Effect of storage time and temperature on clay samples

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Effect of storage time and temperature on clay samples

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NATIONAL RESEARCH COUNCIL CANADA

DIVISION OF BUILDING RESEARCH

E F F E C T OF STORAGE TIME AND TEMPERATURE ON CLAY SAMPLES

by A N A L Y Z E D W. J . Eden Internal Report N o . 310 of the Division of Building Re s e a r c h OTTAWA JANUARY 1965

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PREFACE

When s a m p l e s of clay a r e removed f r o m the ground they a r e subjected t o changes in both s t r e s s and t e m p e r a t u r e environment. T h i s r e p o r t d e s c r i b e s an attempt t o a s s e s s the effect of such changes in t e m p e r a t u r e environment o v e r a five -month period on the s t r e n g t h of Leda clay f r o m one s i t e . Complementary studies a r e proceeding on the t i m e - t e m p e r a t u r e effects on the physico-chemical p r o p e r t i e s of the s a m e clay. Although t h i s r e p o r t cannot be considered t o p r e s e n t conclusive evidence that s u c h effects a r e negligible, it is

hoped that the t e s t information given will be useful t o o t h e r s concerned with s t o r a g e effects on clay s a m p l e s .

The work d e s c r i b e d was conducted in the Soil Mechanics Section of the Division and the r e p o r t was p r e p a r e d by a r e s e a r c h officer in that Section.

Ottawa

January 1965

R. F. Legget D i r e c t o r

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EFFECT OF STORAGE TIME AND TEMPERATURE ON CLAY SAMPLES

by W . J . Eden

In geotechnical investigations, i t i s sometimes n e c e s s a r y to s t o r e clay samples for .a period of months at t e m p e r a t u r e s higher than the normal ground t e m p e r a t u r e . It has been noted that sealed samples stored f o r a year o r m o r e undergo changes in colour indicating that some physico-chemical activity i s in p r o c e s s . Apart f r o m some reference t o the physico-chemical effects, the l i t e r a t u r e reveals little information on the effects of storage on the strength of clays. Thus it was decided t o a s s e s s the storage effects by unconfined compression t e s t s on undisturbed samples. Unconfined compression t e s t s were conducted a t storage t i m e s varying f r o m z e r o t o five months. This r e p o r t presents the r e s u l t s obtained.

THE SAMPLES

It was possible t o obtain four block samples f r o m a tunnel face in Leda clay, 52 ft below the 'surface (Elevation 165 f t ) . Special precautions were taken t o ensure that the t e m p e r a t u r e history of the samples was known.

The temperature of the clay face was 44"F, approximately 4 " below the mean ground temperature for the Ottawa a r e a . The blocks were obtained f r o m two benches cut in the tunnel f a c e , one immediately above the other. Two samples were taken f r o m each bench with

approximately 4 in. between each sample. The two samples f r o m the upper bench were designated 136-3 and f r o m the lower bench, 136-4. The clay a t this site had a stiff consistency and behaved a s a brittle

m a t e r i a l in spite of i t s extreme sensitivity. The geotechnical information for the samples i s presented in Table I.

The blocks were taken during the noonhour break of the tunnelling c r e w on 18 December 1963. At the t i m e , the outside a i r t e m p e r a t u r e was about 1 0 ° F . As soon a s the samples were cut, they were wrapped in a mineral wool insulation blanket, hoisted to the surface and transported about 2 miles by truck to the laboratory.

They were immediately brought into a humid room with the temperature controlled a t 55°F where they were cut into 2-in. by 2-in. by 6-in. p r i s m s a s indicated on the t e s t schedule shown in Figure 1 .

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S a m p l e s t o be t e s t e d i m m e d i a t e l y o r a t one d a y w e r e wrapped in p l a s t i c f i l m t o p r e v e n t m o i s t u r e c h a n g e s . T h o s e t o be s t o r e d f o r l o n g e r p e r i o d s w e r e wrapped in f i l m and dipped in p e t r o l e u m wax. Two t h i r d s of the s a m p l e s r e m a i n e d in the humid r o o m , and the r e m a i n i n g t h i r d w e r e f u r t h e r wrapped in a polythene bag and s t o r e d in a w a t e r t a n k with t h e t e m p e r a t u r e controlled a t 8 5 ° F until t h e y w e r e t r i m m e d and t e s t e d in the l a b o r a t o r y . One t h i r d of the s a m p l e s w e r e s t o r e d in t h e humid r o o m w h e r e t h e y w e r e t e s t e d a t 5 5 ° F . One t h i r d w e r e s t o r e d in t h e humid r o o m but w e r e t r i m m e d and t e s t e d in t h e l a b o r a t o r y a t 70 t o 7 5 ° F . T h u s , one t h i r d of the s a m p l e s had t h e following t e m p e r a t u r e h i s t o r y :

4 8 ° F j 4 4 ° F

+

5 5 ° F ; the second t h i r d , 4 8 ° F j 4 4 ° F

+

5 5 ° F

-+

7 5 ° F ;

and t h e final t h i r d 4 8 ° F -4 4 4 ° F j 5 5 ° F

+

8 5 ° F j 7 5 ° F .

B e f o r e conducting the unconfined c o m p r e s s i o n t e s t s , e a c h p r i s m was t r i m m e d t o a s t a n d a r d s i z e of 1 . 4 in. by 3 in. long. D e n s i t i e s

and w a t e r contents w e r e d e t e r m i n e d on t h e s p e c i m e n s , and c l a s s i f i c a t i o n t e s t s w e r e conducted on the t r i m m i n g s . The unconfined c o m p r e s s i o n t e s t s w e r e conducted on a g e a r - d r i v e n constant r a t e of s t r a i n a p p a r a t u s , the r a t e of s t r a i n being

$

%/mine

TEST RESULTS

Seventy-five t e s t s w e r e m a d e on the two s a m p l e s . The r e s u l t of e a c h t e s t s p e c i m e n i s tabulated .in Appendix A, and the a v e r a g e r e s u l t s a t the end of e a c h s t o r a g e p e r i o d a r e p r e s e n t e d in T a b l e s 11, 111 and IV. It was found that a l l of t h e t e s t s p e c i m e n s failed a t l e s s than one p e r cent s t r a i n . The u s u a l f a i l u r e p a t t e r n w a s one of v e r t i c a l

splitting r a t h e r than a c l e a r l y defined single s h e a r plane.

T o find s t a t i s t i c a l a v e r a g e s a l l the r e s u l t s f r o m s a m p l e 1 3 6 - 3 and 136-4 w e r e a s s e m b l e d , and a v e r a g e s and s t a n d a r d d e v i a t i o n s w e r e d e t e r m i n e d . The p r o c e s s was r e p e a t e d f o r t h e two s a m p l e s combined. T h e s e r e s u l t s a r e p r e s e n t e d in Table V .

The r e s u l t s w e r e then a s s e m b l e d a c c o r d i n g t o t h e i r s t o r a g e t e m p e r a t u r e and t e s t t e m p e r a t u r e without r e g a r d t o t i m e . T h e s e r e s u l t s a r e p r e s e n t e d . in Table VI.

It will be noted t h a t the s a m p l e s s t o r e d a t 8 5 ° F yielded a slightly higher s t r e n g t h but t h e i r w a t e r contents w e r e slightly l o w e r . The r e s u l t s of t i m e s t u d i e s a r e p r e s e n t e d in F i g u r e s 2, 3 and 4 and show n o indication of change in s t r e n g t h with t i m e . T a b l e s 11, I11 and 1V do not indicate any change in w a t e r content with t i m e .

In F i g u r e 5, t h e r e s u l t s of d e n s i t y and w a t e r content d e t e r m i n a t i o n s a r e plotted. L i n e s of r e g r e s s i o n have been e s t a b l i s h e d between the

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density and water content. This figure d e m o n s t r a t e s the variability which o c c u r s within s a m p l e s of a clay of u n i f o r m appearance.

CONCLUSIONS

1. The experiments d e s c r i b e d show no significant effect of s t o r a g e t e m p e r a t u r e o v e r the 5-month t e s t period. Variations found f o r the v a r i o u s s t o r a g e t i m e s and t e m p e r a t u r e s appear to f a l l within the variations which might be expected in a sample.

2 . High s t o r a g e t e m p e r a t u r e s show slightly higher s t r e n g t h s than a v e r a g e , but t h i s m a y be attributed t o a slightly lower water content than the average.

It

cannot be d e t e r m i n e d whether t h i s t r e n d in water

contents was due to the higher t e m p e r a t u r e s o r t o the random distribution of water contents.

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TABLE I GEOTECHNICAL PROPERTIES I Sample No. 136-3 136-4 W ~ '

%

7 0 . 0

*

3 69.0

*

2 \

wLs

%

50.0 4 5 . 0

w

%

27.0 27.0 P*

I

%

23. 0 1 8 . 0 P' ILs

%

1 . 9 2 . 3

%

Clay S i z e 8 0 . 0 79.0 Specific G r a v i t y 2 . 8 4 2 . 8 3

P o r e Water Salt Concentration, gm/l 0 . 1 0. 3

Y,

lb/cu f t 9 9 . 6

*

1 . 3 1 0 0 . 2

*

1 . 0 P r e c o n s o l i d a t i o n P r e s s u r e

-

kg/crn 2

-

3 . 4 NOTE:

w~

=

n a t u r a l w a t e r content.

W

L = liquid l i m i t . W

=

p l a s t i c l i m i t . P I = p l a s t i c i t y index. P IL = liquidity index. Y = wet density.

(8)

TABLE

LZ

SUMMARY OF TEST RESULTS ON SAMPLES STORED AND TESTED AT 55°F

NOTE: = c o m p r e s s i v e strength.

E

=

unit strain at failure.

f A v % E f' 0.80 0.85 0.83 0.80 0.80 0.80 0. 63 0.73 0.68 0.77 0.70 0.73 0.77 0.69 0.73 kg/cm

9

2.44 2.48 2.46 2.34 2. 24 2.29 1.93 2.16 2. 03 2.20 2.19 2.20 2. 26 2.02 2.14 Av. y, lb/cu ft 100.3 101.0 100.7 100.1 101.6 100.8 98.9 100.5 99.7 101.4 98.7 100.1 98.2 89.6 98.9 Av. WN,

'70

70. 3 68.8 69. 5 72. 3 66.8 69.6 72.6 68.6 70. 2 65. 3 70.2 67.8 72.6 68.9 70.7 .No. of T e s t s 3 4 7 3 3 6 3 3 6 3 3 6 3 3 6 Storage T i m e , Days

1

1 1 2 2 2

9

3

2 32 3 2 145 145 145 136-3 136-4 Combined 136-3 136-4 Combined 136-3 136-4 Combined 136-3 136-4 Combined 136-3 1 36-4 Combined

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T A B L E III SUMMARY O F T E S T RESULTS ON S A M P L E S S T O R E D AT 5 5 ° F AND T E S T E D AT 7 5 ° F S t o r a g e T i m e , D a y s 1 1 1 2 2 2 9 9 9 32 3 2 32 1 4 5 1 4 5 1 4 5 Sample 1 3 6 - 3 1 3 6 - 4 C o m b i n e d 1 3 6 - 3 1 3 6 - 4 C o m b i n e d 1 3 6 - 3 1 3 6 - 4 C o m b i n e d 1 3 6 - 3 1 3 6 - 4 C o m b i n e d 1 3 6 - 3 1 3 6 - 4 Combined -No. of T e s t s 3 3

6

2 3 5 2 3 5 2 3 5 2 3 5 Av. WN,

%

72. 5 7 0 . 4 7 1 . 4 7 0 . 2 6 6 . 8 6 9 . 4 7 3 . 0 6 7 . 9 6 9 . 9 6 6 . 0 71. 1 6 9 . 1 71. 1 68.0 6 9 . 2 Av. y, l b / c u f t 9 7 . 9 9 9 . 3 9 8 . 6 100.7 1 0 1 . 0 1 0 0 . 9 98.7 1 0 0 . 5 9 9 . 8 1 0 0 . 5 9 8 . 9 9 9 . 6 9 9 . 0 1 0 0 . 3 9 9 . 8 k

:

.,

v

2. 1 3 1 . 9 2 2. 0 3 2 . 4 7 2 . 4 8 2 . 4 8 1 . 7 6 1 . 9 4 1 . 8 7 3 . 0 0 2. 0 3 2 . 4 2 1 . 4 2 2 . 1 8 1'. 87 "Iv'

70 "

0 . 7 3 0 . 7 7 0 . 7 5 0 . 8 5 0 . 8 0 0 . 8 2 0. 50 0 . 7 7 0 . 6 6 0 . 8 5 0 . 8 0 0 . 8 2 0 . 7 6 0.79 0 . 7 8

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TABLE

IV

SUMMARY O F TEST RESULTS ON SAMPLES STORED AT 85°F AND TESTED AT 75°F Storage T i m e , Days 9 9 9 3 2 32 3 2 145 145 145

-

Sample 136-3 136-4 Combined 136-3 136-4 Combined 136-3 136-4 Combined No. of T e s t s 3 3 6 3 3 6 3 3 6 Av.

4?

kg/cm 2.62 2.15 2. 38 2.79 2.23

2.

61 2.61 2.21 2.41 Av. cf,

'30

0.72 0.72 0.72 0.83 0.80 0.82 0.83 0.80 0.82 Av. WN,

'30

68.9 66.1 67.5 64.9 70.2 67.5 72. 3 67.8 69.9 Av.

Y,

lbfcu ft 99.6 100.8 100.2 100.9 100.1 100.5 98. 3 99.9 99.1

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TABLE V

AVERAGE RESULTS O F ALL TESTS ON SAMPLES

TABLE VI

RESULTS O F TESTS AT VARIOUS STORAGE AND TEST CONDITIONS 0 (Standard deviation)

*

3.4

*

1 . 8

*

2 . 7

Y

lb/cu ft 9 9 . 6 1 0 0 . 2 99.9 W ~ '

%

70. 1 6 8 . 7 69.3 Sample 136-3 1 3 6 - 4 Combined

o

*

1.3 1 . 1 . T e s t s 35 4 0 7 5 1 Sample 1 3 6 - 3 1 3 6 - 4 Combined 1 3 6 - 3 1 3 6 - 4 Combined 1 3 6 - 3 1 3 6 - 4 Combined Storage T e m p . , O F 55 55 55 55 55 55 8 5 8 5 8 5 T e s t T e m p . , O F 55 55 5 5 7 5 7 5 7 5 7 5 7 5 7 5 qu, kg/cm 2 2.32 2.19 2.25 0

*

0 . 6 2 * 0 . 2 8 * 0 . 4 6 No. of T e s t s 1 5 1 6 3 1 1 1 1 5 26 9 9 18 Av. WN,

70

7 0 . 6 68.7 6 9 . 6 70.7 68.8 69.6 68.7 68.0 68.4 Av

.

qus kg/cm 2 2.23 2.23 2. 23 2. 1 5 2 . 1 1 2. 13 2.67 2.20 2 . 4 3

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A P P E N D I X A R E S U L T S O F LNDIVIDUAL 'TESTS T e s t No. 136-3-A4 -C4 -D5 136-4-A5 -A9 -D5 -D9 136-3-B2 - E 2 -C7 136-4-C6 -C 3 -B7 136-3-B5 -C 1 -D7 136-4-A6 -I32 -B10 136-3-A6 - E 4 136-4-A3

-C

₁

-D

7 136-3-A2 -C3 -D4 S t o r a g e T i m e , Days 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 9 9 9 Storage Temp. "F 55 55 55 55 55 55 55 55 55 55 5 5 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 T y p e of F a i . l . ~ l r e Split I 1 1 I 11 I I 11 S h e a r Split II I I I 1

,

I 1 II 1 1 I 1 S h e a r Split I 1 I 1 II I 1 S h e a r Combined Split I 1 I 8 S h e a r T e s t T e m p . , OF 55 55 55 55 55 55 55 75 7 5 75 7 5 7 5 7 5 55 55 55 55 55 55 7 5 7 5 7 5 7 5 7 5 55 55 55 W N' Yo 68.0 71.9 7 1 . 0 69. 5 65.8 70.6 69.4 7 1 . 5 75.2 71.2 69.3 70.7 70.2 74.2 72.2 70.6 66.8 6 7 . 0 66. 6 7 2 . 6 67.8 69. 1 6 7 . 0 70. 3

-

72. 6 72. 5

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S t o r a g e T e m p . , " F 55 5 5 55 55 55 55 5 5 55 8 5 8 5 8 5 8 5 8 5 8 5 55 55 55 55 55 55 55 55 55 55 55 8 5 8 5 8 5 T e s t T e m p . , " F 5 5 55 55 7 5 75 7 5 7 5 75 7 5 7 5 7 5 7 5 7 5 75 55 55 55 55 55 55 7 5 7 5 7 5 7 5 7 5 7 5 7 5 7 5 T e s t NO. 1 36-4 -A2 -B8 -C7 136-3-A7 - D l 136-4-B3 -C4

-C

₁₀ 1 36-3tB4 -C6 - E 6 1 36 -4 -A7 -B 1 -D2 136-3-B6 -C2 -E7 136-4-B5 -B9 -B4 136-3-A1

-E

1 136-4-D3 -D 10 -A1 136-3-A5 -B3 -D3 S t o r a g e T i m e , Days 9 9 9 9 9 9 9 9 9 9

1

9 9 9 9 3 2 32 32 3 2 32 3 2 3 2 32 3 2 3 2 3 2 3 2 32 32

W ~ '

%

66.8 69.4 69.7 7 2 . 7 73. 2 67.4 6 8 . 5 67.7 64.1 71.1 7 1 . 4 6 5 . 5 6 6 . 0 6 6 . 9 64.8 66.2 6 4 . 8 7 1 . 4 7 0 . 5 68.8 6 5 . 4 6 6 . 7 70.9 7 1 . 6 70.9 64.8 64.8

.

6 5 . 1

Y,

lb/cu f t 100.7 100.7 100.0 99.2 98.2 1 0 1 . 3 99.8 100.5 99.4 1 0 0 . 0 99. 3 101.2 101.0 1 0 0 . 3 102.3 100.7 1 0 1 . 2 9 8 . 7 99.1 9 8 . 4 100.7 1 0 0 . 3 98.2 9 8 . 6 100.0 100.8 101.5 100. 3

%S

kg/crn2 1 . 8 4 2.20 2 . 4 4 2 . 2 6 1 . 2 6 1 . 7 2 2.27 1 . 8 4 2 . 4 9 3 . 1 3 2 . 2 5 2.40 2.24 1.80 2.04 2.45 2. 11 2. 26 2.10 2.21 3.10 2.91 1.96 1 . 9 8 2.14 2.78 2.79 2.79 f ' 8

%

0 . 7 0 . 7 0.8 0 . 6 0 . 4 0.7 0.8 0.8 0 . 8 5 0 . 8 0 . 5 0.7 0 . 7 0 . 7 5 0.8 0 . 7 5 0.75 0 . 7 0.7 0 . 7 0 . 9 0 . 8 0 . 7 0 . 8 0 . 9 0.8 0.8 0 . 9 Type of F a i l u r e Split I I I I t I 11 I I I I I I

"

11 S h e a r Split S h e a r Split 11 'I I t II t I I I I I 11 I* t t I I Combined Split I I

(14)

%

_,

kg/cm2 2 . 5 7 2 . 2 8 2 . 4 5 2 . 1 5 1 . 4 4 3.18 1 . 4 2 2. 54 2 . 1 0 1 . 4 1 1 . 4 2 2.12 1 . 9 8 2 . 4 3 2.38 2.98 2 . 4 8 2. 22 2.13 2.29

Y,

lb/cu f t 1 0 0 . 2 9 9 . 5 100.7 9 8 . 3 9 7 . 6 9 8 . 6 9 9 . 6 9 9 . 8 9 9 . 4 9 9 . 2 9 8 . 9 9 9 . 6 1 0 1 . 3 100.1 9 8 . 8 98.4 9 7 . 7 100.0 101.0 9 8 . 7 T e s t No. 136-4-AB -C2 -C8 136-3-C5 -D2 -D6 136-4-B6 -C 5 , -C9 136- 3-A3

-E

5 136-4-D4 - D l -D6 136-3-B1 -B7 - E 3 136-4-A4 -A10 -D8 E: f'

%

0 . 9 0 . 8 0 . 7 0 . 7 0 . 7 0 . 9 0 . 6 0 . 8 0 . 6 5 0.8 0 . 7 0.8 0 . 7 0.7 0 . 6 0 . 9 1 . 0 0 . 8 0 . 8 0 . 8 S t o r a g e T e m p . , O F 8 5 8 5 8 5 55 55 55 55 55 55 55 5 5 5 5 55 55 8 5 8 5 8 5 8 5 8 5 8 5 Storage T i m e , Days 32 3 2 32 145 145 145 145 145 145 145 145 14 5 145 145 145 145 145 145 145 145 Type of F a i l u r e Split S h e a r Split I I 11 I I I I I I I' Combined S h e a r Combined Split Combined Split t t Combined Split 11 Combined T e s t T e m p . , O F 75 75 75 55 55 55 55 55 55 7 5 7 5 7 5 7 5 7 5 75 75 7 5 7 5 7 5 75 WN.

%

6 9 . 6 7 0 . 3 7 0 . 6 71. 3 7 5 . 8 7 0 . 6 67.7 70.2 68.7 7 0 . 2 7 2 . 0 68.0 66.0 70.0 7 0 . 5 71.4 75.1 68. 3 6 5 . 4 69.0

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136-3

flop view of sample)

E

Face

136-4

(Top view of sample)

D

Face

Stored and Tested at 55°F

Stored at 55°F

-

Tested at 75°F

Stored at 85°F

-

Tested at 75°F

(16)

I

CU

I

rn CU

cu'

.LL LL 0 0 \O I1 Inn h h 0

+

-

* * _CCI _CCI O& u u Q, Q, In**

I;!

I n m e n

-I

u

a8

Q , Q , CUCC u I

I

-

ZLLL

-

m o 0

I

Q , n n C. 00

I

o a % E

I

_I

u u u Q, Q, Q, L L L

I

0 0 0 * * * m m m

I

a 0 0

1 I

I

0 l o

=

.

.a

I

-

_I

7

I

-

I

_I

-

I

-

I

-

_"

_I

a - 8

.

I

_I

0 a-

I

_I

I

_I

I

- 0

I

.

I

e

LL,

'

0

I

.

(17)

(18)

I

8 I

K1

I

LLU 0 0

* *

0 + P C C I C I

-

rn rn

-

, U- u u a Q, Y \ - 4 - Y \ - - 0

I

0-0 m I - I -

I

P ' I

SLLL

-

,"'?no*

I

+ * *

O L I ~ ; ; ~

I

u u u

I

a a a L L L

I

0 0 0 C I C I C I

m m V )

I

0 0 0

_I

I

0 0

X, (

0

P. -

I

7

I

-

_I

80,p 0

I

08 I

I

-

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v . 0 8 . d )

I

-

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-

I

_-

-

P .a,

@.

.

= ' @ ( O 0 0-

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-

_4'.

_I

0 . 0 0

I

-

I

8 a-

(19)

A

I

-

_-

-

1 3 6 - 3

~ 1 3 6 - 4

-

o

Ave

-

136-4

136 - 4-21;

127.3 -

,394

W

e

Ave

-

136-3

-

>

I

64 65. 66 67 68 69 70

71 72 73 74 75

76 78 79 80 81

W A T E R C O N T E N T , %

F I G U R E

5 R E L A T I O N B E T W E E N W A T E R C O N T E N T & WET D E N S I T Y F O R T W O B L O C K

S A M P L E S

Rff 3309 -5