Venkat FlexiblePavement Design

DESIGN OF FLEXIBLE PAVEMENTS

 V. VENKATA NARAYANA 

COMPONENTS OF ROAD ROAD WAY FORMATION

CARRIAGEWAY

SHOULDER PAVEMENT SUBGRADE EMBANKMENT

G.L

PAVEMENTS 1.

Pavement : Pave Pavemen mentt is a stru structu cture. re. It consists of superimposed layers of  selected and processed materials.

2.

It is placed on a Sub grade

3.

It supports the applied traffic loads and distributes them to the soil foundation.



ESSENTIL REQUIEMENT OF PAVEMENTS 

1) STRUCTURAL PERFORMANCE  – A PAVEMENT SHOULD BE 





(i) STRONG enough to resist the stresses imposed on it and (ii) THICK  THICK enough enough to distribute the external loads on the earthen subgrade.

2) FUNCTIONAL PERFORMANCE  – A PAVEMENT SHOULD HAVE    

(i) Riding quality, (ii) Surface friction for skid resistance, resistance, (iii) Low noise and (iv) Good geometrics geometrics..

TYPES OF PAVEMENTS 1)

FLEXIBLE PAVEMENTS,

2)

RIGID PAVEMENTS,

3)

SEMI-RIGID PAVEMENTS,

4)

COMPOSITE PAVEMENTS.

1) FLEXIBLE PAVEMENTS 1. 2. 3.

Consists THREE Layers. It has low FLEXURAL strength. Transfers the traffic loads by DISPERSION.

Wearing Course Binding Course

SURFACE COURSE

BASE COURSE

SUB-BASE COURSE

SUB GRADE

1) FLEXIBLE PAVEMENTS

2) RIGID PAVEMENTS 1. 2.

These consist of only TWO Layers. Transfers the traffic loads by FLEXURE.

CC WEARING COURSE

SUB-BASE COURSE

SUB GRADE

Sub-base may be

DLC/ PCC/ WMM/WBM

2) RIGID PAVEMENTS

3) SEMI-RIGID PAVEMENTS •

Surface course is FLEXIBLE.

•

Base/ Sub-base is RIGID.

BITUMINOUS WEARING COURSE

RIGID BASE COURSE

SUB GRADE

Rigid Base may be DLC/ Lime-fly ash/ soil-cement concretes

4) COMPOSITE PAVEMENTS 

These Pavements comprises of  multiple, structural layers of different, heterogeneous, composition. Ex:: Bri ricck sa sand ndw wic ich hed pa pav vem emen entt, which consists CC pavement layers at bottom and top duly sandwiching brick  layer.

DESIGN OF FLEXIBLE PAVEMENTS



Design of FLEXIBLE PAVEMENTS involves the interplay of severable variables Wheel

Loads. Traffic. Climate. Terrain. Subgrade condition.

DESIGN OF FLEXIBLE PAVEMENTS 

TWO CODES for DESIGN Village

Roads and Rural Roads ::

Traffic Less than 450 CVPD  IRC:SP:20-2002 (Rural Road Manual) 

Expressways,

NH, SH, MDR

Traffic Greater than 450 CVPD (1 msa to 150 msa)  IRC:37-2001 (Guide lines for the design of flexible pavements) 

IRC:37-2001 GUIDELENES FOR THE DESIGN OF FLEXIBLE PAVEMENTS

This code uses mathematical modeling of the pavement structure using MULTIPLE LAYER ELASTIC theory

COMPONENTS OF FLEXIBLE PAVEMENTS 

FLEXIBLE PAVEMENTS Essentially consists of

THREE Layers. 1) Surface Course:: i) Wearing Course :: PC, SDBC, BC.

ii) Binding course:: BM, DBM,

2) Granular Base :: WBM, WMM, 3) Granular Sub-Base ::

SUBGRADE

FLEXIBLE PAVEMENTS STRAINS/DEFORMATIONS and their REMEDIES

1. Pavement deformation BITUMINOUS layers.

within

BITUMINOUS COURSE

BASE COURSE SUB-BASE COURSE SUB GRADE

1.

Controlled by meeting the MIX DESIGN requirements as per MORT&H Specifications.

STRAIN STR AINS/D S/DEFO EFORMA RMATIO TIONS NS ---------- REM REMEDI EDIES ES

2. Horizontal Tensile strain at the bottom of  BITUMINOUS layer.

BITUMINOUS COURSE

BASE COURSE SUB-BASE COURSE SUB GRADE

2.

Controlled by selecting the THICKNESSES of  Granular and Bituminous layers as per Design.

STRAIN STR AINS/D S/DEFO EFORMA RMATIO TIONS NS ---------- REM REMEDI EDIES ES

3. Vert Vertic ical al co comp mpre ress ssiv ive e st stra rain in the to top p of  the SUBGRADE.

BITUMINOUS COURSE

BASE COURSE SUB-BASE COURSE SUB GRADE

3.

Controlled by selecting the THICKNESSES of Granular and Bituminous layers as per Design.

PARAMETERS FOR DESIGN 

1 DESIGN TRAFFIC .  – Cumulative number of Standard Axles.



2 CBR value of Subgrade.

TRAFFIC 

IRC:37 Considers traffic in terms of   STANDARD AXLES to be carried by the pavement during the  DESIGN LIFE.

 

STANDA STAN DARD RD AX AXLE LE = 816 8160 0 Kg DESIGN LIFE = Period in which the cumulative number of  standard axles carried by the pavement.



CVPD :: Commer Commercial cial Vehicle Vehicless Per Per Day 

Vehicle having LADEN weight more than 3.00 mt.

TRAFFIC 

For est For stim ima ati ting ng th the e DE DESI SIG GN TR TRAF AFF FIC in inffor orma mati tio on required :: i. INTIAL TRAFFIC :: After construction (before the road is opened to traffic) in terms of CVPD. iiii.. TR TRAF AFFI FIC C GR GROW OWRT RT RA RATE TE :: iiiii. i. DE DESI SIGN GN LI LIFE FE :: in number of years, iv. VEH VEHICLE ICLE DAM DAMAGE AGE FAC FACTOR TOR :: v. DISTRIBU BUT TIO ION N of commercial traffic over the carriageway.

i) INITIAL TRAFFIC



Only the number of commercials (W>3.0t) and



The Th e Ax Axle le-- Lo Loa adi ding ng of Co Comm mme erc rcia iall Veh ehic icle less are considered.



The initial daily average traffic flow based 7 days X 24 hours classified counts.

ii) TRAFFIC GROWTH RATE 

Traffic growth rate is estimated ::  



By studying the past trends of traffic growth and By establishing economic models as per procedure out lined in IRC:108.

The code recommends average annual growth rate as 7.50 % . 

In case adequate data is not available .

iii) DESIGN LIFE 

Definition :: Design life of a pavement is the CUMULATIVE  NUMBER of “standard axles” that can be carried before strengthening of pavement is necessary. n ecessary.



DESIG LIFE for :: Expr Ex pres esss wa ways ys & Ur Urba ban n Ro Road ads. s. -- -- -- 20 yrs.  National Highways & State Highways – 15 yrs.  Othe Ot herr category of roa oad ds -- -- 10 to 15 yrs. 

iv) VEHICLE DAMAGE FACTOR 

Definition :: It is an equivalent number of STANDARD AXLE  per COMMERCIAL VEHICLES. STANDARD AXLE = 8160 kg 



It is a multiplier to convert COMMERCIAL VEHICLES of different axle loads and configuration to STANDAD AXLE ::



COMMERCILA VEHICLE * VDF = STANDARD ST ANDARD AXLE.

iv) VEHICLE DAMAGE FACTOR Single Axle Load ::

 

Equivalency Factor =(Axle Loan in kg/8160) 4    

Equivalency Facto Equivalency Factorr of 4540 kg Equivalency Equiva lency Facto Factorr of 8160 kg Equivalency Factor of 16320 kg Equivalency Factor of 22680 kg

=(4540/8160) =(4540/816 0)4=0.08 =(8160/816 =(816 0/8160) 0)4=1.00 =(16320/8160)4=15.5 =(22680/8160)4=55.0

Tandem Axle Load ::

 

Equivalency Factor =(Axle Loan in kg/14968) 4    

Equivalency Facto Equivalency Factorr of 8160 kg Equivalency Factor of 14968 kg Equivalency Factor of 22680 kg Equivalency Factor of 36288 kg

=(8160/14968) =(8160/149 68)4 =0.07 =(14968/14968)4=1.00 =(22680/14968)4=5.28 =(36288/14968)4=31.7

iv) VEHICLE DAMAGE FACTOR

iv) VEHICLE DAMAGE FACTOR

iv) VEHICLE DAMAGE FACTOR Where sufficient information is not available & project size does not warrant axle load survey INDICATIVE VDF VALUES Initial traffic volume in terms number of CVPD

Terrain Rolling/plain

Hilly

0 – 150

1.50

0.50

150 – 1500

3.50

1.50

More than 1500

4.50

2.50

v) LANE DISTRIBUTION FACTOR Distribution of commercial traffic by



LANE  DIRECTION Nece Ne cess ssar ary y in ar arri rivi ving ng re real alis isti ticc to tota tall eq equi uiva vale lent nt st stan anda dard rd ax axle le load used in design. 

Types of Carriageways Carriageways

  

Single Lane carriageway ( No median of divider), Dual lane carriageway ( With Median or Divider).

Types of Lanes

    

Single - Lane (only in single carriageway) Two – Lane, Three – Lane (only in dual carriageway) Four – Lane

v) LANE DISTRIBUTION FACTOR SINGLE CARRIAGEWAY ROAD SNo

Number of Lanes

Width

L.D.F. (%)

1

Single – Lane

3.75 m

100

2

Two – Lane

7.00 m

75

3

Four – Lane

14.0 /15.0

40

DUAL CARRI CARRIAGEWA AGEWAY Y ROAD 1

Two – Lane

7.0 + 7.0

75

2

Three – Lane

10.5 + 10.5

60

3

Four – Lane

14.0 + 14.0

40

Estimation of TRAFFIC

P

Supp Su ppos ose e TR TRAF AFFI FIC C in th the e ye year ar of CE CENS NSUS US is (CV CVPD PD)) - - - - - - - TRAFFIC after ONE year (C (CVPD) - - - - - - - - - - - - - - - - TRAFFIC after TWO years (CVPD) --

P(1+ r )

P(1 + r )(1 + r ) = P(1 + r )

TRAFFIC after THREE ye year arss (CV CVPD PD)) - - -

2

3

P(1+ r )(1+ r )(1+ r ) = P(1+ r )

- - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - - - --- - - - - - - - - - - - - - - - TRAFFIC after x ye year arss (CV CVPD PD)) - - -

x

P(1+r )(1+r )(1+r )−− x = P(1+r )

=

Estimation of TRAFFIC  A

Supp Su ppose ose TR TRAF AFFI FIC C in in th the e yea yearr of of CO COMP MPLE LETI TION ON is (CV CVPD PD)) - - - - - -

365 *

TOT TO TAL number of vehicle vehicless in FIRST ye year ar (CV CVPD PD)) -- - TOTAL number of vehicles in SECOND year (CVPD) TOT TO TAL number of vehicle vehicless in THIRD year (CVPD)

 A

365* A* (1+ r )

365* A* (1 + r )

2

=== === === === === === === === === === TOTAL number of vehicles in ‘n th’ year (CVPD)

CUMULATIVE TRAFFIC for

n years (CVPD)

(By adding the TRAFFIC from FIRST to n th year)

365 *  A * (1 + r )

[

365 *  A * ( 1 + r  ) r 

n

( n −1)

−

1

]

TRAFFIC For estimating the DESIGN TRAFFIC information



required :: i.

INTIA IN TIAL L TR TRAF AFFI FIC C :: --------------------------------- A CV CVPD PD

ii.

TRAFF TRA FFIC IC GR GROW OWRT RT RA RATE TE :: --------------- r %

iii. DESIG DESIGN N LIFE :: ------------------------------------------- n year yearss iv. VEH VEHICLE ICLE DAM DAMAGE AGE FAC FACTOR TOR ::-::----------- F v.

LANE LA NE DI DISTR STRIB IBUTI UTION ON FA FACTO CTOR R ::::---- D

Estimation of TRAFFIC CUMULATIVE NUMBER OF STANDARD AXLES TO BE CATERED IN THE DESIGN ARE IN TERMS OF msa (Millian Standard Axles)  N 

=

[

365 * ( 1 + r  ) r  * 1000000

n

−

1

]

*

 A



A = Initial Traffic,



r = Growth Rate,



D = Lane distribution factor,



n = Design life in years



F = Vehicle Damage Factor.

*

 D

*

F 

CBR of SUBGRADE (foundation) Definition ::

 

It is the top 500 mm of FORMATION and is FOUNDATION to the pavement.



It should be well copacted .

Density ::

 

The DRY DENSITY not less than 1.75 gm/cc. gm/cc.

Stre St rengt ngth h ::

   

The STRENGTH of subgrade is assesed in terms of  CBR  CBR (( California Bearing Ratioo). Maximum = 10 % and Minimum = 2 % The CBR should be found on remoulded samples in the lab at the weakest condition under the road after construction.

PAVEMENT THICKNSS AND COMPOSITION 

Pavement Paveme nt Thicknes Thicknesss Design CHART CHARTS S :: 

These charts are used to obtain TOTAL thickness of Pavement.



From CBR and Traffic in msa.

Pavement Thickness Design CHARTS  

These CHARTS are use sed d to obtain the total thickness of  pavement from the TRAFFIC and CBR. TRAFFIC ::  Tra Tr affi ficc is assessed in terms of  cu cumu mula lati tive ve nu numb mber er of  standard axles to be carried over the design life. Unit = msa (million standard axles)  Range ::   



1 to 10 msa Fig.1, 10 to 150 msa Fig.2.

CBR :: The CBR of SUBGRADE ,  Minimum = 2 %,  Maximum = 10 %  For CBR less than 2 %, Capping layer 150 mm thickness of  material with 10% CBR should be provided, and consider CBR as 2% for design.

Chart 1 : Traffic 1-10 msa: CBR 2-10 %

Chart 2 : Traffic 10-150 msa: CBR 2-10 %

PAVEMENT THICKNSS AND COMPOSITION 



Pavement Thicknes Pavement Thicknesss Desig Design n CHARTS ::  These charts are used to obta obtain in TOTAL thickne thickness ss of  Pavement. Paveme Pav ement nt Com Compos positio ition n ::  Sub-base course,  Base course, Bituminous Surfacing   



Binder Course, Wearing course.

Pavement Design CATALOG Pavement CATALOGUE UE :: These charts are used to obtain the MINIMUM  THICKNESS and COMPOSITION of pavement layers.

GRANULAR SUB-BASE COURSE (G 

GRADATION :: 





The Su The Subb-ba base se ma mate teri rial alss sh shou ould ld co conf nfor orm m Grading (Grain size distribution)of Clause MORT&H.

The material passing 425 micron should have  LIQUIE LIMIT not more than 25 %,  PLASTICITY INDEX not more than 6 % The CBR Values

GRANULAR SUB-BASE COURSE (GSB)





Construction ::  The GSB should be extended over entire width of formation.  When CBR Value of GSB is less than 2 %, a capping layer of 150 mm thickness of  material with 10 % CBR is provided provided.. MINIMUM THICKNESS ::  

Traffic Traf fic le less ss tha than n 10 ms msa a Min Minimu imum m = 150 mm Traf Tr affi ficc mor more than than 10 msa msa Mini Minim mum = 200 mm

GRANULAR BASE COURSE



MATERIAL :: The unbound granular base comprises of any one of the following.  



WBM – Water Bound Macadam or WMM – Wet Mix Macadam.

THICKNESS :: 



WMM  Traffic  Traffic WMM  Traffic  Traffic

up to 2 msa Min = 225 mm. exceeding 2 msa Min = 250 mm. up to 2 msa Min = 225 mm exceeding 2 msa Min = 300 mm

BITUMINOUS SURFACINGS 

The Bituminous Surfacing consists of   



Wearing Course ony or Binder Course + Weaing Courses

WEARING COURSE Wearing courses are     

::

commonly

Surface Dressing (SD), Open-graded premix carpet (OGPC), Mix seal surfacing (MS), Semidense Bituminous Concrete (SDBC), Bituminous Concretd (BC).

used

BITUMINOUS SURFACINGS 

BINDER COURSE :: commonly used Binder courses are  



BITUMINOUS MACADAM :: 



Bituminous Macadam (BM) , Dense Bituminous Macadam (DBM).

For traffic less than 5 msa .

DENSE BITUMINOUS MACADAM :: 

For traffic more than 5 msa .

BITUMINOUS SURFACINGS 

SELECTION :: The choice of appropriate type of wearing courses depend on    



Desine traffic, Type of Base course, Type of Binder Course, Rainfall of the area.

NOTE NOT E :: The thic thicknes knesss of    

Surface dressing, Open graded premix carpet and Mixseal surfacing

Will not be counted in designing the total thickness of pavement.

PAVEMENT DESIGN CATALOGUE 





Based on the results of  Analysis of Pavement Structure  Specification requirement.  Plate 1  Used to design for the traffic upto 10 msa  1, 2, 3, 5, 10. Plate 2  

 

Used to design for the traffic upto 150 msa 10, 20, 30, 50, 100, 150.

CBR  2, 3, 4, 5, 6, 7, 8, 9 and 10.  For intermediate traffic ranges, the pavement layer thickness will be interpolated linearly.

LINEAR INTERPOLATIO INTERPOLATION N

 y =  y1 + ( y 2 −  y1) *

 y =  y1 + ( y 2 −  y1) *

 y

=

 y1

−

( y 2

−

 y1) *

 x  x1

 x

y2

 x1

y1

x

x

x x1

First Ordinate = y1 Second Ordinate = y2 Distance Distanc e between y1 & y2 = x1

 x  x1

PAVEMENT DESIGN CATALOGUE



PLAT PL ATEE-1 1 :: 



DRECOM DREC OMME MEND NDED ED DE DESI SIGN GN FO FOR R TR TRAF AFFI FIC C RANGE 1-10 msa, for CBR of 2%, 3%, 4%, 5%, 6%, 7%, 8% and 9% &10%.

PLAT PL ATEE-2 2 :: 

DRECOM DREC OMME MEND NDED ED DE DESI SIGN GN FO FOR R TR TRAF AFFI FIC C RANGE 10-150 msa, msa, for CBR of 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% and 10%.

DSIGN

EXAMPLE

DSIGN

EXAMPLE

DSIGN

EXAMPLE

DSIGN

EXAMPLE

DSIGN

EXAMPLE

DSIGN

EXAMPLE

DSIGN

EXAMPLE

DSIGN

EXAMPLE

Chart 2 : Traffic 10-150 msa: CBR 2-10 %

635

DSIGN

EXAMPLE

DSIGN

EXAMPLE

DSIGN

EXAMPLE

DSIGN

EXAMPLE

References   

IRC : 37-2001 Guidelines for the desing of Flexible Pavements. MORT&H Specifications for Road and Bridge works ( Fourth Revision). Principles and practices of Highway Engineering. 



L.R. L. R. Ka Kadi diya yali li..

Some sites in Internet.

acknowledgements 1) 2) 3) 4) 5)

NAC :: National Academy of Construction. Sri F.C.S. Peter, D.G., NAC Sri S. Jaswant Jaswant Kuma Kumar, r, C.E.(D&P), C.E.(D&P), R&B Dept. Dept. Sri A. B. V. Subba Reddy Reddy,, NAC, Hydera Hyderabad. bad. Master V. Shraman,

-- V. VE VENK NKAT ATA A NARA NARAYA YANA NA Dy. Executive Engineer (R&B), 9440818440, 07799139399 [email protected]

THANK YOU 

 V. VENKATA NARAYANA