5.Section-xi Interim Report on Geotechnical Investigation

HINDUJA NATIONAL POWER CORPORATION LIMITED

BHARAT HEAVY ELECTRICALS LIMITED

INTERIM REPORT ON GEOTECHNICAL INVESTIGATION

FOR

2 X 520 MW VIZAG THERMAL POWER PROJECT

AT

VIZAG, ANDRA PRADESH

INTERIM REPORT

SEPTEMBER - 2010

BY

DBM GEOTECHNICS AND CONSTRUCTIONS PVT. LTD.

B-301, Centaur House, 3rd Floor, Shantinagar Industrial Estate, Vakola, Santacruz (E), Mumbai- 400 055

DBM

®

2746/bhel/dbm/drg/4075 Date: 27/09/2010

To,

Bharat Heavy Electricals Ltd.

Power Sector Eastern Region,

DJ-9/1, Sector – II, Salt Lake City,

Kolkata – 700 091 Kind Attn.: Mr. Aloke Mondal / Mr. Debajyoti Saha

General Manager / AGM (SCT)

(Civil Works, Pur & Cont)

Sub: Interim Report on Geotechnical Investigation for 2 x 520 MW VIZAG Thermal

Power Project at Vizag, Andra Pradesh. For Hinduja National Power Corporation Limited (HNPCL)

Ref.: LOI No. PSER:SCT:VIZ:C1113:10:LOI:2306, dated 20th July, 2010.

Dear Sir

With reference to the above mentioned subject, we are pleased to submit

herewith the Interim Report on Geotechnical Investigation. Please find the same in

order.

Thanking you and assuring the best services in all the times.

Yours faithfully

for DBM Geotechnics & Constructions Pvt. Ltd.

Vinita Wajge

Geotechnical Engineer Encl.: As above

For any clarifications on report following personnel

may be contacted

Mr. Jaydeep Wagh (Geotechnical Consultant)

Ph. No. 022-24448985 Mobile No. 9820094574

Mrs. Vinita Wajge (Geotechnical Engineer)

Ph. No. 022-67042336-40 Mobile No. 9819870130

INTERIM GEOTECHNICAL INVESTIGATION REPORT (SEPTEMBER 2010)

2x520 MW HNPCL/ VIZAG THERMAL POWER PROJECT

AT VIZAG, ANDHRA PRADESH

BHARAT HEAVY ELECTRICALS LIMITED (BHEL)

Table of Contents

Item Page 1.0 INTRODUCTION 1 2.0 EXPLORATION PROGRAM 2 2.1 Exploration Scope 2 2.2 Site Approach 3 2.3 Subsurface Conditions 4 2.4 Ground Water Table 5 3.0 FOUNDATION RECOMMENDATIONS 6 4.1 Foundation Protection 7 4.2 Lateral Earth Pressure 8 4.3 Floor Slabs/ Pavements 8 4.4 Structural Fill/ Site Grading 9 4.0 METHODOLOGY OF FIELD WORK AND LABORATORY TESTS 10 3.1 Field Work 10 3.2 Laboratory Tests 11 References/Calculations 12 ANNEXURES Location Plan of Borehole Borehole Logs Laboratory Test Results

1

INTERIM GEOTECHNICAL INVESTIGATION REPORT (SEPTEMBER 2010)

2x520 MW HNPCL/ VIZAG THERMAL POWER PROJECT

AT VIZAG, ANDHRA PRADESH

BHARAT HEAVY ELECTRICALS LIMITED (BHEL)

1.0 INTRODUCTION

Hinduja National Power Corporation Limited (HNPCL), plans construction of 2 x 520

MW Vizag Thermal Power Project at Vizag in Andhra Pradesh. Bharat Heavy Electricals

Ltd., (BHEL) have undertaken the construction work of this project. BHEL awarded the

work of geotechnical investigation to DBM Geotechnics and Constructions Pvt.

Ltd.,(DBM) Mumbai. The field work and laboratory testing work for the geotechnical

investigation are currently in progress. This interim report presents results of the

geotechnical investigation completed till date along with foundation recommendations for the

proposed plant.

2

2.0 EXPLORATION PROGRAM

2.1 Exploration Scope

The scope of work to be completed at this site is summarized below:

a) Completing Eighty Five boreholes at the site. Eleven boreholes (BH1 to BH-11) are

completed till date.

b) Completing Eighteen Trial Pits (TP)

c) Conducting Eleven Plate Load Tests (PLT)

d) Conducting Four Cyclic Plate Load Tests (CPLT)

e) Conducting Fifteen Dynamic Cone Penetration Tests (DCPT)

f) Conducting Thirty Five Electrical Resistivity Tests (ERT)

g) Conducting Ten Field Permeability Tests by Constant Head, Falling Head or Packer

Method

h) Conducting Three Cross Hole Tests

i) Conducting Four Pressuremeter Tests (PMT)

j) Conducting Seismic Refraction Tests

k) Performing Laboratory Tests on selected Soil and Rock samples.

l) Conducting chemical analysis of ground water and soil samples from boreholes

m) Preparing and submitting Geotechnical Investigation Report alongwith foundation

recommendation.

3

The locations of the boreholes, completed till date are illustrated on the Location Plan in

Annexure, and summarized below in Table A.

TABLE A

BOREHOLE LOCATIONS, COORDINATES AND GROUND LEVELS

BORE HOLE NO.

GROUND LEVEL

(m)

CO-ORDINATES BORE HOLE

TERMINATION DEPTH BELOW

GROUND LEVEL(m)

N E

BH -1 5.228 1943094 726868 35.00 BH-2 5.318 1943175 726934 35.00

BH-3 5.343 1943062 726968 35.00

BH-4 5.601 1943232 727009 35.00

BH-5 5.893 1943206 727034 35.00

BH-6 5.410 1943170 727028 35.00

BH-7 5.430 1943118 727044 35.00 BH-8 8.850 1943092 727069 35.00

BH-9 13.805 1943058 727067 35.00

BH-10 9.465 1943214 727095 35.00

BH-11 16.005 1943110 727146 35.00

2.2 Site Approach

At the coast of Bay of Bengal, the site is located near village of Pavalavasa, approximately

22.5km southwest of Vizag, in the state of Andhra Pradesh in India.

4

2.3 Subsurface Conditions

Subsurface profile generally consists of residual soils overlying completely weathered

bedrock underlain by granite bedrock. Encountered soil/rock layers are described in detail

below;

LAYER I: RESIDUAL SOILS

Residual soils, consisting mostly of reddish or yellowish brown sand or silty sand, were

encountered directly at ground surface. This layer is formed by complete in place

disintegration to texture of soil. Based on SPT Tests, relative densities of the granular soils

(sand) within this layer, ranged between medium dense to dense. Intermittent layers of clay

or silt were encountered between the sand layers. Consistency of clay/ silt was typically

hard. The lower boundary of this layer is encountered at depths between 20.50m and

32.50m below ground level.

LAYER II: COMPLETELY WEATHERED BEDROCK

Completely weathered bedrock was encountered below residual soil layer, in all boreholes

except borehole BH-3. This layer is formed by complete in-place disintegration of parent

bedrock material, but still partially retains the original rock mass structure. SPT conducted in

this layer encountered refusals, indicating very dense relative densities. Core recoveries

were typically less than 10 percent. The lower boundary of this layer was encountered at

depths varying between 26.5m and 33.5m below ground surface. Bore holes BH-9, BH-10

and BH-11 were terminated in this layer at a depth of 35.0m below ground level.

5

LAYER III: GRANITE BEDROCK

Yellowish brown or Pink Granite bedrock was encountered at depths typically between

26.5m and 33.5m below ground surface. The bedrock was typically highly weathered. A

layer of Black Phyllitic Slate was encountered at 34.0m depth in borehole BH-8. Core

Recoveries in the bedrock varied between 11 and 57 percent, while Rock Quality

Designations (RQDs) varied between 0 and 12 percent. Rock compressive strengths as

the point load index varies between 4.88 kg/cm2 and 40.09 kg/cm2. Rock compressive

strengths as determined by unconfined compression tests ranged between 280 kg/cm2 and

529 kg/cm2. The boreholes were terminated in the bedrock at a depth of 35.0m below

ground surface.

2.4 Ground water Levels

Groundwater accumulation in boreholes was measured during and after completion of

drilling activities. Groundwater was observed at depths between 1.3m and 12.8m below

ground surface in the boreholes. Seasonal and annual fluctuations in ground water levels

can be expected to occur.

6

3.0 FOUNDATION RECOMMENDATIONS

Proposed main plant should be supported on bored cast in situ piles. Proposed pile

termination depths and corresponding allowable pile capacities with planned finished

ground or formation level of +8.0m for few representative pile sizes are given in Table B

below.

Total settlement of a single pile installed in accordance with Table B below will be less than

12mm. Allowable lateral capacity of each pile can be conservatively taken as 0.017D1.6

tons (where D is pile diameter in cms). Depth of fixity can be taken as 17 D0.8 below pile

cap.

TABLE-B

SAFE ALLOWABLE CAPACITIES FOR BORED PILES

Pile diameter (mm)

Pile termination depth below finished ground level

(+8.0m R.L.)(m)

Vertical Downward Pile Capacity (tons)

Uplift Pile Capacity

(tons)

Lateral Pile Capacity

(tons)

450 20 40 20 7

25 50 25

4D socketing in *CWR 85 40

500 20 50 25 9

25 60 35


600 20 65 35 12

25 88 45


750 20 100 50 17

25 130 70


1070 20 170 90 30

25 245 130 4D socketing in *CWR 440 220

*CWR = Completely Weathered Rock

7

Soils encountered at this site are not susceptible to liquefaction.

Foundation recommendations for shallow foundations for relatively light structures will be

provided in subsequent interim/ final reports.

3.1 Foundation Protection

Results of chemical analysis on soil and groundwater samples are enclosed in the Annexure.

Results of the soils and water samples fall under Class 1 for sulphate and chloride

concentrations (As per IS456 and as per CIRIA Sp. Publication No. 31). A ‘severe’ Exposure

Condition was assigned to this site. Therefore following precautions are recommended to

protect subsurface concrete and reinforcement.

Type of Cement: OPC or PPC

Minimum Grade of Reinforced Concrete: M30

Minimum cement content for piles 400 kg/m3

Maximum Water Cement Ratio: 0.50

Minimum Cover to Reinforcement in pile: 75mm

8

3.2 Lateral Earth Pressures

Basement walls, if any, will be subjected to lateral earth pressures. A soil submerged unit

weight (rsub) and coefficient of active lateral earth pressure (ka) of 0.8 t/m3 and 0.33,

respectively, should be utilized for design of basement walls installed without adjacent pile

shoring walls.

3.3 Floor Slabs / Pavements

The existing soils encountered at this site are capable of providing support for proposed floor

slabs and pavements. A minimum 0.3m of compacted soils should be provided beneath

pavements.

Areas to receive fill or pavements should be proof rolled with heavy equipment or dump

trucks to delineate zones of any loose or soft soils, which may require removal and

compaction. Based on borehole data, a minimum California Bearing Ratio (CBR) value of 6

can be used for design of pavements installed at or near existing ground surface. CBR tests

can be conducted on new fill material or on existing soils to determine whether higher CBR

values are possible.

9

3.4 Structural Fill/Site Grading

Compacted fill for site grading or beneath pavements/floor slabs, should consist of non-

expansive soil, free of organics and rubble. On-site soils are suitable for use as compacted

fill directly at structures. Compaction of granular soils to the recommended degree of

compaction can generally be attained with vibratory compaction equipment. Proper

compaction of soils can be achieved with pneumatic type compactors under optimum

moisture conditions. Structural fill should be placed in loose lifts of 200mm and compacted

to a minimum of 95 percent of its maximum dry density as determined by the Standard

Proctor Test.

10

4.0 METHODOLOGY OF FIELD WORK AND LABORATORY TESTS

4.1 Field Work

The sub-surface investigation was completed generally as per IS: 1892-1979. The field

investigation was carried out using rotary drilling machines. Casing was used to support

sides of borehole until sufficiently stiff strata was encountered. Standard Penetration Tests

(i.e. SPT) were carried out in soil in accordance with IS 2131-1981. Using this procedure, a

split-barrel sampler is driven into the soil by 63.5 kg. weight falling through 75 cm height.

After an initial set of 15cm, number of blows required to drive the sampler an additional 30

cm, is known as “penetration resistance” or “N value”.

When SPT refusal was obtained in hard strata, rock coring was done using diamond bit and

double tube core barrel to obtain good quality rock samples. Percent Rock Core Recovery

and percent Rock Quality Designation (%RQD) were determined. % RQD is defined as =

100 x Sum of length of rock pieces in cms, each having lengths greater than 10cms/Total

length of core run in cms.

11

4.2 Laboratory Tests :

The laboratory tests were conducted in DBM’s well equipped soil testing laboratory under the

supervision of qualified and experienced engineers. Laboratory testing comprised of

following tests conducted as per procedures given in relevant IS codes.

a) Grain Size Distribution by Sieve Analysis and

Hydrometer Analysis

IS-2720

( Part-IV)

b) Consistency limits determination to obtain

liquid limit and plastic limit.

IS 2720

(Part – V)

c) Specific Gravity determination IS 2720 (Part–III)

(S-1)

d) Chemical analysis of soil to determine pH,

Sulphate ( SO3) and Chloride (CI)

IS 2720 (Part-XVI,

XVII) Mohr’s method

e) Chemical analysis of water to determine pH,

Sulphate ( SO3) and Chloride (CI)

IS 3025 (Part XI,

XXIV, XXXII)

f) Soaked crushing strength of rock IS 9143

g) Point Load Index test on rock samples IS 8764

h) Porosity, Density test on rock samples IS 13030

i) Engineering classification of soil IS 1498

Sincerely,

DBM GEOTECHNICS AND CONSTRUCTIONS PVT. LTD. __________________________________ Jaydeep Wagh B.E., M.S., P.E. (Geotechnical)

REFERENCES

1) Foundation Analysis and Design, J.E. Bowles, McGraw Hill Publication, 5th Edition,

1996. 2) Soil Mechanics and Foundation Engineering, K.R. Arora, Standard Publishers

Distributors, Fourth Edition, 1997. 3) Foundation Design Manual, N. V. Nayak, 5th Edition, 1996 4) Geotechnical Engineering & Evaluation, Roy Hunt, 1996. 5) IS 8009, Code of Practice for settlement below Foundations on Soil

6) Pile Design and Construction Practice, M. J. Tomlinson, 1992 7) IS14593-1998, Design and Construction of bored Cast-In-Situ Piles Founded on

Rocks- Guidelines

8) IS 2911 (Part1/ Section 2) 1979 Code of Practise for design and Construction of Pile Foundations (Concrete Piles- Bored Cast in situ Piles).

SAMPLE CALCULATION OF ALLOWABLE BEARING CAPACITY

FOR PILE FOUNDATIONS (Borehole BH-9) ________________________________________________ +0.0m

Layer Ia, Sand Corrected SPT N = 12 Ø=30º, c= 0, γ= 1.7t/m3 ________________________________________________-5.0m Layer Ib, Sand Corrected SPT N = 14 Ø=31º , c= 0, γ= 1.7t/m3 ________________________________________________-9.0m Layer Ic, Sand Corrected SPT N = 17 Ø=33º , c= 0, γ= 1.9t/m3 ________________________________________________-12.0m Layer Id, Sand Corrected SPT N = 18 Ø=34º , c= 0, γ= 2t/m3 _______________________________________________-14.0m Layer Ie, Sand Corrected SPT N = 20 Ø=35º , c= 0, γ= 2t/m3 _______________________________________________-19.0m Layer If, Sand Corrected SPT N = 21 Ø=37º , c= 0, γ= 2t/m3 _______________________________________________-20.0m Layer Ig, Sand Corrected SPT N = 21 Ø=38º , c= 0, γ= 2t/m3 _______________________________________________-26.5m Layer Ih, Sand Corrected SPT N = 20 Ø=38º , c= 0 , γ= 2t/m3 _______________________________________________-32.0m Layer Ij, Completely Weathered Rock SPT N > 50, γ= 2.1t/m3

Clay Layer is assumed at pile tip (20m or 25m below ground)

SAMPLE CALCULATIONS OF PILE CAPACITIES

(BOREHOLE BH-9)

PILE DIAMETER = 0.75 m

PILE DEPTH = 20 m

Cut off level= 3 m (Assumed)

A) END BEARING CAPACITY (IS2911):

Ultimate End Bearing Capacity =

Where,

Cu = soil cohesion

=SPT N/1.5 ( Reference: Foundation Design Manual, N.V. Nayak)

Nc = Bearing Capacity Factor = 9 for clay

Nq and Nr = Bearing Capacity Factor (Obtained from IS2911)

q = Eff. overburden pressure at pile tip (limited to a depth of 15xD) = 9.0 t/m2

r = TOTAL unit weight = 1.8 t/m3

depth of water table = 0 m

B) SKIN FRICTION CAPACITY (IS2911)

Ultimate Skin Friction Capacity =

α= adhesion for clay (Obtained from IS2911)

K = Coefficient of passive pressure (IS2911) = 1 1

δ = angle of friction = soil friction angle (Φ)(From IS6403 )

q = Eff. Overburden pressure (limited to a depth of 15xD)

4]5.0)1([

2D

xNDNqcN qc

Π+−+ γγ

))](tan([ DLKqc Π+ δα


Skin End

SPT Cu δ q α Nc Nq Nr friction Bearing

N (t/m2) (degrees) Capacity Capacity

From To

0 3 14 0.0 31.1 1.2 na 9.0 na na 0.0 na

3 7 17 0.0 32.0 4.0 na 9.0 na na 23.6 na

7 9 18 0.0 32.3 6.4 na 9.0 na na 19.1 na

9 14 20 0.0 32.9 9.0 na 9.0 na na 68.5 na

14 20 21 0.0 33.1 9.0 na 9.0 na na 83.1 na

20 21.5 38 25.3 0.0 9.0 0.3 9.0 1.0 0.0 0.0 104.7

21.5 27 20 0.0 32.9 NA na 9.0 na na na na

27 30 50 0.0 37.0 NA na 10.0 na na na na

30

TOTAL CAPACITY = 194.2 104.7

TOTAL DOWNWARD ULTIMATE PILE CAPACITY = 299 tons

TOTAL DOWNWARD ALLOWABLE PILE CAPACITY = 120 tons (Factor of safety of 2.5)

TOTAL ALLOWABLE UPLIFT CAPACITY = 51.3 tons (Factor of safety of 2.5)

Conservatively, clay Layer is assumed at pile tip (20m below ground)

Depth

of Layer Soil Type

Below Ground

sand

sand

sand

sand

sand

clay

sand

sand

4]5.0)1([

2D

xNDNqcN qc

Π+−+ γγ



(BOREHOLE BH-9)


PILE DEPTH = 25 m




Where,

Cu = soil cohesion













4]5.0)1([

2D

xNDNqcN qc

Π+−+ γγ



Skin End



From To

0 3 14 0.0 31.1 1.2 na 9.0 na na 0.0 na

3 7 17 0.0 32.0 4.0 na 9.0 na na 23.6 na

7 9 18 0.0 32.3 6.4 na 9.0 na na 19.1 na

9 14 20 0.0 32.9 9.0 na 9.0 na na 68.5 na

14 20 21 0.0 33.1 9.0 na 9.0 na na 83.1 na

20 21.5 21 0.0 33.1 9.0 na 9.0 na na 20.8 na

21.5 25 20 0.0 32.9 9.0 na 9.0 na na 47.9 na

25 27 21 0.0 33.1 9.0 na 10.0 na na 0.0 134.2

27 30 50 0.0 37.0 NA na 11.0 na na na na

30






Depth

of Layer Soil Type

Below Ground

sand

sand

sand

sand

sand

sand

sand

sand

sand

4]5.0)1([

2D

xNDNqcN qc

Π+−+ γγ



(BOREHOLE BH-1)


PILE DEPTH = 20 m




Where,

Cu = soil cohesion













Skin End



From To

0 3 15 0.0 31.4 1.2 na 9.0 na na 0.0 na

3 7 15 0.0 31.4 4.0 na 9.0 na na 18.4 na

7 9 16 0.0 31.7 6.4 na 9.0 na na 14.9 na

9 11 18 0.0 32.3 7.2 na 9.0 na na 17.2 na

11 16 21 0.0 33.1 7.2 na 9.0 na na 44.3 na

16 19 21 0.0 33.1 7.2 na 9.0 na na 26.6 na

19 22 21 14.0 0.0 7.2 0.3 9.0 1.0 0.0 7.9 37.7

22 23 22 0.0 33.4 NA na 10.0 na na na na

23 28 25 0.0 34.3 NA na 11.0 na na na na

28 29.5 27 0.0 34.9 NA na 12.0 na na na na

29.5 38 50 0.0 37.0 NA na 13.0 na na na na

38






sand

sand

sand

sand

sand

sand

sand

clay

sand

Depth

of Layer Soil Type

Below Ground

sand

sand

4]5.0)1([

2D

xNDNqcN qc

Π+−+ γγ



(BOREHOLE BH-1)


PILE DEPTH = 25 m




Where,

Cu = soil cohesion

=SPT N/1.5 (Reference: Foundation Design Manual, N.V. Nayak)












Skin End



From To

0 3 15 0.0 31.4 1.2 na 9.0 na na 0.0 na

3 7 15 0.0 31.4 4.0 na 9.0 na na 18.4 na

7 9 16 0.0 31.7 6.4 na 9.0 na na 14.9 na

9 11 18 0.0 32.3 7.2 na 9.0 na na 17.2 na

11 16 21 0.0 33.1 7.2 na 9.0 na na 44.3 na

16 19 21 0.0 33.1 7.2 na 9.0 na na 26.6 na

19 22 21 0.0 33.1 7.2 na 9.0 na na 26.6 na

22 25 22 0.0 33.4 7.2 na 10.0 na na 26.9 na

25 28 25 16.7 0.0 7.2 0.3 11.0 1.0 0.0 0.0 44.5

28 29.5 27 0.0 34.9 NA na 12.0 na na na na

29.5 38 50 0.0 37.0 NA na 13.0 na na na na

38






clay

sand

sand

sand

sand

sand

sand

sand

sand

Depth

of Layer Soil Type

Below Ground

sand

sand

4]5.0)1([

2D

xNDNqcN qc

Π+−+ γγ


SAMPLE CALCULATION OF ALLOWABLE VERTICAL CAPACITY OF 600mm DIA.

PILES SOCKETED 4D IN WEATHERED BEDROCK:

A) SKIN FRICTION CAPACITY IN 4D ROCK SOCKET:

As per Cole and Stroud Method (Reference No. 3) for soft rock, the zero strength bedrock is

assumed to be a hard cohesive soil.

Using a minimum SPT N value of 60 in weathered bedrock.

Allowable Skin End Bearing Capacity = qall = aC / F.S. (Reference No. 3)

Where,

c = cohesion = N/1.5 = 60/1.5 = 40 t/m2

a = adhesion factor

F.S. = Factor of Safety

(a/FS) = 0.3

Therefore, Allowable Skin Friction Capacity = 0.3 x 40 = 12 t/m2

Allowable End Bearing Capacity of 600mm dia piles = πDL (12) = 3.142 x 0.60 x 2.4 x

12 t/m2 = 55 tons

B) END BEARING CAPACITY IN LOW STRENGTH HIGHLY WEATHERED

BEDROCK:

Using a minimum SPT N value of 60 at pile tip in the bedrock.

As per Cole and Stroud Method (Reference No. 3).

Allowable End Bearing Capacity = qall = cNc / F.S. (Reference No. 3)

Where,

c = cohesion = N/1.5 = 60/1.5 = 40 t/m2

Nc = Bearing Capacity Factor = 9 for deep foundations

F.S. = Factor of Safety = 3

Therefore, Allowable End Bearing capacity = 40 x 9 / 3 = 120 t/m2

Allowable End Bearing Capacity of 600mm dia piles = (120)πD2/4 = 35 tons

THEREFORE, TOTAL PILE CAPACITY = 55 + 35 TONS = 90 tons

Adding Skin Friction within the top 22m pile shaft in overburden soils, as shown on

attached sheet,

Pile capacity = 90 + 59 = 149 tons


(BOREHOLE BH-1)


PILE DEPTH = 22 m




Where,

Cu = soil cohesion













Skin

SPT Cu δ q α Nc Nq Nr friction

N (t/m2) (degrees) Capacity

From To

0 3 15 0.0 31.4 1.2 na 9.0 na na 0.0

3 7 15 0.0 31.4 4.0 na 9.0 na na 18.4

7 9 16 0.0 31.7 6.4 na 9.0 na na 14.9

9 11 18 0.0 32.3 7.2 na 9.0 na na 17.2

11 16 21 0.0 33.1 7.2 na 9.0 na na 44.3

16 19 21 0.0 33.1 7.2 na 9.0 na na 26.6

19 22 21 0.0 33.1 7.2 na 9.0 32.9 36.0 26.6

22 23 22 0.0 33.4 7.2 na 10.0 na na 0.0

23 28 25 0.0 34.3 NA na 11.0 na na na

28 29.5 27 0.0 34.9 NA na 12.0 na na na

29.5 38 50 0.0 37.0 NA na 13.0 na na na

38

TOTAL CAPACITY = 148.0




sand

sand

sand

sand

sand

sand

sand

sand

sand

Depth

of Layer Soil Type

Below Ground

sand

sand

4]5.0)1([

2D

xNDNqcN qc

Π+−+ γγ



(BOREHOLE BH-1)


PILE DEPTH = 20 m




Where,

Cu = soil cohesion













4]5.0)1([

2D

xNDNqcN qc

Π+−+ γγ



Skin End



From To

0 3 15 0.0 31.4 1.2 na 9.0 na na 0.0 na

3 7 15 0.0 31.4 4.0 na 9.0 na na 23.0 na

7 9 16 0.0 31.7 6.4 na 9.0 na na 18.6 na

9 11 18 0.0 32.3 8.0 na 9.0 na na 23.8 na

11 16 21 0.0 33.1 9.0 na 9.0 na na 69.2 na

16 19 21 0.0 33.1 9.0 na 9.0 na na 41.5 na

19 22 21 14.0 0.0 9.0 0.3 9.0 1.0 0.0 9.9 59.6

22 23 22 0.0 33.4 NA na 10.0 na na na na

23 28 25 0.0 34.3 NA na 11.0 na na na na

28 29.5 27 0.0 34.9 NA na 12.0 na na na na

29.5 38 50 0.0 37.0 NA na 13.0 na na na na

38






clay

sand

Depth

of Layer Soil Type

Below Ground

sand

sand

sand

sand

sand

sand

sand

sand

sand

4]5.0)1([

2D

xNDNqcN qc

Π+−+ γγ



(BOREHOLE BH-1)


PILE DEPTH = 25 m




Where,

Cu = soil cohesion

=SPT N/1.5 (Reference: Foundation Design Manual, N.V. Nayak)












4]5.0)1([

2D

xNDNqcN qc

Π+−+ γγ



Skin End



From To

0 3 15 0.0 31.4 1.2 na 9.0 na na 0.0 na

3 7 15 0.0 31.4 4.0 na 9.0 na na 23.0 na

7 9 16 0.0 31.7 6.4 na 9.0 na na 18.6 na

9 11 18 0.0 32.3 8.0 na 9.0 na na 23.8 na

11 16 21 0.0 33.1 9.0 na 9.0 na na 69.2 na

16 19 21 0.0 33.1 9.0 na 9.0 na na 41.5 na

19 22 21 0.0 33.1 9.0 na 9.0 na na 41.5 na

22 25 22 0.0 33.4 9.0 na 10.0 na na 42.0 na

25 28 25 16.7 0.0 9.0 0.3 11.0 1.0 0.0 0.0 70.3

28 29.5 27 0.0 34.9 NA na 12.0 na na na na

29.5 38 50 0.0 37.0 NA na 13.0 na na na na

38






Depth

of Layer Soil Type

Below Ground

sand

sand

sand

sand

sand

sand

sand

sand

clay

sand

sand

4]5.0)1([

2D

xNDNqcN qc

Π+−+ γγ


SAMPLE CALCULATION OF ALLOWABLE VERTICAL CAPACITY OF 750mm DIA.

PILES SOCKETED 4D IN WEATHERED BEDROCK:

A) SKIN FRICTION CAPACITY IN 4D ROCK SOCKET:

As per Cole and Stroud Method (Reference No. 3) for soft rock, the zero strength bedrock is

assumed to be a hard cohesive soil.

Using a minimum SPT N value of 60 in weathered bedrock.

Allowable Skin End Bearing Capacity = qall = aC / F.S. (Reference No. 3)

Where,

c = cohesion = N/1.5 = 60/1.5 = 40 t/m2

a = adhesion factor

F.S. = Factor of Safety

(a/FS) = 0.3

Therefore, Allowable Skin Friction Capacity = 0.3 x 40 = 12 t/m2

Allowable End Bearing Capacity of 750mm dia piles = πDL (12) = 3.142 x 0.75 x 3.0 x

12 t/m2 = 84 tons

B) END BEARING CAPACITY IN LOW STRENGTH HIGHLY WEATHERED

BEDROCK:

Using a minimum SPT N value of 60 at pile tip in the bedrock.

As per Cole and Stroud Method (Reference No. 3).

Allowable End Bearing Capacity = qall = cNc / F.S. (Reference No. 3)

Where,

c = cohesion = N/1.5 = 60/1.5 = 40 t/m2

Nc = Bearing Capacity Factor = 9 for deep foundations

F.S. = Factor of Safety = 3

Therefore, Allowable End Bearing capacity = 40 x 9 / 3 = 120 t/m2

Allowable End Bearing Capacity of 750mm dia piles = (120)πD2/4 = 53 tons

THEREFORE, TOTAL PILE CAPACITY = 84 + 53 TONS = 137 tons

Adding Skin Friction within the top 22m pile shaft in overburden soils, as shown on

attached sheet,

Pile capacity = 137 + 87 = 224 tons


(BOREHOLE BH-1)


PILE DEPTH = 22 m




Where,

Cu = soil cohesion













4]5.0)1([

2D

xNDNqcN qc

Π+−+ γγ



Skin

SPT Cu δ q α Nc Nq Nr friction

N (t/m2) (degrees) Capacity

From To

0 3 15 0.0 31.4 1.2 na 9.0 na na 0.0

3 7 15 0.0 31.4 4.0 na 9.0 na na 23.0

7 9 16 0.0 31.7 6.4 na 9.0 na na 18.6

9 11 18 0.0 32.3 8.0 na 9.0 na na 23.8

11 16 21 0.0 33.1 9.0 na 9.0 na na 69.2

16 19 21 0.0 33.1 9.0 na 9.0 na na 41.5

19 22 21 0.0 33.1 9.0 na 9.0 32.9 36.0 41.5

22 23 22 0.0 33.4 9.0 na 10.0 na na 0.0

23 28 25 0.0 34.3 NA na 11.0 na na na

28 29.5 27 0.0 34.9 NA na 12.0 na na na

29.5 38 50 0.0 37.0 NA na 13.0 na na na

38

TOTAL CAPACITY = 217.8




Depth

of Layer Soil Type

Below Ground

sand

sand

sand

sand

sand

sand

sand

sand

sand

sand

sand

4]5.0)1([

2D

xNDNqcN qc

Π+−+ γγ


CALCULATION OF LATERAL CAPACITY OF PILE:

Ref. : Appendix-B (Revised) of IS 2911 (Part 1/Sec. 2) - 1979.

From soil profile it can be seen that top of piles will be through medium dense granular soils.

Constant K1 = 0.525 kg/cm3 for medium dense sand in submerged condition.

5

1K

EIT =

Where,

E = Modulus of Elasticity of pile material = 2.8 x 105 kg/cm

2 for concrete

I = Moment of Inertia = π D4/64 cm

2 (D is pile diameter in cm)

Therefore,

5

45

525.064

108.2

x

DxxT

Π=

T = 7.65 D0.8

(D is pile diameter in cm)

The piles will be fixed head piles.

Unsupported pile length = 0.0m

Length of fixity, Lf, can be obtained from Fig. 2 of the reference mentioned above.

For fixed head pile Lf/T = 2.2 (Refer Fig. 2 of the reference mentioned above.)

Therefore, length of fixity = Lf = 2.2 * T = 2.2 x 7.65 D0.8

= 16.8 D0.8

For fixed head pile, allowable lateral load, Qa corresponding to a deflection Y = 0.5 cm,

Qa = 12 EIY/( L1 + Lf)3

kg = (12 * 2.8 * 105 * π D

4 * 0.5)/(64 * (L1 + Lf)

3)

Qa = 17.4 (D)1.6

Therefore, For 45cm dia piles, Qa = 17.4 (D)1.6 = 7,685 kgs = 7 tons



Date post:	17-Feb-2016
Category:	Documents
Upload:	raghav
View:	230 times
Download:	3 times

5.Section-xi Interim Report on Geotechnical Investigation

Documents