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Undrained cyclic behaviour of Beaufort Sea silt
- -
8ar
1 3
3
2-S;s'
TH1
N21d
3 .
1281
National Research Conseil national
c . 2
I
+
Council Canada
de recherches Canada
BLDG
UNDRAINED CYCLIC BEHAVIOUR OF
BEAUFORT SEA SILT
A N A L Y Z E D
by
J.-M. Konrad
Reprinted from
Proceedings of the Conference Arctic '85
ASCE, San Francisco, CA, March 25
-
27, 1985
DBR Paper No. 1281
Division of Building Research
Le comportement du limon de la mer de Beaufort soumi.s
B
un chargement cyclique a St6 observ6 dans des conditions triaxiales, avec et sans contrainte de cisaillement statique, pour definir la resistanceB
la liquefaction ouB
la deformation cyclique dans diverses conditions de sollicitation cyclique. Le chargement cyclique asymetrique a conduitB
la rupture par compression, dans laquelle le mode de rupture dependait du degr6 d'asymetrie de la contrainte de cisaillement-- L e - c h a r m cvclimue symctrique a men6B
uneruptu' -Csrmations
cycl' cliques
norn ete de
Reprinted from Proceedings of the Conference Arctic '851
ASCEISan Francisco, CAIMarch 25-27,1985
UNDRAINED CYCLIC BEHAVIOUR OF BEAUFORT SEA SILT
J.-M. Konrad*
A b s t r a c t
C y c l i c l o a d i n g behaviour of Beaufort Sea s i l t h a s been s t u d i e d
under t r i a x i a l c o n d i t i o n s , w i t h and w i t h o u t s t a t i c s h e a r s t r e s s , t o d e f i n e t h e r e s i s t a n c e t o l i q u e f a c t i o n o r c y c l i c s t r a i n i n g under
v a r i o u s c y c l i c s t r e s s c o n d i t i o n s . &symmetrical c y c l i c l o a d i n g l e d t o
compressive f a i l u r e , i n which t h e mode of f a i l u r e was dependent on t h e
amount of s h e a r s t r e s s r e v e r s a l . Symmetrical c y c l i c l o a d i n g l e d t o a n
e x t e n s i o n f a i l u r e c h a r a c t e r i z e d by l a r g e c y c l i c s t r a i n s . The
normalized c y c l i c d e v i a t o r s t r e s s a t f a i l u r e f o r t e s t s w i t h KC = 2 was
125% h i g h e r than t h a t f o r t e s t s w i t h KC = 1. I n t r o d u c t i o n
E x p l o r a t i o n and development of n a t u r a l r e s o u r c e s have r e s u l t e d i n t h e c o n s t r u c t i o n of man-made s t r u c t u r e s s u c h a s a r t i f i c i a l d r i l l i n g
i s l a n d s i n t h e Canadian Beaufort Sea. Four s e i s m i c a l l y a c t i v e a r e a s
surround t h e c u r r e n t and f u t u r e e x p l o r a t i o n s i t e s . It h a s t h e r e f o r e
been t h e o b j e c t i v e of r e c e n t e x p e r i m e n t a l i n v e s t i g a t i o n t o q u a n t i f y t h e undrained r e s p o n s e of s e a f l o o r s o i l s t o v a r i o u s combinations o f
s t a t i c and c y c l i c l o a d s . A wide range of l o a d i n g c o n d i t i o n s was
c o n s i d e r e d d e s i r a b l e because o f f s h o r e s t r u c t u r e s may c o n s o l i d a t e t h e foundation sediments t o v a r i o u s d e g r e e s under an a n i s o t r o p i c s t r e s s s t a t e p r i o r t o dynamic loading.
This paper d e a l s o n l y w i t h t h e c y c l i c s t r e n g t h of s e a f l o o r samples o b t a i n e d i n t h e s p r i n g of 1984 i n t h e s o u t h e r n B e a u f o r t Sea between P u l l e n and Hooper I s l a n d s , n e a r Richards I s l a n d and
Tuktoyaktuk, N.W.T. (1). It d i s c u s s e s t h e e f f e c t of c y c l i c l o a d i n g ,
w i t h and without s t a t i c s t r e s s , on t h e mode of f a i l u r e i n t r i a x i a l t e s t s .
T e s t Program and Procedures
Twenty-two b o r e h o l e s were d r i l l e d along t h r e e l i n e s n o r t h e a s t of Hooper I s l a n d and w e s t of P u l l e n I s l a n d (1); s i x s e a l e d Shelby t u b e
samples were s e n t t o Ottawa f o r t e s t i n g . S t a t i c and c y c l i c t r i a x i a l
t e s t s were c a r r i e d o u t on samples from f o u r b o r e h o l e s , two c l o s e t o t h e Richards I s l a n d s h o r e l i n e and two approximately 10 km awaf.
Relevant i n f o r m a t i o n f o r e a c h b o r e h o l e i s g i v e n i n T a b l e 1.
-".
A t t e r b e r g l i m i t s i n d i c a t e t h a t t h e Beaufort Sea s o i l of t h i s
s t u d y i s a n o n - p l a s t i c s i l t w i t h about 30% c l a y s i z e p a r t i c l e s . The
- - - -
*Research O f f i c e r , G e o t r 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 Research, N a t i o n a l Research Council of Canada, Ottawa, KIA OR6
BEAUFORT
SEASILT BEHAVIOR
TABLE 1. Borehole I d e n t i f i c a t i o n Depth b e l o v Water G r a i n S i z e
Borehole Sea F l o o r Depth Water Content
Number m ( f t ) m ( f t ) X S i l t X Clay % Dry Weight
specimens were e x t r u d e d from t h e Shelby t u b e s and trimmed t o 3.6-mm
(1.5-in. ) d i a m e t e r and 80-mm (3.15-in.) h e i g h t . I h d r a i n e d s t r e n g t h s were o b t a i n e d under compression and e x t e n s i o n a t a s t r a i n r a t e of
2% p e r hour. A back p r e s s u r e of 200 kPa ( 3 0 p s i ) was s u f f i c i e n t t o e n s u r e f u l l s a t u r a t i m (B v a l u e of 1.0).
C y c l i c l o a d s , b o t h compression and e x t e n s i o n , were a p p l i e d t o t h e samples w i t h a B e l l o f r a m p i s t o n a c t u a t e d by an a i r p r e s s u r e r e g u l a t o r t h a t was, i n t u r n , powered by an e l e c t r i c - t o - p n e u m a t i c t r a n s d u c e r . A programmable f u n c t i o n g e n e r a t o r p r o v i d e d d i f f e r e n t s h a p e s ,
f r e q u e n c i e s , and amplitudes. For t h e t e s t s r e p o r t e d h e r e a s i n e f u n c t i o n of 1 Hz was used.
C y c l i c t e s t s were performed on samples c o n s o l i d a t e d i s o t r o p i c a l l y t o t h e i n s i t u e f f e c t i v e v e r t i c a l s t r e s s . h i s o t r o p i c a l l y
c o n s o l i d a t e d samples w i t h e f f e c t i v e s t r e s s r a t i o , K C = C J ~ / O $ , of 1.5
and 2.0 were t e s t e d under c y c l i c l o a d i n g . The minor p r i n c i p a l s t r e s s , o j , was i n a l l c a s e s e q u a l t o t h e i n s i t u v e r t i c a l s t r e s s .
S t a t i c T e s t s
S e v e r a l r e f e r e n c e v a l u e s of s t a t i c s t r e n g t h were o b t a i n e d b y p e r f o r m i n g f o u r u n d r a i n e d compression (CIUC) and two u n d r a i n e d
e x t e n s i o n t e s t s (CIUE) on i s o t r o p i c a l l y c o n s o l i d a t e d samples, p l u s one c o n p r e s s i o n t e s t on an a n i s o t r o p i c a l l y c o n s o l i d a t e d specimen (CAUC). A t low c o n f i n i n g p r e s s u r e t h e CIUC t e s t samples developed a
well-defined s h e a r p l a n e a t f a i l u r e , whereas a t h i g h e r c o n f i n i n g p r e s s u r e s t h e y bulged a t f a i l u r e . The s t r e s s p a t h was S-shaped i n conpression. The e f f e c t i v e s t r e s s p a t h f o r t r i a x i a l e x t e n s i o n was q u i t e d i f f e r e n t from t h a t f o r compression and t h e s h e a r s t r e n g t h , Su, i n e x t e n s i o n was o n l y about 60% of t h e compressive s t r e n g t h f o r t h e same c o n s o l i d a t i o n p r e s s u r e . The e f f e c t i v e s t r e n g t h p a r a m e t e r s , c ' and $', however, were approximately t h e same ( F i g u r e 1).
I s o t r o p i c C y c l i c T e s t s
T y p i c a l r e s u l t s f o r c y c l i c l o a d i n g b e h a v i o u r w i t h symmetrical s t r e s s r e v e r s a l o f i s o t r o p i c a l l y c o n s o l i d a t e d B e a u f o r t Sea s i l t a r e shown i n F i g u r e 2. These t e s t s w i l l b e r e f e r r e d t o a s ICR t e s t s . For a l l samples t h e r e s i d u a l p o r e w a t e r p r e s s u r e , A+, i n c r e a s e d
p r o g r e s s i v e l y w i t h c y c l e s of loading. The s t r a i n was n e v e r
ARCTIC
OFFSHORE
ENGINEERING2 0 0
1
I I 1 I 1I
Figure 1. Strength envelope from s t a t i c t r i a x i a l t e s t s
OMPRESS ION
4
---,=LY:-.-.-.
[F-*w
CYCLICI 1
EXTENSION STRAINd
RES lOUAlz,
-
0.21 STRAIN - 1 0I
I I I II
0 20 40 6 0 8 0 100 NUMBER OF C Y C L E SFigure 2. Typical i s o t r o p i c c y c l i c t e s t r e s u l t s f o r Beaufort Sea s i l t
exceeded the compression s t r a i n . Modulus anisotropy, with t h e compressional modulus larger than the extension modulus, could cause t h i s behaviour.
BEAUFORT SEA SIVT BEHAVIOR 833
It was observed t h a t l a r g e c y c l i c s t r a i n s , i n e x c e s s of
lo%,
occur b e f o r e t h e pore p r e s s u r e r a t i o , Aula', becomes 1. The b e h a v i o u r
of t h e s i l t samples is t h e r e f o r e q u i t e d i f 2 e r e n t from t h a t of l o o s e s a t u r a t e d sand, i n which s t r a i n s d e v e l o p o n l y a f t e r t h e p o r e p r e s s u r e r a t i o r e a c h e s a v a l u e r e l a t i v e l y c l o s e t o 1 and a c c e l e r a t e when Aula' i s almost 1. F a i l u r e i s t h e r e f o r e d e f i n e d w i t h r e s p e c t t o s t r a i n a n j c o r r e s p o n d s t o e i t h e r 10% c y c l i c s t r a i n o r 10% r e s i d u a l s t r a i n , whichever o c c u r s f i r s t . ICR t e s t s a r e c h a r a c t e r i z e d by peak-to-peak a x i a l s t r a i n o r c y c l i c s t r a i n , c c , i n c r e a s i n g p r o g r e s s i v e l y w i t h e a c h s u c c e s s i v e s t r e s s c y c l e and by a r e l a t i v e l y s m a l l e x t e n s i o n r e s i d u a l s t r a i n , E ~ .
F a i l u r e o b t a i n e d w i t h ICR t e s t s was always under an e x t e n s i o n s t a t e . A n i s o t r o p i c C y c l i c T e s t s
S o i l behaviour i n a n i s o t r o p i c , c y c l i c t r i a x i a l t e s t s i s g e n e r a l l y q u i t e d i f f e r e n t from t h a t i n i s o t r o p i c c y c l i c t e s t s . When t h e s h e a r s t r e s s e s c y c l e symmetrically about t h e imposed s t a t i c s t r e s s , ads/2, two t y p e s of behaviour may r e s u l t , depending on t h e v a l u e of t h e
c y c l i c s h e a r s t r e s s , adc/2. When odC i s l a r g e r t h a n ads, p a r t i a l
s t r e s s r e v e r s a l o c c u r s and t h e t e s t i s r e f e r r e d t o a s a n ACR t e s t .
When a is l e s s than ads, n o s t r e s s r e v e r s a l o c c u r s and t h e t e s t i s
referred$ t o an ACC t e s t . T y p i c a l ACC t e s t r e s u l t s a r e p r e s e n t e d i n F i g u r e 3 ( a ) . Axial c o n p r e s s i o n s t r a i n c o n t i n u e s t o d e v e l o p a t an approximately c o n s t a n t r a t e , w h i l e r e s i d u a l pore p r e s s u r e s i n c r e a s e d u r i n g t h e f i r s t c y c l e s b e f o r e becoming c o n s t a n t . F u r t h e r , c y c l i c s t r a i n s a r e s m a l l and r e s i d u a l s t r a i n s a r e l a r g e and i n compression. T h i s b e h a v i o u r i s t h e o p p o s i t e of t h a t i n ICR t e s t s and h a s a l s o been o b s e r v e d f o r
sands ( 3 ) .
T y p i c a l ACR t e s t r e s u l t s a r e shown i n F i g u r e 3(b). Both c y c l i c
and r e s i d u a l s t r a i n s i n c r e a s e w i t h i n c r e a s i n g l o a d i n g c y c l e s . cp was
always a compression s t r a i n , even f o r t h e f i r s t c y c l e s . Aur i n c r e a s e d
p r o g r e s s i v e l y a f t e r e a c h c y c l e , b u t i t n e v e r r e a c h e d i t s t e r m i n a l value. For a g i v e n KC t h e r e i s a t h e o r e t i c a l t e r m i n a l v a l u e of A % / + r e l a t e d t o t h e f a i l u r e e n v e l o p e ( 4 ) ; f o r t h e B e a u f o r t Sea s i l t i t i s 0.60 f o r KC = 2 and 0.85 f o r KC = 1.5. R e s i s t a n c e t o C y c l i c S t r a i n i n g R e s i s t a n c e t o c y c l i c s t r a i n i n g i s e x p r e s s e d by t h e c y c l i c s t r e s s r a t i o , o d c / 2 0 j , r e q u i r e d t o develop a s p e c i f i c amount of a x i a l s t r a i n i n a g i v e n number of c y c l e s . The c y c l i c l o a d i n g r e s i s t a n c e a t
f a i l u r e , i.e., E~ o r E =-lo%, of b o t h i s o t r o p i c a l l y and
a n i s o t r o p i c a l l y c o n s o l j d a t e d samples i s shown i n F i g u r e 4. Although
samples were o b t a i n e d from s i t e s about 10 km a p a r t and from d i f f e r e n t d e p t h s , t h e c y c l i c r e s p o n s e from I C R t e s t s i s a b o u t t h e same.
For Beaufort Sea s i l t t h e c y c l i c s t r e s s r a t i o r e q u i r e d t o d e v e l o p 10% s t r a i n f o r specimens w i t h i n i t i a l s t a t i c s h e a r s t r e s s i s h i g h e r than t h a t f o r i s o t r o p i c c y c l i c t e s t s , depending on t h e v a l u e of ads.
834
ARCTIC OFFSHORE
ENGINEERINGFigure 3. Typical anisotropic c y c l i c t e s t r e s u l t s , Beaufort Sea s i l t 1 . 0 r r 1 1 1 1 1 1 I 1 1 1 1 1 1 1 1 I 1 1 , r , n s 1 0
-
BOREHOLE Kc u ' ~ (kPa)-
C a 0 . 8 - LL 0 1 0 + m 1.0 130-
V) 4 4 + 0 0 1.0 81 "l o 7 + 6 0 1.5 150-
E-bm
0.6-
A 4 2 + W 2.0 86-
z -
\ LL U z b v 0.4 "l 0-
2 0.2 U > U\A-
\.*
n ; 0 1' " " " ' ~
' " " " ' 1 ' " ' ~ " ~ 11
0 10 100 1000 2000 N U M B E R O F C Y C L E S TO F A I L U R EBEAUFORT SEA SILT BEHAVIOR 835
The c y c l i c s t r e s s r a t i o s r e q u i r e d f o r f a i l u r e i n 100 c y c l e s a r e 0.2, 0.32 and 0.45 f o r KC of 1 , 1.5 and 2.0, r e s p e c t i v e l y . For comparison w i t h e x i s t i n g d a t a on uniform sand ( 2 ) , i n i t i a l l i q u e f a c t i o n i n t e n s t r e s s c y c l e s was o b t a i n e d f o r a d 1205 of 0.25 t o 0.30 f o r r e l a t i v e d e n s i t i e s between 50 and 70%. ~ h f s i n d i c a t e s t h a t t h e Beaufort Sea
s i l t t e s t e d under t r i a x i a l c o n d i t i o n s e x h i b i t s h i g h e r r e s i s t a n c e t o c y c l i c l o a d i n g than loose-to-medium dense sand.
Undrained C y c l i c Behaviour i n T r i a x i a l T e s t s
Undrained c y c l i c b e h a v i o u r in t r l a x i a l t e s t a i s d i s c u s s e d w i t h t e a p e c t t o i n i t i a l s t a t i c s h e a r stress, the amount of s t r e s s reversal,
and mode of f a i l u r e . F i g u r e 5 shows t h e v a r i o u s s t r e s s c o n d i t i o n 8 i n
e a c h of t h e a b o v e m e n t i o n e d t y p e s o f t e s t by means o f a s t r e s s p a t h i n
a p-q diagram. The e f f e c t i v e s t r e s a p a t h d u r i n g t h e f i r s t few c y c l e s was more o r l e s s p a r a l l e l t o t h e t o t a l s t r e s s p a t h f o r a l l t e s t s .
For c ' = 0 , t h e d e v i a t o r s t r e s s a t f a i l u r e is a f u n c t i o n of 0:
and $'. The maximum compressive s t r e n g t h , odfc, and e x t e n s i v e s t r e n g t h , odfe, a r e given a s
2 s i n
'
2 s i n'
"dfc,
-
sin"l"5
*
"dfe = 1 + sin'$l"5
For s i m p l i c i t y , it is c o n s i d e r e d t h a t t h e combined t o t a l of t h e s t a t i c and c y c l i c components of d e v i a t o r s t r e s s c a n n o t exceed t h e f a i l u r e s t r e n g t h o b t a i n e d from s t a t i c t e s t s . In r e a l i t y , however, t h e combined d e v i a t o r s t r e s s e s may b e l a r g e r t h a n e i t h e r odfc o r odfe. owing t o s t r a i n r a t e e f f e c t s i n c y c l i c t e s t s t h a t r e s u l t from t h e s h o r t d u r a t i o n of l o a d a p p l i c a t i o n d u r i n g e a c h cycle. N e v e r t h e l e s s , under t h e s e c o n d i t i o n s f a i l u r e i s imminent and t h e f a i l u r e envelope from s t a t i c t e s t s may s t i l l p r o v i d e a n a d e q u a t e r e f e r e n c e s t r e n g t h . A COMPRESS ION C 0 EXTENS ION F i g u r e 5. T r i a x i a l c y c l i c t e s t s i n p-q diagram
836
ARCTIC O W S H O h ENGINEERING
T h e o r e t i c a l l y , t h e maxinum c y c l i c s h e a r s t r e s s r a t i o t h a t can b e a p p l i e d t o a specimen i s a l s o a f u n c t i o n of
05
and0'.
Its v a l u e and t h e c o r r e s p o n d i n g KC a r e given below f o r e a c h t y p e of t e s t :'Jdc,
s i n $ ' KC = 1 f o r ICR t e s t s 203 1+
s i n $''
Ode
-
s i n 6 '--
sin 4 '+
1 f o r ACC t e s t s 20; 2-
s i n = 1-
s i n4'
O&
-
s i n $ ',
KCA = 2 t a n 2 g'+
1 f o r ACR t e s t s205 cos2 $ '
F i g u r e 6 p r e s e n t s t h e v a r i o u s t e s t c o n d i t i o n s and t h e u p p e r t h e o r e t i c a l l i m i t of c y c l i c t r i a x i a l l o a d i n g f o r t h e B e a u f o r t Sea s i l t i n terms of c y c l i c s t r e s s r a t i o and i n i t i a l s t r e s s r a t i o . It shows t h e b n u n d a r i e s of e a c h t y p e of t r i a x i a l t e s t , where ICR t e s t s a r e d e f i n e d by t h e segment IJ, ACR t e s t s by t h e a r e a IJKL, and ACC t e s t s by t h e a r e a ILM. The domain IJKL, which i s c h a r a c t e r i z e d by s h e a r s t r e s s r e v e r s a l , h a s been s u b d i v i d e d by l i n e s of e q u a l d e g r e e of s h e a r s t r e s s r e v e r s a l , d e f i n e d a s ad,-ods/ods.
The v a r i o u s s t a t i c and c y c l i c s t r e s s c o n d i t i o n s used i n t h i s s t u d y a r e a l s o p l o t t e d on F i g u r e 6, i n d i c a t i n g t h e o b s e r v e d mode o f f a i l u r e . The s o l i d c i r c l e s d e n o t e t e s t s i n which f a i l u r e o c c u r r e d by r e s i d u a l s t r a i n and t h e open c i r c l e s c o r r e s p o n d t o l a r g e c y c l i c s t r a i n s . It a p p e a r s t h a t t h e t r a n s i t i o n is n o t d e f i n e d by t h e
1.2 I I I I
-
m LARGE RESIDUAL STRAINb
0 LARGE CYCLIC STRAIF;
%
l a O1
DEGREE OFbv STRESS
INITIAL STRESS RATIO. Kc
F i g u r e 6. S t r e s s c o n d i t i o n s and mode of f a i l u r e i n c y c l i c t r i a x i a l t e s t s on B e a u f o r t Sea s i l t
BEAUFORT SEA SILT BEHAVIOR 837
c o n d i t i o n o f s h e a r stress r e v e r s a l , b u t t h a t ACR tests w i t h a b o u t 25% s t r e s s r e v e r s a l s t i l l produce f a i l u r e a t l a r g e E
P'
F i g u r e 6 a l s o i n d i c a t e s t h a t t h e s i l t under s t u d y w i l l e x h i b i t
i t s maximm c y c l i c r e s i s t a n c e f o r
KC
= 2.05. For K>
2.05 t h e maxinumc y c l i c s t r e s s t h a t can b e a p p l i e d t o t h e s o i l d e c r e a s e s w i t h i n c r e a s i n g
KC
s i n c e t h e s t a t i c s h e a r i s p r o g r e s s i v e l y c l o s e r t o t h e f a i l u r e s t r e n g t h .Summary and C o n c l u s i o n s
The undrained c y c l i c b e h a v i o u r of u n d i s t u r b e d s i l t samples from t h e B e a u f o r t S e a , s t u d i e d u n d e r t r i a x i a l c o n d i t i o n s , i n d i c a t e s t h e f o l l o w i n g :
1 ) An e x t e n s i o n f a i l u r e mode p r e v a i l s i n t h e i s o t r o p i c a l l y
c o n s o l i d a t e d , s y m m e t r i c a l c y c l i c (ICR) t e s t , w h i l e compression mode f a i l u r e predominates i n t h e a n i s o t r o p i c , unsymmetrical c y c l i c (ACR and ACC) t e s t s .
2 ) How much s h e a r s t r e s s r e v e r s a l t h e r e i s s t r o n g l y i n f l u e n c e s t h e
modes of f a i l u r e . When t h e r e is l i t t l e o r none, f a i l u r e i s
c h a r a c t e r i z e d by l a r g e r e s i d u a l s t r a i n s , whereas f o r s i g n i f i c a n t r e v e r s a l l a r g e c y c l i c s t r a i n s develop.
3 ) T h e r e i s a n i n c r e a s e i n t h e n o r m a l i z e d c y c l i c r e s i s t a n c e w i t h
i n c r e a s i n g v a l u e s of t h e i n i t i a l stress r a t i o . K
.
The proposeds i m p l e c b n c e p t u a l model s u g g e s t s t h a t f o r t h e s i f t of t h i s s t u d y t h e maximm n o r m a l i z e d c y c l i c s h e a r s t r e s s r a t i o o c c u r s f o r
KC = 2.05.
Acknowledgements
The samples were provided by t h e G e o l o g i c a l Survey of Canada t h r o u g h t h e k i n d n e s s of P. K u r f u r s t a n d K. Moran who were e s p e c i a l l y
i n v o l v e d i n t h e f i e l d program. The a u t h o r is g r a t e f u l t o K.T. Law f o r
f r u i t f u l d i s c u s s i o n 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 f r o m t h e D i v i s i o n of B u i l d i n g Research, N a t i o n a l Research Council of 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 .
1. K u r f u r s t , P., " G e o t e c h n i c a l I n v e s t i g a t i o n s i n t h e Southern B e a u f o r t Sea," G e o l o g i c a l Survey o f Canada, Open F i l e Report 1078, June 1984.
2. Seed, H.B., " E v a l u a t i o n o f S o i l L i q u e f a c t i o n E f f e c t s on L e v e l Ground During Earthquakes." ASCE, N a t i o n a l Convention, P h i l a d e l p h i a , 1976. pp. 1-104.
3. S e l i g , E.T., and C.S. Chang, " S o i l F a i l u r e Modes i n l h d r a i n e d
C y c l i c Loading," ASCE, J o u r n a l o f t h e G e o t e c h n i c a l E n g i n e e r i n g D i v i s i o n , Vol. 107, No. GT5, May 1981, pp. 539-551.
4. Vaid, Y.P., a n d J.C. Chern, " E f f e c t o f S t a t i c S h e a r on R e s i s t a n c e
t o L i q u e f a c t i o n , " S o i l s and Foundations, Vol. 23, No. 1, March 1983, pp. 47-60.
T h i s p a p e r , w h i l e b e i n g d i s t r i b u t e d i n r e p r i n t f o r m by t h e 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 , r e m a i n s t h e c o p y r i g h t of t h e o r i g i n a l p u b l i s h e r . It s h o u l d n o t be r e p r o d u c e d i n whole o r i n p a r t w i t h o u t t h e p e r m i s s i o n of t h e p u b l i s h e r . A l i s t of a l l p u b l i c a t i o n s a v a i l a b l e f r o m t h e D i v i s i o n may be o b t a i n e d by w r i t i n g t o 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 o f 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 o f C a n a d a . O t t a w a , O n t a r i o , K1A 0R6.
