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Soil particle

Shear surface

Relative displacement

of soil in the mass

Interparticle force

normal to shear surface

N

F

Load platenN(applied normal load)

P(shear force)

Soil specimen

Induced

shear surface

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vuf/ w

Failure

zone

su

uo/ w

Excess pore

pressure at

failure

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v

Failure

zone

sd

uo/ w

No excess pore

pressure

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vol

vcrit

v

P

C Initially dense

Initially loose

Initially dense

Initially loose

(a)

(b)

(c)

c

pDilation

Compression

Critical specific

volume

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Peak

strength

envelope

12

34

0

0

Critical state line

= tan crit

(a)

(b)

c

Actual

peak strength

over estimated

at low

p= c + tan tgt

tgt

crit

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n

f

O-C peak

N-C peak

N-C peak

O-C peak

Residual

ResidualShearstress:

Displacement:

Effective stress normal to

shear plane

c r

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Remote

transducer

Digital

control

circuit

steps

Stepper motor

and gearbox

Linear bearing

Analogue feedback

Pressure

cylinderPiston

Pressure

outlet

Pressure

transducerDeaired water

(b)

(a)

Axial load

Ram in rotating

bushing

Top cap

Water-filled cell

Top platen

Rubber O-ring

Soil specimen enclosed

in rubber membrane

Clear acrylic tube

Saturated porous disc

Base pedestal

To pore pressure

transducer

Saturated

pore-water ductsValve open during

drainage

Cell pressure

Back pressure

Captiveball nut

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f=c+(

u)tan

c

Drained (back-

pressure zero)

Consolidated-

undrained

Unconfined

compression

Unconfined

compression

u

Drained

uf

(13)f = su

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0

0 0

0 0

0

50/w 50 /w 50 /w

550/w

555/w

355/w

155/w

350/w

150/w

600

600

400200

200 400

680480280

400200 600

(c)

(b)

(a)

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:kPa

:k

Pa

c

u

(1)

cu (1) cu (2) cu (3)(u): kPa

cu (2)

cu (3)

ud (1)

ud (1,2,3)

ud (2) ud (3)

155355

555

235155

200

280

390

480

400

680

600

730

1080: kPa

22

70

10

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200 400 600

600

600

1080

400

400

200

390 730

200

100/w100/w100/w

155/w235/w

70/w

(a)

(b)

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200 400 600

600

600

1230

400

400

200

350 785

200

100/w 100/w100/w

100/w 100/w100/w

(a)

(b)

:kPa

f=10

+0404

(u)k

N/m2

10

100 250 300 500 685 1130

22

u: kPa

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:kPa

:kPa

(u): kPa

: kPa

ud

ud

cd d

cu d

785730480400355

155

10022

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(1+3) / 2

(1

3

)/2

(1

3

)/2

Failure line

Failure line

(a)

(1+3) / 2

(b)

max

=(

13

)/2

(u)

3 1

1 +3/ 2

c

K

Failure envelope

Failure line

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0 050 50 100

Undrained shear strength : sukPa

LL=75

PL=24LL=80

PL=25

Heavily over-consolidated

clay

Normally

consolidated

clay

10

8

6

4

2

0

Depthbelowgroundsurface:m

Su

p = 03

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050

040

030

020

010

0

su

/pratio

0 10 20 30 40 50 60 70

Plasticity index: PI

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Torque

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00

5

100 200 300 600

Shear strength: kPa

10

15

Depthbelow

groundlevel:m

865 mm dia. plate tests

38 mm dia. triaxial

98 mm dia. triaxial

Penetration tests

Sand and gravel

Soft brown clay

Brown and grey

mottled clay

Stiff grey clay

865 mm dia.

plate tests

400 500

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100

100

100

100

80

80

80

80

60

60

60

60

40

40

40

40

20

20

20

20

0

00

0

%o

fstrengthwith=90

%o

fsu

with

=90

100

120

140

160

80

60

40

20

0

%o

fsu

with

=90

% of suwith = 90

% of strength with = 90

100

100

80

80

60

60

40

40

20

20

0

0

%o

fstrengthwith

=9

0

% of strength with = 90(c)

Circle, centre origin

Ellipse fitted

at axes

Cubical triaxial cell (after Arthur and Menzies, 1971)

Modified conventional triaxial cell (after Arthur and

Philips, 1973)

(a)

(b)

100806040200

% of suwith = 90(d)

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Direct shear

Compression

Extension

Circle

Ellipse fitted at axes

140

140 160

120

120

100

100

80

80

60

60

40

40

20

200 0

%o

ftriaxialcompress

ionsu

withbeddinghorizontal

% of tr iaxial compression suwith bedding horizontal

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12

10

08

06

04

Correctionfac

tork

v

su(field) =su(vane)kv

0 20 40 60 80 100 120

Plasticity index: %

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25

001 05

20

15

10

05

0

25

20

15

10

05

0

(

13)max(kg/cm

2)

10 min 1 hour 1 day 1 week 1 month5 10 50 100 1000500

(a)

(b)

c= 10 kg/cm2

c= 20 kg/cm2

c= 40 kg/cm2

Time to failure: hours

Porepressureparam

eter:A

f

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