The Gloucester test fill

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The Gloucester test fill

Bozozuk, M.; Leonards, G. A.

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CONSEIL NATIONAL D E RECHERCHES DU CANADA

f

BUILDING RESEARCH

-

L I B R A R Y

-

KAY

10 1973

\N4TIOI.ISL P E 5 - i " C I I C O U I 4 C I L T H E GLOUCESTER T E S T F I L L by

M. Bozozuk and G.A. L e o n a r d s

R e p r i n t e d f r o m P r o c e e d i n g s of t h e ASCE S p e c i a l t y C o n f e r e n c e o n P e r f o r m a n c e of E a r t h and E a r t h - S u p p o r t e d S t r u c t u r e s held a t P u r d u e U n i v e r s i t y , 1 1 - 1 4 J u n e 1972 Vol. 1 , P a r t 1 , p. 299-317 R e s e a r c h P a p e r No. 529 of the D i v i s i o n of Building. R e s e a r c h OTTAWA J u l y 1972 P r i c e 25 c e n t s NRCC 12729

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SOMMAIRE

On a exgcutk, dans l e fond d'une excavation de 4 p i e d s (1.2 m) de profondeur dans de l'argile m a r i n e p r k s dlOttawa au Canada, un r e m b l a i granuleux experimental de 12 pieds (3. 7 m) de hauteur, de 30 pieds ( 9 . 1 m) de l a r g e u r au sommet et de 120 pieds (36.6 m) de longueur, avec d e s pentes l a t k r a l e s de 1.5 3 1. Des cellules de p r e s s i o n des t e r r e s ont kt6 m i s e s e n p l a c e afinde m e s u r e r l e s con- t r a i n t e s n o r m a l e s ( v e r t i c a l e s et horizontales) et de cisaillement t r a n s m i s e s 3 l a b a s e du remblai. On a e n r e g i s t r k l e s p r e s s i o n s de l'eau interstitielle, l e s t a s s e m e n t s verticaux et l e s deformations horizontales en d i v e r s e s positions e t 3 d i v e r s e s profondeurs, a u s s i bien 3 l'intkrieur du r e m b l a i qu'au-dessous de lui. Une solution f e r m g e , supposant l'klasticitk linkaire, p e r m e t une bonne kvalua- tion d e s contraintes b l a fin des travaux. Une solution supposant un chargement trapkzoidal du r e m b l a i ne concorde pas avec l e s con- t r a i n t e s m e s u r k e s . On a fait en l a b o r a t o i r e des e s s a i s "CIU1', "CAU" et de f o r c e de dkformationplane afind'obtenir des donnkes p e r m e t - tant de p r k d i r e la distribution et l e s dkplacements de l a contrainte et d e l a p r e s s i o n d e l'eauinterstitielle. On a obtenu une bonne concordance e n t r e les v a l e u r s prkvues e t m e s u r k e s de l'exckdent initial des p r e s s i o n s de l'eau i n t e r s t i t i e l l e au moyen d'une Bquation de p r e s - sion i n t e r s t i t i e l l e qui rend compte d e s changements d e s t r o i s p r i n - c i p a l e s contraintes. On a kgalement obtenu l a concordance e n t r e l e s v a l e u r s prkvues et m e s u r t e s du soulkvementklastique da

b

l'ex- cavation et de l a r e c o m p r e s s i o n due 3 l'exkcution du remblai.

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THE G L O U C E S T E R T E S T F I L L M . ~ o z o z u k ' a n d G . A . ~ e o n a r d s ~ F . A S C E ABSTRACT A g r a n u l a r t e s t f i l l 12 f t ( 3 . 7 m ) h i g h , 30 f t ( 9 . 1 m ) wide a t t h e t o p , a n d 120 f t ( 3 6 . 6 m ) long w i t h 1 . 5 t o 1 s i d e s l o p e s w a s c o n s t r u c t e d on t h e f l o o r of a 4-ft (1. 2 m ) d e e p e x c a v a t i o n i n m a r i n e c l a y n e a r O t t a w a , C a n a d a . E a r t h p r e s s u r e c e l l s w e r e i n s t a l l e d t o m e a s u r e t h e n o r m a l ( v e r t i c a l a n d h o r i z o n t a l ) a n d s h e a r s t r e s s e s t r a n s m i t t e d a t t h e b a s e of t h e f i l l . P o r e w a t e r p r e s s u r e s , v e r t i c a l s e t t l e m e n t s and h o r - i z o n t a l d e f o r m a t i o n s w e r e m o n i t o r e d a t v a r i o u s p o s i - t i o n s a n d d e p t h s , both within a n d below t h e f i l l .

A c l o s e d f o r m s o l u t i o n , a s s u m i n g l i n e a r e l a s t i c i t y , p r o v i d e d a good e s t i m a t e of t h e s t r e s s e s a t t h e end of c o n s t r u c t i o n . A s o l u t i o n t h a t a s s u m e d a t r a p e z o i d a l l o a d i n g f o r t h e e m b a n k m e n t d i d n o t c o r r e l a t e w i t h the m e a s u r e d s t r e s s e s . L a b o r a t o r y CIU, CAU a n d p l a n e s t r a i n s t r e n g t h t e s t s w e r e p e r f o r m e d t o p r o v i d e d a t a f o r p r e d i c t i n g s t r e s s a n d p o r e w a t e r p r e s s u r e d i s t r i b u t i o n a n d d i s - p l a c e m e n t s . A good a g r e e m e n t w a s o b t a i n e d b e t w e e n m e a s u r e d a n d p r e d i c t e d i n i t i a l e x c e s s p o r e w a t e r p r e s s u r e s u s i n g a p o r e p r e s s u r e e q u a t i o n t h a t a c - c o u n t e d f o r c h a n g e s i n a l l t h r e e p r i n c i p a l s t r e s s e s . A g r e e m e n t w a s a l s o o b t a i n e d b e t w e e n t h e m e a s u r e d a n d p r e d i c t e d v a l u e s f o r e l a s t i c h e a v e d u e t o e x - c a v a t i o n a n d f o r r e c o m p r e s s i o n d u e t o c o n s t r u c t i o n of t h e f i l l . ' ~ e s e a r c h O f f i c e r , G e o t e c h n i c a l S e c t i o n , D i v i s i o n of B u i l d i n g R e s e a r c h , N a t i o n a l R e s e a r c h C o u n c i l of C a n a d a , O t t a w a , C a n a d a . 2 ~ c h o o l of C i v i l E n g i n e e r i n g . P u r d u e U n i v e r s i t y .

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300 EARTH STRUCTURES

In the f a l l of 1967 t h e Division of Building R e s e a r c h , National R e s e a r c h Council of Canada, c o n s t r u c t e d a t e s t f i l l a t a s i t e adjacent t o CFS G l o u c e s t e r , a m i l i t a r y station t h i r t e e n m i l e s f r o m Ottawa. It c o m p r i s e d a 12-ft ( 3 . 7 m ) high g r a n u l a r embankment, 30 ft ( 9 . l m ) wide a t t h e top and 120 f t (36. 6 m ) long, with 1. 5 t o 1 side s l o p e s , and w a s built in a 4-ft ( 1 . 2 m ) d e e p excavation. E a r t h p r e s s u r e c e l l s w e r e i n s t a l l e d to m e a s u r e n o r m a l ( v e r t i c a l and horizontal) and s h e a r s t r e s s e s t r a n s m i t t e d at t h e b a s e of t h e fill; p o r e w a t e r p r e s s u r e s , v e r t i c a l s e t t l e m e n t s and h o r i z o n t a l deformations w e r e m o n i t o r e d a t v a r i o u s positions and depths within and beneath the fill. F i g u r e 1 shows a plan of t h e t e s t p r o j e c t . Locations of p r e s s u r e c e l l s , open standpipe p i e z o m e t e r s , s e t t l e m e n t and horizontal move

-

m e n t gages a r e shown in F i g u r e s 2 t o 5.

L a b o r a t o r y t e s t s w e r e conducted t o provide data f o r predicting s t r e s s and p o r e w a t e r p r e s s u r e d i s t r i b u t i o n s and f o r calculating the r e s u l t i n g d i s p l a c e m e n t s using v a r i o u s analytical techniques. T h e predictions w e r e c o m p a r e d with c o r r e s p o n d i n g field m e a s u r e m e n t s . T h i s p a p e r i n t e r p r e t s t h e r e s u l t s obtained t o the end of construction.

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GLOUSTER TEST

FILL

O i r l a n c e E a r l 01 C e n l e r L l n e . I I P I C U R E 2 SETTLEhlENT G A U G E I N S T A L L A T I O N c _-N o l e : G a u g e r I - 25 A r e

I

V - l H 0 ~ 1 2 0 n l l l h l o v e m e n l G a u s e P l a l e r t h e

!

4 0 Il l I I ' : I I I I l l I 1 I 3 0 2 0 1 0 0 1 0 2 0 3 0 4 0 5 0 D l r l a n c e W e l l 0 1 C e n l e r L i n e . I t D l r t a n c e f a r 1 0 1 C e n l e r L l n e . I t F l G U R f 3 I N S T A L L A T I O N i O R M E A S U R I N G H O R I Z O N T A L M O V f h l f N T S

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EARTH STRUCTURES

70

p.5A

R ~ I U I I I '

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I I I I I I I 70 6 0 5 0 40 30 20 10 0 D l r l a n r e W e s l o l C e n l e r Line, I1 F I G U R E 4 P I E Z O M E T E R I N S T A L L A T I O N N o l e . C o m p l e t e d . 1 3 O c l . 167 4 I 1 , c? - ' C a m b r i d g e ' - - - P r e s s u r e C e l l

1

- V l b r a l i n g \'(,re ' B U S ' P r e s s u r e C e l l

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- 5 A E T r a n s d u c e r . - - - - - - i'!COL - - - - - - - - - S u r f a c e ' 3 1 . 9 29.9 26.6 24.0 1 2 0 . 9 1 1 . 9 1 5 . 1 1 1 . 9 6 . 0 3 . 0 0 2 2 . 0 D l s l a n c e i V e r l o l C e n l e r Line, I 1 F I G U R E 5 L O C A T I O N O F E A R T H P R E S S U R E C E L L S A T B A S E O F E h l B A N K h l E N T

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GLOUSTER TEST FILL

SITE CONDITIONS

The t e s t s i t e i s located on m a r i n e d e p o s i t s of the Champlain Sea, which invaded the a r e a following the r e t r e a t of the l a s t conti- nental ice s h e e t ( K a r r o w , 1961; Gadd, 1963). F o r a t i m e the i c e f r o n t f o r m e d the n o r t h e r n shoreline a few m i l e s t o the e a s t . M e l t - w a t e r s f r o m the g l a c i e r t r a n s p o r t e d and deposited clayey s i l t s and

sands into the s e a . As the g l a c i e r r e t r e a t e d , f r e s h w a t e r s t r e a m s t r a n s p o r t e d c l a y s and s i l t s e r o d e d f r o m exposed s o i l s f a r t h e r inland; the inflow of f r e s h w a t e r diluted the s e a and the s o i l s w e r e deposited in b r a c k i s h w a t e r . As a r e s u l t of t h e s e events and owing t o u n d e r - w a t e r c u r r e n t s and possible ocean s t o r m s , the s e d i m e n t s now a t the

s i t e a r e r e m n a n t s of various s t a g e s of deposition, e r o s i o n , and redeposition c y c l e s .

T h r e e in situ vane borings and two undisturbed sample b o r - ings w e r e m a d e a t locations round the p e r i p h e r y of the t e s t s i t e . Samples w e r e obtained with both the NGI s a m p l e r ( B j e r r u m , 1954) and the O s t e r b e r g s a m p l e r ( O s t e r b e r g , 1952). In the softer clays the quality of the s a m p l e s obtained with the O s t e r b e r g s a m p l e r was usually s u p e r i o r . Differences i n t e s t r e s u l t s of borings w e r e m i n o r and a composite of the d a t a was used t o obtain the soil profile shown in F i g u r e 6. The s u r f a c e c r u s t (zone A) i s shallow, t e r m i n a t i n g abruptly a t a depth of 6 ft ( 1 . 8 m ) , with the lower 3 ft ( 0 . 9 m ) of medium-stiff f i s s u r e d c l a y . The c r u s t r e s t s on a soft s i l t y clay l a y e r ( B ) containing v e r t i c a l root h o l e s , s o m e filled with decayed woody m a t e r i a l . The underlying g r e y s i l t y c l a y , extending t o a depth of 60 f t (18 m ) , contains d i s t i n c t zones ( C , D - E , and F ) that c a n be identified by the w a t e r content and A t t e r b e r g l i m i t p r o f i l e s , although they a r e m o r e c l e a r l y defined by the v a r i a t i o n with depth of undrained s h e a r s t r e n g t h o r preconsolidation p r e s s u r e . P r e c o n s o l i d a t i o n p r e s s u r e s w e r e obtained f r o m the r e s u l t s of one-dimensional c o n s o l - idation t e s t s such a s those shown in F i g u r e 7 .

LABORATORY TESTS T r i a x i a l T e s t s

I s o t r o p i c a l l y (CIU) and a n i s o t r o p i c a l l y (CAU) consolidated, undrained t r i a x i a l t e s t s and plane s t r a i n t e s t s w e r e p e r f o r m e d t o obtain e s t i m a t e s of p o r e p r e s s u r e p a r a m e t e r s and 'elastic' constants of the f i l l and underlying clay s t r a t a . It w a s found that i s o t r o p i c consolidation at c e l l p r e s s u r e s equal t o the effective v e r t i c a l o v e r - burden s t r e s s d i s t u r b e d the clay s t r u c t u r e and affected the i n t e r - p r e t e d e l a s t i c moduli and pore p r e s s u r e p a r a m e t e r s significantly. R e s u l t s of r e p r e s e n t a t i v e CAU t e s t s a r e shown i n F i g u r e s 8 and 9 . The a p p a r e n t value of cp' a t consolidation p r e s s u r e s comparable t o

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GLOUSTER TEST FILL

in s i t u effective s t r e s s e s was 38 deg; the Skempton (1948) p o r e p r e s s u r e p a r a m e t e r A w a s typically about 0.3. Young's modulus E = Doaxial /DEaxial ( c e l l p r e s s u r e constant during undrained s h e a r , and the change in tangential s t r e s s a s s u m e d equal to z e r o ) ranged f r o m 130 to 180 tons p e r s q f t (kg/cm2). The r a t i o of E t o the un- d r a i n e d s h e a r s t r e n g t h Su f o r zones B through F in t h e foundation c l a y ranged f r o m 630 to 1070, averaging 900. The r e l a t i o n E o 1000 Su a p p e a r s to be valid f o r n e a r l y n o r m a l l y consolidated clay d e p o s i t s ( L e o n a r d s , 1968; Hoeg, e t a l , 1969).

Specimens of the g r a n u l a r embankment fill w e r e t e s t e d i n t r i a x i a l c o m p r e s s i o n a t field w a t e r content and d e n s i t y and a t s t r e s s l e v e l s c o m p a r a b l e t o the mid-height of the fill. Volume changes w e r e m e a s u r e d during testing. During s h e a r , f o r DO, = bo, = 0, and f o r s m a l l s t r a i n s 'volumetric = 1 - 2 p E

.

( 1 ) axial

his

i s a n approximation, a s i s t h e a s s u m p t i o n of e l a s t i c i t y f o r g r a n u l a r soil.

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EARTH STRUCTURES

0 0 1 2 3 4 5 6 A X I A L S T R A I N . C I b F I G U R E 8 C A U T R l A X l A L S T R E N G T H T E S T S l l G U R l s P O R E P R [ S S U R t . S I R [ I S R C L I l l O N I i l l P I N C i U l R l A X l l l I t 5 1 8 " 1 . 0

g

1_9 . 8 - c...:~l

...,,..

.:

...,

.,

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m 7 . 0 . 6 7 PA

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1 2 3 . 1 . I . 6 . I . 8 D C V I A I O R S I R [ S S . 1 8 0 , . O ( r , l k 9 1 t m 7

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CLOUSTER TEST FILL

w h e r e e = s t r a i n and p = P o i s s o n ' s r a t i o .

The m e a n value of E obtained f r o m t h e s e t e s t s was 190 tons/sq f t ( k g / c m 2 ) and the m e a n value of p computed f r o m equation ( 1 ) a t a x i a l s t r a i n s up t o 0. 5 p e r cent was 0 . 4 .

Plane S t r a i n T e s t s

Typical c o m p a r i s o n s of CAU and plane s t r a i n t e s t s a r e shown i n F i g u r e 10. The m e a n value of cot was n e a r l y 10 p e r cent higher in the plane s t r a i n t e s t s than in the CAU t e s t s . In undrained plane s t r a i n t e s t s , with Au, = 0 ( e l a s t i c i t y and i s o t r o p y a s s u m e d ) Auaxial/~e axial i s r e l a t e d t o the corresponding r a t i o obtained i n

CAU t e s t s (with Au, = Au, = 0) by A0

-

( t r i a x i a l ) A e _{= l}_{- p "}

_{. . . .}

A0 ( 2 )

-

(plane s t r a i n ) A e

Values of E (plane s t r a i n ) ranged about 200 tons/sq ft ( k g / c m 2 ) , and the a v e r a g e value of p f o r zones B through F ( d e t e r m i n e d f r o m equation ( 2 ) ) was 0 . 4 . In p r i n c i p l e , p = 0. 5 f o r an isotropic e l a s t i c m e d i u m a t constant volume. It i s probable that t h e d i s c r e p a n c y i s due t o the effects of a n i s o t r o p y . Values of p = 0 . 4 have a l s o been d e t e r m i n e d f r o m the r e s u l t s of field m e a s u r e m e n t s in the m a r i n e clay n e a r Ottawa (Bozozuk, 1963).

A X I A L 5 1 R A I H . C I I.

...,:,

5 *I- ,,,." ,.,. . AS, . u,,, A" : I... , An, - A#,# > U"

!...

, as, - an,,, b~

A ' , . z..-

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EARTH STRUCTURES

It w a s a f o r t u n a t e coincidence t h a t t h e a v e r a g e v a l u e s of the e q u i v a l e n t e l a s t i c c o n s t a n t s ( E and p) f o r the embankment and i t s foundation w e r e e s s e n t i a l l y equal.

PREDICTIONS AND OBSERVATIONS S t r e s s e s along B a s e of F i l l

B a l a d i (1967) and P e r l o f f e t a1 (1967) d e t e r m i n e d t h e s t r e s s e s and d i s p l a c e m e n t s within and u n d e r a n e m b a n k m e n t ( o r e x c a v a t i o n ) r e s u l t i n g f r o m i t s s e l f - w e i g h t , a s s u m i n g t h a t t h e e m b a n k m e n t and the foundation s o i l with which i t i s continuous a r e h o m o g e n e o u s , l i n e a r e l a s t i c , and i s o t r o p i c , and t h a t plane s t r a i n conditions apply. T h i s m e t h o d , h e r e a f t e r c a l l e d t h e P u r d u e s o l u t i o n , w a s u s e d t o d e t e r m i n e t h e s t r e s s e s f o r t h e t e s t f i l l . T h e f i n i t e e l e m e n t m e t h o d d e s c r i b e d by F i n n (1967) w a s a l s o u s e d ; r e d u c t i o n i n load due t o e x c a v a t i o n i s m a d e in two s t e p s and t h e e m b a n k m e n t load applied i n s i x i n c r e m e n t s T h e g r i d i s shown i n F i g u r e 11.

M e a s u r e d s t r e s s e s along the b a s e of t h e f i l l a r e p r e s e n t e d in F i g u r e s 12 t h r o u g h 1 4 , and a r e c o m p a r e d with t h e p r e d i c t e d v a l u e s i n F i g u r e s 1 5 and 16. T h e P u r d u e solution a g r e e s well w i t h the m e a - s u r e d v a l u e s in a l l c a s e s . T h e a r e a u n d e r t h e v e r t i c a l s t r e s s d i s - t r i b u t i o n d i a g r a m w a s within 4 p e r c e n t of t h e e f f e c t i v e weight of t h e e m b a n k m e n t d e t e r m i n e d f r o m i n - p l a c e d e n s i t y t e s t s .

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GLOUSTER TEST FILL

F I G U R E 1 2 V i R T I C A L E i F E C T I V i S I R E 5 5 h l E A 5 U R E D A L O N G B A I L O F T E S T F l L l F I G U R E 13 H O R I Z O N T A L E F F E C T I V E S T R E S S E S M E A S U R E D A T B A S E O F T E S T F I L L

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EARTH STRUCTURES

c _{D I S T A N C E F R O M C E N T E R}_{L I N E . I!} F I G U R E I 4 S H E A R S T R E S S M E A S U R L D A L O N G B A S E O F l E S T F I L L I - H F I G U R E I 5 C O M P A R I S O N O i P R E D I C T E D W l l H M E A S U R E D V I R T I C A L E i f E C l I V C S T R E S S A L O N G B A S E O F T E S T E M B A N K X E N T AT E N D OF C O N S l R U C l l O N

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GLOUSTER TEST FILL

f l G U R f 16 P R E O I C T f D V S . M E A S U R E D H O R I Z O N T A L A N D S H E A R S T R E S S E S A L O N G B A S E O F F I L L A T E N D O F C O N S T R U C T I O N P o r e W a t e r P r e s s u r e s In p r e d i c t i n g the d i s t r i b u t i o n of i n i t i a l ( u n d r a i n e d ) e x c e s s p o r e w a t e r p r e s s u r e ( h i ) due t o e x c a v a t i o n and e m b a n k m e n t c o n s t r u c t i o n t h e P u r d u e solution w a s u s e d t o c a l c u l a t e t h e c h a n g e s i n p r i n c i p a l s t r e s s e s . Aui w a s obtained f r o m the r e l a t i o n

Au. = Auoct

+

n

.

Aq

.

. .

( 3 ) w h e r e , A U = 1/3 ( A u ,

+

Au,

+

Au,) oct [Schofield and W r o t h , 1968)

n

= p o r e w a t e r p r e s s u r e p a r a m e t e r , d e t e r m i n e d f r o m plane s t r a i n t e s t s . T h e v a r i a t i o n of Cl with l e v e l of s h e a r s t r e s s i s i l l u s t r a t e d in F i g u r e 17.

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EARTH STRUCTURES

" 6 1 o~ 2 3 . 4 . 5 . 6 C H A N G E I N S H E A R S T R E S S L E V E L . A q , k g l c m 2 F I G U R E 1 7 P O R E P R E S S U R E P A R A M E T E R n V S . S H E A R S T R E S S L E V E L . P L A N E S T R A I N T E S T S

P i e z o m e t e r r e a d i n g s a s a function of t i m e a t the c e n t e r line of the e m b a n h e n t a r e plotted in F i g u r e 18. T o obtain the e x c e s s p o r e p r e s s u r e s the head of w a t e r in r e f e r e n c e p i e z o m e t e r s located s o m e d i s t a n c e f r o m the t e s t s i t e w e r e s u b t r a c t e d f r o m t h e s e values. C o m - p a r i s o n s of p r e d i c t e d and o b s e r v e d e x c e s s p o r e w a t e r p r e s s u r e s a t the end of excavation and following completion of the f i l l a r e shown i n F i g u r e 19. A g r e e m e n t between p r e d i c t e d and m e a s u r e d values i s exceptionally good a t m a n y l o c a t i o n s .

Applying equation ( 3 ) t o CAU t e s t s , assuming

a,

=

a3

a f t e r consolidation and

AD,

=

Aa,

r: 0 during undrained s h e a r ,

Hence, f o r an i s o t r o p i c s o i l ,

n

should equal (A

-

1/3). In general, r e s u l t s f r o m CAU and plane s t r a i n t e s t s did not s a t i s f y t h i s r e l a t i o n , although in s o m e c a s e s a g r e e m e n t was approached a t f a i l u r e . Devia- t i o n s a t s t r a i n s below f a i l u r e probably r e s u l t f r o m the a n i s o t r o p i c r e s p o n s e of the c l a y .

D i s p l a c e m e n t s

The v e r t i c a l d i s p l a c e m e n t s m e a s u r e d a t the c e n t e r line of the e m b a n b e n t f r o m the beginning of c o n s t r u c t i o n in August 1967 through J u l y 1971 a r e shown in F i g u r e 2 0 . At the m i d - p o i n t of the b a s e of the f i l l the m e a s u r e d heave r e s u l t i n g f r o m excavation w a s

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GLOUSTER TEST FILL

F I G U R E I 6 P O R L P R L 5 I U R E t ~ I I A S U R E Y E N l S I N l 0 U N O A l l O N C L A Y

OISTAHCE FROM C E N T E R L I M E . I I

FIGURE 19 OBSERVED AND PREDICTED EXCESS PORE WATER PRESSURES

n - 2 0 m - 0 9 ' I o . , ! - - n l o "0 6 - m I 6 1 ' ~ 2 0 - EXCAVATION n 1 5 rn .60 " P - 7 3 m - S B 4 9 p - 7 6 m - 5 6 < ' P - 5 1 m - 6 0 5 7 p - 5 9 ( ' 5 2 5 0 6 0 7 0 n - 2 2 m - 5 1 5 6 p - 5 3 " 1 7 I 4 0 - m . ~ ~ " p - 6 6 r n - 4 3 a ' 9 - 4 9 .,

.

- 3 2 I - * " . ? 7

,

P - 2 3

1

1 - KO-TL

r YEISUREO E X C E I I PORC I R I S S U R E 111 01 .ol,rl

- 9

.

PREDlCTEO EXCESS PORE P U E I S U R r 111 01 .01.11

I I I I

20

5 0 4 0 3 0 2 0 10 0 10 2 0 3 0 4 0 5 0 6 0

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EARTH STRUCTURES

0. 012 ft (. 37 c m ) a n d t h e s e t t l e m e n t upon c o m p l e t i o n of the e m b a n k - m e n t w a s 0. 087 f t ( 2 . 6 5 c m ) ; the p r e d i c t e d v a l u e s , u s i n g the P u r d u e solution with E = 200 tons/sq ft ( k g / c m 2 ) and C( = 0 . 4 , w e r e 0.011 f t

(. 34 c m ) and 0.069 ft ( 2 . 10 c m ) , r e s p e c t i v e l y . A g r e e m e n t between

m e a s u r e d and p r e d i c t e d d i s p l a c e m e n t s w a s c l o s e r than e x p e c t e d . O b s e r v e d d i f f e r e n t i a l s e t t l e m e n t s a t t h e top of the e m b a n k - m e n t i n t h e longitudinal a n d t r a n s v e r s e d i r e c t i o n s and a t the b a s e in t h e t r a n s v e r s e d i r e c t i o n show t h a t p l a n e s t r a i n conditions w e r e a c h i e v e d o v e r the i n s t r u m e n t e d l e n g t h of t h e f i l l ( F i g u r e 21). S o m e m e a s u r e d h o r i z o n t a l d i s p l a c e m e n t s a r e i l l u s t r a t e d in F i g u r e 22. T i m e and s p a c e l i m i t a t i o n s d i c t a t e t h a t d i s c u s s i o n of t h e s e d i s p l a c e - m e n t s be d e f e r r e d t o a l a t e r d a t e .

SUMMARY AND CONCLUSIONS

D e t a i l e d l a b o r a t o r y s t u d i e s of u n d i s t u r b e d s a m p l e s of a d e p o s i t of m a r i n e c l a y n e a r O t t a w a , C a n a d a , show that: 1 ) the d e p o s i t c o n t a i n s s e v e r a l d i s t i n c t s t r a t a whose u p p e r z o n e s w e r e m o r e highly o v e r c o n s o l i d a t e d t h a n t h e i r l o w e r p o r t i o n s ; 2) i s o t r o p i c c o n s o l i d a t i o n a t c e l l p r e s s u r e s e q u a l to the e f f e c t i v e o v e r b u r d e n p r e s s u r e d i s t u r b e d the c l a y s t r u c t u r e a n d a f f e c t e d t h e r e s p o n s e t o s u b s e q u e n t c h a n g e s i n s t r e s s significantly; 3) a f i r s t a p p r o x i m a t i o n of Young's m o d u l u s ( E ) w a s obtained by multiplying the u n d r a i n e d s h e a r s t r e n g t h ( S ) by 1000; U

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GLOUSTER TEST FILL

SOUTH OlSTAHCE. I t NORTH 6 0 40 20 0 20 40 6 0 I Z l , l b l ~ l ~ / , l ( , I - I N I T I A L 3,

.

I

----

7Fx-"+--

l a 1 L O H C I T U D I H A L SECTION WEST D I S T A H C E . I1 CAST 3 0 20 10 0 10 20 3 0 I ' I ' I ' I ' I ~ I ' I ' t 1 - I H I T I A L I b l T R A H S V E R S I SECTION 20 O c t . 1967 6 M a y 1969 2 1 J u l y 1 9 1 1 FIGURE 21 O B S E R V I D V I R T I C A L O I S P L A C C M I N T S OF T E S l EMBAHKhlCHT F I G U R E 22 O B S E R V E D H O R I Z O N T A L h l O V L M E N T S F R O M I d O C T O B E R . 1 9 6 1 TO 2 1 J U L Y . 1 9 1 1

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EARTH STRUCTURES

4) t h e r e l a t i o n between s t r e s s and s t r a i n was d i r e c t i o n a l l y depen-

dent ( a n i s o t r o p i c ) ; accordingly, plane s t r a i n t e s t s a r e p r e f e r r e d t o CAU t e s t s in obtaining r e l e v a n t s o i l p a r a m e t e r s applicable t o p r e d i c t i o n of t h e r e s p o n s e t o embankment c o n s t r u c t i o n .

Although the nominal f a c t o r of s a f e t y with r e s p e c t t o founda- tion s t a b i l i t y w a s l e s s than 1. 3 , replacing the embankment and i t s foundation by a n equivalent l i n e a r e l a s t i c i s o t r o p i c m e d i u m provided a good a p p r o x i m a t i o n f o r p u r p o s e s of calculating undrained r e s p o n s e of the foundation c l a y . T h i s m a y not be t h e c a s e f o r o t h e r , l e s s bonded, c l a y d e p o s i t s . Good a g r e e m e n t w a s obtained f o r m e a s u r e d values of n o r m a l (both v e r t i c a l and h o r i z o n t a l ) and s h e a r s t r e s s e s along t h e b a s e of t h e f i l l with values p r e d i c t e d using t h e P u r d u e solution. Assuming a n equivalent t r a p e z o i d a l ( n o r m a l ) loading f o r t h e embankment i n t r o d u c e s s e r i o u s e r r o r s i n the p r e d i c t i o n of

s t r e s s e s and d i s p l a c e m e n t s , m a i n l y b e c a u s e s h e a r s t r e s s e s along the b a s e of the f i l l a r e neglected. The u s e of t h i s approximation of loading conditions should be discontinued. The finite element method p r e d i c t e d v e r t i c a l and h o r i z o n t a l n o r m a l s t r e s s e s , but u n d e r e s t i - m a t e d s h e a r s t r e s s e s along the b a s e of the f i l l .

A g r e e m e n t was a l s o obtained between m e a s u r e d and p r e d i c t e d d i s t r i b u t i o n s of i n i t i a l e x c e s s p o r e w a t e r p r e s s u r e s , implying t h a t a good p r e d i c t i o n was m a d e of the r e s u l t i n g changes in s t r e s s in the foundation clay. The u s e of a p o r e p r e s s u r e equation t h a t accounts f o r changes in a l l t h r e e p r i n c i p a l s t r e s s e s i s r e c o m m e n d e d f o r p r e d i c t i n g i n i t i a l e x c e s s p o r e w a t e r p r e s s u r e s r e s u l t i n g f r o m e m - bankment c o n s t r u c t i o n .

ACKNOWLEDGEMENTS

T h e a u t h o r s wish t o thank the t e c h n i c a l staff of the G e o t e c h - n i c a l Section, DBR/NRC, who c a r r i e d out the l a b o r a t o r y t e s t s and field s u r v e y s . Special thanks a r e a l s o due t o D r . W. H. P e r l o f f , P u r d u e U n i v e r s i t y , who provided the c o m p u t e r p r o g r a m f o r t h e P u r d u e solution.

T h i s p a p e r i s a contribution f r o m the Division of Building R e s e a r c h , National R e s e a r c h Council of C a n a d a , and i s published with the a p p r o v a l of the D i r e c t o r of t h e Division.

REFERENCES

B a l a d i , G. Y . 1967. D i s t r i b u t i o n of s t r e s s e s and d i s p l a c e m e n t s within and u n d e r long e l a s t i c and v i s c o e l a s t i c e m b a n k m e n t s . P h . D. T h e s i s , P u r d u e U n i v e r s i t y , L a f a y e t t e , Indiana.

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317

B j e r r u m , L . 1954. G e o t e c h n i c a l p r o p e r t i e s of N o r w e g i a n m a r i n e c l a y s . GBotechnique, Vol. 4 , No. 2, p p . 49-69.

Bozozuk, M . 1963. T h e m o d u l u s of e l a s t i c i t y of L e d a c l a y f r o m f i e l d m e a s u r e m e n t s

.

C a n a d i a n G e o t e c h n i c a l J o u r n a l , Vol. 1 , No. 1 , pp. 4 3 - 5 1 .

F i n n , W . D . L . 1967. S t a t i c and s e i s m i c behaviour of a n e a r t h d a m . Canadian G e o t e c h n i c a l J o u r n a l , Vol. IV, No. 1, pp. 28-44. Gadd, N. R. 1963. S u r f i c i a l geology of O t t a w a m a p - a r e a O n t a r i o

and Quebec 31 6/5. G e o l o g i c a l S u r v e y of C a n a d a , Dept. o f M i n e s and T e c h n i c a l S u r v e y s , P a p e r 6 2 - 1 6 , 4 p .

H6eg, K . , A n d e r s l a n d , O . B . and R o l f s e n , E . N . 1969. Undrained b e h a v i o u r of quick c l a y u n d e r load t e s t s a t A s r u m . GBotechnique, Vol. XIX, No. 1 , pp. 101-115.

K a r r o w , P . F . 1961. T h e C h a m p l a i n S e a and i t s s e d i m e n t s . S o i l s i n C a n a d a , Univ. of T o r o n t o P r e s s , i n c o o p e r a t i o n w i t h the Royal S o c i e t y of C a n a d a , pp. 97-108. L e o n a r d s , G . A . 1968. P r e d i c t i n g s e t t l e m e n t s of buildings on c l a y s o i l s . P r o c e e d i n g s , L e c t u r e S e r i e s J a n u a r y - M a y 1968, I l l i n o i s S e c t i o n ASCE, N o r t h w e s t e r n U n i v e r s i t y . E v a n s t o n , I l l . O s t e r b e r g , 3 . 0 . 1952. New p i s t o n tube s a m p l e r . E n g i n e e r i n g N e w s - R e c o r d , Vol. 148, pp. 77-78. P e r l o f f , W . H . , B a l a d i , G . Y. and H a r r , M . E . 1967. S t r e s s d i s t r i b u t i o n within and u n d e r long e l a s t i c e m b a n k m e n t s .

E m b a n k m e n t s and T h e i r F o u n d a t i o n s , Highway R e s e a r c h R e c o r d , No. 181, p p . 12-40.

Schofield, A. and W r o t h , P. 1968. C r i t i c a l S t a t e Soil M e c h a n i c s . M c G r a w - H i l l , London.

S k e m p t o n , A. W. 1948. The e f f e c t i v e s t r e s s e s i n s a t u r a t e d c l a y s s t r a i n e d a t c o n s t a n t v o l u m e . P r o c e e d i n g s , I n t e r n a t i o n a l

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T h i s p u b l i c a t i o n is b e i n g d i s t r i b u t e d by t h e Division of Building R e s e a r c h of the N a t i o n a l R e s e a r c h C o u n c i l of C a n a d a . I t s h o u l d n o t b e r e p r o d u c e d i n whole o r i n p a r t without p e r m i s s i o n of the o r i g i n a l p u b l i s h e r . T h e Di- v i s i o n would b e g l a d t o b e of a s s i s t a n c e i n obtaining s u c h p e r m i s s i o n . P u b l i c a t i o n s of t h e D i v i s i o n m a y b e o b t a i n e d by m a i l - ing t h e a p p r o p r i a t e r e m i t t a n c e ( a Bank, E x p r e s s , o r P o s t Office M o n e y O r d e r , o r a c h e q u e , m a d e p a y a b l e t o t h e R e c e i v e r G e n e r a l of Canada, c r e d i t NRC) t o t h e N a t i o n a l R e s e a r c h C o u n c i l of Canada, Ottawa. K1A OR6. S t a m p s a r e n o t a c c e p t a b l e .

A l i s t of a l l p u b l i c a t i o n s of t h e D i v i s i o n i s a v a i l a b l e a n d m a y b e obtained f r o m t h e P u b l i c a t i o n s S e c t i o n , D i v i s i o n of Building R e s e a r c h , N a t i o n a l R e s e a r c h C o u n c i l of C a n a d a , Ottawa. KIA OR6.