READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE. https://nrc-publications.canada.ca/eng/copyright
Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n’arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca.
Questions? Contact the NRC Publications Archive team at
PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information.
NRC Publications Archive
Archives des publications du CNRC
This publication could be one of several versions: author’s original, accepted manuscript or the publisher’s version. / La version de cette publication peut être l’une des suivantes : la version prépublication de l’auteur, la version acceptée du manuscrit ou la version de l’éditeur.
Access and use of this website and the material on it are subject to the Terms and Conditions set forth at
Measured strengths under fills on sensitive clay / resistance mesuree
d'argile sensible sous remblais
Law, K. T.; Bozozuk, M.; Eden, W. J.
https://publications-cnrc.canada.ca/fra/droits
L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site
LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.
NRC Publications Record / Notice d'Archives des publications de CNRC:
https://nrc-publications.canada.ca/eng/view/object/?id=39a5120b-567e-4531-8d8d-b2c55c0d721e
https://publications-cnrc.canada.ca/fra/voir/objet/?id=39a5120b-567e-4531-8d8d-b2c55c0d721e
S e r
TH1
N21d
no.
746
National Research
Conseil national
C.
2
+
Council Canada
de recherche Canada
MEASURED STRENGTHS UNDER FILLS
ON SENSITIVE CLAY
by
KT.
Law,
M.
Bozozuk
and W.J.
Eden
//
ANALYZED
Reprinted,
with permission, from
Proceedings,
IXth
International Conference on
I-
6 ,
-
r 1Soil Mechanics
and
Foundation Engineering
,
1Vol. 1,1977
PUILDINC
RCSEARCM
1
p.
187 192
v - * - ,.
.,
DBR Paper No. 746
Division of Building Research
SO
MMAIRE
Une s 6 r i e de m e s u r e s de l a r e s i s t a n c e au cisaillement avec
un scissom'etre menCe dans l e sous - s o l de q u a t r e r e m b l a i s
de g6om6trie diffdrente e t construits s u r l e s a r g i l e s de l a
m e r Champlain pr'es dlOttawa, au Canada, ont domC l e s
mbmes v a l e u r s que c e l l e s trouvCes avant l a construction.
D1autre p a r t , lea e s s a i s de compression triaxiale e n l a b o r a -
t o i r e effectubs s u r des Cchantillons intacts, p r i s e n mBme
temps que l e s m e s u r e s du scissom'etre ont montr6 une aug-
mentation definitive de l a rCsistance au cisaillement lorsque
m i s
&
l ' e s s a i dans d e s conditions d e contraintes comparables
&
celles sous l e s remblais. L e s f a c t e u r s
quiont pu contri-
buer
'a ce dCsaccord sont discutgs.
Measured Strengths under Fills on Sensitive Clay
Rksistance Mesuree dlArgile Sensible sous Remblais
K.T.LAW,
M.BOZOZUK and
W.J.EDEN
Geotechnical Section, Division of Building Research, National Research Council of Canada, CanadaSYNOPSIS A s e r i e s o f f i e l d vane s t r e n g t h measurements c o n d u c t e d i n t h e s u b s o i l o f f o u r f i l l s o f d i f f e r e n t
geometry and c o n s t r u c t e d o n Champlain Sea c l a y s n e a r Ottawa, Canada, gave v a l u e s t h e same a s t h o s e found p r i o r t o c o n s t r u c t i o n . On t h e o t h e r hand, l a b o r a t o r y t r i a x i a l compression t e s t s c o n d u c t e d on u n d i s t u r b e d p i s t o n samples t a k e n a t t h e same t i m e a s t h e vane measurements showed a d e f i n i t e i n c r e a s e i n s h e a r r e s i s t a n c e when t e s t e d a t s t r e s s c o n d i t i o n s comparable t o t h e e f f e c t i v e s t r e s s e s e x i s t i n g under t h e f i l l s . The p o s s i b l e f a c t o r s c o n t r i b u t i n g t o t h i s d i s c r e p a n c y a r e d i s c u s s e d . INTRODUCTION a p a r t t o a v o i d mutual i n f l u e n c e . When s o f t , s e n s i t i v e marine c l a y s a r e l o a d e d , s e t t l e - ments o c c u r o v e r l o n g p e r i o d s o f t i m e owing i n p a r t , i t i s b e l i e v e d , t o a breakdown i n s t r u c t u r e and r e s u l t i n g i n c r e a s e i n p o r e w a t e r p r e s s u r e (Crawford and Burn, 1976). Under s u c h c i r c u m s t a n c e s s t a g e c o n s t r u c t i o n i s somewhat hazardous i f used t o a c h i e v e a g a i n i n s t r e n g t h and an i n c r e a s e i n s t a b i l i t y w i t h t i m e . A number o f f i l l s i n t h e Ottawa r e g i o n have b e e n under o b s e r v a t i o n o v e r a p e r i o d o f s e v e r a l y e a r s . T h i s p a p e r r e p o r t s some o f t h e long- t e r m o b s e r v a t i o n s , t h e measured s t r e n g t h s under t h e f i l l s ( u s i n g f i e l d and l a b o r a t o r y t e c h n i q u e s ) , and d i s c u s s e s f a c t o r s a f f e c t i n g t h e measurement o f s t r e n g t h when t h e f i e l d vane i s used. A t h i r d f i l l i s l o c a t e d a t Kars B r i d g e , 40 km s o u t h o f Ottawa. T h i s i s a n approach embankment, b u i l t i n s t a g e s , o f . g r a n u l a r s o i l . The f i r s t l i f t was p l a c e d i n November 1959 t o a h e i g h t o f 6 . 1 m and was b r o u g h t t o i t s f i n a l e l e v a t i o n o f 8 . 0 m 20 months l a t e r . The t o p w i d t h o f t h e f i l l i s 15.2 m and t h e s i d e s l o p e s 2 : l .
SITES AND FILLS
Four f i l l s c o n s t r u c t e d a t t h r e e s i t e s on Champlain
Sea c l a y s i n t h e Ottawa r e g i o n a r e c o n s i d e r e d . The 4
g e n e r a l c h a r a c t e r i s t i c s o f t h e s u b s o i l s i n v o l v e d
are similar t o those r e p o r t e d e a r l i e r by Crawford ( 1 9 6 1 ) . A t e a c h site, s u b s o i l s were sampled w i t h t h e
5 4 - m & a NGI p i s t o n sampler (Bjerrum, 1954) o r t h e
Osterberg 127-mrn d i a sampler (Osterberg, 1952). E a
Routine c l a s s i f i c a t i o n , t r i a x i a l and c o n s o l i d a t i o n
t e s t s were c a r r i e d o u t ; and t h e r e s u l t s , t o g e t h e r I ,- 0.
w i t h t h e a p p l i e d v e r t i c a l p r e s s u r e s , a r e summarized ", 0
i n F i g u r e s 1 t o 3 . The f i l l s were i n s t r u m e n t e d
e x t e n s i v e l y and some o f t h e measurements were 1 2
r e p o r t e d e l s e w h e r e (Eden and Poorooshasb, 1968; Bozozuk and Leonards , 1972)
.
I > V E R T I C A L PRESSURE, WATER C O N T E N T , % m ' 2 ; k g / c r n 2 -SILTY CLAY' G R E Y S I L T Y C--C
-
C L A Y.
-
-
-
1 0 0 G R E Y C L A Y-
- .
G R E Y - S I L T Y C L A Yc--(.
C L A Y (L - S I L T 6.
-
S A N D L S T O N E S,
I I 1 10 1 1 1 1 Two f i l l s were c o n s t r u c t e d i n t h e f a l l o f 1967 n e a rSouth G l o u c e s t e r , 21 km s o u t h - e a s t o f Ottawa, Canada. 1 b One, a t e s t embankment c o n s t r u c t e d i n a n e x c a v a t i o n
1 . 2 m deep, i s a g r a n u l a r f i l l 3 . 7 m h i g h , 9 . 2 m wide and 36.6
m
l o n g a t t h e t o p , w i t h 1 . 5 : l s i d es l o p e s . A p l a n e s t r a i n c o n d i t i o n p r e v a i l s a t i t s 20
middle s e c t i o n where t h e b u l k o f t h e i n s t r u m e n t a t i o n was i n s t a l l e d . The second f i l l , b u i l t o f m a t e r i a l s f r o m t h e e x c a v a t i o n , i s c i r c u l a r , a b o u t 2.4
m
h i g h and 22.4 m i n d i a m e t e r a t t h e t o p , w i t h 1 . 5 : l
16
F i g u r e 2 G e o t e c h n i c z l P r o f i l e a t Kars Bridge The f o u r t h f i l l i s s i t u a t e d a b o u t 6 . 5 km e a s t o f t h e
G l o u c e s t e r s i t e on Boundary Road where i t c r o s s e s Highway 417. This was c o n s t r u c t e d i n June 1970 a s a t w o - l e v e l t e s t embankment w i t h h e i g h t s o f 2 . 7 and 4 . 3 m, r e s p e c t i v e l y . I t was g r a d e d a y e a r l a t e r t o form an approach f i l l with a maximum h e i g h t o f 4 . 3 m.
S O I L O R G A N I C - S I L T - B R O W N ~ C L A Y 8 - S A N D
-
G R E Y - C L A Y-
-
- S T R A T I F I E D-
C L A Y S I L T Y G L A C I A L T I L LSETTLEMENT A N D PORE PRESSURE RECORDS
1 > W A l t R C O N T t N l , ''L, vlr V E R T I C A L S T R E S S , k g / c m 2 > 0 2 0 4 0 6 0 8 0 :LO 0 . 5 1 . 0 1 . 5 2 . 0 2 . 5 3 . 0 3 . 5 4 . 0 4 . 5 1 1 1 1 1 1 7 T 1 1 1 1 1
*
",.
",P ?",L 7 I I-
3 2.
'
2 9 Y . , 1 0 0- .
,I 0 0 2 4 l b l l T 1 A L I IF i g u r e s 4 t o 6 show t h e v e r t i c a l compression and e x c e s s p o r e p r e s s u r e measured i n t h e s o i l f o r m a t i o n s i n which t h e imposed l o a d exceeded t h 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 below t h e c e n t r e l i n e o f t h e f i l l s . S u b s t a n t i a l compression (4 t o 8 p e r c e n t ) h a s t a k e n p l a c e , w i t h t h e a c t u a l amount depending on t h e i n t e n s i t y , geometry, and d u r a t i o n o f l o a d i n g . These a r e s i m i l a r t o t h o s e o b s e r v e d b e n e a t h t h e s h o u l d e r o f t h e f i l l s . The r a t i o s o f s u r f a c e s e t t l e m e n t below t h e s h o u l d e r t o t h a t below t h e c e n t r e a r e 6 2 p e r c e n t a t t h e G l o u c e s t e r c i r c u l a r f i l l , 9 2 p e r c e n t a t Kars B r i d g e and 86 p e r c e n t a t t h e Boundary Road.
Excess p o r e w a t e r p r e s s u r e g e n e r a l l y developed immediately on l o a d i n g . Following c o n s t r u c t i o n , i t d i s s i p a t e d r e l a t i v e l y r a p i d 1 y a t f i r s t , t h e n s l o w l y dropped t o a v a l u e o f l e s s t h a n 1 m o f w a t e r head. T h i s r e s u l t e d i n a v e r t i c a l e f f e c t i v e s t r e s s exceed- i n g t h 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 i n a l l c a s e s . FIELD VANE SilEAR TESTS UNDER FILLS
During 1974 and 1975, s e r i e s o f f i e l d vane t e s t s were performed a t t h e f o u r f i l l s . A t G l o u c e s t e r , one b o r i n g was made through t h e c e n t r e o f t h e t e s t embankment and t h r e e were made through t h e c i r c u l a r f i l l a t v a r y i n g d i s t a n c e s from t h e c e n t r e . A t t h e approach embankment o f Kars B r i d g e two vane b o r i n g s were performed through t h e s h o u l d e r where t h i c k n e s s e s o f f i l l were 7.9 and 5 . 2 m, r e s p e c t i v e l y . The i n d u c e d s t r e s s e s a t t h e s e l o c a t i o n s were s i g n i f i c a n t l y
d i f f e r e n t . F o r u n d r a i n e d c o n d i t i o n s ( s h o r t - term l o a d i n g ) no zone o f l o c a l f a i l u r e ( r e g i o n i n which t h e s o i l i s s t r a i n e d beyond t h e peak s t r e n g t h ) was d e t e c t e d i n t h e lower s e c t i o n , b u t an e x t e n s i v e zone was found b e n e a t h t h e h i g h e r s e c t i o n (Law, 1974).
The l a s t vane b o r i n g was c a r r i e d o u t through t h e s h o u l d e r o f t h e Boundary Road f i l l a t a s e c t i o n where t h i c k n e s s was a b o u t 3 . 0 m .
The r e s u l t s o f t h e vane t e s t s a r e shown i n F i g u r e s 7 t o 9 . Also p l o t t e d on t h e s e f i g u r e s a r e t h e p r e - c o n s t r u c t i o n i n s i t u f i e l d vane s t r e n g t h s measured w i t h t h e same equipment. I n g e n e r a l . t h e r e i s l i t t l e d i f f e r e n c e between t h e two s e t s o f r e s u l t s , i m p l y i n g t h a t t h e s u s t a i n e d l o a d i n g and r e s u l t i n g l a r g e compression d i d n o t e f f e c t t h e s h e a r s t r e n g t h o f t h e s o i l .
END OF C O N S T R U C T I O N
1
I I
TEST L M B A N K M E N I
--
- - -
\ -
---
Figure 4 Records of Settlement and Excess Pore Water Pressure Under C e n t r e l i n e o f t h e F i l l s a t Gloucester
E - 5 L = .A .A - 4
::
1 . 6 m A N 0 1 0 . 7 m-
= - 3:
.A .A - 2z
u AT 1 0 m DEPTH F I N A L GRADEFigure 5 Compression and Pore Pressure Records a t Centre l i n e , Kars Bridge F i l l
M P R E S S I O N BETWEEN DEPTHS I I 6 6 m A N D 1 . 6 m I I I G R A D E D L I I I I I I I I I ~ l I I I I I ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ l l I 1 l ~ l l
Figure 6 Settlement and Excess Water Head Under Shoulder o f Embankment a t Boundary Road
V A N E S T R E N G T H , k g l c m 2
o O 0 . 2 0 . 4 0 . 6 0 8 0 0 . 2 0 . 4 0 . 6 0 . 8 1.0
I I 1 I 1 I I I
la1 U N D E R T H E T E S T E M B A N K M E N T l b l U N D E R THE C I R C U L A R F l l l
Figure 7 F i e l d Vane S t r e n g t h s a t Gloucester (All T e s t s Restored t o P r e - c o n s t r u c t i o n E l e v a t i o n s )
0 B E N E A T H 7 9 m F l l l . I 6 Y E I R S A F T E R P L A C E M E N T
1
Figure 8 F i e l d Vane S t r e n g t h s Under Kars Bridge F i l l ( A l l T e s t s R e s t o r e d t o P r e - c o n s t r u c t i o n E l e v a t i o n s )
a p p r e c i a b l e d i f f e r e n c e i n measured s h e a r s t r e n g t h beneath t h e c e n t r e and t h e s h o u l d e r , implying t h a t t h e r o t a t i o n o f p r i n c i p a l s t r e s s e s beneath t h e s h o u l d e r d i d n o t change t h e vane s t r e n g t h . A t Kars Bridge a l s o , t h e r e s u l t s i n d i c a t e no change i n u n d r a i n e d s h e a r s t r e n g t h , whether o r n o t l o c a l f a i l u r e c o n d i t i o n s e x i s t .
TRIAXIAL COMPRESSION TESTS
A program o f undrained t r i a x i a l compression t e s t s was c a r r i e d o u t on t h e s o i l s from Kars Bridge and
G l o u c e s t e r . There were t h r e e s e r i e s o f t e s t s : (1) CIU and CAU t e s t s performed a t d i f f e r e n t c o n s o l i - d a t i o n p r e s s u r e s on u n d i s t u r b e d samples o b t a i n e d p r i o r t o c o n s t r u c t i o n ( p r e - c o n s t r u c t i o n s o i l s ) ; (2) same a s (1) e x c e p t on u n d i s t u r b e d s o i l samples t a k e n from under t h e f i l l s ( p o s t - c o n s t r u c t i o n s o i l s ) a t t h e time o f vane s h e a r t e s t i n g ; ( 3 ) CAU t e s t s performed on p o s t - c o n s t r u c t i o n s o i l samples c o n s o l i d a t e d t o s t r e s s c o n d i t i o n s comparable t o t h o s e e x i s t i n g under t h e f i l l s . The r e s u l t s o f t h e t e s t s a r e shown i n F i g u r e s 10 t o 12.
The s t r e n g t h envelope d e p i c t e d i n F i g u r e s 10 and 1 1 i s s i m i l a r t o t h a t d e s c r i b e d by Eden and J a r r e t t (1971). I t h a s a pronounced c u r v e a t low e f f e c t i v e p r e s s u r e s and i s l i n e a r a t h i g h e r p r e s s u r e s . T h i s envelope remains p r a c t i c a l l y unchanged f o r t h e p o s t - c o n s t r u c - t i o n s o i l .
The u n d r a i n e d s t r e n g t h s deduced from t h e f i e l d vane and t r i a x i a l t e s t s c o r r e s p o n d i n g t o p r e - c o n s t r u c t i o n and 1975 c o n d i t i o n s a r e shown on F i g u r e s 10 and 1 1 . A
s i z a b l e s t r e n g t h i n c r e a s e c a n b e n o t e d from t h e t r i a x i a l t e s t s . A f u r t h e r comparison o f t h e t r i a x i a l s t r e n g t h s o f t h e Kars Bridge s o i l i s p r e s e n t e d i n F i g u r e 1 2 . R e s u l t s F I E L D V A N E S T R E N G T H . k g i c m 2
-
P R I O R T O C O N S T R U C T I O N o 5 Y E A R S A F T E R P L A C E M E N 1Figure 9 F i e l d Vane S t r e n g t h s Under Boundary Road F i l l ( A l l T e s t s R e s t o r e d t o P r e - c o n s t r u c t i o n E l e v a t i o n s )
-
t
o PRIOR T O C O N S T R U C T I O N 7 YEARS AFTER C O N S T R U C T I O N a,' , a3' = E F F E C T I V E V E R T I C A L A N D H O R I Z O N T A L PRESSURES AT F A I L U R E'
2
U N D R A I N E D T R l A X l A L S T R E N G T H U N D E R F l L L S T R E N G T H U N D E R I N - S I T U 0 S T R E N G T H , BEFORE A N D AFTER P L A C E M E N T O F F I L LF i g u r e 10 S t r e n g t h Envelope f o r S o i l Layer Between Depths 2 . 3 m and 5 . 3 m ( G l o u c e s t e r )
0 PRIOR T O C O N S T R U C T I O N 1 . 5
-
AFTER 1 6 YEARS O F P L A C E M E N T-
O F F l L L ul' , = EFFECTIVE V E R T I C A L A N D H O R I Z O N T A L PRESSURE AT F A I L U R E 1 . 0-
-
0 . 3-
u N D R A l N E D T R I A X I A I S T R E N G T H - U N D E R I N - S I T U PRESSURE c0 F I E L D V A N E SHEAR STRENGTH, BEFORE A N D AFTER P L A C E M E N T 0 I I I I I I 0 . 5 1 .O F I L L,
,
,
1 . 5 2 . 0 2.5 3 .O 3 . 5 4 .OF i g u r e 11 S t r e n g t h Envelope f o r S o i l Layer Between Depths 7.0 m and 1 1 . 3 m (Kars)
a r e shown o f CIU t e s t s on t h e p r e - and p o s t - c o n s t r u c t i o n s o i l s a t v a r i o u s d e p t h s , b o t h c o n s o l i - d a t e d t o t h e same p r e s s u r e c l o s e t o t h e e f f e c t i v e F i g u r e 12 Comparison o f S h e a r S t r e n g t h s o f P r e - and Pos t - c o n s t r u c t i o n S o i l s (Kars) overburden l o a d . A d i s t i n c t s t r e n g t h i n c r e a s e may a g a i n b e o b s e r v e d . DISCUSSION To r e s o l v e t h e q u e s t i o n o f w h e t h e r t h e r e i s any s t r e n g t h i n c r e a s e b e n e a t h f i l l s , two more o b s e r v a - t i o n s may b e n o t e d . (1) There i s a marked r e d u c t i o n i n m o i s t u r e c o n t e n t i n t h e s u b s o i l b e n e a t h t h e f i l l s . T h i s r e d u c t i o n i s compatible w i t h t h e observed compression ( T a b l e I ) , i n d i c a t i n g t h a t l a t e r a l
TABLE I COMPARISON OF OBSERVED
AND DEDUCED COMPRESSIONS
Compression deduced from Observed change o f Depth Compression w a t e r c o n t e n t S i t e m p e r c e n t p e r c e n t G l o u c e s t e r 2.4 t o 5 . 0 5.20 4.64 Kars 7 . 6 t o 1 0 . 7 8.14 7.72
y i e l d i n g had l i t t l e influence on conpression. The s u b s o i l s b e n e a t h t h e f i l l s had reached, t h e r e f o r e , a d e n s e r s t a t e . (2) Based on measurement o f l a t e r a l p r e s s u r e beneath t h e G l o u c e s t e r t e s t embankment
(Bozozuk, 1974), t h e deduced maximum s h e a r s t r e s s exceeded t h e vane s t r e n g t h down t o a depth o f 5 . 3 m.
A t 3 m f o r i n s t a n c e , s h e a r s t r e s s i s 50 p e r c e n t i n e x c e s s o f vane s t r e n g t h . These o b s e r v a t i o n s t e n d t o throw a d d i t i o n a l s u p p o r t t o t h e b e l i e f t h a t t h e r e i s a c t u a l l y a s t r e n g t h i n c r e a s e .
Reasons why t h e f i e l d vane f a i l e d t o measure any s t r e n g t h g a i n i n c l u d e :
(1) E s s e n t i a l l y , t h e f i e l d vane measures s h e a r r e s i s t a n c e a l o n g a v e r t i c a l p l a n e , which corresponds
t o t h e s t r e n g t h o f a h o r i z o n t a l specimen (Lo and M i l l i g a n , 1 9 6 7 ) . As t h e s o i l d i s p l a y s s t r e n g t h a n i s o t r o p y ( M i t c h e l l , 1970). t h e r e may n o t be an i n c r e a s e of s t r e n g t h a l o n g t h e v e r t i c a l p l a n e w i t h i n t h e v e r t i c a l p r e s s u r e i n t e n s i t y e n c o u n t e r e d i n t h e s e c a s e s . ( 2 ) By r e c o g n i z i n g t h a t vane s t r e n g t h c o r r e s p o n d s t o t h a t a l o n g a v e r t i c a l p l a n e , one can argue t h a t t h e s t r e n g t h change depends l a r g e l y on t h e change i n e f f e c t i v e h o r i z o n t a l p r e s s u r e , A u ~ . Bozozuk (1974)
showed by means of h y d r a u l i c f r a c t u r e t e s t s t h a t Au{
i s a p p r o x i m a t e l y e q u a l t o zero beneath the G l o u c e s t e r t e s t embankment. Numerical a n a l y s e s r e v e a l t h a t under t h e o t h e r f i l l s t h e f i n a l e f f e c t i v e h o r i z o n t a l
p r e s s u r e i s l e s s t h a n 60 p e r c e n t o f t h e v e r t i c a l p r e c o n s o l i d a t i o n p r e s s u r e . Hence, i n a l l t h e s e c a s e s
Au,', i s r a t h e r s m a l l . This may l a r g e l y e x p l a i n t h e anomaly between t r i a x i a l and vane s t r e n g t h s .
(3) P r e l i m i n a r y n u m e r i c a l a n a l y s e s c a r r i e d o u t f o r t h i s s t u d y show t h a t i n t r u s i o n o f t h e vane b l a d e i n t o t h i s p a r t i c u l a r s o i l i n d u c e s a s h e a r s t r a i n t h a t c a n exceed t h e s t r a i n a t f a i l u r e a l o n g t h e p r o s p e c t i v e c y l i n d r i c a l f a i l u r e s u r f a c e . Thus t h e vane would measure a s t r e n g t h i n t e r m e d i a t e between t h e peak and t h e r e s i d u a l . How t h i s i n t e r m e d i a t e s t r e n g t h v a r i e s w i t h c o n f i n i n g p r e s s u r e i s n o t c l e a r , b u t i t would c o n t r i b u t e t o t h e o b s e r v e d d i s c r e p a n c y .
CONCLUSIONS
F i e l d and l a b o r a t o r y measurements o f s h e a r s t r e n g t h under f o u r f i l l s c o n s t r u c t e d on Champlain Sea c l a y s l e a d t o t h e f o l l o w i n g c o n c l u s i o n s :
(1) F i e l d vane s t r e n g t h does n o t change with ( a ) time up t o 16 y e a r s a f t e r placement o f f i l l ; (b) l o a d i n g geometry c o r r e s p o n d i n g t o e i t h e r p l a n e s t r a i n o r axisymmetric c o n d i t i o n s ; ( c ) l o a d i n t e n s i t y t o v a l u e s moderately beyond t h 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 ; (d) r o t a t i o n o f p r i n c i p a l s t r e s s e s e x i s t i n g beneath t h e s h o u l d e r o f f i l l . (2) T r i a x i a l t e s t s show t h a t t h e r e h a s been s t r e n g t h i n c r e a s e b e n e a t h t h e f i l l s . (3) Fie1 d e v i d e n c e and p r e l i m i n a r y a n a l y s e s s u p p o r t t h e view t h a t t h e r e i s s t r e n g t h g a i n under s u s t a i n e d l o a d i n g . ACKNOWLEDGEMENTS The a u t h o r s g r a t e f u l l y acknowledge t h e c o n s c i e n t i o u s e f f o r t s o f A . Laberge and T . J . Hoogeveen, Technical O f f i c e r s , D i v i s i o n o f B u i l d i n g Research, f o r c a r r y i n g o u t t h e f i e l d vane s h e a r t e s t s .
T h i s p a p e r i s a c o n t r i b u t i o n from t h e D i v i s i o n o f B u i l d i n g Research, N a t i o n a l Research Council o f Canada, and i s p u b l i s h e d w i t h t h e a p p r o v a l o f t h e D i r e c t o r o f t h e D i v i s i o n .
REFERENCES
Bjerrum, L . (1954), Geotechnical P r o p e r t i e s o f Norwegian Marine C l a y s , GBotechnique, Vol
.
4. N O . 2, pp. 49-69.Bozozuk, M. (1974), Minor P r i n c i p a l S t r e s s
Measurements i n Marine Clay w i t h H y d r a u l i c F r a c t u r e T e s t s , P r o c . o f Eng. Found. Conf. on S u r s u r f a c e E x p l o r a t i o n f o r Underground E x c a v a t i o n and Heavy C o n s t r u c t i o n , Henniker, N . H . , p p . 333- 349.
Bozozuk, M. and G.A. Leonards (1972), The G l o u c e s t e r T e s t F i l l , P r o c . ASCE S p e c i a l t y Conf. on
Performance o f 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 , Purdue Univ., Vol. 1 , P a r t 1 , pp. 299-317.
Crawford, C.B. ( 1 9 6 l ) , E n g i n e e r i n g S t u d i e s o f Leda Clay, S o i l s i n Canada, Royal S o c i e t y Canada, S p e c i a l P u b l i c a t i o n s No. 3 , 1961, pp. 200-217. Crawford, C . B . and K . N . Burn (1976), Long-term
S e t t l e m e n t s on S e n s i t i v e Clay, B jerrum Memorial Volume, Norwegian Geotech. I n s t . , O s l o .
pp. 117-124.
Eden, W . J . and P.M. J a r r e t t (1971), L a n d s l i d e s a t O r l e a n s , O n t a r i o , N a t i o n a l Research Council o f Canada, D i v i s i o n o f B u i l d i n g Research, NRCC 11856. Eden, W . J . and H . B . Poorooshasb (1968), S e t t l e m e n t
O b s e r v a t i o n s a t Kars B r i d g e , Can. Geotech. J . ,
Vol. 5 , p p . 28-45.
Law, K.T. (1974), A n a l y s i s o f Embankment on S e n s i t i v e C l a y s , T h e s i s , U n i v e r s i t y o f Western O n t a r i o . London, O n t a r i o .
O s t e r b e r g , J . O . (1952), New P i s t o n Tube Sampler, E n g i n e e r i n g News- Record, Vol
.
148, pp. 77-78. Lo. K . Y . and V. M i l l i g a n (1967), S h e a r S t r e n g t hP r o p e r t i e s o f Two S t r a t i f i e d C l a y s , ASCE, J . S o i l Mech. Found. Div., Vol. 9 2 , SM1, pp. 1-15. M i t c h e l l , R . J . ( 1 9 7 0 ) , On t h e Y i e l d i n g and
Mechanical S t r e n g t h o f Leda Clay. Can. Geotech. J . , Vol. 7, pp. 297-312.
This publication is being distributed by the Division of
Building R e s e a r c h of the National R e s e a r c h Council
of
Canada. I t should not be reproduced in whole o r in p a r t without permission of the original publisher. The Di- vision would be glad to b e of a s s i s t a n c e in obtaining such permission.
Publications of the Division may be obtained by rnail- iag the appropriate remittance (a Bank. Express, o r P o s t Office Money Order, o r a cheque, made payable
to the Receiver General of Canada, c r e d i t NRC) to
the
National R e s e a r c h Council
of
Canada, Ottawa. KIA OR6. +Stamps a r e not acceptable.
A l i s t of allpublications of the Division ie available and may be obtained f r o m the Publications Section, Division of Building Research, National R e s e a r c h Council of
