Triaxial tests on Leda clay

(1)

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Triaxial tests on Leda clay Crawford, C. B.

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NATIONAL RESEARCH COUNCIL CANADA D I V I S I O N O F B U I L D I N G RESEARCH T R I A X I A L T E S T S ON LEDA CLAY by C. B. C r a w f o r d I n t e r n a l R e p o r t No. 269 of t h e D i v i s i o n o f B u i l d i n g R e s e a r c h OTTAWA A p r i l

1963

(3)

PREFACE

It has n o t been p o s s i b l e i n papers published by t h e Division on i t s s h e a r r e s e a r c h on Leda a l a y t o

include a complete record of a l l t e s t s . Several workers who wanted t o make a d e t a i l e d study of t h e t e s t s have asked f o r more complete information. This r e p o r t provides supplementary information on t h e more important t e s t s and should t h e r e f o r e be used t o g e t h e r with t h e quoted references. 'Phe a u t h o r , a c i v i l

e n g i n e e r , i s Read o f t h e S o i l Mechanics S e c t i o n ,

DB R/NRC

.

Ottawa

(4)

T R I A X I A L TESTS ON LEDA CLAY

C. B. Crawford

General engineering p r o p e r t i e s o f Leda c l a y have been recorded (1) b u t t h i s record i s f a r from complete. Detailed s t u d i e s of s h e a r s t r e n g t h have been confined t o samples from t h e Ottawa a r e a . E a r l i e r t e s t s on tube samples i n d i c a t e d t h e need f o r fundamental s t u d i e s on good undisturbed block samples. A t every opportunity, t h e r e f o r e , block samples have been obtained f r o m deep excavations.

To d a t e it h a s been p o s s i b l e t o c a r r y out compre- hensive t e s t s on specimens c u t f r o m r e l a t i v e l y uniform l a y e r s

of undisturbed block samples obtained from t h r e e l o c a t i o n s . The average p r o p e r t i e s o? t h e s o i l i n t h e s e blocks a r e given i n Table I. A l l specimens were s a t u r a t e d and undisturbed.

TESTS AND TEST RESULTS

The f i r s t s e r i e s of c o n s o l i d a t e d undrained (CU)

t e s t s , designed t o i n v e s t i g a t e t h e i n f l u e n c e of r a t e of s t r a i n on t e s t r e s u l t s , has been published ( 2 ) . Detailed supplemen- t a r y information on each t e s t i s given i n Table I1 of t h i s p r e s e n t r e p o r t . Consolidated drained ( C D ) t e s t s w i t h i n c r e a s - i n g a x i a l s t r e s s r e s u l t e d i n such d i s t o r t i o n of t h e s o i l

t h a t t h e t e s t s were judged t o be u n s a t i s f a c t o r y . Detailed information f o r each consolidated drained t e s t specimen i s ,given i n Table I11 and t h e s t r e s s - s t r a i n curves a r e shown i n Figure 10 of Reference ( 2 ) .

The second s e r i e s of consolidated undrained t e s ' designed t o i n v e s t i g a t e t h e i n f l t e s t r e s u l t s and i n t e r p r e t a t i o n , F u r t h e r d e t a i l e d infor.&ation on- .uence ha s each o f a x i a been pub t e s t i s 1 s t r a i n on l i s h e d

( 3 ) .

given i n Tables I V and V. The consolidated d r a i n e d t e s t s on t h i s

s o i l have n o t been published and a r e r e p o r t e d i n Table

VI

and Figures 1 t o 8.

These consolidated drained t e s t s were considered t o confirm t h e e a r l i e r i n t e r p r e t a t i o n t h a t t h e o r d i n a r y consolidated drained t e s t w i t h a x i a l l o a d i n g i s an u n s a t i s - f a c t o r y t e s t method. Figures 1 t o 4 show t h e normal t r e n d of continuing i n c r e a s e i n d e v i a t o r s t r e s s a t s t r a i n s i n excess o f 20 p e r c e n t . This may prove t o be a t e s t o f t h e

(5)

remoulded s o i l b u t cannot be c o n s i d e r e d t o r e p r e s e n t t h e performance of t h e u n d i s t u r b e d s o i l . F i g u r e s

5

and 6

i l l u s t r a t e s i m i l a r performance of specimens from a n a d j a c e n t block.

Consolidated d r a i n e d t e s t s w i t h a x i a l s t r e s s

d e c r e a s i n g may be b e t t e r s u i t e d t o t h i s m a t e r i a l ; F i g u r e s 7

and 8 show r e s u l t s of such t e s t s . Each specimen was f i r s t c o n s o l i d a t e d and t h e n t h e l a t e r a l s t r e s s was d e c r e a s e d i n s t a g e s while t h e a x i a l s t r e s s remained c o n s t a n t . I n t h e s e c a s e s , it was p o s s i b l e t o a p p l y a b o u t 3/4 of t h e u l t i m a t e s h e a r s t r e s s under f u l l y d r a i n e d c o n d i t i o n s while a x i a l l y s t r a i n i n g t h e specimen by o n l y 1 p e r c e n t . F u r t h e r i n c r e a s e s i n t h e s h e a r i n g s t r e s s would cause much r e a t e r a x i a l s t r a i n u n t i l t h e l a s t increment c a u s e s f a i l u r e probably under o n l y p a r t i a l l y d r a i n e d c o n d i t i o n s )

.

7

The volume changes noted on F i g u r e s 7, and 8 a r e probably u n r e l i a b l e . Due t o t h e l o n g d u r a t i o n of t h e t e s t t h e i n d e p e n d e n t l y e s t i m a t e d magnitude of membrane leakage i s of t h e same o r d e r a s t h e measured volume change. Assessment of membrane leakage i s d i f f i c u l t b u t i n t h e average s t r e s s

v

range t h e s e

2

t e s t s it may amount t o a b o u t 0 . 1 cm3

o r 1.5 cm' d u r i n g t h e p e r i o d of s h e a r . Membrane leakage may i n f a c t account f o r most of t h e measured volume change d u r i n g t h e l o n g s h e a r i n g p e r i o d of t e s t s 9 6 - 3 - 3 and 9 6 - 3 - 4 . Since volume change d u r i n g t h e c o n s o l i d a t i o n s t a g e i s computed by s u b t r a c t i n g volume change d u r i n g t h e p e r i o d of s h e a r from t o t a l volume change t h i s may a c c o u n t f o r t h e lower t h a n average aVc

recorded f o r t h e s e two t e s t s .

A t h i r d s e r i e s of t e s t s , designed t o i n v e s t i g a t e s h e a r a t low e f f e c t i v e s t r e s s l e v e l s , h a s been completed and i s i n p r o c e s s of p u b l i c a t i o n ( 4 ) . T h i s s e r i e s , p r i m a r i l y on block sample 94-21, i n c l u d e s unconfined compression, c o n s o l i - d a t e d undrained t e s t s , and c o n s o l i d a t e d d r a i n e d t e s t s a t c o n s t a n t volume,

T h i s r e p o r t was i n t e n d e d t o supplement p u b l i s h e d i n f o r m a t i o n by g i v i n g d e t a i l e d t e s t r e s u l t s . I t i n c l u d e s t h e r e s u l t s of a number of c o n s o l i d a t e d d r a i n e d t e s t s which have n o t been p u b l i s h e d , These t e s t s round o u t t h e t e s t

s e r i e s b u t a r e n o t c o n s i d e r e d t o be s u f f i c i e n t f o r a g e n e r a l assessment of s h e a r s t r e n g t h of Leda c l a y .

(6)

REFERENCES

1.

Crawford, C. B. Engineering studies of Leda clay. Soils

in Canada, Roy. Soc. Can., Special Publications

No.

3,

1961, p. 200-217.

2. Crawford, C. B. The influence of rate of strain on

effective stresses

in

sensitive clay. Papers on

Soils

-

1959 Meetings, ASTM STP No. 254, Am. Soc.

Testing Mats.,

1960, p. 36-61.

NRC 5529.

3. Crawford, C. B. The influence of strain on shearing

resistance of sensitive clay. Proceedings, AS!TM,

Vol.

61, 1961, p. 1250-1276. XRC 6662.

4. Crawford, C. B. Cohesion in an undisturbed sensitive

clay. To be published in GBotechnique,

June 1963.

(7)

TABLE I

PROPERTIES OF SOILS TESTED

Sample Depth, f t E l e v a t i o n , f t P r e c o n s o l i d a t i o n p r e s s , kg/cm2 w a t e r c o n t e n t ,

$

Liquid l i m i t ,

.%

P l a s t i c l i m i t , $ L i q u i d i t y index Clay c o n t e n t ,

%

S p e c i f i c g r a v i t y A c t i v i t y S a l t c o n t e n t , g r a m s / l i t r e 83-27 83-28 16 234 2.2 67 65 26 1.0 60

-

0.65 0.5 96-3 96-4 33 222 2.0 58 53 25 1 . 2 62 2.80 0.45 1.7 94-21 53 117 4.5 53 31 23 3.7 65 2.83 0.12 0.03

(8)

TABLE

I1

COI?SOLIDATED

UNDRAINED TESTS ON SAMPLE

8 3 -27

( s e e a l s o Reference ( 2 ) )

A

=

d e v i a t o r

stress, kg/sq cm

B

= pore pressure, kg/sq cm Specimen No.

83-27-8

S t r a i n , $

0.25

A

0 . 6 0

0.32

G.27

0.55

0.50

0.46

0.33

0.23

0.62

0.72

0.52

0.56

0.82

2.0

1.76 1 . 9 1

1.72

7 1 . 7 3

1 . 9 1

1 . 9 8

2.06

2.25

2.39

3.34

3.47

11

I

0.81

0.50 1 . 2 8

3.36

1 . 2 9

1.32 1 . 2 7

1 . 3 2

1 . 4 1

1.40 1 . 7 5

1.78

2.45

2.76

3.0

1.64 1 . 7 2

1 . 6 9

1 . 7 0

1 . 7 2

1.88

1 - 9 7

2.06 -

2.38

3.31

3.42 B

0.28 A

1 . 5 0

1 . 1 5

1 . 2 8

1.87

1.70 1 . 5 3

1 . 4 3

1 4 5

2.38

2.50

2.06

3.39

10

3

2 1

6

7

9

5

4

1 3

12

A

1.09

0.55

0.54

0.97 0 . 9 1

0.78

0.64

0.50

1.12

1.29

1 . 0 1

1.27

1.62

A

1 . 4 6

1.32 1 . 4 4

2.02

1.97

1.68

1.62 1 - 6 4

-

2 . 3 3

3.98

3.77

i B 1.18

0.e7

0.82

0.84

0.85

0.78

0.85

0.95 1 . 2 0

1 . 2 0

6 1 . 9 0

B

0 . 5 1

B

1 . 3 3

1 . 5

1.80

1.97 1 . 7 2

1.74

1.72

1.88

2.00

1.99

2.22

2.36

3.27

3.46

0.75

1.58

A

1 . 5 1

1 . 0 3

1 . 1 4

1.75

1.55

1.34 1 . 2 5

1 3 0

2.08

2.27

1.89

3.00 3 . 0 1

1.0

1 . 7 3

1.88

1 . 6 3

1.64 1 . 6 3

1.75

1.89

1.80

2.11

2.23

3.07

3.37

A

1.35 0 . 7 1

B 1.04 A

1 . 4 8

0 . 8 3

0 . 9 1

1.47 1 . 3 3

1 . 1 7

1 . 0 3

0.98 1 . 6 9

1.92

6

2.37

2.52

B

0.70

B

0.83 1.72 j 0.74

1 . 5 1

1 . 5 3

1 . 5 1

1.50

1.74

1.65 1 . 9 8

2.07

2.85

3.18

1.26

1.16

1.02

0.87

0.75

1.43 1 . 6 5

1.38

1.88

2.13

(9)

TABLE I11

CONSOLIDATED DRAINED TESTS ON SMvlPLE 83-28 ( s e e a l s o Reference ( 2 ) ) bcl = E f f e c t i v e c o n s o l i d a t i o n s t r e s s Tc = Time of c o n s o l i d a t i o n a V c = Volume change d u r i n g c o n s o l i d a t i o n s t a g e A V ~ = T o t a l volume change d u r i n g t e s t Specimen No. 83-28-1 83-28-2 83-28-3 1 bc

,

kg/cm2 2.0 2.8 4.0 Water C o n t e n t ,

%

T c , min 2300 4300 7000 I n i t i a l 66.7 67.3 67.4 F i n a l 46.7 41.5 36.8 d V c ,

%

3.5 12.8 19.4 AVT,

$

20.5 24.8 29.3 .I Rate of s t r a i n , %/b 0.17 0.17 0.17

(10)

TABLE IV

CONSOLIDATED UNDRAINED

TESTS

OW SAMPLE

96-4

( s e e a l s o Reference ( 3 ) )

o

D e v i a t o r s t r e s s c o n s t a n t ( s e e F i g u r e 2 of Reference 3 )

Sp;cinen IT0

.

--

36-4-1

2

3

4

5

6

7

8

9

10 11

1 2

A =

D e v i a t o r s t r e s s , kg/cm

2

B =

Pore p r e s s u r e ,

kg/cm 2 I

S t r a i n ,

%

0.25

A

0.66

0.99

6

2.20

0.65

0.96 1 . 2 2

1 . 8 3

0 . 5 0

0.75

B

0.46

0.60

0.52 0 . 8 3

0 . 3 1

0.44

0.20

0.35 0 . 4 3 ~ ~ 0 . 4 ~ ~ ~ 0 . 8 8

0.85;':-0.32%0.85

0 . 8 9 - 0 . 7 3 : ' 1 . 7 3

1 . 3 0 z 0 . 5 7 :

A

0 . 9 3

1 . 3 2

1 . 9 1

2.93 0 . 9 3

1 . 3 0

1.72

2.56

2.18

A

1.07 1 . 5 0

2.15

3.30

1.07 1 . 5 0

1 . 9 4

2.98

1.04 1 . 5 1

2.05

2.89 B

0.74

0.95

0.96 1 . 5 3

0.60

0.77

0.39

0.84

0.77

0.74 1 . 2 1

1 . 1 3

B

0 . 9 3

1 . 2 0

1 . 3 3

2.06

0.85 1 . 0 9

0.58

1.36

0.96

1 . 0 8

1 . 5 5

1.58

1 . 0 A

1.14 1 . 6 0

2.23

3.49

1.18

1 . 6 3

2.07

3.26 1 . 1 3

1 . 6 8

2.18

3.21

B

1 . 0 7

1 . 4 0

1 . 6 1

2.44

1 . 0 1

1 . 2 8

0.75 1 . 8 2

1.07 1 . 3 0

1 . 7 8

1 . 9 8

1 . 5

A

1 . 2 3

1 . 7 2

2.44

3.70 1 . 2 7

1 . 7 6

2.23

3.56

1.19

1.81

2 . 3 1

3.50 B

1.25 1 . 6 7

1 . 9 8

2.92 1 . 2 4

1 . 5 8

1 . 0 7

2.52

1.24 1 . 5 9

2.11

2.60

2.0

A

1 . 2 5

1 . 7 8

2.50

3.79 1 . 2 9

1 . 8 2

2.30

3.70 1 . 2 2

1.86

2.37

3.64 B

1 . 3 6

1.85

2.18

3.27 1 . 4 0

1 . 7 5

3

2.97

1.36

1 - 7 8

2.33

2.99

3.0

5.0

A

1 . 2 5

1 , 8 0

2.55

3.83 1 . 2 7

1 . 8 4

2.33 3 . 8 1

1 . 2 1

1 . 8 7

2.40

3.74

A 1 . 2 0

1 . 7 8

2 . 5 1

3.77 1 . 2 0

1 . 8 2

2.30

3.80 s

1 . 5 1

2.02 2 . 5 1

3.72 1 . 5 6

2.00 1 . 6 8

3.56 1 . 5 2

2.01

2.62

3.50 a

1 - 6 5 )

2 . 3 0

2 - 8 5

4 * 1 6

1.55 2 . 2 4

2.05 4 * 1 4

(11)

h CI) M H -m W a ,

" 3 :

W 4 a I 4 H f i - i P9 m

2

F1

2

W O [I)

E

d - - 0 LA 0 M 0 CV d C V M d C V d - m a w c u c u o t - r o r l l n c n C O C V \ L ) c n m In

*

A

&

A

&

k? a 3 * c u m W c u t - N t - d - t - C V a w C n

-

F:

A A & < A A & <

-I+ ' a - k W o - 8 d W M M C V W 4= m C V W C V O M W M CI) o

d

A

&

A

&

PI 4 P9 4 m d - - -- - - - - - - - -

-

- -- cD 0 d- M d +- t- 0 Ln \O In \O to CV M t- ~n a cn t- d I 0 CV +- W a r n t- cv t- t - d d t-

.

CV CV d C V M d C V M a m r l M ~ O t - e m m t - A o 0 Ln

.

0 Ln CV 0 \oo F: a, 8

-

- r i 0 O k % + F7

*

C V M d - \ O C V M d - W t- a3 rl rl I I -d- d- I 1 Sn,

x

o a r n e d m ~ n t -d -d - O C V -d W C V M

A A & < A A & <

C V m C V d c n W o d - W t - c n c u W a 0 - t 0 0 0 d 0 0 d d d I n t - I n W M t -m C V t - t - -m + - a 3 a

d

A

&

G

A

d

M M I n M C V O O t - r o d - d - m d - n m t -

d d d d d d d d

C O a 3 I n t - * L n M a \ D C U d t - W O C V m

d

A

G

A

S

A

(12)

TABLE V I

CONSOLIDATED DRAINED TESTS ON SAMPLES 96-3 AND 96-4

6c1 = E f f e c t i v e c o n s o l i d a t i o n s t r e s s Tc = Time of c o n s o l i d a t i o n d V C = Volume change d u r i n g c o n s o l i d a t i o n s t a g e a V t = T o t a l volume change d u r i n g t e s t Specimen No. 96-4-13 96-4-14 96-4-15 96-4-16 96-3-1 96-3-2 96-3-3 96-3-4 Water Content,

$

_6,1

_,

kg/cm2 3 3 6 6 6 6 6 6 I n i t i a l 57.1 58.3 61.6 57.5 57.6 52.6 57.4 55.9 F i n a l 35.1 35.9 30.6 30.2 29.8 25.3 38.3 36.4- Tc, min 6200 4000 6700 4200 4300 4000 4000 3900 b V c ,

%

13.6 12.5 22.4 21.3 20.9 21.8 18.8 18.3 I Avt9

%

23.6 23.6 31.6 29.0 29.6 31.6 20.6 21.2 Rate of s t r a i n ,

%fir

2.0/0.4 0.2 0.4 0.2 0.2 0.2

-

(13)

I

1

1 SPECIMEN

9 6 - 4 - 1 3

-

0 A V

-

/'

/

-

_I

-

FIGURE

I

15

20 S T R A I N ,

O/o

(14)

15 2 0

STRAIN,

%

1 I

-

I

SPECIMEN 9 6 - 4 - 1 4

-

A V

-

To;

-

I

FIGURE

2 S T R E S S - S T R A I N R E L A T I O N ( D R A I N E D

T E S T )

B R 2889-2 L

(15)

I

1 I

I

>

q-

q

SPECIMEN 9 6 - 4 - 1 5

-

AV

-

3

-

I

15

20 S T R A I N ,

O/o

FIGURE

3 S T R E S S

-

S T R A I N R E L A T I O N ( D R A I N E D

T E S T )

(16)

I

1 I

S P E C I M E N

9 6 - 4 - 1 6

-

q-

3

-

A V

_-

-

1

15

20 S T R A I N ,

O/o

FIGURE

4 STRESS

-

STRAIN R E L A T I O N [ D R A I N E D T E S T )

(17)

1 I

I

S P E C I M E N

9 6 - 3 - 1

-

o;-0;

-

A V

-

1

15

20 S T R A I N ,

O/o

FIGURE

5

(18)

I

-

1 S P E C I M E N 9 6 - 3 - 2

-

/-

-

I

15 2 0

S T R A I N ,

O/o

FIGURE

6 STRESS

-

S T R A I N R E L A T I O N (DRAINED T E S T )

AR 2489-4

(19)

I0

15 STRAIN,

OIo

I

T I M E I N T E R V A L

FIGURE

7 STRESS

-

STRAIN RELATION (DRAINED TEST

W I T H

DECREASING

6,)

w

>

n Cc 1 V) > 4 0 to < > a 0

-

c-

c 3 1

-

> a 0

-

4 HOURS

4 b

- .

-

I

-

cr;

----

I

---

-

/

-

_{A V}

-

1 % I =

KGICM*

-

/ b

/

SPECIMEN

9 6 - 3 - 3

/

1 I

I

(20)

I0

15 S T R A I N ,

O/o

I

_I

T I M E I N T E R V A L

FIGURE

8

V) > a Q In

STRESS

-

STRAIN RELATION (DRAINED TEST

I DAY 4 b

WITH DECREASING

6,)

-

q-q

I

-

_-

~ y - - -

4 / - / / - / /'