Geotechnical Report

GEOTECHNICAL INVESTIGATION REPORT

FOR

PROPOSED PROJECT OF METRO LINE 2 (AC 1) AT MUMBAI.

CLIENT

DELHI METRO RAIL CORPORATION M/s J Kumar Ltd CRTG (JV)

LOCATION

P 242E, P 261 & P 262 Viaduct

REPORT NO.

UES / ADI / SBC-BH / 160009 / 12 / 16-17, Dated: 17/04/2017

INDEX DESCRIPTION

Page No.

1. ABSTRACT

3

2. ABOUT SITE AND INVESTIGATION

4

2.1 LOCATION

4

2.2 FIELD WORK

4

2.3 BOREHOLES

4

3. LABORATORY TEST

4

4. GROUND WATER TABLE

4

5. SUB SOIL PROFILE

5

6. DESIGN

5

7. SUMMARY OF DESIGN ANALYSIS

6

8. RECOMMENDATION

6

9.

ANNEXURE

10. BORELOG & SUMMARY 11. CORE TEST RESULT 12. SAMPLE CALCULATION

7–9 10 – 12 13 14 – 16

1.0

ABSTRACT

We (Unique

Engineering Services, Adipur )

have carried out the Geotechnical Investigation, which

covers the field sampling and tests, necessary laboratory tests and finally analyzing the sub soil characteristics and behavior of the soil of the proposed site. The objective of the geotechnical investigation was to explore the sub soil profile up to predetermined depth and to work out the design capacity of the soil beneath at a required foundation depth for the  proposed type of foundation. Following pages represents the conceptual investigation and analysis based on the geotechnical investigation and study and presenting the same as a detailed report. The detailed scope of work was as per the instruction of Engineer in-charge. A complete geotechnical investigation work was undertaken to obtain the required subsurface information to study and define the nature and behavior of soil, under the application of loads of proposed structures. Such information was obtained through following steps: 

By making bore hole and collecting disturbed and undisturbed soil samples.



Performing required in situ tests (SPT Test).



Conducting laboratory tests to classify it and to determine the engineering properties of soil.

An analysis was made to derive the allowable bearing capacity, taking into considerations the anticipated settlements and the present soil conditions with future possibilities. Based on such analysis of the soil  properties, the conclusions are made regarding the precautions and protective measures to be taken, if found necessary. This report has been prepared after a careful study of the field testing and laboratory test results. The type and depth of foundation are suggested.

2.0

ABOUT THE SITE AND INVESTIGATIONS

2.1

LOCATION: - The site is located at Ch P 242E, P 261 and

2.2

FIELD WORK: -

P 262 VIADUCT.

The site investigation work was started on 24 th March, 2017 and completed on

09th April 2017. 2.3

BORE HOLES: -

Three boreholes were conducted by rotary drilling up to the depth decided by

the Agency. Table 1: Location, Depth of Borehole Sr. No.

Borehole No.

Co-Ordinate

1

P 242E Viaduct

N 19  13’ 27.5”, E 72 50’ 26.9”

2

P 261 Viaduct

N 19  13’ 7.1”, E 72 50’ 26.0”

3

P 262 Viaduct

N 19  13’ 6.7”, E 72 50’ 25.6”

0

0

Depth below EGL, m 31.0

0

0

26.5

0

0

31.0

Boring was carried out in accordance with I.S 1892 and the undisturbed soil samples were collected in thin walled tube as per IS: 2132 – 1986 were sealed packed and brought to our laboratory at Adipur for further investigation. During the advancement of the boring Disturbed and Undisturbed samples are collected at every 1.5m interval or at the change of strata whichever occurs earlier. Along with the samplings, field Standard Penetration Tests is conducted to correlate the strata denseness & stiffness. Detail procedures are explained in Annexure. 3.0

LABORATORY TESTS: - Following laboratory tests were carried out to determine the

 physical and engineering properties of undisturbed and disturbed soil samples. Detail procedures are explained in Annexure.

4.0

(a)

Field Dry Density & Field Moisture Content

(e) Shear Parameters i.e. C

–

(b)

Atterberg’s Limits

(f) Water Absorption of Rockc

(c)

Particle size distribution

(g) Swelling Parameters

(d)

Specific Gravity

(h) Strength parameters of Rock

GROUND WATER TABLE: - Water table was encountered at about 7.0 to 12.5m below

EGL upto the depth of termination during the sub soil exploration work. 5.0

SUB SOIL PROFILE: - The field data and laboratory classification is as follows: 5.1 Layer 1 – Filled up soil upto 2.5m depth. 5.2 Layer 2 – Gravels &

Boulders & Brownish Silty Clay of Intermediate Plasticity.

5.3 Layer 3 – Highly Weathered Basalt Rock 5.4 Layer 4 – Moderately to Strong Hard Basalt Rock

6.0

DESIGN OF PILE: - As per IRC 78 – 2014, the axial load carrying capacity has been

evaluated. Pile in rocks and weathered rocks of varying degree of weathering derive their capacity by end bearing and socket side resistance. The ultimate load carrying capacity may be calculated from one of the two approaches given below: Where core of the rock can be taken and UCS directly established using standard method of testing, the approach described in

Method 1 shall be used.

In situations where strata is highly fragmented, where RQD is nil or (CR + RQD)/2 is less than 30% or where strata is not classified as a granular or clayey soil or when the crushing strength is less than 10 MPa, the approach described in

Method 2 shall be used.

Method 1

Qu

=

Re

+

Raf

=

Ksp . qc . df . Ab

Qallow =

(Re / 3) + (Ra/6)

Where,

Qu = Ultimate Capacity of pile socketed into rock in Newtons

+

As . Cus

Qallow = Allowable Capacity of Pile Re

= Ultimate End Bearing

Ra

= Ultimate Side Socket Shear

Ksp

= Co-efficient ranges from 0.3 to 1.2

CR

= Core Recovery, %

RQD = Rock Quality Designation, % qc

= Average Unconfined Compressive Strength of Rock Core below base of pile for the

depth twice the diameter / least lateral dimension of pile in Mpa.* Ab

= Cross Sectional Area of base of pile

Df

= Depth Factor = 1 + 0.4 x (Length of Socket / Diameter of Socket), max 1.2.

As

= Surface Area of Socket

Cus

= Ultimate shear strength of rock along socket length = 0.225 √qc, but restricted to shear capacity of concrete of pile.

7.0

SUMMARY OF DESIGN ANALYSIS – Looking to the types of proposed structure and

the soil strata encountered, following conclusions are drawn and recommendations are given accordingly. TABLE 1: LOAD CARRYING CAPACITY Borehole No

PILE TYPE

P 242E

P 261

PILE DIA (mm)

1000

Bored Cast in situ pile

P 262

1000

1000

Length Below Cutoff Level, m

Pile Capacity, MT

26.25

413

26.50

425

27.00

449

18.25

437

18.50

449

19.00

472

23.25

437

23.50

449

24.00

472

8.0

Recommendation –

8.1

Precaution for dewatering shall be adopted during construction work.

8.2

Pile Cap shall be rested over 100mm thick P.C.C.

8.3

Pile efficiency in group shall be taken as 80% of Design capacity of Pile.

8.4

Adequacy of Pile capacity shall be checked by Static / Dynamic Pile Load Test at 2.5 times the design load.

8.5

Working pile shall be checked at 1.5 times design load for the permissible settlement of 12mm.

8.6

Minimum spacing between two piles shall not be less than 2.5 times diameter of the pile.

For Unique Engineering Services, Adipur. Authorized Signatory

9.0

ANNEXURE

9.1

SAMPLING:

9.1.1

Disturbed soil samples :

- Disturbed samples were collected during the boring and also from

the split spoon sampler. The samples recovered were logged, labeled and placed in polythene  bags and sent to laboratory for testing. The samples collected at every 1.50m depth. 9.1.2

Undisturbed soil samples :

- Undisturbed soil samples were collected in 75mm diameter

Shelby tubes at every 1.50 m depth at the site location. The sampler used for the sampling had smooth surface and appropriate area ration and cutting edge angle thereby minimizing disturbance of soil during sampling. The samples were sealed with wax, labeled and transported to our laboratory at Vadodara for testing. Sampler was coupled together with a sampler head to form a sampling assembly. The sampler head provide a non-flexible connection between the sampling tube and the drill rods. Vent holes are provided in the sampler head to allow escape of water from the top of sampler tube during penetration. Coating of oil is applied on both sides to obtain the undisturbed samples in best possible manner. The sampler was then lowered inside the borehole on a string of drill rods and was driven to predetermined level. On completion of driving the sampler was first rotated within the borehole to shear the soil sample at bottom and then pulled out. The disturbed material in the upper end of the tube, if any, is completely removed before applying wax for sealing. The soil at the lower end of the tube is trimmed to about 10 to 15 mm. After trimming, both ends are sealed with wax applied in such a way that will prevent the soil from giving up from its sample. The  polythene bags cover both the ends. The identification mark was then made on each sample. 9.1.3

Standard Penetration Tests :

- SPT is conducted in accordance with IS: 2131-1981 in bores

holes at every change of strata or at an interval of 1.50m depth in uniform strata. The test gives  N-value; the blow counts of last 30cm of penetration of the split spoon sampler with 65kg. Hammer falling freely from 75cm height. The rods to which the sampler is attached for driving are straight, tightly coupled and straight in alignment. There after the split spoon sampler is further driven by 30cm. The number blows required to drive each 15cm penetration is recorded. The first 15cm penetration is termed as a seating value. The last 30cm penetration termed as ‘N’ Value. Respective tables and bore logs in the report shows the detail of N value.

7

9.2

LABORATORY TEST PROCEDURES:

9.2.1

Field Dry Density & Field Moisture Content:  Field

dry density and Field moisture content

were carried out in accordance with I.S. 2720 (Part-2 – 1983). The field density is found out by following equation. The value of F.D.D. & F.M.C. is shown in summary table. Field Density (bulk) = Weight of soil mass / Volume of soil mass And Field Dry Density = Bulk Density/ (1 + w), Where w is field moisture content. 9.2.2

Atterberg’s Limit: - Liquid

limit and Plastic limits are carried out for the determination of

different characteristic of soil. The tests performed in accordance with I.S.2720 P-5-1985 by using con  penetrometer. Liquid limit and plastic limit of soils are both depend up on the amount and type of clay in a soil and form the basis for the soil classification system for cohesive soils based on the Plasticity index. The liquid limit of the soil with corresponds to the moisture content of a paste which would give 25mm penetration of the cone is determined by using following formula. WL = Wx / (0.65+0.0175*X).

Where, X = Penetration of cone in the sample Wx = Moisture Content of the soil sample at the respective penetration For Plastic Limit, a soil sample weighing at least 20 gm of the soil sample passing 425 micron IS sieve is thoroughly mixed with water such that it can be easily molded with fingers. A ball is formed with about 8 to 10 gm of this soil and is rolled between the fingers and the glass plate with just sufficient pressure to roll the mass into a thread of uniform diameter of 3mm throughout its length. The soil is kneaded to a uniform mass and rolled again. The process is continued until the thread crumbles. The pieces of crumbled soil thread are collected for moisture content determination and reported as plastic limit. Values of LL, PL & PI are shown in summary 1. 9.2.3

Particle Size Distribution (IS: 2720 Part IV):  -The sieve analysis is carried out in

accordance

with IS. The results are shown in the summary-1. 9.2.4

Specific Gravity (IS: 2720 Part 3): -  In

order to determine specific gravity of soil particles

these tests were conducted on Selected samples in 50ml volumetric density bottle using  procedure described in IS. The value of Specific Gravity is shown in summary –2. 9.2.5

Triaxial Shear Test:

Triaxial shear (Quick) tests are conducted to determine the shear

 parameters of clayey samples. The shear tests are carried out in accordance with IS: 2720 (part

X, XI, XII & XIII). For unconsolidated undrained (Quick) Triaxial compression test, the specimen having dia 38mm and height to diameter ration of 2 is prepared and placed on the  pedestal of the triaxial cell after enclosing it in rubber membrane. The cell is then assembled with the loading ram and then placed in the loading machine. The fluid is admitted to the cell and the pressure is raised to the desired value. Initial reading of the gauge measuring the axial compression of the specimen is recorded. The test is then commenced and sufficient number of simultaneous readings of load and compression measuring gauge being taken. The test is continued until the maximum value of the stress has been reached or until an axial strain of 20  percent has been attained. The test is carried out at confining stress of 0.5, 1.0, 1.5 and 2.0 kg/cm2. The shear parameters are obtained from a plot of Mohr circles. 9.2.6

Differential Free Swell test (IS: 2720 (P-40, 41)):   -In

order to determine the swelling

characteristics of the soil, differential free swell test is carried out. An oven dried soil sample, 10 gm passing through 425 micron is poured in two 100 ml graduated cylinder. One cylinder was filled with distilled water and in kerosene up to 100 ml mark. After the removal of entrapped air, sample was allowed sufficient time to attain equilibrium state of volume. The final volume of soil in each cylinder was recorded. Sp = Free swell Soil volume in water – Soil volume in kerosene Sp = Soil volume in kerosene

ROCK CORE TEST RESULTS

Uniaxial Compressive Strength

kN

kg/cm  

kg/cm

Corrected UCS

Depth

Diameter

Height

m

cm

cm

1

10.0

5.2

10.0

1.92

28.0

134

134

2

17.5

5.2

10.2

1.96

37.2

179

179

2

25.0

5.4

10.5

1.94

27.7

123

123

26.5

5.4

10.5

1.94

33.8

150

150

4

28.0

5.3

10.8

2.04

36.4

168

168

5

29.5

5.3

10.8

2.04

43.6

201

201

6

31.0

5.3

10.8

2.04

81.8

378

378

1

10.0

5.1

10.2

2.00

22.8

114

114

2

13.0

5.2

10.2

1.96

39.0

187

187

3

16.0

5.3

10.8

2.04

42.8

198

198

2

17.5

5.3

11.6

2.19

59.2

274

274

19.0

5.3

12.4

2.34

66.0

305

305

2

20.5

5.3

12.8

2.42

69.4

321

321

3

22.0

5.3

12.2

2.30

64.0

296

296

4

23.5

5.3

12.0

2.26

60.5

280

280

5

25.0

5.3

12.4

2.34

45.4

210

210

6

26.5

5.3

13.6

2.57

100.6

465

465

1

13.0

5.3

10.2

1.92

25.2

116

116

2

14.5

5.4

10.8

2.00

22.6

101

101

3

16.0

5.3

11.2

2.11

25.8

119

119

2

19.0

5.4

11.8

2.19

25.8

115

115

3

20.5

5.3

12.6

2.38

28.8

133

133

22.0

5.4

11.8

2.19

67.8

302

302

3

23.5

5.3

12.6

2.38

62.6

289

289

4

25.0

5.4

13.4

2.48

69.6

310

310

5

26.5

5.4

13.0

2.41

74.0

329

329

5

28.0

5.4

13.8

2.56

67.0

298

298

5

29.5

5.4

13.6

2.52

69.5

309

309

6

31.0

5.4

13.2

2.44

94.6

421

421

Sr.  No.

3

Borehole  No.

P 242E

3

H/D

Failure Load, KN

2

2

P 261

2 P 262