5. BEARING CAPACITY OF SOIL :

Formula used for computationSquare Footing Non-cohesive soil

Formula used for computation

Cohesive soil: qa = 720 ( N-3) {( B+1)/2B}2 Rw'

Qult = CNCSC + DfNq + 0.5BNS Ref: Foundation Design by Wayne C. Teng(Ref:Foundation Analysis and Design by J.E. Bowles) Where,

Qallowable = Qult/3 qa = Allowable bearing capacity of soil in psf

         Hole No. Depth below the existing

N field qu in

Net allowable bearing capacity of soil for

  ground level in ft. (avg) psf square footing in Ksf ( F.S. used 3 )

1

5.00 4 - 1.18

7.00 4 - 1.18

8.50 5 - 1.65

10.00 5 - 1.65

12.00 5 - 1.65

13.50 6 - 1.88

15.00 6 - 1.88

2

5.00 3 - 0.90

7.00 3 - 0.90

8.50 4 - 1.18

10.00 4 - 1.18

12.00 4 - 1.18

13.50 5 - 1.65

15.00 5 - 1.65

* qu = Unconfined compressive strength of soil

ULTIMATE SKIN FRICTION FOR CONCRETE PILE ( fs )───────────────────────────────────────────────Formula usedCohesive Soil : fs = α Cd ( Cd = qu/2 )Non-cohesive Soil : fs = Ks Pd tan δ ( δ = 3/4 φ )( Ref: Foundation Design & Construction by M.J. Tomlinson. Fifth Edition. Chapter Seven.)┌────┬─────────────┬─────┬───────┬──────┬──────┬──────┬──────┬──────┬──────┐│ │Depth in ft. │τ' │_ │N │ _ │ │ │ q │ f ││Hole├──────┬──────┤ soil│Pd=τ'Df│ field│ K │ φ │ α │ u │ s ││No. │ From │ To │ pcf.│ Ksf. │ (avg)│ s │degree│ │ Ksf. │ Ksf. │├────┴──────┴──────┴─────┴───────┴──────┴──────┴──────┴──────┴──────┴──────┤│ 1 5.00 18.00 45.00 0.58 6 1.10 18.00 ─ ─ 0.08 ││ 18.00 22.00 50.00 0.20 13 ─ ─ 0.45 3.25 0.73 ││ 22.00 27.00 50.00 0.25 10 ─ ─ 0.45 2.50 0.56 ││ 27.00 32.00 50.00 0.25 12 ─ ─ 0.45 3.00 0.67 ││ 32.00 37.00 55.00 0.28 15 ─ ─ 0.45 3.75 0.84 ││ 37.00 42.00 50.00 0.25 11 ─ ─ 0.45 2.75 0.62 ││ 42.00 45.00 50.00 0.15 9 ─ ─ 0.45 2.25 0.51 ││ 45.00 47.00 50.00 0.10 9 ─ ─ 0.45 2.25 0.51 ││ 47.00 50.00 50.00 0.15 12 ─ ─ 0.45 3.00 0.67 ││ 50.00 53.00 50.00 0.15 12 ─ ─ 0.45 3.00 0.67 ││ 53.00 55.00 60.00 0.12 37 1.30 33.00 ─ ─ 1.45 ││ 55.00 60.00 60.00 0.30 35 1.30 33.00 ─ ─ 1.58 ││ 60.00 65.00 60.00 0.30 40 1.30 33.00 ─ ─ 1.76 ││ 65.00 75.00 60.00 0.60 47 1.30 35.00 ─ ─ 2.17 ││ 75.00 77.00 60.00 0.12 45 1.30 35.00 ─ ─ 2.30 ││ 77.00 85.00 65.00 0.52 50 1.30 36.00 ─ ─ 2.30 ││ 85.00 90.00 65.00 0.32 50 1.30 36.00 ─ ─ 2.30 ││ ││ 2 5.00 17.00 40.00 0.48 5 1.00 12.00 ─ ─ 0.04 ││ 17.00 22.00 50.00 0.25 10 ─ ─ 0.45 2.50 0.56 ││ 22.00 27.00 50.00 0.25 11 ─ ─ 0.45 2.75 0.62 ││ 27.00 32.00 50.00 0.25 14 ─ ─ 0.45 3.50 0.79 ││ 32.00 37.00 55.00 0.28 16 ─ ─ 0.45 4.00 0.90 ││ 37.00 42.00 50.00 0.25 10 ─ ─ 0.45 2.50 0.56 ││ 42.00 45.00 50.00 0.15 8 ─ ─ 0.45 2.00 0.45 ││ 45.00 47.00 50.00 0.10 8 ─ ─ 0.45 2.00 0.45 ││ 47.00 50.00 50.00 0.15 12 ─ ─ 0.45 3.00 0.67 ││ 50.00 52.00 50.00 0.10 12 ─ ─ 0.45 3.00 0.67 ││ 52.00 55.00 60.00 0.18 24 1.25 32.00 ─ ─ 1.31 ││ 55.00 60.00 60.00 0.30 30 1.25 32.50 ─ ─ 1.46 ││ 60.00 65.00 60.00 0.30 34 1.30 33.00 ─ ─ 1.73 ││ 65.00 75.00 60.00 0.60 41 1.30 34.00 ─ ─ 2.07 ││ 75.00 83.00 60.00 0.48 47 1.30 35.00 ─ ─ 2.30 ││ 83.00 85.00 65.00 0.13 50 1.30 36.00 ─ ─ 2.30 ││ 85.00 95.00 65.00 0.65 50 1.30 36.00 ─ ─ 2.30 ││ 95.00 100.00 65.00 0.32 50 1.30 36.00 ─ ─ 2.30 │└──────────────────────────────────────────────────────────────────────────┘

CARRYING CAPACITY OF PILE:─────────────────────────┌────────┬─────┬───────┬────────────────────────────────┬──────────────────┐│ Type │B.H. │Length │Ultimate Carring Capacity(Kips) │Allowable Carrying││ of │No. │of pile├───────────────┬────────────────┤Capacity of pile ││ pile │ │(feet) │Base Resistance│Shaft Resistance│(Kips) F.S.=2.5 │├────────┼─────┴───────┴───────────────┴────────────────┴──────────────────┤│ 18"dia │ 1 40 18 89 43 ││cast-in-│ 45 24 104 51 ││situ RCC│ 50 153 127 112 ││pile │ 55 167 164 132 ││ │ 60 185 205 156 ││ │ 70 312 307 248 ││ │ 80 366 416 313 ││ │ ││ │ 2 40 16 89 42 ││ │ 45 24 103 51 ││ │ 50 120 128 99 ││ │ 55 150 162 125 ││ │ 60 182 203 154 ││ │ 70 257 301 223 ││ │ 80 360 409 308 ││ │ 90 407 517 370 ││ │ 95 434 572 402 │├────────┼─────────────────────────────────────────────────────────────────┤│ 20"dia │ 1 40 22 99 49 ││cast-in-│ 45 29 115 58 ││situ RCC│ 50 189 141 132 ││pile │ 55 206 182 155 ││ │ 60 228 228 183 ││ │ 70 385 342 291 ││ │ 80 452 462 366 ││ │ ││ │ 2 40 20 99 48 ││ │ 45 29 115 58 ││ │ 50 149 142 116 ││ │ 55 185 180 146 ││ │ 60 225 226 180 ││ │ 70 317 334 261 ││ │ 80 445 454 360 ││ │ 90 502 575 431 ││ │ 95 535 635 468 │└────────┴─────────────────────────────────────────────────────────────────┘

Note : Pile length is effective from 5 ft below the existing ground level.

8. DISCUSSION AND COMMENT:

8.1 The proposed 8-storied residential building of Mr. Md. Abdul Mannan is going to be

constructed at Plot No. 674/35, Katashurre, Bochila Road, Mohammadpur, Dhaka

where the location of 2nos. of bore hole points are shown on the site plan attached

in this report.

8.2 The net allowable bearing capacity of soil for square footing at 5ft, 7ft. 8.5ft, 10ft,

12ft, 13.5ft and 15ft depth below the existing ground level of each bore hole has

been furnished in this report considering a factor of safety of 3 for necessary

utilization .

8.3 The field exploration data , SPT values and the net allowable bearing capacity of

soil for square footing represent that the underlying subsoil stratum within the load

bearing zone up to 18ft depth in the region of BH-1 and 17ft depth in the region of

BH-2 is not good enough to sustain the superimposed load of the proposed

structure .

8.4 Therefore, transmission of superimposed load of the proposed structure to a deeper

and resistive stratum by means of RCC piling as commented below.

8.5 In view of the above discussion and observation supported with exploration data

and the laboratory test results the following suggestion has been furnished for

founding the proposed 8-storied residential building in the explored area.

18"dia. or 20" dia. cast-in-situ RCC pile of suitable length may be provided for construction of the proposed structure. The allowable carrying capacity of cast-in-situ RCC pile of said dimension of different lengths has been furnished in this report for necessary utilization. A factor of safety of 2.5 and the pile cut-off length of 5ft depth below the existing ground level have been used for computation of allowable carrying capacity of RCC pile. * Finally , it is noted here that the design engineer will take the appropriate decision about the type, depth and extent of foundation considering the economy and safety of the proposed structure based on geological condition of the site and physical properties of the underlying subsoil stratum as furnished in this report.

THE NATIONAL SOIL ENGINEERSDHAKA

CLIENT : MR. MD.ABDUL MANNAN

LOCATION : PLOT NO.674/35,KATASHURE,BOCHILA ROAD,

MOHAMMADPUR, DHAKA.

Not to scale

BH-1

R O A D

25’

61'

51'-6’’

BH-2

15'

15'

12'

THE NATIONAL SOIL ENGINEERSDHAKA.

BORE LOGCLIENT : MR. MD. ABDUL MANNANLOCATION : PLOT NO. 674/35, KATASHURE, BOCHILA ROAD,

MOHAMMADPUR, DHAKA.

BORE HOLE NO. 01 DEPTH:- 90'-0" DIA:- 4" DATE:- 11-11-2012DEPTH

INFEET

THICKNESS CLASSIFICATION OF SOIL LOG

STANDARD PENETRATION TEST/FEET

10 20 30 40 50

REMARKSON

SAMPLES

DEPTH INFEET

G.W.T

18'-0"

27'-0"

53'-0"

77'-0"

90'-0"

18'-0"

9'-0"

26'-0"

24'-0"

13'-0"

Yellowish brown fine SAND, trace silt & mica (very loose to loose)

Light yellowish brown & grey medium Compressible SILT (stiff)

Light grey medium Compressible SILT, trace fine sand (stiff)

Light yellowish brown fine SAND, some silt trace mica (dense)

Light yellowish brown fine SAND, trace silt & mica (very dense)

4

5

6

13

10

12

11

9

12

15

37

35

40

48

45

50

50

50

D-1 = 3'-6" to 5'-0"

D-2= 8'-6" to 10'-0"'

D-3=13'-6" to 15'-0"

D-4= 18'-6" to 20'-0"

D-5= 23'-6" to 25'-0"

D-6= 28'-6" to 30'-0"

D-7= 33'-6" to 35'-0"

D-8= 38'-6" to 40'-0"

D-9= 43'-6" to 45'-0"

D-10= 48'-6" to 50'-0"

D-11= 53'-6" to 55'-0"

D-12= 58'-6" to 60'-0"

D-13=63'-6" to 65'-0"

D-14=68'-6" to 70'-0"

D-15=73'-6" to 75'-0"

D-16=78'-6" to 80'-0"

D-17=83'-6" to 85'-0"

D-18=88'-6" to 90'-0"

6'-0"

DISTURBED SAMPLE UNDISTURBED SAMPLE

THE NATIONAL SOIL ENGINEERSDHAKA.

BORE LOGCLIENT : MR. MD. ABDUL MANNANLOCATION : PLOT NO. 674/35, KATASHURE, BOCHILA ROAD,

MOHAMMADPUR, DHAKA.

BORE HOLE NO. 02 DEPTH:- 100'-0" DIA:- 4" DATE:- 12-11-2012DEPTH

INFEET

THICKNESS CLASSIFICATION OF SOIL LOG

STANDARD PENETRATION TEST/FEET

10 20 30 40 50

REMARKSON

SAMPLES

DEPTH INFEET

G.W.T

17'-0"

32'-0"

37'-0"

52'-0"

83'-0"

100'-0"

17'-0"

15'-0"

5'-0"

15'-0"

31'-0"

17'-0"

Light yellowish brown fine SAND, trace silt & mica (very loose)

Bluish grey & medium Compressible SILT (stiff)

Light grey medium plastic CLAY (very stiff)

Light grey medium Compressible SILT, trace fine sand (stiff)

Light yellowish brown fine SAND, some silt trace mica

(medium dense to dense)

Light yellowish brown fine SAND, trace silt & mica (very dense)

3

4

5

10

11

14

10

8

12

16

24

30

34

40

42

47

50

D-1 = 3'-6" to 5'-0"

D-2= 8'-6" to 10'-0"'

D-3=13'-6" to 15'-0"

D-4= 18'-6" to 20'-0"

D-5= 23'-6" to 25'-0"

D-6= 28'-6" to 30'-0"

D-7= 33'-6" to 35'-0"

D-8= 38'-6" to 40'-0"

D-9= 43'-6" to 45'-0"

D-10= 48'-6" to 50'-0"

D-11= 53'-6" to 55'-0"

D-12= 58'-6" to 60'-0"

D-13=63'-6" to 65'-0"

D-14=68'-6" to 70'-0"

D-15=73'-6" to 75'-0"

D-16=78'-6" to 80'-0"

D-17=83'-6" to 85'-0"

D-18=88'-6" to 90'-0"

D-19=93'-6" to 95'-0"

D-20=98'-6" to 100'-0"

6'-0"

Over

DISTURBED SAMPLE UNDISTURBED SAMPLE