisions is normally granted by Railway Board on the requests of Zonal Railways. 7.3 It has also been observed that AREMA recommends for not using soil having plasticity index more than 12 in top 4 feet thickness of sub-grade; UIC provides layer of prepared sub-grade of 35 cm to 50 cm of better material and Australian Railways provide 50 cm to 1 metre of sub-grade having CBR value more than 8. 7.4 Similar to AAR, UIC or Australian Railways, total requirement of blanket layer can be provided with two types of materials, upper layer which is in contact with ballast can be of superior quality and lower layer which is in contact with sub-grade can be with

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specifications such that poor material should not appear in top portion of sub-grade. 7.5 Proposed thickness of blanket material & prepared sub-grade and types of sub-grade alongwith soil types as per IS Classification belonging to various ‘Soil Category SQ’ have been given in Table-2 & also shown in Fig.-3. Soil Quality Categories SQ1, SQ2 & SQ3 have been modified slightly to suit Indian conditions & BIS Classification system. 7.6 Prepared sub-grade should be preferable with SQ3 soils, having fines less than 12%. If prepared sub-grade is of SQ1 or SQ2 type soils, geo-textile layer shall be provided at junction of bottom of blanket layer & top of prepared sub-grade. It has been observed that formation consisting of soils having sufficient fines and having plasticity index more than 15 poses formation problems. Therefore, if SQ1 or SQ2 soils are used as prepared sub-grade, its Plasticity Index should not be more than 15. 7.7 From the stress analysis, it is evident that most of stresses for heavy axle load up to 32.5 T load are dissipated upto 1.5 m depth below bottom of ballast, thereafter the stresses are within tolerable limit of stresses including reasonable factor of safety for soils. The major stress region occurs upto depth of 1 to 1.5m below bottom of ballast. This region is to be provided with blanket layer which or in lower layers supplemented / replaced by prepared subgrade particularly in bottom portion. Also, below the blanket layer, the layer of prepared/ good imported soil with minimum prescribed CBR value is essential and has been recommended as prepared subgrade layer upto depth of about 1.5m below top of formation. 8.0 Formation Design Based on CBR Concept 8.1 From the ages, Highways system are using the CBR (California Bearing Ratio) as the basis for design of subgrade and Granular Sub-base (GSB – similar to blanket material in railways) and this system is still prevalent now. California Bearing Ratio (CBR) test is a penetration test developed by the California State Highway Department of USA for the evaluation of subgrade strengths for roads and pavements. California Bearing Ratio (CBR) is defined as the Ratio of Force per unit Area required to penetrate a soil mass with a circular plunger of 50 mm diameter at the rate of 1.25 mm/minute to that required for corresponding penetration of a standard material. From

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the perusal of UIC and Australian railways system of formation design, it is evident that they are also using the CBR value as the basis of selection of material viz. soil, blanket material and basis for design the thickness of various layers. 8.2 Indian Railways is also considered to adopt the CBR value as the criteria for selection of formation materials and design of formation since CBR value of soil gives direct indication of strength of soil and its behavior as a embankment material. This test is well established and easy to determine in the laboratory as per procedure laid down in BIS Code– IS : 2720 (part 16) – 1979. From the literature and experience, it has been established that Clayey soils with high plasticity i.e. CH & MH type have the CBR value less than 3 which should be avoided to be used in embankment. Prepared subgrade material which is to be used in top layer of formation should have CBR value more than 8 so that blanket thickness requirement is reduced substantially. Blanket material should have sufficient CBR value to avoid penetration of ballast particles into blanket layer. Thus, on Indian Railways, CBR value of soil which is used as embankment fill is recommended as minimum 3 and CBR value of prepared subgrade as a material for top layer of formation as a minimum 6-8 and for blanket material is decided as minimum 25. 8.3 Considering the relevant good features of Indian Highway system (Ref; Indian Road Congress Code, IRC:37 on ‘Guidelines & Design of Flexible Pavements) and foreign railway practices, strength based design system has been evolved. Minimum CBR value of subgrade/ prepared subgrade have been prescribed for selection of soil/material for the subgrade. 9.0 Revised Specifications of Blanket : 9.1 Specifications of the material for blanket layer over prepared subgrade should be such that it is well-graded sandy gravel layer of adequate hardness. Particles size gradation curve should be more or less within Enveloping Curves of blanket material as shown in Fig. 6 below & Grading Percentages within the range given in Table 5. below and should also have following criteria satisfied : i)

Cu > 7 and Cc between 1 and 3.

ii)

Fines (passing 75 microns) : 3% to 10%.

iii)

Los Angeles Abrasion value < 35%.

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iv)

Minimum required Soaked CBR value 25 of the blanket material compacted at 100% of MDD

In exceptional cases on technical and economic considerations, LAA value may be relaxed upto 35 % by PCE on Open Line & CAO/C in construction projects. v)

Filter Criteria should be satisfied with prepared subgrade/ subgrade layer just below blanket layer, as given below :

Criteria–1: D15 (blanket) < 5 x D85 (sub-grade) Criteria–2: D15(blanket) > 4 to5 D15 (sub-grade) Criteria–3: D50(blanket) < 25 x D50 (sub-grade) Filter Criteria is optional, at present. This can be adopted with the experienced gained of its compliance for different types of soils with blanket. Table 5. : Grading Percentage of Blanket Material SL

IS Sieve Size

Percent Passing (by weight)

1.

40 mm

100

2.

20 mm

80 - 100

3.

10 mm

63 - 85

4.

4.75 mm

42 - 68

5.

2 mm

27 - 52

6.

600 micron

13 - 35

7.

425 micron

10 - 32

8.

212 micron

6 - 22

9.

75 micron

3 - 10

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Fig. 6 : Enveloping Curves for Blanket Material

10.0 Qualifying And Quality Assurance Tests (Mandatory) : Qualifying tests as part of pre-selection of good earth for track subgrade, embankment fill is required to be carried out. Also, quality of compaction is required to be done to ensure good quality construction. i)

Selection of soil: For selection of soil to be used as embankment fill CBR test is required to be conducted on material. CBR test is conducted on ground soil, embankment fill, prepared sub-grade & blanket material to ensure the minimum specified CBR value of these materials to be used in construction. This test is carried out on soil sample in laboratory as per procedure given in IS:2720 (Part 16)-1987 & in field as per IS:2720 (Part 31)– 1969.

ii) Quality Assurance Test on Compacted Layer : Quality Assurance Tests are required to be conducted on part completion stages of formation, prior to clearing for further earthwork, track linking work: Heavy Proctor test is required to be conducted to determine the Maximum Dry Density of soil as per IS: 2720 (part 8). In-situ density is measured in the field by Sand Replacement Method (IS: 2720 – part 28) or Core Cutter Method (IS: 2720 – part 29) to calculate the degree of compaction. This shall be determined in laboratory as per BIS procedure with the specified frequency of earthwork quantity, as envisaged in ‘Guidelines of Earthwork in Railway Projects, GE:G-1, July 2003.

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Second Step Plate Load Test (Optional) is required to be conducted in-situ for measurement of Deformation Modulus EV2 of compacted layers of embankment, blanket, prepared subgrade etc. The test procedure has been detailed in German Code DIN:181342001,’Determining Deformation & Strength Characteristics Of Soil By Plate Loading Test”. The minimum value of EV2 should be ensured at different levels as specified. 10.1 Frequency of Quality Assurance Tests : a) CBR test for selection of formation materials and other tests required for ensuring conformation of the materials (blanket, crusher run) as per specification e.g. size gradation, Cu, Cc, Los Angles Tests, OMC/MDD etc. shall be conducted at following frequency : i) Embankment Fill : one set of tests for every 5000 cum ii) Prepared subgrade : one set of tests for every 2000 cum iii) Blanket material : one set of tests for every 500 cum b)

c)

In-situ Degree of Compaction (or In-situ dry density measurement) test shall be conducted on each compacted layers in random pattern at following frequency for the different layers : o

Embankment Fill : one density measurement at every 500 sqm surface area of each of the compacted layers

o

Blanket layer & Prepared Subgrade : one density measurement at every 200 sqm surface area of each of the compacted layers.

Second step Plate Load Test is optional quality assurance test on compacted surface. This should be done for EV2 measurement at top of each formation layers eg. at sub-soil, compacted subgrade, prepared subgrade, crusher run, blanket etc. at the frequency of one test per km length of section.

11.0 Ground Improvement Methods : 11.1 Field tests are required to be conducted on sub-soil strata, such as Plate load test for determination of Elastic Modulus at second loading (EV2), Standard Penetration test to determine N-value, and Unconfined Compression Test or Vane Shear Test to determine unconfined compressive strength or undrained cohesion, Cu. If values

2.85

of these test parameters, as specified in following para are not achieved then ground improvement is required. 11.2 For ground soil/ sub-strata layers with low bearing capacities, assessed by following evaluation parameters: (i)

Ev2 value less than 20 MPa, (Optional) or

(ii) undrained cohesion (Cu) < 25 kPa, or (iii) N-value (determined from Standard Penetration Test – SPT < 5, shall require Ground Improvement.

-

Strengthening of sub-strata soil layers can be carried out using one or more of the following techniques, like: removal and replacement ( R&R) of weak soil, stage constructions of the fill, preloading and surcharging, Installation sub drainage system, In-situ pile, Sand Gravel Compaction pile, Stone Columns

-

Vibro-floatation,

-

lime pile, Injection/ lime slurry pressure injection/ion exchange,

-

Stir & Mixing, Sand mat, Geosynthetics etc.

12. Formation Specifications for Heavy Axle Load : 12.1 The following Specifications for two different systems for blanket subgrade, embankment fill are mandatory provisions to be adopted, as follows: i) Conventional blanket layer over formation subgrade ii) Blanket layer over prepared subgrade layer (good/imported soil) Any of the two system may be considered for adoption in the field based on good soil availability and material cost economics. The detailed technical specifications for design of formation for heavy axle loads has already been circulated vide RDSO report no. RDSO/ 2007/GE: 0014 in Nov 2009 as approved by Railway Board vide letter no. 2007/CE-I/Geotech/02 dated 26.10.2009. 12.2 In order to design & construction of stable formation for heavy axle load, EV2 should be determined in the field as per procedure given in German Code DIN : 18134 at ground. Undrained shear

2.86

strength, Cu of ground soil from Unconfined Compression (UCC) test or Vane Shear Test and Penetration Number (N – Value) from Standard Penetration Test should also be determined. If EV2 value is less than 20 MPa or Sub-soil strata having (Cu) < 25 KPa (mostly in Marshy area) or N-value < 5 will also require ground improvement. 12.3 If, naturally available materials do not meet the desired specifications, blanket material can be produced by mechanical process from crushing or blending method or combination of these two methods. Naturally available sand, quarry dust or crusher run, if available at low cost, can be used as prepared subgrade also. 13.0 Cost implication for new specification - Case Study 13.1 Two case study have been done regarding cost implications for the projects involving earthwork and blanketing 13.2 Chandigarh Ludhiana Single Line : The work is presently going on with GE-G1 2003 specifications. The soil being used in embankment fill is SM type i.e. SQ 2 type as per new specification. The blanket is manufactured by Crushing and mixing methodology and found as per specification. The cost of the material including execution is as under Type of Material

Rate (in Rs./cum)

Rate of blanket material

948 (Actual)

Rate of SQ2 Soil (SM Type)

133 (Actual)

Analysis has been done for Bank Height of 1.75m ( maximum depth of variation in Formation Layers) The total cost as per GE- G 1 2003 is Rs 87,54,070 The total cost as per new specification is Rs 52,53,645 Hence there is 40% saving if the work is executed as per new specification 13.3 Manmadurai-Virudunagar Gauge conversion : The work is presently going on with GE-G1 2003 specifications. The soil being used in embankment fill is SM type i.e. SQ 2 type as per new specification. The blanket is manufactured by blending methodology and found as per specification The cost of the material including execution is as under

2.87

Type of Material

Rate (in Rs./cum)

Rate of blanket material

825 (Actual)

Rate of SQ2 Soil (SC Type)

180 (Actual)

Analysis has been done for Bank Height of 1.75m ( maximum depth of variation in Formation Layers) The total cost as per GE- G 1 2003 is Rs 82,82,025 The total cost as per new specification is Rs 55,11,750 Hence there is 33.4% saving if the work is executed as per new specification The cost implication has been worked out for RVNL projects also and it was found that there is huge savings with the implementation of new specifications. The saving has arisen because of less thickness of blanket material provided over the embankment fill/ prepared subgrade 14.0 Conclusions : 14.1 Running of heavy axle load requires design and construction of stable & durable formation to minimize in service maintenance. Proper selection of construction material viz. embankment soil, top layer of subgrade/prepared subgrade, blanket material is necessary based on some rational criteria like CBR value, size gradation etc. 14.2 Ground improvement in case of weak sub-soil strata and adequate quality assurance tests are essential to achieve desired quality of formation. The thickness requirement of sub-structure layers between ballast & sub-grade specially weak sub-grade for higher axle load is of the order of one metre or even more. Part of the blanket requirement can be substituted with good quality of soil as prepared subgrade layer resulting in economy as well as strength requirement. Mechanical production of blanket material to achieve desired specification is a viable alternative. 14.3 Recommended Multi-layer formation systems based on CBR value is better option and will result in reduced blanket requirement and economic formation system as per requirement of heavy axle loads including DFC. Thus, the new formation specifications are better for heavy axle load including DFC which will require minimum maintenance during operation.

2.88

References : (i) AREMA Manual, 2002 (ii)

Australian Railway (ARTC) Code RTS 3430, March 2006

(iii) Guidelines of Earthwork in Railway Projects, RDSO, No. GE:G-1, July, 2003 (iv) Heukelom and Klomp (1962): ‘Dynamic Testing as a means of controlling Pavements during and after Construction, Proceedings of 1st International Conference on Structural Design of Asphalt Pavements. (v)

State Of The Art Report On Provision Of Railway Formation, RDSO Report No. GE – 35.

(vi) State of the Art Report on sub-grade stress and design of track substructure, Civil Engineering Report No. C – 271. (vii) IRC:37- ‘Guidelines & Design of Flexible Pavement’, Indian Road Congress. (viii) ORE Reports D – 71, RP – 12 & D-117, RP 28. (ix) ‘Modern Railway Track’, Esveld, Conrad MRT Productions NL, TU Delft, Second Edition 2001. (x)

‘Procedure For Railway Track Granular Layer Thickness Determination’, Dingqing Li, Theodore R. Sussmann Jr., and Ernest T. Selig, Report no. R-898, October, 1996, Assosiation of American Railroads ( AAR), TTC, Pueblo, Colorado, USA.

(xi) ‘Design Issues and Sub-grade Assessment for the Rawang-Ipoh High Speed Track’, Sondhi, J.S., Dasari, G. Rao, and Tan, Siew Ann, RailTech Conference, Kuala Lumpur, Malaysia, 2003. (xii) Track Compendium– Formation, Permanent Way, Maintenance, Economics, by Dr. Bernhard Lichtberger, 2005, Eurail Press, Hamburg, Germany. (xiii) UIC Code 719: ‘Earthworks and Track-bed layers for Railway Line’, Third ed., 2008

***

2.89

Impact of Increasing Axle Load on Fatigue Life of Standard Steel Girder Bridges – A Study Based on Revised Fatigue Provisions

R.K. Goel* H.O. Narayan** Synopsis: Increasing the axle load of railway wagons has been a matter of concern for railway engineers as it’s effect on residual fatigue life of steel girder bridges was not clearly understood. There had been no accepted provisions or guidelines to assess the fatigue life of steel girder bridges till RDSO discussed the “Draft Provisions for Fatigue Assessment” in 78th BSC. The simplified approach of these provisions has been used to assess the design fatigue life of standard plate girder bridges for MBG loading and new 25 t Loading -2008 for different average annual GMTs of the routes. It has been found that the reduction in design fatigue life depends on the bridge span. The design fatigue life gets improved substantially, if the coefficient of dynamic impact (CDA) is controlled either by imposing speed restriction or by improving track maintenance on girder bridges. 1.0 Introduction 1.1 Indian Railway has recently permitted over utilization of carrying capacity of it’s wagons for generating extra revenue. This has increased axle loads of wagons. The magnitude of trailing load (TLD) has been increased from Carrying Capacity (CC) to CC+6+2 and subsequently to CC+8+2. A new loading standard 25 t loading -2008 has also been included in existing IRS Bridge Rules and this loading has been permitted on existing bridges. RDSO has also issued guidelines for running 25 t loading - 2008 on existing bridges. It is to be noted that most of the railway bridges have been designed for Indian Railways standard loadings such as BGML, RBG & MBG which are having varying equivalent uniformly distributed loads. The *Director/Steel Bridges - I/RDSO **Asstt. Design Engineer/B&S Directorate/RDSO

2.90

net effect of increased trailing load is to increase the number of cycles of maximum stress range to which the members are subjected and therefore greater fatigue damage is caused therein. The ultimate effect of running heavy axle load is thus, to reduce the residual fatigue life of the existing bridges. 1.2 The issue of revision of fatigue provisions in IRS steel bridge code had been under discussion for quite some time. Detailed studies have been carried out by RDSO on the issue and draft provisions have been issued for adoption. These provisions have also been discussed in 78th Bridge Standard Committee and as per Railway Board Orders the workability and suitability of these provisions is being ascertained before final adoption. In this connection a study on assessment of fatigue life of existing standard steel girders has been done by RDSO based on the simplified approach of the draft revised provisions. This paper presents the approach used and the results of study, showing the extent to which the fatigue life of standard steel girders has been affected by running 25 t axle load vis-à-vis MBG loading. 2.0 Simplified Approach of Revised Irs Provisions 2.1

Fatigue stress spectra

2.1.1 For the simplified fatigue loading the following procedure is adopted to determine the design stress spectrum. 2.1.2 The recommended equivalents for train loads shall be adopted in accordance with existing provisions of IRS Bridge Rules, including the dynamic impact factor Φ, which is calculated as (1.0 + CDA), where CDA is the coefficient of Dynamic Augment as specified in IRS Bridge Rules. 2.1.3 The maximum stress σP,max and the minimum stress σP,min should be determined for a detail or structural connection. The σP,max is for Dead Load + Full Live Load with dynamic impact factor ‘φ’ whereas the σP,min is for dead load effects only. 2.1.4 The reference stress range ΔσP for determining the damage due to the stress spectrum should be obtained from: ΔσP = | ΔσP,max - ΔσP,min | 2.1.5 The damage effects of the stress range spectrum may be 2.91

represented by the damage equivalent stress range related to 2 million cycles as ΔσE,2 = λ * Φ * ΔσP Where, λ is the damage equivalence factor, and Φ is the dynamic impact factor (1.0 + CDA), CDA is the coefficient of Dynamic Augment as specified in Bridge Rules 2.1.6 The value of damage equivalence factor, ‘λ’ are specific to the type of loading and the values are dependent on loaded length, ‘L’ which is defined in para 2.3.3. 2.2 Fatigue assessment The fatigue assessment shall be carried out by ensuring the satisfaction of the following criteria:

γFf *ΔσE,2 ≤ ΔσC / γMf Where, ΔσC is the reference value of the fatigue strength at NC = 2 million cycles γMf is the partial safety factor for material γFf is the partial safety factor for loads 2.3 Damage equivalence factors 2.3.1 The damage equivalent factor for railway bridges should be determined from: λ = λ1 * λ2 * λ3 * λ4 subject to the condition that λ ≤ λmax where λ1

is a factor that takes into account the damaging effect of traffic and depends on the base length of the longest loop of the influence line diagram 2.92

λ2

is a factor that takes into account the annual traffic volume in million tonnes

λ3

is a factor that takes into account the design life of the bridge in years

λ4

is a factor to be taken into account when the bridge structure is loaded on more than one track

λmax is the maximum l value taking into account the fatigue limit and is equal to 1.4 2.3.2 The loaded length for the determination of the appropriate λ1 should be taken as follows: (a)

for moments: - For a simply supported span, the span length, L - For cross girders supporting rail bearers (or stiffeners), the sum of the spans of the rail bearers (or stiffeners) carried by the cross girder.

(b)

for shear for a simply supported span - For the support section, the span length - For the mid-span section, 0.4 * the span under consideration

(c)

In other cases - the same as for moments

(d)

for truss members - base length of the largest loop of Influence line diagram

2.3.3 The value of λ2, in terms of the annual volume of traffic may be obtained from the following expression: λ2 = 0.5193 * Ta0.2036 Where Ta is the annual volume of traffic expressed in million tonnes.

2.93

2.3.4 Unless otherwise specified by the competent authority the value of λ3 will be taken as 1.04 for a design life of 120 years. For other values of design life the corresponding value may be calculated from the following expression where LD is the design life in years λ3 = 0.3899 * LD0.2048 2.3.5 The value of λ4, assuming 15% of the total traffic on both tracks crosses whilst on the bridge, unless specified otherwise by the competent authority, shall be obtained from λ4 = 0.7926 * a2 - 0.7280 * a + 0.9371 where a = Δσ1 / Δσ1+2 Δσ1 = Stress range at the section being checked due to train on one track. Δσ1+2 = Stress range at the same section due to train load on two tracks. The values of λ4 may be calculated for other proportions of crossing traffic from λ4 = 5 n + (1 - n) [a5 + (1 - a)5] where n is the proportion of traffic that crosses whilst on the bridge. 2.3.6 The value of λ should not exceed λmax which is specified as 1.4. 3.0 Determination of λ1 Parameters 3.1 The fatigue life assessment has been done for MBG loading and 25t loading as given in IRS Bridge Rule. The fatigue load model for these loading have been developed and λ1 parameters worked out in association with IIT/Roorkee using Artificial Neural Network Technique. 2.94

3.2 The value of λ1 is to be obtained from tables 1 & 2 for MBG loading and 25t loading - 2008 respectively as a function of the loaded length. These values have been worked out as per the train types included in the respective standard fatigue load models for MBG loading and 25t loading. The loaded length shall depend upon the influence line diagram of the structural detail/connection under consideration. 4.0

Assessment Method and Assumptions

(i)

Maximum stress range taken as the difference of dead load stress and the maximum stress likely to come in the member with DL, Impact load and live load. The maximum bending stresses due to equivalent uniformly distributed load for IRS loadings given in Bridge Rules have been worked out and the maximum stress range calculated.

(ii)

In the analysis of plate girder only the bending stresses due to maximum bending moment have been taken into consideration to find out the maximum stress range and the design fatigue life of spans has been assessed.

(iii)

Occasional loads have not been considered.

(iv)

For plate girders, the loaded length for considering λ1 has been taken, as effective span length.

(v)

GMT factor is taken as per proposed fatigue criteria in 78th BSC.

(vi)

Fatigue categories are chosen as per the Table – 3 which is based on the tables given in draft provisions, discussed in 78th BSC and the engineering judgment applied. The analyzed fatigue life may vary on this account.

2.95

2.96

Train-1

1.1996

1.1775

1.1615

1.1470

1.1288

1.1050

1.0741

1.0386

0.9986

0.9503

0.8699

0.8451

0.8300

0.8175

Span (m)

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

6.00

7.00

8.00

9.00

0.9282

0.9389

0.9574

0.9994

1.0694

1.1100

1.1537

1.1963

1.2339

1.2651

1.2903

1.3106

1.3266

1.3377

Train-2

1.0628

1.1075

1.1341

1.1606

1.2014

1.2157

1.2270

1.2367

1.2460

1.2559

1.2674

1.2820

1.3111

1.3342

Train-3

0.6437

0.6797

0.7469

0.8247

0.8953

0.9294

0.9639

1.0063

1.0502

1.0820

1.1039

1.1218

1.1360

1.1477

Train-4

1.2884

1.2957

1.3031

1.3112

1.3188

1.3222

1.3254

1.3281

1.3303

1.3317

1.3318

1.3314

1.3320

1.3353

Train-5

1.4952

1.5299

1.5590

1.5663

1.5636

1.5627

1.5620

1.5614

1.5618

1.5617

1.5650

1.5756

1.5893

1.5986

Train-6

Table 1: λ1 for MBG Loading

1.5621

1.5736

1.5823

1.5876

1.5860

1.5856

1.5859

1.5856

1.5839

1.5809

1.5769

1.5730

1.5698

1.5681

Train-7

1.3117

1.3142

1.3184

1.3362

1.3327

1.3312

1.3291

1.3270

1.3254

1.3252

1.3267

1.3293

1.3318

1.3336

Train-8

1.2146

1.2173

1.2216

1.2286

1.2367

1.2406

1.2442

1.2474

1.2502

1.2523

1.2537

1.2552

1.2590

1.2672

Train-9

1.1102

1.1446

1.1666

1.1843

1.1961

1.2024

1.2077

1.2121

1.2174

1.2290

1.2473

1.2634

1.2748

1.2849

Train-10

2.97

Train-1

0.8676

0.8462

0.8263

0.8162

0.8558

0.7783

0.7553

0.7307

0.7162

0.6884

0.6494

0.5494

0.5282

0.5020

0.4739

0.4521

Span (m)

10.00

12.50

15.00

17.50

20.00

25.00

30.00

35.00

40.00

45.00

50.00

60.00

70.00

80.00

90.00

100.00

0.4893

0.5128

0.5398

0.5849

0.6384

0.6555

0.6742

0.7040

0.7225

0.7700

0.7977

0.9087

0.9168

0.9376

0.9549

0.9588

Train-2

0.5039

0.5324

0.6156

0.6367

0.6346

0.6411

0.6497

0.6632

0.6843

0.7163

0.7779

0.8477

0.9056

0.9505

0.9896

1.0191

Train-3

0.4047

0.4127

0.4219

0.4211

0.4315

0.5154

0.5367

0.5391

0.5103

0.5551

0.5846

0.5905

0.5563

0.5439

0.5421

0.5600

Train-4

0.7205

0.7781

0.8213

0.8868

0.9696

1.0048

1.0243

1.0403

1.0649

1.0888

1.1146

1.1604

1.0956

1.1252

1.1416

1.1653

Train-5

0.6416

0.6456

0.6506

0.6692

0.7129

0.7993

0.8560

0.9096

0.9918

1.0312

1.0770

1.1808

1.1457

1.1911

1.2469

1.2961

Train-6

0.6593

0.6807

0.7126

0.7579

0.8208

0.8834

0.9229

0.9651

1.0005

1.0675

1.1297

1.1717

1.1787

1.2392

1.2912

1.3417

Train-7

Table 1 : λ1 MBG Loading (Continued)

0.8836

0.9048

0.9286

0.9474

0.9619

0.9739

0.9781

0.9787

0.9729

0.9646

0.9740

0.9881

1.1047

1.1087

1.1127

1.1167

Train-8

0.6921

0.7785

0.8037

0.8288

0.8765

0.9546

0.9996

1.0377

1.0455

1.0616

1.0955

1.1445

1.0814

1.1114

1.1205

1.1238

Train-9

0.6272

0.6367

0.6516

0.6658

0.6847

0.7101

0.7234

0.7437

0.7745

0.8149

0.8607

0.8985

0.9170

0.9302

0.9585

1.0127

Train-10

2.98

Train-1

1.2278

1.2042

1.1862

1.1707

1.1556

1.1410

1.1227

1.0910

1.0393

0.9765

0.8968

0.8796

0.8692

0.8626

Span (m)

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

6.00

7.00

8.00

9.00

0.9473

0.9717

1.0144

1.0749

1.1453

1.1835

1.2195

1.2503

1.2750

1.2951

1.3124

1.3283

1.3435

1.3574

Train-2

1.0537

1.0911

1.1493

1.2128

1.2656

1.2924

1.3274

1.3660

1.4001

1.4279

1.4509

1.4708

1.4886

1.5043

Train-3

0.4997

0.5069

0.5148

0.5239

0.5443

0.5631

0.5859

0.6073

0.6246

0.6383

0.6500

0.6625

0.6762

0.6903

Train-4

1.2605

1.3073

1.3371

1.3494

1.3724

1.3811

1.3865

1.3915

1.3971

1.4038

1.4114

1.4198

1.4284

1.4369

Train-5

1.5930

1.5971

1.5981

1.5961

1.5930

1.5906

1.5889

1.5895

1.5910

1.5928

1.5948

1.5970

1.6003

1.6074

Train-6

1.3186

1.3204

1.3215

1.3216

1.3182

1.3154

1.3132

1.3132

1.3218

1.3301

1.3297

1.3230

1.3160

1.3131

Train-7

Table 2: λ1 for 25 T Loading

1.2665

1.2680

1.2705

1.2728

1.2761

1.2802

1.2858

1.2922

1.2987

1.3049

1.3106

1.3156

1.3199

1.3236

Train-8

1.2515

1.2870

1.3307

1.3610

1.3674

1.3644

1.3617

1.3639

1.3712

1.3766

1.3804

1.3842

1.3883

1.3923

Train-9

1.2494

1.2586

1.2669

1.2736

1.2778

1.2829

1.2884

1.2932

1.2965

1.2982

1.2988

1.2998

1.3031

1.3121

1.1163

1.1416

1.1742

1.2039

1.2296

1.2412

1.2515

1.2605

1.2681

1.2746

1.2801

1.2847

1.2889

1.2930

Train-10 Train-11

2.99

Train-1

0.9047

0.8925

0.8806

0.8274

0.8262

0.8065

0.7899

0.7706

0.7554

0.7270

0.6863

0.5832

0.5486

0.5090

0.4738

0.4532

Span (m)

10.00

12.50

15.00

17.50

20.00

25.00

30.00

35.00

40.00

45.00

50.00

60.00

70.00

80.00

90.00

100.00

0.5173

0.5367

0.5570

0.6046

0.6552

0.6814

0.7037

0.7290

0.7643

0.7774

0.8712

0.8995

0.8937

0.9198

0.9620

0.9682

Train-2

0.5554

0.5849

0.6458

0.6601

0.6815

0.7148

0.7470

0.7835

0.8657

0.8768

0.8906

0.8962

0.9165

0.9468

0.9572

1.0109

Train-3

0.5113

0.4999

0.4861

0.4823

0.4813

0.4877

0.4955

0.5019

0.5055

0.5091

0.5104

0.5253

0.5157

0.5220

0.5315

0.5456

Train-4

0.6520

0.7276

0.7976

0.8529

0.8197

0.8171

0.8395

0.8702

0.9058

0.9401

0.9690

0.9897

1.0076

1.0534

1.0711

1.0825

Train-5

0.6921

0.7245

0.7703

0.8500

0.9241

0.9733

0.9766

0.9786

1.0415

1.1004

1.1650

1.2124

1.2011

1.2432

1.3002

1.3503

Train-6

1.1286

1.1400

1.1484

1.1552

1.1637

1.1706

1.1733

1.1759

1.1781

1.1797

1.1806

1.1808

1.1833

1.1971

1.2022

1.1921

Train-7

1.0313

1.0743

1.0992

1.1164

1.1318

1.1444

1.1497

1.1546

1.1577

1.1588

1.1591

1.1590

1.1917

1.1877

1.1743

1.1708

Train-8

Table 2: λ1 for 25 T Loading (Continued)

0.6131

0.6793

0.7609

0.8249

0.7877

0.8364

0.8677

0.9056

0.9472

0.9804

0.9911

0.9845

0.9964

1.0566

1.0851

1.0788

Train-9

0.6460

0.6579

0.6729

0.7086

0.7392

0.7789

0.8156

0.8550

0.8938

0.9241

0.9302

0.9422

0.9946

1.0317

1.0845

1.1092

0.5724

0.5898

0.6087

0.6352

0.6610

0.6778

0.6101

0.6224

0.6568

0.7012

0.7540

0.8102

0.8925

0.9249

0.9463

0.9719

Train-10 Train-11

Table – 3 Fatigue Categories Adopted for Member Detail/Connections S. Member detail or No. connection to be assessed

Fatigue category Category

Reference

1

Stringer, X-girder & Plate girders (welded type)

100

Details 5 & 6 of Table 9.2

Stringer, X-girder & Plate girders (rivetted type)

80

Detail 8 of Table 9.1

2

Fillet weld of web-flange connection of stringer/xgirder

80

Detail 8 of Table 9.5

Shear stress at throat area of weld.

3

Gusset connections

80

Detail 8 of Table 9.1

Axial stresses on net area.

4

Stringer and x-girder connection

100

Detail 11 of Table 9.1

Shear stress on shank area of rivet/bolt

Remark Bending stresses at mid of span

5.0 Fatigue Life Assessed 5.1 Based on above assumptions, the design calculations for assessment of fatigue life of plate girder bridges are given in Table 4 for MBG loading and in Table - 5 for 25t loading. 5.2 It is to be noted that the annual GMT for a particular route may not be comprised of the trains causing maximum stress range. Situation may vary route wise and partial GMT may be due to trains causing much lower stress range. In such cases a more detailed fatigue assessment would be required taking into consideration the representative load model of actual set of trains running on the route. 5.3 It is further to be observed that due to change of loading, the l1values and the maximum design stress-ranges have increased marginally. However, the effect on design fatigue life has been considerable on higher spans as compared to smaller spans.

2.100

2.101

B-16009 (4 million)

B-16012 (10 million)

B-16010 (4 million)

B-16013 (10 million)

B-16011 (4 million)

B-16005 (10 million)

B-11003 (2million)

B-11004 (2 million)

B-11005 (2 million)

12.2m MBG

18.3m MBG

18.3m MBG

24.4m MBG

24.4m MBG

12.2m BGML

18.3m BGML

24.4m BGML

RDSO Drg. No.

12.2m MBG

Std. Span

107.2

111.86

112.88

84.15

93.02

84.22

109.35

95.75

118.33

25.6

19.4

13.1

25.6

25.6

19.4

19.4

13.1

13.1

Stress Range Loaded Length ‘L' σ Rmax (N/mm2) (m)

1.125

1.18

1.28

1.125

1.125

1.18

1.18

1.28

1.28

66.311

42.671

27.440

642.927

394.140

507.201

141.727

182.219

64.802

33.290

21.422

13.776

322.772

197.872

254.633

71.152

91.480

32.533

16.713

10.755

6.916

162.043

99.339

127.834

35.721

45.926

16.333

11.168

7.187

4.622

108.285

66.383

85.426

23.870

30.690

10.914

8.390

5.399

3.472

81.351

49.871

64.177

17.933

23.057

8.200

6.721

4.325

2.781

65.166

39.949

51.409

14.365

18.469

6.568

Loading Design Life (years) for GMT & corresponding average route GMT factor (Lamda2) factor, 5 10 20 30 40 50 Lamda1 0.721 0.830 0.956 1.038 1.101 1.152

Table - 4 Assessed fatigue life of standard plate girder bridges (MBG Loading)

2.102

B-16009 (4 million)

B-16012 (10 million)

B-16010 (4 million)

B-16013 (10 million)

B-16011 (4 million)

B-16005 (10 million)

B-11003 (2million)

B-11004 (2 million)

B-11005 (2 million)

12.2m MBG

18.3m MBG

18.3m MBG

24.4m MBG

24.4m MBG

12.2m BGML

18.3m BGML

24.4m BGML

RDSO Drg. No.

12.2m MBG

Std. Span

113.28

117.38

112.86

88.92

98.3

88.38

114.75

95.73

118.31

25.6

19.4

13.1

25.6

25.6

19.4

19.4

13.1

13.1

Stress Range Loaded Length ‘L' σ Rmax (N/mm2) (m)

1.18

1.21

1.29

1.18

1.18

1.21

1.21

1.29

1.29

Loading factor, Lamda1

40.122

30.446

26.440

389.066

238.428

361.811

101.106

175.603

20.143

15.285

13.274

195.325

119.699

181.642

50.759

88.159

31.346

0.721 62.437

10 0.830

5

10.112

7.674

6.664

98.060

60.093

91.191

25.483

44.259

15.737

0.956

20

6.758

5.128

4.453

65.529

40.157

60.938

17.029

29.576

10.516

1.038

30

5.077

3.852

3.345

49.229

30.169

45.781

12.793

22.220

7.900

1.101

40

4.067

3.086

2.680

39.435

24.167

36.673

10.248

17.799

6.329

1.152

50

Design Life (years) for GMT & corresponding average route GMT factor (Lamda2)

Table - 5 Assessed fatigue life of standard plate girder bridges (25 t Loading)

6.0 Effect of Speed on the Assessed Design Fatigue Life 6.1 It is evident from the perusal of Table 4 & 5 that the assessed fatigue life is quite low for high GMT routes and the spans designed for 2 million cycles as per old fatigue provisions based on stress ratio concept. This is apparently due to the fact that the stress ranges considered in analysis are based on full CDA (Coefficient of Dynamic Augment) which is applicable for a speed 125 kmph for goods trains. Practically, goods trains do not run with a speed more than 100 kmph. Therefore, the design fatigue life has been re-assessed with reduced stress ranges corresponding to a sectional speed of 100 kmph by proportionately reducing the maximum design stress range. The results for re-assessed design life for MBG loading and 25t loading are shown in table 6 & 7 respectively. 6.2 It is further noted that the new 25t loading has been permitted with a sectional speed of 75 kmph due to strength considerations. Accordingly, the fatigue life of bridges with new 25t loading at 75 kmph has been again worked out with reduced CDA value corresponding to 75 Kmph and the results are given in Table – 8. 7.0 Limitation of the Results Obtained The results of analysis may be interpreted keeping in view the following: i)

ii) iii) v)

Assessment is based on average GMT of the route over the life span of the bridge. The GMT being carried in present may be actually different. The GMT may be comprised of no. of trains which may not give the maximum stress range. Partial factor of safety is assumed as 1.0 for analysis of existing bridges. It is assumed that the physical condition of the bridge is otherwise sound from other considerations and effect of corrosion, pitting and other defects developed during service have not been accounted for.

2.103

2.104

B-16009 (4 million)

B-16012 (10 million)

B-16010 (4 million)

B-16013 (10 million)

B-16011 (4 million)

B-16005 (10 million)

B-11003 (2 million)

B-11004 (2 million)

B-11005 (2 million)

12.2m MBG

18.3m MBG

18.3m MBG

24.4m MBG

24.4m MBG

12.2m BGML

18.3m BGML

24.4m BGML

RDSO Drg. No.

12.2m MBG

Std. Span

CDA with 100 Kmph

101.1

104.8

104.7

79.31

87.7

78.9

102.5

88.8

109.8

25.6

19.4

13.1

25.6

25.6

19.4

19.4

13.1

13.1

Stress Range Loaded σ Length ‘L' Rmax (N/mm2) (m)

1.125

1.18

1.28

1.125

1.125

1.18

1.18

1.28

1.28

Loading factor, Lamda1

GMAfF = 1,

Fatcat =

100

100

80

80

88.272

58.666

39.619

858.574

525.457

697.510

194.372

263.261

44.316

29.452

19.890

431.034

263.798

350.174

97.582

132.166

46.879

0.721 93.378

10 0.830

5

22.248

14.786

9.986

216.394

132.436

175.800

48.989

66.352

23.535

0.956

20

14.867

9.881

6.673

144.606

88.500

117.479

32.737

44.340

15.727

1.038

30

11.169

7.423

5.013

108.637

66.487

88.258

24.594

33.311

11.815

1.101

40

8.947

5.946

4.016

87.024

53.259

70.698

19.701

26.684

9.465

1.152

50

Design Life (years) for GMT & corresponding average route GMT factor (Lamda2)

GMAmf = 1,

Table – 6 Assessed fatigue life for different GMTs (MBG Loading) with sectional speed of 100 kmph

2.105

B-16009 (4 million)

B-16012 (10 million)

B-16010 (4 million)

B-16013 (10 million)

B-16011 (4 million)

B-16005 (10 million)

B-11003 (2 million)

B-11004 (2 million)

B-11005 (2 million)

12.2m MBG

18.3m MBG

18.3m MBG

24.4m MBG

24.4m MBG

12.2m BGML

18.3m BGML

24.4m BGML

RDSO Drg. No.

106.8

109.9

104.7

83.8

92.7

82.8

107.5

88.8

109.7

25.6

19.4

13.1

25.6

25.6

19.4

19.4

13.1

13.1

Stress Range Loaded Length ‘L' σ Rmax (N/mm2) (m)

1.125

1.18

1.28

1.125

1.125

1.18

1.18

1.28

1.28

Loading factor, Lamda1

GMAfF = 1,

Fatcat =

100

100

80

80

53.493

41.991

38.142

519.735

317.497

497.486

139.052

253.445

26.855

21.081

19.149

260.925

159.395

249.755

69.809

127.238

45.332

0.721 90.297

10 0.830

5

13.482

10.583

9.613

130.993

80.022

125.386

35.046

63.878

22.758

0.956

20

9.010

7.072

6.424

87.537

53.475

83.789

23.420

42.687

15.208

1.038

30

6.769

5.313

4.826

65.763

40.174

62.948

17.595

32.069

11.425

1.101

40

5.422

4.256

3.866

52.679

32.181

50.424

14.094

25.689

9.152

1.152

50

Design Life (years) for GMT & corresponding average route GMT factor (Lamda2)

GMAmf = 1,

Table – 7 Assessed fatigue life for different GMTs (25 t Loading) with sectional speed of 100 kmph

12.2m MBG

Std. Span

CDA with 100 Kmph

2.106

B-16009 (4 million)

B-16012 (10 million)

B-16010 (4 million)

B-16013 (10 million)

B-16011 (4 million)

B-16005 (10 million)

B-11003 (2 million)

B-11004 (2 million)

B-11005 (2 million)

12.2m MBG

18.3m MBG

18.3m MBG

24.4m MBG

24.4m MBG

12.2m BGML

18.3m BGML

24.4m BGML

RDSO Drg. No.

12.2m MBG

Std. Span

100.3

102.5

96.5

78.7

87

77.2

100.2

81.84

101.15

25.6

19.4

13.1

25.6

25.6

19.4

19.4

13.1

13.1

Stress Range Loaded Length ‘L' σ Rmax (N/mm2) (m)

1.125

1.18

1.28

1.125

1.125

1.18

1.18

1.28

1.28

Loading factor, Lamda1

72.686

59.018

56.800

706.208

432.826

700.297

196.021

377.543

36.491

29.629

28.516

354.541

217.294

351.573

98.409

189.540

67.372

0.830

0.721 134.198

10

5

18.320

14.875

14.316

177.992

109.089

176.502

49.405

95.156

33.823

0.956

20

12.242

9.940

9.567

118.944

72.899

117.948

33.015

63.588

22.602

1.038

30

9.197

7.468

7.187

89.358

54.766

88.610

24.803

47.771

16.980

1.101

40

7.367

5.982

5.757

71.580

43.870

70.981

19.868

38.267

13.602

1.152

50

GMAmf = 1, GMAfF = 1, Fatcat = 100 100 80 80 Design Life (years) for GMT & corresponding average route GMT factor (Lamda2)

Table – 8 Assessed fatigue life for different GMTs (25 t Loading) with sectional speed of 75 kmph

CDA with 75 Kmph

8.0 Conclusions 8.1 The design fatigue life of standard plate girders is found reduced as a result of running of 25t loading – 2008 vis-à-vis existing MBG loading. 8.2 Reduction in design fatigue life is nominal (3-4%) for smaller span (12.2m) and significantly high (40%) for higher span (24.4m). 8.3 Route GMT and sectional speed are important parameters which affect the design fatigue life considerably. The Effect of reducing CDA is to improve the design fatigue life by reducing the maximum design stress range and the reduction is substantial. 8.4 Plate girders designed for 10 million cycles as per existing fatigue criteria in IRS Steel Bridge Code give better estimate of fatigue life as compared to those designed for 4 million cycles. 8.5 Plate girders designed for 2 million cycles as per existing fatigue criteria in IRS Steel Bridge Code gives very low estimate of fatigue life and the same need to be verified again using detailed fatigue life analysis with respect to train loads and actual GMT on the routes where these girders are provided.

***

2.107

.

Notes

Notes