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CHAPTER 4

CASE STUDY III

ADDRESS: Malvani no.8, beside Malvani Agar bus depot, Malad (W)

DATE OF VISIT:25/01/2013Description:Before commencement of the construction work, plot was empty. G+7 storied

residential building has to be constructed.

Surrounding detailsThe surrounding buildings were constructed on shallow foundation as it was slum

area. So it was economical for the surrounding buildings to rest on shallow

foundation. Residential houses were present nearby site. Bus depot was just

adjacent to the site.Site detailsThe piling work was started from January. Total 8 piles have been constructed up

to 24th of January.

Piling was carried out with Percussion drilling (Traditional bailer & chisel

method).

Percussion drilling (Traditional bailer & chisel method)Adoptable in the areas where rock strata was available at lesser depths.

Efficiency is 1 pile per day.

Cheaper method as compared to rotary method.

Some important points Piles are resting on brown completely weathered tuffaceous breccias.

Diameter of pile varying from 600mm.

Depth at site varying from 9 to 12m.

Spacing between two piles: 3 times the diameter of pile.

Piles are bored in cast situ piles.

Designed as percole & stroud approach (N.V NAYAK)

Concrete having good workability i.e. having slump value about 150 to

200mm.

Initial setting time about 1 hour (by using retarders)

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Tests carried out on piles : a) Pile integrity test

b) Dynamic load test

Concrete was poured by trimie method of concreting.

End bearing piles.

The details regarding the total depth of each bore hole and the level at which the rock is first

struck, are given in Table -1 below.

Table -1

Table 2

STANDARD PENETRATION TESTS

Bore Hole

No.

Depth of Test (m) N Value

(Blows / 30 cm)

Remarks

1 3.00 3.60 8 Yellowish soft clay

1 4.50 5.10 13 Yellowish medium clay

1 6.00 6.60 27 Yellowish stiff clay

2 4.50 5.10 10 Yellowish medium clay2 6.00 6.60 12 Yellowish medium clay

3 6.00 6.45 27 Yellowish stiff clay

SUB - SURFACE STRATIFICATION AND ENGINEERING PROPERTIES

The sub soil profile as revealed by drilled holes can be divided in the following layers.

Layer I: DEBRIS FILL

This layer extends up to a depth varying from 1.50 m below ground level. It is composed ofrecent loose debris material deposited at the site to raise the plot ground level.

Layer II: YELOWISH BROWN SOFT TO MEDIUM CLAY

This layer extends from 1.50m to 5.0m below ground level. It is yellowish brown soft to

medium clay. It is a highly plastic residual soil having SPT blow count, N, ranging between 8

-13 along the depth.

Bore Hole No. Depth to Rock Top, m Total Depth, m

1 8.50 15.00

2 8.50 15.00

3 9.50 15.00

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Layer III: YELLOW STIFF TO VERY STIFF SANDY CLAY

This layer underlies Layer II and extends from 5.00m to 7.00m below ground level. It is

yellow stiff to very stiff sandy clay having high plasticity. The SPT blow count, N, of this

layer is 28.

Layer IV: BROWN COMPLETELY WEATHERED TUFFACEOUS BRECCIA

This layer underlies Layer-III and extends from 7.00m to 8.50m at bore hole no. 1 and 2 and to

9.0m at bore hole no.3below ground level. It is brown completely weathered tuffaceous

breccia. The core recovery is less than 10 % and RQD is 0 %.

Layer V: REDDISH BROWN HIGHLY WEATHERED TUFFACEOUS BRECCIA

This layer underlies Layer-IV and extends from 8.50m to 15.00m below ground level. It is

reddish brown highly weathered tuffaceous breccia. The core recovery ranges between 8 -

42% and RQD is 0 - 30%.

GROUND WATER TABLE

The ground water table is observed at a depth of4.50m below ground level.

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SITE:Proposed residential building at Gaikwad Nagar, MHADA

layout, Malvani, Malad(W) Mumbai.

CLIENT: M/s RASHMIN CONSTRUCTION CO. Andheri(E).

CONTRACTOR: M/s Advanced Geo-Tech Solutions, Mumbai.

BORE HOLE NO.: 1

DATE OF EXECUTION : 03/ 10/ 11 to 05/10/11

CASING : 4.0 M

METHOD OF BORING : ROTARY WASH

TYPE OF BIT : DIAMOND BIT

0.00

DIA

OFBORE

HOLE

VISUAL SOIL / ROCKDESCRIPTION G

RAPH

LOG L

AYER

SAMPLESPENETRATION TEST,

(Blows / 30 cm)

CORE

RECOVERY

%

RQD

IN

ROCK

%DEPTH TYPE-NO 15 30 45 60 N

100

MmDebris fill I

1.00

2.00

brown soft to medium clay of

high plasticityII

3.00

3.00m-

3.60mSPT-1 3 3 5 7 8

4.00

76mm 4.50 to5.10m

SPT-2 3 5 8 12 13GWT

5.00

Yellowish brown stiff to verystiff sandy clay with gravel

III6.00

6.00m-

6.60mSPT-3 7 12 15 31 27

7.00

brown completely weatheredtuffaceous breccia

IV8.00

9.00

Reddish brown highlyweathered tuffaceous breccia

V

C.P.10.00 26.7 20.0

11.00C.P. 8.7 0.0

12.00

C.P.13.00 42.0 16.7

C.P.

14.00

C.P.15.00 41.0 13.0

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REMARKS:UDS UNDISTURBED SAMPLE SPT - STANDARD PENETRATION TESTDS DISTURBED SAMPLE C.P. - CORE PIECES

SITE:Proposed residential building at Gaikwad Nagar, MHADA

layout, Malvani, Malad(W) Mumbai.

CLIENT: M/s RASHMIN CONSTRUCTION CO. Andheri(E).

CONTRACTOR: M/s Advanced Geo-Tech Solutions, Mumbai.

BORE HOLE NO.: 2

DATE OF EXECUTION : 05/ 10/ 11 to 08/10 / 11

CASING : 4.0 M

METHOD OF BORING : ROTARY WASH

TYPE OF BIT : DIAMOND BIT

0.00

DIA

OF

BORE

HOLE

VISUAL SOIL / ROCK

DESCRIPTION GRAPH

LOG

L

AYER

SAMPLESPENETRATION TEST,

(Blows / 30 cm)

CORE

RECO

VERY

%

RQD

IN

ROCK

%DEPTH TYPE-NO 15 30 45 60 N

100Mm

Debris fill I1.00

2.00

brown soft to medium clay ofhigh plasticity

II

3.00

4.00

76mm4.50 to5.10m SPT-1 3 4 6 8 10

GWT

5.00

Yellowish brown stiff to very

stiff sandy clay with gravelIII

6.00

6.00m-

6.60mSPT-2 4 5 7 11 12

7.00

brown completely weatheredtuffaceous breccia

IV8.00

C.P.9.00

Reddish brown highlyweathered tuffaceous breccia

V

C.P.10.00 19.3 9.3

11.00

C.P. 18.0 0.0

12.00

C.P.13.00 22.7 0.0

C.P.14.00

C.P.

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15.00 16.0 9.0

REMARKS:UDS UNDISTURBED SAMPLE SPT - STANDARD PENETRATION TEST

DS DISTURBED SAMPLE C.P. - CORE PIECES

SITE:Proposed residential building at Gaikwad Nagar, MHADAlayout, Malvani, Malad(W) Mumbai.

CLIENT: M/s RASHMIN CONSTRUCTION CO. Andheri(E).

CONTRACTOR: M/s Advanced Geo-Tech Solutions, Mumbai.

BORE HOLE NO.: 3

DATE OF EXECUTION : 08/ 10/ 11 to 11/10/11

CASING : 4.0 M

METHOD OF BORING : ROTARY WASH

TYPE OF BIT : DIAMOND BIT

0.00

DIA

OF

BORE

HOLE

VISUAL SOIL / ROCK

DESCRIPTION GRAPH

LOG L

AYER

SAMPLESPENETRATION TEST,

(Blows / 30 cm)

CORE

RECO

VERY

%

RQD

IN

ROCK

%DEPTH TYPE-NO 15 30 45 60 N

100Mm

Debris fill I1.00

2.00

brown soft to medium clay ofhigh plasticity

II

3.00

4.00

76mm GWT

5.00

Yellowish brown stiff to verystiff sandy clay with gravel

III6.00

6.00m-

6.45mSPT-1 6 4 23 - 27

7.00

brown completely weathered

tuffaceous brecciaIV

8.00

9.00

Reddish brown highly

weathered tuffaceous brecciaV

C.P.10.00

11.00 19.3 10.7

C.P.

12.00

C.P.21.3 0.0

13.00

14.00 27.3 24.0

C.P.

C.P.

15.00 30.0 30.0

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REMARKS:UDS UNDISTURBED SAMPLE SPT - STANDARD PENETRATION TESTDS DISTURBED SAMPLE C.P. - CORE PIECES

DESIGN OF PILE:By COLE & STROUD APPROACH

Formula,

Qap = (CuNc/FOS) x (D2/4) + (aCu1FOS) x (DL)

Where,

Qap=stress on pile due to applied or allowable or design load

Cu=shear strength of rock below the base of pile

Nc=bearing capacity factor taken as 9

FOS=factor of safety taken as 3

a/FOS=0.3

Cu1=average shear strength of rock adjacent to the shaft in the socket length

L=length of socket (3D)

Grade of concrete=M30

Diameter of pile=600mm

Socket length=3x0.6=1.8m

Using formula,

Qap= {(600x9xx0.62) / 12 }+{0.3x600xx0.6x1.8}

=1119.66 KN=114.14 t

Structural capacity=0.25x2500x3.14x0.62

As, Qap < structural capacity of pile

Therefore provide group piles

Provide 2 piles in group.