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GEOTECHNICAL INVESTIGATION

REPORT

PROJECT

REPORT ON SOIL INVESTIGATION WORK FOR PROPOSED SUB-STATION AT C-BLOCK,

KRISHNA NAGAR, DELHI

SUBMITTED BY

RAO ENGINEERING ENTERPRISES GEOTECHNICAL CONSULTANTS & LAND SURVEYORS

91-D-3, STREET NO.1, EAST MOTI BAGH , OLD ROHTAK ROAD, DELHI-110007. PHONES: 011-23698806, Mob. 09310502435, 09310402435, 09811108174, TeleFax-23691434

e-mail : [email protected],[email protected]

PROJECT : REPORT ON SOIL INVESTIGATION WORK FOR PROPOSED

SUB-STATION AT C-BLOCK, KRISHNA NAGAR, DELHI. CLIENT : BSES YAMUNA POWER LIMITED 1ST FLOOR, D-BLOCK, BSES BHAWAN, NEHRU PLACE, DELHI REPORT NO. : 7038 DATE : 14.04.2015

RAO ENGINEERING ENTERPRISES - - - GEOTECHNICAL REPORT

REPORT ON SOIL INVESTIGATION WORK FOR PROPOSED SUB-STATION AT C-BLOCK, KRISHNA NAGAR, DELHI.

C O N T E N T S

PAGE NO.

1.0 INTRODUCTION 1 1.1 PROJECT DESCRIPTION 1 1.2 AIM OF SOIL INVESTIGATION 1 1.3 SCOPE OF WORK 2 2.0 INVESTIGATIONS CONDUCTED 3 2.1 INSITU TESTS 3 2.1.1 BOREHOLES PROCEDURE 3 2.1.1.1 WATER TABLE 4 2.1.1.2 STANDARD PENETRATION TEST RESULTS 4 2.1.2 ELECTRICAL RESISTIVITY TEST PROCEDURE 5 2.2 LABORATORY TESTS AND RESULTS 6-11 3.0 OBSERVATIONS 12 4.0 DISCUSSIONS 12 4.1 TYPE & DEPTH OF FOUNDATION 13 4.2 ALLOWABLE BEARING PRESSURE 13 5.0 RECOMMENDATIONS 14 5.1 OPEN/RAFT FOUNDATIONS 14 5.2 PILE FOUNDATIONS 14-15 6.0 INTERPRETATION OF ERT 15-16 7.0 CHEMICAL RESULTS 16 8.0 CLOSURE 17 ------ FIGURES 1-12

*****************************

RAO ENGINEERING ENTERPRISES -- GEOTECHNICAL REPORT -- PAGE 1

1.0 INTRODUCTION

1.1 PROJECT DESCRIPTION

This soil investigation work, whose results are being presented herewith, has been carried out for the Proposed Sub-Station at C-Block, Krishna Nagar, Delhi.

1.2 AIM OF SOIL INVESTIGATION

Soil investigation has been conducted at the site in order to evaluate the parameters required for design of foundations. These parameters are :

(a) Type of foundation on which the

proposed super structure will be supported.

(b) Depth of foundation , and (c) Allowable bearing pressure at the

founding level.


To evaluate these parameters , following engineering properties of the sub - soil have been studied :

(a) Sub-soil Penetration Resistance characteristics

which have been determined insitu. (b) Properties like particle size distribution,

Atterberg limits, bulk density, specific gravity, moisture content, and shear strength parameters; which have been determined in the laboratory by conducting testing of both disturbed as well as undisturbed samples.

1.3 SCOPE OF WORK

The stipulated scope of work comprised of the following : 1. Mobilization of equipment and personnel to the

site and back. 2. Sinking 5 boreholes to 18.0m depth or refusal

whichever is encountered earlier, observing ground water table levels, conducting required field and laboratory tests and their analysis.

3. Conducting 5 Nos. Electrical Resistivity Tests at

the site. 4. Preparation and submission of technical report in

triplicate.

RAO ENGINEERING ENTERPRISES -- GEOTECHNICAL REPORT -- PAGE 3 2.0 INVESTIGATIONS CONDUCTED 2.1 INSITU TESTS

Locations of field-testing points have been marked at the site as per the direction of the client. These locations have been designated as BH-1 to BH-5, ERT-1 to ERT-5 in this report.

2.1.1 BOREHOLES PROCEDURE

The boreholes were progressed to the specified depth of 18.0m.The diameter of the borehole was 150mm. Where caving of the boreholes occurred, casing was used to keep the borehole stable. The work was in general accordance with IS:1892-1979. Standard Penetration Tests (SPT) were conducted in the borehole at 1.5-3.0m interval by connecting a split spoon sampler to ‘A’ rods and driving it by 45 cm using a 63.5 kg hammer falling freely from a height of 75 cm. The tests were conducted in accordance with IS:2131-1981.

The number of blows for each 15 cm of penetration was recorded. The blows required to penetrate the initial 15 cm of the split spoon for seating the sampler is ignored due to the possible presence of loose materials or cuttings from the drilling operation. The cumulative number of blows required to penetrate the balance 30 cm of the 45 cm sampling interval is termed the SPT value or the ‘N’ value.

Disturbed samples were collected from the split spoon after conducting SPT. The samples were preserved in transparent polythene bags. Undisturbed samples were collected by attaching a 100 mm diameter thin walled ‘Shelby’ tubes and driving the sampler lightly using a 63.5 kg hammer in accordance with IS:2132 .

RAO ENGINEERING ENTERPRISES -- GEOTECHNICAL REPORT -- PAGE 4 2.1.1.1 WATER TABLE

In the boreholes, groundwater was encountered at about 3.80-4.10 m depth below ground surface during the time of our field investigation (April, 2015). Fluctuations may occur in measured water table due to variation in rainfall and surface evaporation rates.

2.1.1.2 STANDARD PENETRATION TEST RESULTS

Following Standard Penetration Resistance (‘N’) values have been recorded at various depths in the five boreholes.

DEPTH(M) ‘N’ VALUES - - - - - - - - - - - - - - - - - - - - - - - - BH1 BH2 BH3 BH4 BH5 - - - - - - - - - - - - - - - - - - - - - - - - 1.5 10 11 9 9 12 3.0 13 12 15 12 7 4.5 9 16 17 15 13 6.0 16 4 13 8 16 7.5 7 6 11 9 9 9.0 4 20 18 12 15 10.5 29 16 26 24 27 12.0 24 14 19 16 32 13.5 30 21 27 19 35 15.0 37 20 34 36 28 18.0 41 45 39 27 42 -----------------------------------------------


2.1.2 ELECTRICAL RESISTIVITY TEST PROCEDURE

Electrical resistivity of the soil at the site was determined at the locations specified by the client. The earth resistivity test is used for shallow subsurface exploration by means of electrical measures made at the ground surface. Resistivity measurements are made by driving four electrodes about 10 to 15 cm into the ground at a pre-selected electrode spacing.

The four electrodes were spaced at equal distance along different locations. The average of the resistivity values for each direction was taken as the mean resistivity for that spacing. The test procedure is in accordance with IS:3043:1987. Measurements are made by causing a current, I, to pass through the earth and distribute within a relatively large hemispherical earth mass. The portion of the current that flows along the surface produces a voltage drop, V.

The resistance “R” is the ratio of voltage drop ‘V’ to current I is directly measured by digital earth resistance tester. The resistivity is determined from the following equation - = 2 a R where : = apparent resistivity, ohm-m. a = spacing between the electrodes, metres

R = Resistance, ohms.


2.2 LABORATORY TESTS AND RESULTS

Following tests have been conducted on various soil and water samples in the laboratory:

Laboratory Test IS : Code Referred

Natural moisture content IS : 2720 (Part-2)-1973

Grain size analysis IS : 2720 (Part-4)-1985

Liquid & Plastic limit IS : 2720 (Part-5)-1985

Unconsolidated Undrained Triaxial shear test

IS : 2720 (Part-11)-1993

Consolidated Drained Direct Shear Test IS : 2720 (Part-13)-1986

Unconfined Compression Test IS : 2720 (Part-10)-1991

Specific Gravity Test IS : 2720 (Part-3)-1980

Determination of pH value IS : 2720 (Part-26)-1987

Chemical Analysis of soil

Determination of total soluble sulphate

IS : 2720 (Part-27)-1977

Determination of total soluble sulphate

IS : 3025 (Part-11)-1996

Determination of chloride content IS : 3025 (Part-24)-1998

Chemical Analysis of water

Determination of pH value IS : 3025 (Part-32)-1993

Results are being tabulated as follows :


LABORATORY TEST RESULTS

BOREHOLE LOCATION : 1

DISTURBED SAMPLES

DEPTH GRADATION ANALYSIS (%) ATTERBERG LIMITS(%) SP.GR (M) GRAVELS SAND SILT CLAY LIQUID PLASTIC ------------------------------------------------------------ 0.00 0 27 62 11 28.3 18.5 2.70 6.00 0 93 7 0 NON PLASTIC 2.66 11.25 0 95 5 0 NON PLASTIC 2.65 18.00 0 90 10 0 NON PLASTIC 2.67 ------------------------------------------------------------

UNDISTURBED SAMPLES

DEPTH BULK DENSITY WATER DRY COHESION ANGLE OF BELOW (gms/cc) CONTENT DENSITY SHEARING G.L. (%) (gms/cc) (kg/sq.cm) RESISTANCE (M) (Ø) -------------------------------------------------------------- 5.25 1.79 16.3 1.54 0.00 30O

8.25 1.87 17.9 1.59 0.00 31O

14.25 1.97 19.3 1.65 0.00 340 --------------------------------------------------------------




DISTURBED SAMPLES

DEPTH GRADATION ANALYSIS (%) ATTERBERG LIMITS(%) SP.GR (M) GRAVELS SAND SILT CLAY LIQUID PLASTIC ------------------------------------------------------------ 1.50 2 29 57 12 28.8 18.6 2.71 5.25 0 92 8 0 NON PLASTIC 2.66 12.00 0 95 5 0 NON PLASTIC 2.65 18.00 37 9 46 8 27.8 17.9 2.70 ------------------------------------------------------------

UNDISTURBED SAMPLES

DEPTH BULK DENSITY WATER DRY COHESION ANGLE OF BELOW (gms/cc) CONTENT DENSITY SHEARING G.L. (%) (gms/cc) (kg/sq.cm) RESISTANCE (M) (Ø) ------------------------------------------------------------ 2.25 1.70 12.9 1.51 0.00 28O

8.25 1.90 17.5 1.62 0.00 30O

11.25 1.93 18.3 1.63 0.00 320

17.25 2.03 19.9 1.69 0.98 80 ------------------------------------------------------------




DISTURBED SAMPLES


UNDISTURBED SAMPLES


8.25 1.89 16.9 1.62 0.00 30O

14.25 1.98 19.5 1.66 0.00 330 ------------------------------------------------------------




DISTURBED SAMPLES


UNDISTURBED SAMPLES


5.25 1.77 15.2 1.54 0.00 29O

11.25 1.91 16.9 1.63 0.00 320

17.25 2.03 19.5 1.70 0.00 340 ------------------------------------------------------------




DISTURBED SAMPLES


UNDISTURBED SAMPLES


8.25 1.85 16.1 1.59 0.00 31O

14.25 1.98 18.3 1.67 0.00 340 ------------------------------------------------------------

RAO ENGINEERING ENTERPRISES -- GEOTECHNICAL REPORT -- PAGE 12 3.0 OBSERVATIONS

Following points are observed from results obtained:

(a) A fill is met at the site to about 0.50m depth. Below fill, the soils met at the site are light brown sandy silt to about 1.5-3.0m depth. Below this, Light grey fine sand is met to the final explored depth of 18.0m.

(b) Bulk density values vary from 1.69 to 2.03 gms/cc whereas dry density values vary from 1.50 to 1.70 gms./cc. in the five boreholes.

(c) In silt strata, cohesion is 0.49 – 0.98 g./sq.cm with angle of shearing resistance values range from 5 to 8 degrees. However, in sand strata average cohesion is 0.00 kg./sq.cm and angle of shearing resistance varies from 28 to 34 degrees.

4.0 DISCUSSIONS

For designing the foundation system, the following Parameters are required:

(a) Suitable type of foundation on which the proposed super – structure can be supported.

(b) Depth of these foundations, and

(c) Allowable bearing pressure at the founding level Corresponding to various footing sizes.


4.1 TYPE & DEPTH OF FOUNDATION

Type of foundation to be adopted for a particular structure depends upon the loading intensity at the foundation level and the configuration of loading points. Reviewing the stratigraphy of the site, SPT values & laboratory test results, We recommend as follows:

(a) Isolated Open spread foundations or Raft foundations may be provided at the site to support the structural loads for lightly loaded foundations. We recommend a minimum foundation embedment depth of 2.0m below the existing ground surface. Recommendations for the same are provided in section 5.1 of the report.

(b) For heavily loaded foundations, we recommend that

Bored –cast-in-situ piles may be provided at the site. 300mm, 400mm, 450mm or 600mm diameter Bored–Cast-in-situ piles may be used. Recommendations for the same are provided in section 5.2 of the report.

4.2 ALLOWABLE BEARING PRESSURE FOR OPEN/RAFT FOUNDATIONS

Following criterion have been considered for evaluating the bearing capacity values :

(a) Settlement criteria

(b) Shear failure criterion

Shear failure condition as per I.S. 6403 has been considered for allowable bearing pressure computation.

Allowable settlement value of 50 mm has been considered for deducing shear strength value.


5.0 RECOMMENDATIONS

5.1 OPEN/RAFT FOUNDATIONS

The following table presents our recommended values of net allowable bearing pressure for 1-5m wide Isolated Open Spread foundations or Raft foundations(width>6.0m) bearing at or below 2.0m depth below the existing ground surface.

Foundation Depth below existing ground level, m

Recommended Net Allowable Bearing Pressure, T/m²

2.0 7.5

2.5 8.2

3.0 9.0

The above values include a safety factor of 2.5. Total settlement of foundation designed for the above net bearing pressure is expected to be about 50 mm. Net bearing pressure for foundations at intermediate depths may be interpolated linearly between the values given above.

5.2 PILE FOUNDATIONS Bored cast-in-situ piles are a feasible foundation scheme to support the structural loads.

The following table presents our recommended Compressive pile capacities for 300 mm, 400mm,450mm and 600 mm diameter bored piles with a cut off level of 2.0m below the ground level. For pile capacity design, water table has been considered to rise upto ground surface for worst condition.


Pile Diameter ,

mm

Pile Tip Length Below COL, m

Recommended Compressive Pile

capacities , Tonnes

12.0 13

14.0 15 300

16.0 18

12.0 23

14.0 27 400

16.0 32

12.0 29

14.0 35

450

16.0 41

12.0 47

14.0 58

600

16.0 68

The above values are based on as per IS:2911, Part-1, Section-2 and include a safety factor of 2.5. Safe capacities of piles of intermediate length may be interpolated linearly between the values given above. Piles should be load tests to verify capacities.

6.0 INTERPRETATION OF ELECTRICAL RESISTIVITY TESTS

Five Electrical resistivity tests were conducted at the site as per IS : 3043-1987 . The tests were conducted using the Wenner configuration along different directions at various electrode spacings ranging from 1 to 6 m. The average apparent resistivity values are presented graphically and also tabulated on Figs.7 to 11.The test results are also tabulated below:


Average Resistivity, ohm-m Electrode Spacing, m

ERT-1 ERT-2 ERT-3 ERT-4 ERT-5

1.0 2.5 3.2 5.8 9.2 5.7

3.0 4.8 2.5 4.8 10.5 3.8

5.0 5.6 5.6 3.9 4.8 4.9

6.0 7.2 7.3 3.2 6.7 7.2

These resistivity data are used as an indicator for potential for corrosion of buried metallic pipes and other utility lines.

7.0 CHEMICAL RESULTS

Chemical test results on soil and groundwater are presented in our report on sheet no. 12. The results indicate that the soils contain sulphate in the range of 0.11 to 0.13 percent and chlorides 0.02 to 0.04 percent. The pH value of soil is between 8.1 to 8.2 indicating slightly alkaline conditions. The groundwater contains 205 to 310 mg/litre of sulphate and 170 to 220 mg/litre of chlorides. The pH value of groundwater is 7.8-8.0 indicating somewhat alkaline condition.

We recommend the following measures to limit the potential for chemical attack:

(1) Concrete for Open/Raft foundations should contain a minimum cement content of 330 kg/m3 of cement.

(2) Water cement ratio in foundation concrete should

be in the range of 0.50. (3) A clear concrete cover over the reinforcement

steel of at least 50mm should be provided for all foundations.


8.0 CLOSURE

We appreciate the opportunity to perform this investigation for you and have pleasure in submitting this report. Please contact us when we can be of further service to you.

For RAO ENGINEERING ENTERPRISES

(G.R.RAO) ( PUSHPENDRA KUMAR ) DIRECTOR EXECUTIVE DIRECTOR

1

SYMBOL

Gravely siltWater table

PROPOSED SUB-STATION AT C-BLOCK, KRISHNA NAGAR, DELHI

LEGEND

Fill

Fine sandSandy silt

DESCRIPTION

6

D E

P T

H,

m0

SUMMARY OF BOREHOLE PROFILE

N-ValueBH-1

13

9

16

N-ValueBH-2

16

12

1

2

3

4

5

7

18.00m 18.00m

87

4

6

9

1029 16

4 20

1.5m10 111.5m

15.0m

11

12

13

14

15

14

21

20

24

30

37

0.5m

16

17

18 4541

N-ValueBH-3

17

15

18.00m

13

11

26

18

9

19

27

34

0.5m

39

N-ValueBH-4

15

12

18.00m

8

9

24

12

9

16

19

36

0.5m

27

N-ValueBH-5

13

7

18.00m

16

9

27

15

12

32

35

28

0.5m

42

3.0m

1.5m 1.5m

3.80m 4.00m 4.10m 3.90m 4.05m

2

GRAVEL SAND SILT CLAY% % % %

0 27 62 11

0 93 7 0

0 95 5 0

0 90 10 01/18.00 Fine sand

GRAIN SIZE ANALYSIS


1/0.00

SYMBOL DESCRIPTION

Fine sand

Sandy silt

Fine sand1/6.00

1/11.25

BH.NO/DEPTH.

0

10

20

30

40

50

60

70

80

90

100

0.001 0.01 0.1 1 10P A R T I C L E S I Z E , m m

PER

CEN

T FI

NER

BY

WEI

GH

T

GRAVELFINE MEDIUMS I L T COARSE

S A N DCLAY

3


2 29 57 12

0 92 8 0

0 95 5 0

37 9 46 8

2/1.50

SYMBOL DESCRIPTION

Fine sand

Sandy silt

Fine sand2/5.25

2/12.00

BH.NO/DEPTH.

GRAIN SIZE ANALYSIS


2/18.00 Gravely silt

0

10

20

30

40

50

60

70

80

90

100

0.001 0.01 0.1 1 10P A R T I C L E S I Z E , m m

PER

CEN

T FI

NER

BY

WEI

GH

T


S A N DCLAY

4


4 33 53 10

0 94 6 0

0 96 4 0

0 93 7 03/18.00 Fine sand

GRAIN SIZE ANALYSIS


3/2.25

SYMBOL DESCRIPTION

Fine sand

Sandy silt

Fine sand3/7.50

3/13.50

BH.NO/DEPTH.

0

10

20

30

40

50

60

70

80

90

100

0.001 0.01 0.1 1 10P A R T I C L E S I Z E , m m

PER

CEN

T FI

NER

BY

WEI

GH

T


S A N DCLAY

5


0 25 62 13

2 92 6 0

0 93 7 0

0 95 5 0

4/1.50

SYMBOL DESCRIPTION

Fine sand

Sandy silt

Fine sand4/6.00

4/12.00

BH.NO/DEPTH.

GRAIN SIZE ANALYSIS


4/18.00 Fine sand

0

10

20

30

40

50

60

70

80

90

100

0.001 0.01 0.1 1 10P A R T I C L E S I Z E , m m

PER

CEN

T FI

NER

BY

WEI

GH

T


S A N DCLAY

6


3 27 59 11

0 93 7 0

0 95 5 0

0 96 4 05/15.00 Fine sand

GRAIN SIZE ANALYSIS


5/1.50

SYMBOL DESCRIPTION

Fine sand

Sandy silt

Fine sand5/5.25

5/10.50

BH.NO/DEPTH.

0

10

20

30

40

50

60

70

80

90

100

0.001 0.01 0.1 1 10P A R T I C L E S I Z E , m m

PER

CEN

T FI

NER

BY

WEI

GH

T


S A N DCLAY

7

Electode ApparentSpacing,m Resistivity, Ohm-m

1.0 2.53.0 4.85.0 5.66.0 7.2

ELECTRICAL RESISTIVITY TEST NO - 1

1

10

100

0 2 4 6 8 10 12 14 16Electrode Spacing , m

App

aren

t Res

istiv

ity ,O

hm-m


8


1.0 3.23.0 2.55.0 5.66.0 7.3


1

10

100


App

aren

t Res

istiv

ity ,O

hm-m


9


1.0 5.83.0 4.85.0 3.96.0 3.2


1

10

100


App

aren

t Res

istiv

ity ,O

hm-m


10


1.0 9.23.0 10.55.0 4.86.0 6.7


1

10

100


App

aren

t Res

istiv

ity ,O

hm-m


11


1.0 5.73.0 3.85.0 4.96.0 7.2


1

10

100


App

aren

t Res

istiv

ity ,O

hm-m


12

SOIL :

Borehole No.

pH Value

1 8.12 8.23 8.15 8.2

WATER

Borehole No.

1234 310 190 7.8


260 200 8.0

280 170

0.13 0.02

2.25

7.9

0.11 0.04

CHEMICAL TEST RESULTS

Depth, (m)

Sulphate Content ,%

(SO3)

Chloride Content ,%

1.50 0.12 0.03

3.00 0.12 0.04

205 220 7.8

Sulphate Content mg/l (SO3)

Chloride Content, mg/l

pH Value

1.50

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