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7/25/2019 [email protected]

1/19


2/19

1

2

3

0

Piles and raft

yieldingPiles

yielding

No

yield

Allowable

settlement

Settlement

Load

Design

load

Curve 0:Raft only (settlement excessive)

Curve 1:Raft with pile designed for conventional safety factor

Curve 2:Raft with piles designed for lower safety factor

Curve 3:Raft with piles designed for full utilization of capacity


3/19

Young's modulus, Es

Bearing

stratum Depth

Soil

d= 2ro

Eso Esav Esl Esb

rc

L

Settlement

Load

Pile +

raftelastic

Pile + raft

ultimate capacityreached

Pile capacity fully utilized,

raft elastic

B

A

Pu

P1


4/19

010

009

008

007

006

3

5

4

0 16 32 48 64 80

Number of piles

(a)

0 20 40 60 80

Number of piles

(b)

Settlement:m

Factorofsafety

Soil: Es, s(very deep layer)

Raft Er, s

t

x

c

P

01

01

02

0

02

0 005 010 015x/a

MomentfactorsA,B

A

B

0

Loadlocation

x

P


5/19

0

10

20

0 01 02 03 04 05 06x/a

Shearforce,cq

0

Load

location

x

P

0

02

04

06

08

10

12

0 05 1510 20x/a

q

0

Loadlocation

Contact pressure below load q=q(P/a2)

x

P

0

02

01

03

05

07

04

06

0 05 1510 20x/a

0

Load

location

Settlement below load S= ( (12s )P)/Esa

x

P


6/19

0

0

5

10

0

10

20

5

10

0 05

Raft thickness: m

10

Values of pur

: MPa

(Es=33p

ur)

Maximuml

oadPc3:MN

150

075

030

0

5

10

0 05

Raft thickness: m

10

Values of Es:MPa

Maximuml

oadPc4:MN

Maximuml

oadPc1

:MN

Maximuml

oadPc2:MN

50

25

10

Values of Es: MPa

50

25

10

Values of Es: MPa

50

10

(c) (d)

(a) (b)


7/19

y

x

P1 P1

P1

P1

P1

P1

P1

P1

P2

P2

P2

P2

A A

A A

A A

2

2

1

1 m

1 m 2 2 2 2 1

s= 2

d= 05 m

l=10m

H=20m

tr= 05 m

2 2 2 m

Ep= Er= 30 000 MPa

p= r= 02

E= 20 MPa

= 03

Bearing capacity of raft = 03 MPaLoad capacity of each pile = 0873 MN (compression)

= 0786 MN (tension)


8/19

50

40

30

20

10

0

Average

settlement:mm

02

04

06

08

10

12

0

Mome

nt:MNm/m

0

20

40

80

60

100

%loadon

piles

0

2

4

8

6

10

Differentialsettlement:mm

Method

(a)

Method

(c)

Method

(b)

Method

(d)

Poulos&Davis

Randolph

Strip(GASP)

Plate(GARP)

FETa&Small

FE+BESinha

Randolph

Strip(GASP)

Plate(GARP)

FETa&Small

FE+BESinha

Strip(GASP)

Plate(GARP)

FETa&Small

FE+BESinha

Strip(GASP)

Plate(GARP)

FETa&Small

FE+BESinha

60

50

40

30

20

10

0

0

025

050

075

100

Maximum

settlement:mm

Maximum

moment,Mx:MNm/m

10

0

2

4

6

8

0

25

50

75

100

Differentialsettlementbetweencentre

andcornerpiles:mm

%loadonpiles

0 10 20 30 40 50

Number of piles(c)

0 10 20 30 40 50

Number of piles(d)

(a) (b)

Concentratedloading

Concentrated loading

Uniform

loading

Uniform loading

Concentrated loading

Concentrated anduniform loading

Uniform loading


9/19

0

0

50

100

0

10

20

05

10

0 05

Raft thickness,t: m Raft thickness,t: m

100

50

100

0 05 10

(c) (d)

(a) (b)

Number of piles

0

3

9

15

45

Maximum

settlement:mm

Maximummoment,Mx:MNm/m

Differentialsettlementbetweencentre

andcornercolumns:mm

%loadonpiles

60

48

36

24

12

0

Totalload:MN

0 50 100

Central settlement: mm

Number of pilesbelow raft

15

9

3

0

45

25


10/19

40

30

20

10

0

L/d

0 5010 20 30 40Number of piles, n

020

030

040

050

060

070

080

Values of s/ssf

s= settlement of piled raft

ssf= settlement of raft alone


11/19

00 1 2

02

04

06

08

10

z/L

Pile load/ultimate capacity of single pile

00 1 32

02

04

06

08

10

z/L

Pile friction/ultimate capacity of single pile

Settlement = 19 times settlement at permissable working load on raft alone

Corner pile

Centre pile

Corner pile

Centre pile

Piled raft: Fully piled foundation: Single pile:

Main

tower

Side

building

(a)

(b)

m

m

m

40 piles

Main towerraft

Side building raft


12/19

50

100

200

150

0 0

20

40

60

80

Settlement:mm

0

5

10

15

20

Pile

load:MN

0

5

10

15

20

Pile

load:MN

%p

ileload

Method

(a)

Method

(c)

Method

(b)

Method

(d)

Poulos&D

avis

Randolph

Frankeetal.

GASP

GARP

Ta&Small

Measured

Sinha

Frankeetal.

GASP

GARP

Ta&Small

Measured

Sinha

Randolph

Frankeetal.

GASP

GARP

Ta&Small

Measured

Sinha

Frankeetal.

GASP

GARP

Ta&Small

Measured

Sinha


13/19

0

10

20

30

40

50

Depth:m

1

58m

1

7

1

m

24m

Ground

surface

Kanyoloam

Loose tomedium sand

Stiffsiltyclay

Stiffsiltyclay

Stiffclayeysilt

Stiffsilt

Medium todense sand

Medium siltysand

Hardclay

Hardsilt

Dense sandandgravel

Dense sand

0 0

0 10002000

0 250 50005 1050

Wave velocity

P-wave Vp: m/s

S-wave Vs: m/s

Vs Vp

Consolidation

yieldstress:MPaN-value

Unconfined

compressive

strength:MPa

WLo

Effective

overburden

pressure

(a)

(b)

Pile no.

P1

P2

P3

P4

Borehole dia.: m

080

080

070

070

Size ofsteel-H: mm

4144051828

4004001321

3503501219

3003001015

P4 P4 P4 P4 P4

P3 P2 P4 P2 P3

P2 P1 P1 P1 P2

P3 P2 P2 P2 P1

1 2 3

Pit

Line D

Line C

Line B

Line A

6m 6m 6m 6m

24m

23m

1

2m

5m

6m


14/19

0

10

20

30

0

10

20

30

0

10

20

Settlement:m

m

0 6 12 18 24

1Line 2 3 4 5Distance, x: m

Line A

Line B

Line C

Measured (Yamashita et al. 1994)

Computed (Yamashita et al. 1994)Computed via GARP5

1 2 3

Line

Measured

Computed from GARP5

Computed by Yamashita et al. (1994)

3

2

1

0

3

2

1

0

3

2

1

0

3

2

1

0

Pileload:MN

Line D

Line C

Line B

Line A

0 6 12

Distance, x: m

0 6 12

Distance, x: m

0 6 12

Distance, x: m

0 6 12

Distance, x: m


15/19

80

70

60

50

40

30

20

10

0

0

200

200

400

400

600

800

1000

Mom

ent,Mxx:kNm/m

Settlement:m

0 5 10 15 20 25

0 5 10 15 20 25

Distance: m

(b)

Distance: m

(a)

20 piles

No piles

20 pilesNo piles

30

20

25

10

15

0

5

0

200

100

300

500

100

400

600

Moment,Mxx:kNm/m

Settlement:m

0 5 10 15 20 25

0 5 10 15 20 25

Distance: m(b)

Distance: m

(a)

t= 03 mt= 075 m

t= 03 mt= 075 m

Core

14m

349m

588m

6m

Exterior cornercolumn

Total vertical load

1880 MN

64 piles 13 m dia.

28 piles 269 m long20 piles 309 m long16 piles 349 m long


16/19

1600

1200

800

400

0

4

8

12

16

20

Buildingload:MN

Settlement:mm

1988 1989 1990 1991 1992 1993 1994 1995 1996

May1994

Assumed for calculations

Actual

1st subwaydewatering

2nd subwaydewatering

Measured settlement

at raft centre

Calculated rangeof settlement

0 5 10Scale: m

40

40

4040

40 40

4040

35 30

253035

45 45

35

35

House 1: Conventional foundation

(211 piles, 28 m long)

House 2: Settlement-reducing piles (104 piles, 26 m long)

1981 1982 1983 1984 1985 1986 1987 1988 1989 1990

House 2

House 1

0

20

40

60Averag

esettlement:mm


17/19

163 m

160 m

12 m

09 m

13 m

(a)

(b)

CL of building

Instrumented quadrant

Foundation plan (351 piles 450 mm diameter and 13 m long)

y

y

xx

16 26 m= 416 m

Longitudinal section xx Cross section yy

0

0

4

8

12

16

20

24

20 40 60 80 100 120 140 160

Total load: MN

Settlement:mm

Measured

NAPRA drained

NAPRA undrained


18/19

2

1

00 100 200 300 400

0

50

100

w

w351=

ettem

entsettementwt

pes

Qr

/Q=%o

floadonraft

w/w351

Qr/Q

Number of piles

RuadasCaneleiras

S2S4

S5

S1 S3

SP11

Indicates borehole location0 10

Scale: m

0

5

10

15

20

25

RL:m

0 10 20 30 40 50 60 70 80 90 100SPT

S1

S2

S3

S4

S5

Foundation level

'Porous' silty clay

Medium clay

Medium dense sand

Stiff clay

Clayey sand

Stiffhard clay

Stiff clay

Finemedium

Medium dense sand

Dense sand

60

50

40

30

20

10

0

Maximum

settlemen

t:mm

157 20 3025

Overall safety factor

0 5 10 2015

Number of piles

Raft thickness

t = 1 m

t = 075 m

t = 05 m


19/19

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