DEPARTMENT OF THE INTERIOR - Alaska DGGSUNITED STATES DEPARTMENT OF THE INTERIOR GEOLOG l CAL SURVEY...
123
UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOG l CAL SURVEY Geotechnical Framework Study of Shelikof Strait, Alaska b Y Monty A. Harnpton OPEN-F I LE REPORT 83 - 200 This report is preliminary and has not been reviewed for conformity with Geological Survey editorial standards and stratigraphic nomenclature. Any use of trade names is for descriptive purposes only and does not imply endorsement by the USGS.
Transcript of DEPARTMENT OF THE INTERIOR - Alaska DGGSUNITED STATES DEPARTMENT OF THE INTERIOR GEOLOG l CAL SURVEY...
UNITED STATES DEPARTMENT OF THE INTERIOR
GEOLOG l CAL SURVEY
Geotechnical Framework Study o f S h e l i k o f S t r a i t , Alaska
b Y
Monty A. Harnpton
OPEN-F I LE REPORT
83 - 200
T h i s report i s p r e l i m i n a r y and has not been reviewed for conformity w i t h
Geological Survey e d i t o r i a l standards and s t r a t i g r a p h i c nomenclature. Any use
of trade names i s f o r d e s c r i p t i v e purposes only and does not imply endorsement
by the USGS.
INTRODUCTION
S t u d i e s have been conducted by t h e U.S. G e o l o g i c a l Survey t o ' i d e n t i f y
g e o l o g i c c o n d i t i o n s t h a t might impose c o n s t r a i n t s on o f f s h o r e i n d u s t r i a l
a c t i v i t i e s i n She l ikof S t r a i t , Alaska, an a r e a d e s i g n a t e d f o r pe t ro leum
l e a s i n g ( F i g . 1; Hampton and o t h e r s , 1981; Hampton and Winters , 1981) . A s
par t of t h e s e s t u d i e s sediment c o r e s were c o l l e c t e d th roughout the s t r a i t
( F i g . 2 ) , and p h y s i c a l p r o p e r t i e s of sed iment samples were measured by
l a b o r a t o r y q e o t e c h n i c a l t e s t i n g methods. The g e o t e c h n i c a l d a t a a r e p r e s e n t e d
i n t h i s r e p o r t and a r e e v a l u a t e d from a r e g i o n a l p e r s p e c t i v e t o i n f e r t h e
d e f o r m a t i o n a l r eponse of the sed imenta ry d e p o s i t s t o s t a t i c and dynamic l o a d s .
A p p l i c a t i o n of t h e t e s t d a t a t o a r e g i o n a l a n a l y s i s is r e s t r i c t e d by the
degree t o which c o r e samples a r e r e p r e s e n t a t i v e of t h e sed imenta ry d e p o s i t s .
I n t e r p r e t i v e g e o l o g i c s t u d i e s i n d i c a t e t h a t t he c o r e s used f o r g e o l o g i c
t e s t i n g cover t h e range of s u r f i c i a l sediment t y p e s in t h e She l ikof S t r a i t
l e a s e a r e a , b u t a n a l y s i s of s e i s m i c - r e f l e c t i o n p r o f i l e s r e v e a l s t h e e x i s t e n c e
of b u r i e d s t r a t i g r a p h i c u n i t s t h a t were n o t sampled because t h e y lie beneath
t h e maximum c o r e l e n g t h of 3 m ampto ton and o t h e r s , 1981; Hampton and Winters ,
1981) . There fo re , the c o n c l u s i o n s reached i n t h i s r e p o r t app ly d i r e c t l y t o
t h e upperlnost d e p o s i t s i n t h e s t r a t i g r a p h i c section, o n l y . Extrapolat ion
beyond t h e d e p t h s of sampl ing i s l i m i t e d by the v e r t i c a l u n i f o r m i t y of
sediment type .
GEOLOGIC SETTING
She l ikof S t r a i t i s a n e a r l y p a r a l l e l - s i d e d marine channe l s i t u a t e d
between t h e Kodiak I s l a n d group and t h e Alaska Pen insu la (Fig . 1). The s t r a i t
marks the l o c a t i o n of a n o r t h e a s t - t r e n d i n g i n n e r forearc b a s i n t h a t i s l o c a t e d
n e a r the c o n v e r g e n t margin of the North America p l a t e where it is b e i n g
u n d e r t h r u s t by t h e p a c i f i c p l a t e (von Huene, 1979) . Large e a r t h q u a k e s are
common t o t h e r e g i o n ; a t least 95 p t e n t i a l l y d e s t r u c t i v e e v e n t s (magni tude
>6) have o c c u r r e d s i n c e r e c o r d i n g began i n 1902. Twelve vo lcanoes have
e r u p t e d w i t h i n t h e l a s t 10,000 y e a r s a l o n g t h e Alaska P e n i n s u l a a d j a c e n t t o
t h e s t r a i t .
The s e a f l o o r of S h e l i k o f Strait c o n s i s t s of a g e n t l y s o u t h w e s t - s l o p i n g
c e n t r a l p l a t f o r m b o r d e r e d by narrow m a r g i n a l c h a n n e l s p a r a l l e l t o t h e Kodiak
i s l a n d s and t h e Alaska P e n i n s u l a (Fig. 3 ) . Sha l low s h e l v e s t r e n d a l o n g t h e
a d j a c e n t l andmasses , and t h e y a r e connec ted t o t h e m a r g i n a l c h a n n e l s by
s t e e p l y s l o p i n g s e a f l o o r . Water d e p t h i n t h e n o r t h e a s t p a r t of t h e s t r a i t i s
g e n e r a l l y less t h a n 200 rn, whereas i n t h e s o u t h w e s t it g e n e r a l l y e x c e e d s 200 m
and i s a s much as 300 m. Superimposed on t h e p l a t f o r m a r e some l o c a l h i g h s
and lows t h a t have as much a s 100 m r e l i e f . Along t h e axes of t h e m a r g i n a l
c h a n n e l s are s e v e r a l c l o s e d d e p r e s s i o n s on t h e o r d e r of 30 m r e l i e f .
Sed imen ta ry d e p o s i t s of presumed P l e i s t o c e n e and Holocene age o v e r l i e a n
i r r e g u l a r unconf o r m i t y above T e r t i a r y and o l d e r bedrock. Th ickness of t h e
s e d i m e n t above bed rock , measured from s e i s m i c - r e f l e c t i o n p r o f i l e s , i s a b o u t 80
t o 100 m i n t h e n o r t h e a s t h a l f of t h e s t r a i t and i n c r e a s e s a b r u p t l y t o more
t h a n 800 1n i n the s o u t h w e s t ( F i g . 4 ) . The t h i c k e n i n g r e f l e c t s a deepen ing of
t h e unconf o r m i t y .
Four s e i s m i c - s t r a t i g r a p h i c u n i t s can be d i s t i n g u i s h e d above bedrock ( k i g .
5 ) . The l o w e s t u n i t ( u n i t 1 i n F ig . 5 ) f i l l s t h e bedrock d e p r e s s i o n and
r e a c h e s a t h i c k n e s s of 800 m. T h i s unit i s i n t e r p r e t e d as b e i n g of g l a c i a l
and g l a c i o m a r i n e o r i g i n (Whitney and o t h e r s , 1980 a , b ) . The n e x t h i g h e s t
u n i l ( u n i t 2 i n P ig . 5 ) i s r e l a t i v e l y thin (<60 rn) and o c c u r s main ly i n t h e
c e n t r a l p a r t of t h e s t r a i t . Sediment of t h i s u n i t was d e p o s i t e d w i t h i n low
a r e a s on the upper surface of bedrock and t h e g l a c i a l unit, and it a p p a r e n t l y
was emplaced by marine p r o c e s s e s d u r i n y t h e Holocene s e a - l e v e l rise. The
t h i r d u n i t ( u n i t 3 i n Fig . 51, which covers e s s e n t i a l l y a l l of the s e a f l o o r i n
t h e c e n t r a l par t of t h e s t r a i t ( p l a t f o r m and marg ina l c h a n n e l s ) , is up t o 180
m t h i c k ( F i g . 6 ) and was d e p o s i t e d by t h e modern-day o c e a n i c c u r r e n t regime of
s o u t h w e s t e r l y b a r o c l i n i c f low from Cook I n l e t and t h e e a s t e r n Gulf of Alaska
(Muench and Schumacher, 1980). Uni t 4 i n F i g u r e 5 u n d e r l i e s t h e s h a l l o w
s h e l v e s and i n t e r f i n g e r s seaward with u n i t 3. It is composed of sediment
e roded from t h e a d j a c e n t landmasses. The cores s u b j e c t e d t o g e o t e c h n i c a l
t e s t i n g and d i s c u s s e d i n t h i s paper were t a k e n from u n i t 3.
METHODS
Sediment c o r e s were c o l l e c t e d a t 65 s t a t i o n s on two c r u i s e s i n She l ikof
S t r a i t , i n June 1980 aboard t h e USGS R/V S.P. LEE and i n J u l y and August 1981
aboard t h e NOAA s h i p DISCOVERER ( P i g . 2 ) . A g r a v i t y c o r i n g sys tem wi th 8.5-cm
d i a m e t e r p l a s t i c l i n e r s i n s t e e l c o r e b a r r e l s was used on t h e 1980 c r u i s e ,
whereas a v i b r a c o r i n g sys tem wi th a 10-cm s q u a r e c r o s s - s e c t i o n p l a s t i c l i n e r
i n t h i n - w a l l s t a i n l e s s s t e e l b a r r e l was employed on t h e 1981 c r u i s e . Sorne
grab samples were t aken a t l o c a t i o n s of c o a r s e sediment where the c o r i n g
d e v i c e s were i n e f f e c t i v e .
Two c o r e s were t aken a t most s t a t i o n s . One was d e s i g n a t e d mainly f o r
g e o l o g i c a l a n a l y s i s . It was c u t i n t o 1-m o r 1.5-m-long s e c t i o n s , then s p l i t
l e n g t h w i s e f o r g e o l o g i c a l d e s c r i p t i o n and vane-shear s t r e n g t h t e s t i n g .
Subsamples were t a k e n f o r index p r o p e r t y d e t e r m i n a t i o n s .
The second c o r e was t aken e x p r e s s l y f o r g e o t e c h n i c a l t e s t i n g . It was c u t
i n t o 1-m-long s e c t i o n s , wrapped i n c h e e s e c l o t h , covered w i t h m i c r o c r y s t a l l i n e
wax, and s t o r e d u p r i g h t i n a r e f r i g e r a t o r . These c o r e s were l a t e r s u b j e c t e d
t o a s u i t e of g e o t e c h n i c a l tests i n l a b o r a t o r i e s a t t h e U S G S and a t a
commercial t e s t i n g company.
S e v e r a l index p r o p e r t i e s were determined f o r subsamples of t h e sediment
c o r e s . Grain size was measured by s i e v i n g and p i p e t t i n g i n t o f o u r s i z e
c l a s s e s : gravel. 0 2 m m ) , sand (2-0.062 mm), s i l t (0.062-0.004 mrn) , and c l a y
((0.004 m m ) . Water c o n t e n t , a s a pe rcen tage of d r y sediment weight , was
de te rmined from t h e weight of sediment samples b e f o r e and a f t e r even d r y i n g a t
105OC. A c o r r e c t i o n f o r s a l t c o n t e n t of s e a water (3 .5%) w a s made t o t h e
weighing 's . A t t e r b e r g l i m i t s were determined a c c o r d i n g t o s t a n d a r d procedures
(American S o c i e t y f o r T e s t i n g and M a t e r i a l s , 19761, e x c e p t t h a t samples were
n o t s i e v e d p r i o r t o t e s t i n g . Carbon c o n t e n t was measured wi th a LECO carbon
d e t e r m i n a t o r w i t h i n d u c t i o n f u r n a c e and a c i d d i g e s t i o n . Vane s h e a r
d e t e r m i n a t i o n s of undrained s h e a r s t r e n g t h were made on s p l i t c o r e h a l v e s wi th
a motorized d e v i c e a t a vane r o t a t i o n r a t e of 90°/min. The vane is 1 /2 inch
diamete r by 1 /2 i n c h high and was i n s e r t e d i n t o t h e sediment t o a dep th twice
the h e i g h t of t h e vane.
C o n s o l i d a t i o n tests were run on subsamples from g e o t e c h n i c a l c o r e s t o
de te rmine sub- fa i l u r e de format iona l p r o p e r t i e s . Most t e s t s were run on an
oedometer i n a s t r e s s - c o n t r o l l e d mode (Lambe, 1951). Others w e r e run i n a
t r i a x i a l l o a d i n g c e l l under c o n s t a n t r a t e of s t r a i n c o n d i t i o n s (Wissa and
o t h e r s , 1971). The c o n s o l i d a t i o n tests measure change i n volume with change
i n a p p l i e d load. The r e s u l t s a r e normally p l o t t e d as void r a t i o ( e = volume
of voids/volume of s o l i d s ) ve rsus the l o g a r i t h m of e f f e c t i v e (buoyan t )
v e r t i c a l s t r e s s I ) . Two u s e f u l parameters a r e d e r i v e d from t h e s e curves :
the compression i n d e x and t h e maximum p a s t p r e s s u r e . The compression i n d e x
(C,) i s t h e s l o p e of t h e s t r a i g h t - l i n e p o r t i o n of the e- log p a curve and
i n d i c a t e s the amount of compression produced by a p a r t i c u l a r load increment .
I
The maximum p a s t p r e s s u r e ( u ) i s t h e g r e a t e s t e f f e c t i v e overburden s t r e s s t o Vm
which the sediment has e v e r been exposed and i s determined from t h e e-Log p '
curve by a s imple g r a p h i c a l c o n s t r u c t i o n (Casagrande, 1936) . The r a t i o
I I
of a t o t h e e f f e c t i v e overburden stress a t t h e t ime of sampling ( u ) i s t h e Vm vo
o v e r c o n s o l i d a t i o n r a t i o (OCR), which i s a measure of unloading t h a t t h e
sediment may have exper ienced , by e r o s i o n f o r example, A t h i r d parameter , the
c o e f f i c i e n t of c o n s o l i d a t i o n ( c v ) , i s determined f o r each load increment of
t h e one-dimensional c o n s o l i d a t i o n tes t and i s r e l a t e d t o t h e r a t e of
c o n s o l i d a t i o n .
S t a t i c t r a x i a l t e s t s were run on c y l i n d r i c a l samples 3.6-cm diamete r and
7.6-cm long i n o r d e r t o determine s t r e n g t h p r o p e r t i e s of t h e sediment . T e s t s
were run under undrained c o n d i t i o n s wi th pore p r e s s u r e measurements isho hop
and Henkel, 1964) . Most samples were 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 p r i o r t o
t e s t i n g , b u t some were c o n s o l i d a t e d a n i s o t r o p i c a l l y .
Dynamically loaded t r i a x i a l t e s t s were a l s o run, wi th t h e a x i a l s t r e s s on
samples v a r i e d s i n u s o i d a l l y a t 0.1 Hz. Both con~press ion and t e n s i o n were
a p p l i e d a t a predetermined percen tage of t h e s t a t i c s t r e n g t h . These t e s t s can
be used t o e v a l u a t e t h e f a i l u r e c o n d i t i o n s of sediment under repea ted load lng ,
such as by ea r thquakes .
A f i r s t set of t r i a x i a l t e s t s was run on sediment samples t h a t were
c o n s o l i d a t e d t o somewhat a r b i t r a r y s t r e s s l e v e l s . However, the later t e s t i n g
program fo l lowed t h e normalized st.ress parameter (NSP) approach (Ladd and
Foot t , 1974), whereby consol ida t ion s t r e s s e s a r e chosen on the b a s i s of
I
maximum p a s t p r e s su re ( o ) , a s determined from conso l ida t ion tests. vm
I
Typica l ly , t h e t r i a x i a l t e s t specimen was consol ida ted t o fou r t imes u Vm '
which e l imina t e s some of t he d i s turbance e f f e c t s a s soc i a t ed with cor ing .
~ v e r c o n s o l i d a t i o n w a s a r t i f i c i a l l y induced i n some tests by rebounding t h e
specimen t o lower s t r e s s l e v e l s before applying the t r i a x i a l load. Measured
values of undrained shear s t r e n g t h (SU) a r e normalized with respect t o
e f f e c t i v e overburden s t r e s s ( 0 ) . A premise of the NSP method i s t h a t the v
I
r a t i o S / a i s cons tan t f o r a p a r t i c u l a r value of oCR. Moreover, a r e l a t i o n u v
e x i s t s between s /uv1 and W R t h a t allows p r e d i c t i o n of sediment s t r e n g t h a t u
depths below the l e v e l of sampling (Mayne, 1980).
RESULTS
Sediment d e s c r i p t i o n , index p rope r t i e s : Sediment samples could only be
c o l l e c t e d t o shal low depths ( c 3 m) beneath t h e s e a f l o o r . Therefore, most a r e
from t h e highest s t r a t i g r a p h i c u n i t ( u n i t 3, Fig . 5 ) . However, judging from
se i smic - r e f l ec t i on p r o f i l e s over sampling s t a t i o n s , a few outcrops of o t h e r
u n i t s were a l s o sampled. Se ismic- re f lec t ion p r o f i l e s a l s o show t h a t u n i t 3
has a t y p i c a l th ickness of about 80 t o 100 m ( ~ i g . 6). The appearance of
a c o u s t i c ref l e c t o r s wi th in t h i s u n i t i n d i c a t e s some l i t h o l o g i c v a r i a b i l i t y
with depth, b u t t h e r e i s no reason t o suspec t r a d i c a l changes i n sediment
type, except f o r pos s ib l e t h i n beds of volcanic ash. The phys i ca l p r o p e r t i e s
for t he cores should t he re fo re be r ep re sen t a t i ve of t he t e r r i genous component
of the u n i t a s a whole, but d r i l l - h o l e samples would be necessary t o confirm
t h i s .
The t e x t u r e of s u r f i c i a l sediment on the c e n t r a l p l a t f o r m and i n t h e
a d j a c e n t marginal channe l s g r a d e s from g r a v e l l y and sandy m a t e r i a l i n t h e
n o r t h e a s t p a r t of the s t rai t t o mud i n the sou thwes t (~igs. 7 and 8; Appendix
A ) . A g e n e r a l f i n i n g t r e n d from nor thwes t t o s o u t h e a s t a c r o s s t h e p l a t f o r m
a l s o e x i s t s .
The two g r a b samples of c o a r s e sediment r ecovered from Stevenson Entrance
appear t o have been t a k e n from o u t c r o p s of u n i t 1. Most of t h e c o a r s e c l a s t s ,
which range t o bou lde r s i z e , a r e a n g u l a r t o subangu la r , and some a r e f a c e t e d .
This s u p p o r t s t h e h y p o t h e s i s t h a t u n i t 1 was d e p o s i t e d by g l a c i a l p r o c e s s e s .
A few g r a b samples of c o a r s e m a t e r i a l were also recovered from the
sha l low s h e l v e s and from t h e a d j a c e n t s lopes. They probably are from u n i t
4. Coarse c l a s t s have s i m i l a r morphology t o t h o s e from u n i t 1, perhaps
r e f l e c t i n g g l a c i a l t r a n s p o r t a t some p o i n t i n t h e i r h i s t o r y .
Sediment c o r e s from t h e p l a t f o r m and marg ina l channe l s i n t h e c e n t r a l
p o r t i o n of t h e s t r a i t have a f a i r l y uniform s t r a t i g r a p h y wi th dep th . Sandy
sed iment i n t h e n o r t h e a s t end of t h e s t r a i t i s predominant ly g reen i sh -gray ,
wi th v a r i a t i o n s from black t o ye l lowish brown. S a n d - f i l l e d burrows, pebb le
c l a s t s , and whole o r broken s h e l l s a r e common. I n p r o g r e s s i v e l y f i n e r - g r a i n e d
c o r e s t o the sou thwes t , c o l o r remains g reen i sh -gray b u t i s l e s s v a r i e d , and
s h e l l s and c l a s t s a r e r a r e .
A l a y e r of v o l c a n i c a s h occurs i n many c o r e s . Maximum t h i c k n e s s of t h e
l a y e r i s n e a r l y 20 cm. It i s s ize -g raded , w i t h t h e c o a r s e s t b a s a l f ragments a
few m i l l i m e t e r s d iamete r . The c o l o r i s from t a n t o whi te wi th a pink cast.
The r e f r a c t i v e i n d e x of t he ash i s 1.485 + 0.002, which i n t h i s r eg ion i s
unique t o the o u t f a l l from the 1 9 1 2 Katmai e r u p t i o n (Nayudu, 1964; P r a t t and
o t h e r s , 1973) . Depth of t h e ash beneath the s e a f l o o r waq used t o c a l c u l a t e
v a l u e s of post-1912 sediment accumulat ion r a t e ( F i g . 9 ) . Accumulation r a t e
v a r i e s s i g n i f i c a n t l y th roughout t h e s t r a i t . It is g r e a t e s t n e a r t h e Alaska
P e n i n s u l a a t t h e southwest end of t h e s t r a i t , whereas it i s n e a r z e r o a t
p l a c e s i n t h e marginal channe l a l o n g t h e Kodiak i s l a n d group.
Water c o n t e n t o f sediment is shown i n F igure 10 a s i n t e r p o l a t e d v a l u e s a t
1-m dep th i n c o r e s . It is c a l c u l a t e d a s a p e r c e n t a g e of dry sediment weight ,
and t h e r e f o r e , v a l u e s i n excess of 100% a r e p o s s i ~ l e i f t h e weight of wa te r
exceeds t h e weight of sediment g r a i n s . Water c o n t e n t g e n e r a l l y d e c r e a s e s t o
t h e n o r t h e a s t , i n v e r s e l y c o r r e l a t i n g wi th g r a i n s i z e . Moreover, wa te r c o n t e n t
i n c r e a s e s a c r o s s t h e s t r a i t , from t h e Alaska p e n i n s u l a t o Kodiak I s l a n d . Bulk
sediment d e n s i t y a t 1 - m dep th , which is c a l c u l a t e d from water c o n t e n t and
g r a i n spec i f ic g r a v i t y , co r respond ing ly d e c r e a s e s down and a c r o s s the s t r a i t
( F i g . 11). Average g r a i n s p e c i f i c g r a v i t y i t s e l f shows no d i s c e r n i b l e t r e n d
( ~ i g . 12).
A t t e r b e r g l i m i t s d e s c r i b e t h e p l a s t i c i t y of sed iment , i n t e r n s of the
l i q u i d limit (wa te r content t h a t s e p a r a t e s p l a s t i c and l i q u i d b e h a v i o r ) and
t h e p l a s t i c l i m i t (wa te r c o n t e n t t h a t s e p a r a t e s semi - so l id and p l a s t i c
b e h a v i o r ) . Useful d e r i v a t i v e s a r e t h e p l a s t i c i t y i n d e x ( d i f f e r e n c e between
t h e l i q u i d and p l a s t i c l i m i t s ) , and t h e l i q u i d i t y i n d e x ( p o s i t i o n of tne
n a t u r a l wa te r c o n t e n t r e l a t i v e t o t h e l i q u i d and p l a s t i c l i m i t s ) . C e r t a i n
t r e n d s i n p l a s t i c i t y are e v i d e n t i n She l ikof S t r a i t . Average l i q u i d l i m i t ,
p l a s t i c l i m i t , and p l a s t i c i t y i n d e x i n c r e a s e down t h e s t r a i t toward t h e
sou thwes t , and a l s o g e n e r a l l y across the s t r a i t , toward t h e s o u t h e a s t ( F i g s .
13, 14, and 15; Appendix A ) . These p r o p e r t i e s also g e n e r a l l y i n c r e a s e wi th
d e c r e a s e i n mean g r a i n s i z e ( F i g s . 16, 1 7 , and 181, a l though t h e d a t a fo r
p l a s t i c l i m i t are q u i t e s c a t t e r e d . P l a s t i c l i m i t i s l e s s v a r i a b l e t h a n l i q u i d
l i m i t , which i s t y p i c a l l y t h e c a s e ( M i t c h e l l , 1976; R ichards , 1962) .
C o r r e l a t i o n s have been made between l i q u i d l i m i t and c o m p r e s s i b i l i t y
(Herrmann and o t h e r s , 1972; Skempton, 1 9 4 4 ) . The m a j o r i t y of She l ikof S t r a i t
samples f a l l w i t h i n t h e medium (30 < l i q u i d l i m i t < 5 0 ) and h igh ( l i q u i d l i m i t
>50) c o m p r e s s i b i l i t y ranges .
Near ly a l l measured l i q u i d i t y i n d i c e s i n She l ikof S t r a i t a r e g r e a t e r than
1 (Appendix A ) , which i s u s u a l f o r n e a r - s e a f l o o r marine sediment . Sediment
w i t h a l i q u i d i t y i n d e x g r e a t e r than one behaves as a l i q u i d when remolded.
A p l o t of L i q u i d i t y i n d e x ve r sus p l a s t i c i t y i n d e x - termed a p l a s t i c i t y
c h a r t (Casagrande, 1948) - shows a t r e n d p a r a l l e l t o t h e A-line t h a t d i v i d e s
b a s i c s o i l t y p e s (F ig . 1 9 ) . Most sediment samples from She l ikof S t r a i t p l o t
below t h e A-line, which i s t y p i c a l of i n o r g a n i c s i l t and s i l t y c l a y of h igh
c o m p r e s s i b i l i t y . The l i n e a r t r e n d of d a t a p o i n t s i s expec ted for samples
t a k e n th roughout t h e same sed imenta ry d e p o s i t ( ~ e r z a g h i , 1955; R ichards ,
1962) .
Undrained s h e a r s t r e n g t h of sediment samples (SU), a s measured wi th a
l a b o r a t o r y m i n i a t u r e vane s h e a r d e v i c e , g e n e r a l l y d e c r e a s e s toward t h e
sou thwes t end of t h e s t r a i t , and t h u s c o r r e l a t e s w i t h t h e wa te r c o n t e n t t r e n d ,
a l though t h e r e is much s c a t t e r ( F i g s . 20 and 21; Appendix A ) . The c o n s i s t e n c y
of most of t h e n e a r - s e a f l o o r sediment can be c l a s s i f i e d as very soft (SU < 1 2
k i l o p a s c a l s ) , h u t some is s o f t (12 kPa < Su < 24 kPa) t o medium ( 2 4 kPa < Su <
48 kPa) (Terzagh i and Peck , 1948). Harnpton and o t h e r s (1981) showed t h a t
s h e a r s t r e n g t h i s a n i s o t r o p i c i n She l ikof S t r a i t sediment c o r e s . Values of
s h e a r s t r e n g t h measured with the a x i s of vane r o t a t i o n p e r p e n d i c u l a r t o t h e
a x i s of c o r e samples exceed t h e va lues of s t r e n g t h measured wi th t h e a x i s o f
vane r o t a t i o n p a r a l l e l t o the c o r e a x i s . The magnitude of sediment s t r e n g t h
t h e r e b y depends on t h e o r i e n t a t i o n of t h e a p p l i e d s t r e s s .
Sediment samples from She l ikof S t r a i t are c h a r a c t e r i z e d by low t o
i n t e r m e d i a t e c o n t e n t of o r g a n i c carbon, compared t o o t h e r marine a r e a s
( ~ o r d o v s k i y , 1965, 1969; Gardner and o t h e r s , 1980; L i s i t z i n , 1972; Rashid and
Brown, 1975) . Most va lues a r e between 0.40% and 1.50%. Organic carbon
g e n e r a l l y i n c r e a s e s down t h e s t r a i t toward the sou thwes t , as w e l l as a c r o s s
t h e s t r a i t toward t h e s o u t h e a s t (F ig . 2 2 ; Appendix A ) . C o r r e l a t i o n s with
o t h e r p h y s i c a l p r o p e r t i e s were shown by Hampton and o t h e r s (1981) . Organic
carbon c o n t e n t c o r r e l a t e s p o s i t i v e l y wi th water c o n t e n t and p l a s t i c i t y index ,
whereas an i n v e r s e c o r r e l a t i o n i s found wi th g r a i n s i z e and vane s h e a r
s t r e n g t h . C o r r e l a t i o n s s i m i l a r t o those d e s c r i b e d above have been r e p o r t e d by
o t h e r s f o r low organic-carbon c o n t e n t sediment (Bordovskiy, 1965, 1969; Bush
and K e l l e r , 1981; K e l l e r and o t h e r s , 1979; L i s i t z i n , 1972; M i t c h e l l , 1976;
Ode11 and o t h e r s , 1960) .
P e r c e n t ca lc ium carbona te i s t y p i c a l l y low i n She l ikof S t r a i t sediment
( F i g . 23; Appendix A ) . Most va lues a r e less than 3.50%. Two l o c a t i o n s wi th
anomalously high va lues , off Shuyak I s l a n d and i n Stevenson Entrance, a r e near
t h e boundary of t h e s t r a i t .
C o n s o l i d a t i o n p r o p e r t i e s : Conso l ida t ion p r o p e r t i e s a s determined f r o m
l a b o r a t o r y tests a r e l i s t e d i n Table 1. A l l t e s t s i n d i c a t e a maximum p a s t
I I
p r e s s u r e ( a ) g r e a t e r t h a n t h e p r e s e n t overburden p r e s s u r e ( a ) . 'I'h e vm VO
I I
r a t i o am/Ovo is t h e o v e r c o n s o l i d a t i o n r a t i o n (OCR) and i s g r e a t e r than 1 .0
f o r a l l t e s t s . The u s u a l i m p l i c a t i o n i s t h a t t h e sediment has exper ienced
un load ing a s a consequence of e r o s i o n . However, t h e r e i s no g e o l o g i c a l
ev idence f o r e r o s i o n ; i n f a c t , sediment i s accumulat ing a t h igh rates
throughout most of t h e s t r a i t (F ig . 9). The high va lues of OCR probably
r e p r e s e n t i n i t i a l c e m e n t a t i o n of s e d i m e n t p a r t i c l e s o r g r a i n i n t e r l o c k i n g and
are n o t i n d i c a t i v e of o v e r c o n s o l i d a t i o n i n t h e s t r i c t s e n s e of t h e term.
Compression i n d e x (Cc) i s a measure of the amount of c o n s o l i d a t i o n t h a t
o c c u r s f o r a g i v e n i n c r e m e n t i n l o a d . The c o a r s e s e d i m e n t a t t h e n o r t h e a s t
end o f t h e s t r a i t i s less c o m p r e s s i b l e t h a n the p r o g r e s s i v e l y f i n e r s ed imen t
t o t h e s o u t h w e s t , as i n d i c a t e d by a s o u t h w e s t t r e n d of i n c r e a s i n g Cc ('L'able
1). R i c h a r d s (1962) r e p o r t e d a r ange of 0.20 t o 0.87 f o r Cc measured on
samples of mar ine s e d i m e n t from many a r e a s , and r ~ ~ o s t v a l u e s from S h e l i k o f
S t r a i t f a l l w i t h i n this range.
Compress ion i n d e x commonly shows a l i n e a r r e l a t i o n t o l i q u i d l i m i t
(LL). The d a t a f rom S h e l i k o f S t r a i t , when p l o t t e d i n t h i s manner, e x h i b i t a
g e n e r a l t r e n d , n u t w i t h much s c a t t e r ( F i g . 2 4 ) . Skempton (1944) found t h a t
t h e r e l a t i o n can be e x p r e s s e d as
cc = 0.009 (LL - l o ) ,
and t h e r e g r e s s i o n e q u a t i o n f o r S h e l i k o f S t r a i t s e d i m e n t i s s i m i l a r :
C, = 0.006 (LL + 5.7).
The r a t e a t which c o n s o l i d a t i o n o c c u r s i n r e s p o n s e t o l o a d i n g d e t e r m i n e s
t h e c o e f f i c i e n t of c o n s o l i d a t i o n ( c v ) . I t i s d i r e c t l y r e l a t e d t o p e r m e a b i l i t y
of a s e d i m e n t and i n v e r s e l y r e l a t e d t o t h e c o m p r e s s i b i l i t y . The c o e f f i c i e n t
i s c a l c u l a t e d f o r e a c h l o a d i n c r e m e n t d u r i n g a l a b o r a t o r y c o n s o l i d a t i o n test
from p l o t s of d e f o r m a t i o n v e r s u s t i n e . As shown i n Tab le 1, c, c~mmonly
v a r i e s t h rough one t o two o r d e r s of magni tude f o r a s i n g l e tes t . No g e n e r a l
t r e n d i n t h e d a t a i s e v i d e n t , a l t h o u g h t h e h i g h e x p e c t e d p e r m e a b i l i t y and low
c o m p r e s s i b i l i t y of c o a r s e - g r a i n e d s e d i m e n t would s u g g e s t a d e c r e a s e of c v to
t h e s o u t h w e s t , Measurements of cv f o r c l a y s e d i m e n t f rom v a r i o u s mar ine
l o c a t i o n s by R i c h a r d s and Hamilton (1967) a r e i n t h e r a n g e 3.2 - 6.0 x cm
2/sec, which are lower t h a n t y p i c a l v a l u e s i n SheLikof S t r a i t .
S t a t i c s t r e n g t h p r o p e r t i e s : Sediment p r o p e r t i e s derived from s t a t i c t r i a x i a l
s t r e n g t h tests a r e l i s t e d i n Table 2 . ?'he primary measured p r o p e r t y is t h e
undrained s h e a r s t r e n g t h (SU). ~t is t h e maximum s u s t a i n a b l e s h e a r s t r e s s
1
w i t h i n a sample s u b j e c t e d t o a p a r t i c u l a r c o n s o l i d a t i o n s t r e s s (ac) . SU a c t s
a long a p l a n i n c l i n e d a t 45O t o t h e a x i a l load . The a r e s i n e of S, d i v i d e d by
t h e e f f e c t i v e normal s t r e s s a c r o s s t h i s p lane i s t h e e f f e c t i v e ang le of
i n t e r n a l f r i c t i o n ( ) whose magnitude i s an i n d i c a t i o n of t h e s t r e n g t h
behav ior of the sediment under slow ( d r a i n e d ) l o a d i n g c o n d i t i o n s . In
I
comparison, t h e r a t i o S / O g i v e s an i n d i c a t i o n of t h e s t r e n g t h behav ior U C
d u r i n g r a p i d ( u n d r a i n e d ) load ing c o n d i t i o n s . The d i f f e r e n c e i n d ra ined and
undrained s t r e n g t h behavior depends on t h e p o r e wa te r p r e s s u r e genera ted i n
response t o t h e tendency f o r volume change when t h e sediment is a x i a l l y
loaded. If a sediment has a high tendency f o r volume change, t h e d i f f e r e n c e
i n s t r e n g t h between r a p i d and slow load ing can be s u b s t a n t i a l .
The e f f e c t i v e a n g l e of i n t e r n a l f r i c t i o n f o r t h e normally c o n s o l i d a t e d
sediment samples (OCR = 1) i n t h i s s t u d y i s r e l a t i v e l y high (35' - 46" ) .
Compare w i t h va lues given by Lambe and Whitman 1969, p. 149 and 306). The
h i g h e r v a l u e s ( > 40°) a r e i n t h e f i n e r sediment c o r e s from t h e southwest h a l f
of t h e s t r a i t able 2 ) . There fore , sediment from She l ikof S t r a i t appears t o
be a t y p i c a l l y s t r o n g under c o n d i t i o n s of d r a i n e d l o a d i n g , with the f i n e r
sediment e x h i b i t i n g h i g h e r s t r e n g t h . Samples t e s t e d a t OCR > 1 tend t o have
$' comparable t o t h a t of normally c o n s o l i d a t e d samples, e x c e p t f o r s t a t i o n 649
where some o v e r c o n s o l i d a t e d samples have s i g n i f i c a n t l y h i g h e r values. The
d a t a i n d i c a t e s i m i l a r d r a i n e d behavior of normal ly c o n s o l i d a t e d and
o v e r c o n s o l i d a t e d sediment i n t h e s t r a i t .
Lambe and Whitman (1969, p. 307, Fig . 21.4) d e t e c t e d a r e l a t i o n between
4' and p l a s t i c i t y index f o r normally c o n s o l i d a t e d s o i l . T r i a x i a l d a t a f o r
which t h e r e a r e p l a s t i c i t y index va lues i n She l ikof S t r a i t p l o t w i t h i n t h e
range of Lambe and Whitman's d a t a , e x c e p t f o r t h e c o r e a t s t a t i o n 511, which
i s abnormally s t r o n g f o r sediment wi th such high p l a s t i c i t y ( ~ i g . 25) .
Eva lua t ion of undrained s t r e n g t h , i n terms of S / a , r e q u i r e s some U C
judgement i n o r d e r t o d e t e c t t r e n d s . I n p a r t i c u l a r , t n e tests run a t law
I I
c o n s o l i d a t i o n s t r e s s ( a 1 seem t o g ive e r r a t i c va lues of S / a . This was C U C
a l s o shown t o be t h e c a s e f o r t r i a x i a l d a t a from nearby Kodiak Shelf wh amp ton,
i n p r e s s ) . T e s t s run a t high va lues of c o n s o l i d a t i o n stress (which c o r r e c t s
I
some of t h e e f f e c t s of d i s t u r b a n c e ) and OCR = 1 have v a l u e s of S / a between U C
1
0.3 and 0.6, with no a r e a l t r e n d able 2 ) . The va lue of s / u i n c r e a s e s wi tn u C
OCR f o r each c o r e t e s t e d .
The s t a t i c t r i a x i a l t e s t d a t a a r e p l o t t e d a c c o r d i n g t o t h e NSP approacn
i n F igure 26. The s l o p e ( A ) of t h e l i n e f o r each c o r e i s a measure of t h e
change i n undrained s t r e n g t h wi th OCR. Most c o r e s have A va lues between 0.79
and 0.97. Mayne (1980) compiled t h e r e s u l t s of many t r i a x i a l tests and found
a mean va lue of A = 0.64 wi th a s t a n d a r d d e v i a t i o n of 0.18. The sediment i n
She l ikof S t r a i t , wi th i ts r e l a t i v e l y high va lues of A, would t e n d t o r e t a i n
more of i t s s t r e n g t h a f t e r unloading compared t o most sediment examined by
Mayne (1980) . The A = 1.43 c a l c u l a t e d f o r t h e sediment of s t a t i o n 5 2 8 i s
g r e a t e r than t h e t h e o r e t i c a l l i m i t of = 1.0 , and f u r t h e r t e s t i n g i s r e q u i r e d
t o r e s o l v e t h i s c o n f l i c t .
Dynamic s t r e n g t h p r o p e r t i e s : The d a t a from t r i a x i a l s t r e n g t h t e s t s a r e given
i n Table 3. The q u a n t i t y rCy,/Su is t h e c y c l i c s t r e s s l e v e l , t h e average
v a l u e of s h e a r stress ( T ~ ~ ~ ) a p p l i e d s i n u s o i d a l l y w i t h f u l l stress r e v e r s a l a t
0.1 Hz, e x p r e s s e d as a p e r c e n t a g e of t h e s t a t i c u n d r a i n e d s h e a r s t r e n g t h
(SU). Pore w a t e r p r e s s u r e and s t r a i n accumula t e w i t h r e p e a t e d a p p l i c a t i o n of
T~ y c A t some p o i n t , t h e p o r e w a t e r p r e s s u r e a p p r o a c h e s t h e c o n f i n i n g stress,
s t r a i n i n c r e a s e s a b r u p t l y , and t h e s e d i m e n t f a i l s . I n o u r tests, f a i l u r e was
chosen when 20% s t r a i n was r eached .
Samples t y p i c a l l y fail i n f ewer c y c l e s a t p r o g r e s s i v e l y h i g h e r s t r e s s
l e v e l s . F i g u r e 27 shows t n e number of c y c l e s t o f a i l u r e v e r s u s s t r e s s Level
f o r S h e l i k o f S t r a i t samples . Although t h e r e i s some scat ter , the d a t a f a l l
w i t h i n t h e r a n g e of t e s t r e s u l t s on t e r r i g e n o u s s e d i m e n t from o t h e r a r e a s (Lee
and others, 1981; Anderson and o t h e r s , 1980; Hampton, i n p r e s s ) . Moderate
c y c l i c s t r e n g t h d e g r e d a t i o n is i n d i c a t e d ; t h a t i s , a f t e r 1 0 c y c l e s of l o a d i n g
( a s migh t be i m p a r t e d by a n e a r t h q u a k e , f o r e x a m p l e ) , t h e samples f a i l a t
stress l e v e l s between 60% and 80% of t h e i r s t a t i c s t r e n g t h .
DISCUSSION
The p r i m a r y g e o t e c h n i c a l c o n c e r n s i n S h e l i k o f S t r a i t i n c l u d e s e t t l e m e n t
of s t r u c t u r e s , h e a r i n g c a p a c i t y unde r s t a t i c and c y c l i c l o a d i n g l a t e r a l l o a d
c a p a c i t y , and anchor b r e a k o u t r e s i s t a n c e . N a t u r a l s l o p e f a i l u r e s a r e n o t a
s e r i o u s problem because o n l y one small s e d i m e n t s l i d e has been documented
(Hampton and o t h e r s , 1981 1. There i s some e v i d e n c e f o r gas -charged sediment,
b u t t h e problem of l o w s t r e n g t h t h a t might e x i s t i n s e d i m e n t of t h l s t y p e was
n o t a d d r e s s e d i n t h e p r e s e n t s t u d y .
m a t e r n a r y s e d i m e n t i n S h e l i k o f S t r a i t c o v e r s bedrock t o a t h i c k n e s s of
from 20 m t o more t h a n 800 m ( F i g . 4 ) . The sequence c o n s i s t s of P l e i s t o c e n e
g l a c i d l and g l a c i o m a r i n e s e d i m e n t a t t h e b a s e , o v e r l a i n by Holocene mar ine
d e p o s i t s . The h i g h e s t s t r a t i g r a p h i c u n i t , d e p o s i t e d by o c e a n i c c u r r e n t s a s
e x i s t today , has accumulated t o a t h i c k n e s s of 80-100 rn over most of t h e
s t r a i t ; the t o t a l range is abou t 20 m t o 180 m. Geo techn ica l t e s t i n g was
performed on ly on samples from t h i s uppermost u n i t . A g e o t e c h n i c a l a n a l y s i s
based on t h e s e d a t a p robab ly a d d r e s s e s most s i t u a t i o n s of e n g i n e e r i n g
concern . Deeper s t r a t i g r a p h i c u n i t s appear from i n t e r p r e t i v e g e o l o g i c s t u d i e s
t o be r e l a t i v e l y coarse -g ra ined ampto ton and Win te r s , 1981; Whitney and
o t h e r s , 198Oa, b ) , and they probably a r e s t a b l e , b u t deep d r i l l - c o r e samples
would have t o be o b t a i n e d i n o r d e r t o conf i rm t h i s by g e o t e c h n i c a l t e s t i n g .
The p a t t e r n of g r a i n - s i z e v a r i a t i o n ( F i g s . 7 and 8 ) e v i d e n t l y r e f l e c t s
p r o g r e s s i v e s o r t i n g by t h e s o u t h w e s t e r l y f lowing b a r o t r o p i c c u r r e n t t h a t
dominates c i r c u l a t i o n i n t h e s t r a i t . The p r e s e n t s t u d y and t h e p r e v i o u s
r e p o r t by Hampton and o t h e r s (1981) show t h a t some i n d e x p r o p e r t i e s vary i n
r e l a t i o n t o g r a i n s i z e . P r o p e r t i e s t h a t show a d i r e c t c o r r e l a t i o n and
t h e r e f o r e i n c r e a s e t o t h e sou thwes t down t h e s t r a i t and t o t h e s o u t h e a s t
a c r o s s t h e s t r a i t i n c l u d e wa te r c o n t e n t , l i q u i d l i m i t , p l a s t i c L i m i t ,
p l a s t i c i t y index , and o r g a n i c carbon c o n t e n t ( F i g s . 10 , 13, 14 , 15, and 2 2 ) .
P r o p e r t i e s t h a t c o r r e l a t e i n v e r s e l y wi th g r a i n s i z e i n c l u d e bulk sed iment
d e n s i t y and undrained ( v a n e ) s h e a r s t r e n g t h ( F i g s . 11 and 2 0 ) .
C o n s o l i d a t i o n t e s t s i n d i c a t e t h a t sediment samples a r e o v e r c o n s o l i d a t e d ,
b u t t h i s p robab ly i s a n e a r - s e a f l o o r d i a g e n e t i c o r f a b r i c phenonenon r a t h e r
than a r e s u l t of e r o s i o n , because n e t sediment accumula t ion i s p r e s e n t l y
o c c u r r i n g th roughout t h e s t r a i t (Tab le 1, Fig . 9 ) . The f i n e - g r a i n e d sediment
t o t h e sou thwes t nas h igh va lues of compression i n d e x (C',), which i n d i c a t e s
t h a t it i s more compress ib le t h a n the c o a r s e r m a t e r i a l t o the n o r t h e a s t . The
r a t e of c o n s o l i d a t i o n , a s shown by t h e c o e f f i c i e n t of c o n s o l i d a t i o n ( c V ) l is
h i g h l y v a r i a b l e f o r each c o n s o l i d a t i o n t e s t and does n o t show an a r e a l t r e n d
(Tab le 1). I n t u i t i v e l y , a h i g h e r va lue of c, would be expec ted f o r t h e
c o a r s e r - g r a i n e d sediment because of i t s normal ly h i g h e r p e r m e a b i l i t y and lower
c o m p r e s s i b i l i t y , b u t a p p a r e n t l y t h i s i s n o t t h e case .
Another unexpected r e s u l t i s t h a t t h e s t a t i c d r a i n e d s t r e n g t h , i n terrns
of t h e e f f e c t i v e a n g l e of i n t e r n a l f r i c t i o n , i s h i g h e r f o r t h e f i n e -
g r a i n e d sediment t h a n i t i s f o r t o t h e c o a r s e r - g r a i n e d samples (Table 2 ) .
u r a i n e d s t r e n g t h does n o t vary a p p r e c i a b l y w i t h OCR. Undrained s t a t i c
s t r e n g t h behav io r does no t e x h i b i t s i g n i f i c a n t a r e a l v a r i a t i o n . Values
I
of SU/oc f o r t e s t s run a t OCR = 1 a r e between 0 . 3 and 0.6. This pa ramete r
i n c r e a s e s w i t h OCR f o r each c o r e t h a t was t e s t e d . The NSP p r e - p r e s s u r e
pa ramete r ( A ) v a r i e s from 0.79 t o 0.97, which i n d i c a t e s s i g n i f i c a n t s t a t i c
s t r e n g t h i n c r e a s e w i t n OCR ( ~ i g . 26) . Again, no a r e a l t r e n d i s apparent.
But, because few d a t a p o i n t s were used t o plot t h e l i n e s i n F igure 26 and
because l a r g e s c a t t e r of data e x i s t s f o r some i n d i v i d u a l c o r e s , a d d i t i o n a l
s t r e n g t h t e s t i n g a t more l e v e l s of OCR would add p r e c i s i o n t o t h e p l o t s and
pe rhaps r e v e a l some s y s t e m a t i c v a r i a t i o n .
T e s t d a t a for most cores d e f i n e s i m i l a r r e sponse t o c y c l i c l o a d i n g over a
broad range of number of c y c l e s r e q u i r e d t o cause f a i l u r e ( e .q . , c o r e s 511,
525, 528, and 540 i n Fig . 271. bynamic s t r e n g t h d e g r e d a t i o n v a r i e s over a
L i m i t e d range a t low number of c y c l e s ; f o r i n s t a n c e , i t i s between abou t 60%
and 80% f o r 1 0 c y c l e s .
G e o t e c h n i c a l p r o p e r t i e s of She l ikof S t r a i t sed iment can be compared wi th
data from o t h e r s t u d i e s t o de te rmine i f t h e sediment h a s normal d e f o r m a t i o n a l
behav io r . However, few d a t a e x i s t f o r some p r o p e r t i e s , which makes the
e v a l u a t i o n s t e n t a t i v e .
Most v a l u e s of compression i n d e x f a l l w i t h i n t h e range of 0.20 t o 0.87
r e p o r t e d by Richards and Hamilton (1962) fo r s i l t y c l a y t o h i g h l y c o l l o i d a l
clay; one test on t h e c o r e from s t a t i o n 507 has a h igh va lue of 0.94 (Table
1). Skempton's (1944) c l a s s i f i c a t i o n of c o m p r e s s i b i l i t y based on l i q u i d l i m i t
i n d i c a t e s t h a t She l ikof S t r a i t samples a r e moderate ly t o h i g h l y compress ible
(Appendix A ) . S u b s t i t u t i o n of t h e c lass-boundary va lues of l i q u i d l i m i t
(moderate c o m p r e s s i b i l i t y : 30 < LL < 50; high c o m p r e s s i b i l i t y : LL > 50) i n t o
t h e r e g r e s s i o n e q u a t i o n f o r She l ikof S t r a i t d a t a (F ig . 2 4 ) ,
c c - 0.006 (LL + 5 . 7 ) ,
i n d i c a t e s t h a t t h e range of moderate c o m p r e s s i b i l i t y i s 0.21 < Cc < 0-33 and
t h e h igh range i s Cc < 0.33, which i s c o n s i s t e n t wi th c l a s s i f y i n g t h e sediment
a s moderate ly t o h i g h l y compress ible able 1).
E f f e c t i v e f r i c t i o n a n g l e ( 4 ' ) f o r sediment i n Shel ikof S t r a i t i s high
( 3 5 O - 46O) compared t o t h e range (20° - 40°) r e p o r t e d by Lambe and Whitman
(1969, p. 149 and 306) f o r normally c o n s o l i d a t e d sediment . Apparent ly , no
compi la t ions of ' e x c l u s i v e l y f o r t e r r i g e n o u s marine sediment have been
made. Hampton ( i n p r e s s ) r e p o r t s ' most ly i n t h e 30° - 40° range f o r
t e r r i g e n o u s samples from t h e Kodiak S h e l f . She l ikof S t r a i t t e r r i g e n o u s
sediment is r e l a t i v e l y s t r o n g under d r a i n e d l o a d i n g c o n d i t i o n s .
Lambe and whitman (1969, p. 452, Fig . 29.19) p r e s e n t d a t a on t h e
undrained s t r e n g t h o f normally c o n s o l i d a t e d marine c l a y , and va lues
1
of s / o a r e between about 0.2 and 0.4. The range f o r normal ly c o n s o l i d a t e d u C
She l ikof S t r a i t samples i s 0.3 t o 0.6, s o t h e y are r e l a t i v e l y s t r o n g under
c o n d i t i o n s of undrained load ing . S / cr ' f o r normal ly c o n s o l i d a t e d t e r r i g e n o u s U C
sediment from the Kodiak She l f a r e a l s o h igh , from 0.4 t o 1 .0 (Hampton, i n
p r e s s 1.
Values of t h e NSP f a c t o r A are h igh (0.79 - 0.97) compared t o the average
va lue of 0.64 ( s t a n d a r d d e v i a t i o n = 0.18) i n t h e e x t e n s i v e compi la t ion by
Mayne (1980). The i m p l i c a t i o n i s t h a t t h e i n c r e a s e of s t r e n g t h wi th
o v e r c o n s o l i d a t i o n i s h i g h e r than normal.
The low t o moderate c y c l i c s t r e n g t h d e g r e d a t i o n of She l ikof S t r a i t
samples is s i m i l a r t o t h e behav io r of c l a y sediment r e p o r t e d i n o t h e r s t u d i e s
(Lee and o t h e r s , 1981; Anderson and o t h e r s , 1980; Hampton, i n p r e s s ) .
Sediment f a i l u r e i n r esponse t o l a r g e ea r thquakes c e r t a i n l y i s a p o s s i b i l i t y ,
b u t t h e p o t e n t i a l i s not a s g r e a t a s has been p r e d i c t e d for some d e p o s i t s of
s i l t i n t h e n o r t h e a s t Gulf of Alaska ( c y c l i c s t r e n g t h a t 1 0 c y c l e s a s low a s
40% of t h e s t a t i c s t r e n g t h ; Lee and Schwab, i n p r e s s ) and v o l c a n i c a s h on t h e
Kodiak Shelf ( c y c l i c s t r e n g t h a t 1 0 c y c l e s i s 1 2 % of t h e s t a t i c s t r e n g t h ;
Hampton, i n p r e s s ) . The d e p o s i t of Katmai a s h i n She l ikof S t r a i t was n o t
s u b j e c t e d t o g e o t e c h n i c a l t e s t i n g . However, i t s i n s i t u d e n s i t y i s so g r e a t
t h a t normal g r a v i t y c o r i n g d e v i c e s cou ld n o t p e n e t r a t e t h e Layer. The
r e l a t i v e d e n s i t y appears t o be high and t h e r e f o r e t h e l i q u e f a c t i o n p o t e n t i a l
is low. The p o s s i b i l i t y that more deep ly b u r i e d a s h l a y e r s are p r e s e n t and
might be h i g h l y s u s e p t i b l e t o l i q u e f a c t i o n canno t be e v a l u a t e d w i t h t h e
i n f o r m a t i o n p r e s e n t l y a v a i l a b l e .
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2 3
Table 1. Consolidation test results.
Depth . in a a
VO vm C" X lo-': S t a t i o n core C c number (cm (kPa) (kPa 1 OCR
Table 2. S t a t i c t r i a x i a l s t r e n g t h test r e s u l t s .
Depth I
in o C Su I
S t a t i o n core Induced S / O
OCR u C 4'
number (cm) ( k P a ) (kPa (degrees )
Table 2. ( c o n t i n u e d )
Depth I
in o C Su 1
S t a t i o n core Induced S"'"c 9 Number (cm) (kPa) OCR (kPa (degrees )
Table 3 . Dynamic triaxial s trength test r e s u l t s .
Depth I
in u T cyc'su
Cycles C
Station core Induced to number (cm (kPa ) OCR ( % ) f a i l u r e
FIGURE CAPTIONS
1. Loca t ion map of the study a r e a i n She l ikof S t r a i t .
2. A. T r a c k l i n e s of con t inuous s e i s m i c - r e f l e c t i o n p r o f i l e s . S o l i d l i n e s
r e p r e s e n t a r e g i o n a l su rvey c o n t r a c t e d by the USGS Conserva t ion D i v i s i o n ,
and dashed l i n e s r e p r e s e n t s i t e su rveys on cruises of t h e R/V S .P. Lee
(1980) and NOAA s h i p Discovere r (1981).
B. Loca t ions of sediment sampl ing s t a t i o n s .
3. Bathymetry of She l ikof S t r a i t , 20-m con tour i n t e r v a l . Depths c o r r e c t e d
t o mean lower low wate r .
4. Thickness of sed imenta ry u n i t s of p robab le P l e i s t o c e n e and younger age .
Contour i n t e r v a l : 50 meters e x c e p t f o r t h i c k n e s s g r e a t e r than 500 rn
where con tour i n t e r v a l i s 100 rn.
5 . R e p r e s e n t a t i v e s e i s m i c - r e f l e c t i o n p r o f i l e s showing s e i s m i c - s t r a t i g r a p h i c
u n i t s .
6. Thickness of h i g h e s t s e i s m i c - s t r a t i g r a p h i c u n i t that covers most of t h e
s e a f l o o r of She l ikof S t r a i t . Contour i n t e r v a l : 20 m.
7. Pie-diagrams showing r e l a t i v e abundances of t e x t u r a l c l a s s e s i n s e a f l o o r
sed iment samples.
8. Mean g r a i n size of s e a £ I ~ J o ~ sediment , i n p h i - u n i t s .
9. Sediment accumulat ion r a t e s , i n cm/100 y r .
10. Water c o n t e n t ( p e r c e n t d r y weigh t ) a t 1-rn dep th i n sediment c o r e s .
11. Bulk sediment d e n s i t y (qn/crn3) a t 1 - m dep th i n sediment c o r e s .
12. Average g r a i n s p e c i f i c g r a v i t y i n sediment c o r e s .
13. Average l i q u i d l i m i t ( p e r c e n t d r y w e i g h t ) i n sediment c o r e s .
14. Average p l a s t i c l i m i t ( p e r c e n t d r y weigh t ) i n sediment c o r e s .
15. Average p l a s t i c i t y index i n sediment c o r e s .
16. Liquid l i m i t ve r sus g r a i n s i z e .
17. P l a s t i c limit versus g r a i n size.
la. P l a s t i c i t y index versus g r a i n size.
19. P l a s t i c i t y c h a r t .
20. Vane s h e a r s t r e n g t h (kPa) a t lm dep th i n sediment cores.
21. Vane shear s t r e n g t h ve rsus water c o n t e n t .
22. Average o r g a n i c carbon c o n t e n t i n sediment c o r e s .
23. Average calc ium carbona te c o n t e n t i n sediment c o r e s .
24. Graph of compression index versus liquid l i m i t .
25. Graph of e f f e c t i v e a n g l e of i n t e r n a l f r i c t i o n versus p l a s t i c i t y index .
S o l i d l i n e shows e m p i r i c a l r e l a t i o n d e r i v e d by Lambe and Whitman (1969) ;
dashed l i n e i n d i c a t e s l i m i t s of t h e i r d a t a .
26. Graph of normalized undrained s h e a r s t r e n g t h ve rsus o v e r c o n s o l i d a t i o n
r a t i o .
27. Graph of c y c l i c stress l e v e l versus number of c y c l e s t o f a i l u r e .
-FJW 4 I
I t SE+ I
I
t
P l l l l l l l l , , meters
1000 I
I t central platform I I
I marginal chamel
, .
Fig. 5
10 0 8 7 6 5 4 3
Fig . 16 mean grain size (9)
Q 8 7 6 5 4 3 Fig. 17 mean grain size (0)
4 8 - -
10 0 8 7 6 5 4 3 Fig. 18 . mean grain size (0)
49
0s
Plasticity index
Fig. 26 OCR
Appendix A. Index property charts for sediment cores from Shel ikof Strait.
Station 508 Locafjon 57O21.01 'N 1 5 ~ ~ 3 6 . 4 1 'W Water depth 27om
Depth (cml
rn 0
200
2 5 0
300
Grain slze (weight 96)
Bulk den I ty 8 lgmlcm 1
b
Bulk density at lm.: 1 . 5 6
I b
s i l t
Water content Plasticity Atterberg limits- Index (% dry weight)
0 50 100 1% 0 50 - I
c l a y
Water content Average at Im.: 87 .2 plasticity Average plastic index: limit: 36 31) Average liquid limit: 65
Llquldit y index
0 1.02.0
Liquidity index at Im.:
1.58
Grain Organlc speciflc carbon gravity (%dr wei ht)
21) 2.5 3.0 0 7 2 8 4
Average Average grain speclflc organic &avi t y : carbon:
2.84 0.931
Carbonate (%dry weight)
0 t 2 3 4
T C ' I
b
Average carbonate:
1 . 2 9 1
Vane bhear strength (kPa)
0
Vane shear strength at lm*
1 - 5 8
Station 509 Location ~ 7 ~ 2 1 . 2 9 ~ ~ 15S008.66'N' Waferdepth 225111
Grain slre (welght %I
Depth
Bulk den Ity t (grn/cm 1
(cm)
rn P
50
1.0 1.5 2.0 r r I I l ~ ~ ~ ~ n n A
b
b I D
I
Bulk density at Im.: 1.46
-- -
Water content Plastlclty At terberg limits- lndex (% dry weight)
0 50 100
Water content Average at dm.: 104.5 plasticity Average plastic index: limit: 40 34 Average liquid limit: 75
- 100 -
- 150-
Llquidity Grain Organtc index speciflc carbon
2 0 0
gravity (%dr we4 ht) 0 1.0 2.0 2.0 2.5 3.0 0 7 2 ! 4
. - - - ?77
Liquidity Average Average index grain specific organic at lm.: gravity: carbon:
3 . 5 6 2 . 8 1 1.009
Carbonmte (%dry weight)
2 5 0 -
T' I
Average
C
- . - *
carbonate: 0 .990
300-
Vane shear
Vane shear strength at lm.: 6%
Station 511 Locsfion57O39.08~~ 1 ~ 4 ~ 5 0 . 1 4 ~ ~ Waterdepth 2141-11
Bulk den I ty Water content a Plasticity 8 (gmlcm ) Atterberg I l m i t s H Index (% dry weight)
1.0 1.5 2.0 0 50 1 0 0 150 0 50 Depth
Bulk density Water content Average a t Im. :1 .49 atlrn.:100.6 plasticity
Average plastic index: limit: 36 36 Average liquid limit: 72
(crn)
0 W
50
100-
150-
- -
.. - b
- - -
200 - -
250
- 300-
t lqu id l t y Grain Organic Carbonate Vans ahear index 8peclfic carbon (%dryweight) strength
gravity (%dr wei ht) (kPa1 01.02.0 2.0 2.5 3.0 () 7 2 8 4 0 1 2 3 4 0 50
Liquidity Average index grain specif lc organic carbonate: strength at 1 m.: gravity : carbon: 0 .873 at l m -
1 .74 2 . 8 4 1.075 6.70'
1 3
&
I L
Average Average Vane shear 1
$ 0 =E m .e OF 5 ;go C O O
I 8, . O h -
Station 513 Location 5 7 0 5 4 . 5 ' ~ 1 5 4 ~ 1 9 . 8 ' 1 ~ Waterdepth 205m
Depth
0-l Ln SO"
100-
1 so -
Grain 812e twelght 96)
200
0204qeoso
Fsiit Z c l a y 1 1 1 1 1 1 1
- - - - -
Bulk den ity S (gm/cm 1
Bulk density at lm.: -
250
- - - - - .;
6
Llquidit y index
Water content o Plastlclty Atterberg l i m i t s w index (% dry weight)
300- tiquidit y index at lm.:
Qraln Organlc s ~ s c l f l c carbon
1500 50 r l ~ 1 7 1 I
a
0
Average Average grain speclfic organic
Water content Average at lm.: plasticity Average plastic index: limit: 37 30
50 100 f " m ' l " l r ~
+I
gravity: carbon: 2 . 7 7 0 -863
Carbonate (Wdryweight)
0 1 2 3 4
Average carbonate:
1-10
Vane shear strenath
Vane shear strength at lm.:
Average liquid limit: 67
1 8 - n-7
- Y C C s .E .F - - m s i 5 ? % - - o w * ~ e G g : gl u @ a = # 3:ewo-
: -
-:
- - I
Station 515 Location 57059 .o I N 154027.3 ' W Water depth 238m
Grain size (welght %I
Depth (cm)
0 4
200
250
300
Bulk den I ty Water content Plestlcity Liquidity Grain 8 ( g m l c m 1 Atterberg limits- Index index specif lc
Bulk density Water content Average Liquidity Average at lm.: at lm.: plasticity index grain specific
Average ptastic index: at Im.: gravity: limit: 2 . 6 5 Average liquid
(% dry weight)
Organlc Carbonate Vane shear
0
(%dry weight) strength I (kPa)
0 1 2 3 4 0 50 50 100 1 8 1 ' ' ' ' 1 " 1 ' 1
Average Average Vane shear organic carbonate: carbon: 1 .02 at lm.:
0 .721
limit:
Station 516 Locsfjon s s 0 0 0 . 3 t ~ 154010.6'1t~ Water depth 205
Depth ( c m l
0-l m
2 00
250
300
Graln size (weight %)
020406060 1 1 1 1 1 1 1 1
silt c l ay
Bulk den i t y Water content e Plasticity Ltquldlty Graln f Organlc Carbonate Vans shear (gm/crn 1 Atterberg I i r n i t s H lndex index specific carbon (%dryweight) strength
(% dry weight) gravity ( I d r wei ht) (k Pa) 1.0 1.5 2.0 0 50 1 W ,500 60 01.02.0 2.0 2.5 3 . 0 0 7 2 8 4 0 1 2 3 4 0 50
a
8ulk density Water content Average Liquidity Average Average Average Vane shear at lm.: at lm.: plasticity index grain speclflc organic carbonate: strength
Average plastic index: at lrn.: gravity: carbon: 1 .05 at tm.:
limit: 2.65 0 .898 Average liquid limit:
I " 1 I f I l [ I 1 . 1 .
-
b " Itt ?? * F k o so
t o u
Station 518 Location 58O00.3 I N 1 5 3 ~ 5 1 . 6 w Water depth 180m
Graln slre (weight %I
Depth (cm)
4 0 50
100-
Bulk den I ty Water content Plast lc l ty Llquldlty Grain 8 Organic Carbonate Vane shear (gm/cm Atterberg l i m i t s w index Index specif lc carbon (%dryweight) strength
I% dry weight) gravi ty (%dr wei ht) (k Pa) 1.0 3.5 2.0 O 50 3 0 0 150 0 50 0 1.02.0 2.0 2.5 3.9 O 7 2 8 4 0 1 2 3 4 0 50
-
n -
150
Butk density Water content Average Liquidity Average Average Average Vane shear at Im.: at lm.: plasticity index grain specffic organic carbonate: strength
Average ptastic index: at lm.: gravity: carbon: 0.940 at 1 m.: limit: 2 .62 1.104
Average liquid limit:
m ' 1 . 1 ' 1 1 1 1 I r I I I
t
- - - - -
l r r I l l l j l ~
i
I F T
t
1
I I
t
200
2 5 0
300-
- C - - - - - - - *
Station 524
Grain sire (welght % I
Bulk den I t y 8 (grn/crn 1
Bulk density at lm.:
Llquldlt y index
Water content Plastlclty Atterberg I h i t s H Index (% dry weight)
Liquidlt y index at Im.:
0 50 100 l " " i " " 1
Water content
Water depth 175m
Grain Organic speclflc carbon
at lm.: plasticity Average plastic index:
1500
grain specific organic gravity : carbon:
50 1 1 1 1 I I
Average
Carboneta (%dryweight)
carbonate:
Vane shear strength (kPa1
0 50
Vane shear strength at Im.:
limit: Average liquid limit:
Depth (cm)
1 so
200
Station 525 Location 5 s 0 2 3 . 7 ' ~ 1 ~ 3 ~ 3 7 . 2 ' W Water depth ls8m
Grain size (welght %I
Bulk den Ity 8 (gm/cm 1
0201080# I I I 1 1 I W I I
sand s i l t
Bulk densit at im.: 1 - 8 2
Liquldit y index
Water content Plastlcl ty Atterberg I i m i t s H index (% dry weight)
Liquidity index at lm.:
1 . 4 1
Grain Organlc speclflc carbon
1500 50 I I I I I I -
I Average
0
Average Average grain speclfic organic at lm.: 45.2 plasticity
Average plastic index: limit: 2 7 13 Average llquid limit: 39
50 100 I ' I T ' 1 ' l T ' 1
i Water content
gravity : carbon: 2.79 0 .882
Carbonate (%dry weight)
Average carbonate:
1 . 0 3 4
Vane shear strenath
Vane shear strength at im.:
22 .59
Depth (cm) -
so - 03 0
100- - *
b - 150-
- - - 200 - -
250 - - -
300-
Station 528 tocstjon 58039 -4 I N 15300.7 'W Water depth 159m
Graln s i ts (weight %)
Bulk den Ity 8 (gmjcrn 1
Bulk density at lm.: J - J L
Water content Plastlclty Atterberg limits- Index (% dry weight)
0 50 100 1500 50 P---
- Water content Average at lm.: 46 .9 plasticity Average plastic index: limit: 26 11 Average liquid Ilmit: 37
at lm.: gravity: carbon: 2 . 2 3 2 - 7 3 0 .643
Carbonate Vane shear (%dry weight) strength
Average Vane shear carbonate: strength
2 . 1 9 7 at Im.: 16.91
Station 531 Location 5 8 0 5 4 . 9 ~ ~ 15z037.3tw Water depth
Grain slze (welght 96)
Depth (cm)
SO
Bulkden ity W a t e r c o n t e n t * Plasticity Liquidity Grain 8 Organic Carbonate Vane 8hear (gm/cm 1 Atterberg l i m i t s H index index speclflc carbon (%dryweight) strength
(% dry weight) gravity (lbdr we! ht) (k Pa)
-
1.0 1.5 2.0 0 50 100 150 0
100 -
150 L
200
250
300
50 ; 2 P l I I r r I I 2.5 3.007 I - 2 ! 4 T ' f 7 0 1 2 3 4 I , -
0 1-1 I I 50
C
b - - - - - - * - -
I
. Bulk density Water content Average Liquidity Average Average Average Vane shear at lm.: at lm.: plasticity index grain specific organic carbonate: strength
Average plastic index: at lm.: gravity: carbon: 3 . 2 5 at Im.: Hrnit: 0 .388 Average liquid limit:
-3 Zbg = N
F 52". E t o o
0 - r 8
Ql p ..a p : ~ ? 8 3" <Ebb
Station 535 Lo~afion58~37.0~N 1 5 ~ ~ 4 2 . 0 ~ ~ Water depth 98m
Grain size (weight %I
Depth
Q3 4
1 0 0 -
1 5 0 -
2 0 0 -
Bulk den i ty Water content Plasticity Liquidity Grain S Organlc Carbonate Vane shear (gm/crn Atterberg I h i t s H index index apeclffc carbon (%dryweight) strength
(% dry weight) gravity ( I d r we1 ht) (kPa) 1.0 1.5 2.0 0 50 100 1 W O 5 0 . 01.02.0 2.0 2.5 3.00 7 2 ! 4 0 1 2 3 4 0
- - - - - - - - - C
Bulk density Water content Average Liquidity Average Average Average Vane shear at Im.: at lm.: plasticity index grain specific organic carbonate: strength
Average ptastic index: at lm.: gravity: carbon: 21.67 at lm.: limit: 2.76 0 . 2 0 9 Average Iquid limit:
250
300-
- - - - - -
I € 1
;
a 1 f , !
a I I Z I ] I l ~ l ' ~ f l l l
a 1 . r . 1 .
i
Station 538 Location s s 0 2 s - 2 ' N 153"oo .2'w Water depth 190m
Depth t c m )
LQ 0
200
250
300
Graln size (weight %I
Bulk den ity Water content Plastlclty LIquldity Grain J Organic Carbonate Vane shear (gmlcrn 1 Atterberg limits- index index specific carbon (%dryweight) strength
(% dry weight)
Bulk density Water content Average Liquidity Average Average Average Vane shear at Im.: 1.61 at Im,: 74 . 7 plasticity index grain specific organic carbonate: strewth
Average plastic index: at lm.: gravity: carbon: 1 . 4 2 at lm.: tlmit: 33 2 9 1 . 4 6 2 . 7 8 0 . 8 7 1 16 . O Y
Average liquid limit: 62
Station 539 Location 58'21 - 3 ' ~ 153'12 - 4 ' 1 ~ Wafer depth 175m
Grain sirs (welght %I
Depth (cm)
w so
- -
020408080
Butk den i t y Water content Plasticity Liquidity Oraln S Organlc Carbonate Vane shear (grnicrn 1 Atterberg I i rni tsH Index index specific carbon (%dry weight) strength
(% dry weight) gravity ( I d r wei ht) (k Pal .O 1.5 2.0 0 50 1 0 0 1500 W 01.02.0 2.0 2.5 3.0072!4 0 1 2 3 4 0 50
s i l t
I
Bulk densit
c l a y
w 1 D a
looL
5 Water content Average Liquidity Average Average Average Vane shear at lm.: 1.4 at tm.: 109.7 plasticity index grain specif lc organic carbonate: ,trewth
Average plastic index: at Im.: gravity: carbon: 1 .70 at Im.: limit 2 . 5 2 1.102 9 .07 Average tiquid limit:
1 1 1
1
L
L - 150
C
I I I I l I 1 1 1 I I 1 1 -
1 I
Station s40 Location ~ 8 ~ 2 1 . 5 ' ~ 153O07.6'W Waterdepth Z l O r n
Graln sirs (welght %I
Depth (cm)
19 5 0 -
N
100-
150-
Bulk den I ty Wster content Plastlclty Liquldlty Qraln 8 Organlc Carbonate Vane shear (gm/cm ) Atterberg I i rn i tsH index index specific carbon (%dry weight) strength
(% dry weight) gravity (%dl wei ht) (kPa) 1.0 1.5 2.0 0 50 100 1500 50 01.02.02.0 2.5 3.0072!4 0 1 2 3 4 0 50 -
- - : : 200
Bulk den;I1ll Wetter content Average Liquidity Average Average Average Vane shear a t l m . : . a t I m . : 7 4 , 0 plasticity index grain specifk organic carbonate:
Average plastic index: at 1 m.: gravity: carbon: 1 . 1 0 at lm.:
limit: 2 . 7 6 0 .799 15.86
Average liquid limft:
C - - - -
I 1 1 I '
: 250 -
300-
! 7 1 1 ] & ~
Station 541 Location ~ 8 ~ 1 5 . s Y x 153022 - 0 I I Y Water depth 167m
Graln size (welght %I
Depth I c m )
cD 50 W
100-
150C
200
Bulk den I ty Water content Plasticity Llquldlty Grain 8 Organic Carbonate Vane shear (grn/cm ) Atterberg I i rni tsH index Index specific carbon (%dryweight) strength
(% dry weight) gravity (Jdr wei h t l (kPa) .O 1.5 2.0 0 50 100 1500 50 01.02.0 2.0 2.5 3 . 0 0 7 2 8 4 O f 2 3 4 0
- rm -
L
- - - - - - - - - b -
1 1 -
A 1
250
Bulk density Water content Average Liquidlt y Average Average Average Vane shear at lm.: at Im.: plasticity index grain specif lc organic carbonate: strength
Average plastic index: at tm.: gravity: carbon: .270 at lm.: limit: 3'3 24 1.082 Average liquid limit: 63
- - - P -
300-
H * 1 1 1 1
a
L
~ I I I T I I I
L
k g c .. a t $ O h -
> a m
I l l l l . l l l l l l I l l l I l . I
f - 0 0 0 0 0 0 n o n o Y)
r 0
E 5 v PU 04 m P -
Station 545 Location 5 8 O 2 2 - 5 ' N 153O53.5 ' w Water depth 175.
Grain 812s (weight %)
Depth (crn)
a 50 rn
Bulk den tty Water content Plasticity Llquldtty Qraln d Organtc Carbonrta Vans shear (gm/cm ) Atterberg l i m i t ~ H index Index speclflc carbon (%dryweight) 8trsngth
(% dry weight) gravity %dr wel (kPe1 1.0 1.6 2.0 0 50 100 150 0 50 0 1.02.0 2.0 2.5 36 0 r 2 , O ! 2 3 4 0 50
-
! 1 - ~ 100-
i-
150- -
Bulk density Water content Average Liquidity Average Average Average Vane shear
a t lm. :1 .64 a t l m 6 9 . 1 plasticity index grain speclfic organic carbonate: strength
index: at lm.: gravity - carbon: 0.710
Average Iastic f9
at IF.'
limit: 2 0 2 . 0 2 2 . 7 9 0 .663 & Average liquid limit: 49
,
250 w : , : 2 , , H - - - - m -
H
300 -
Depth
ID CO
200
250
300
Station 547 tocation ~ 8 ~ 3 3 . 0 ' ~ 153034 - 4 ' ~ Water depth 89m
Graln slze (welght %)
Bulk den Ity 8 (gm/cm 1
Bulk density at Im.:
Liquidity Grain Organlc index speciflc carbon
gravity (%dr wei ht) 01.02.0 2.0 2.5 3.0 0 7 2 8 4
Water content Plasticity Atterberg I i m i t s H Index (% dry weight)
Liquidity Average Average index grain specfflc organic at lm.: gravity: carbon:
2 . 7 9 0 .591
Carbonate (%dry weight)
1500 50 F I I I I I '
I
Average
0 0 1 2 3 4 I "
Average
at lm.: plasticity Average plastic index: limit: 28 14 Average Iquid limit: 42
50 100 1 " " I " " I
H "i
Water content carbonate:
1.05
Vane shear strength
Vane shear strength at lm.:
7 4
$,g i='b a'C 0 9 & a n > P z = C O O
Station 551 Location 5 8 0 ~ 3 . 6 ' ~ 1 5 2 0 5 4 . 4 1 ~ Water depth lssm
Depth (cm) -
Bulk den Ity J (gm/cm 1
50 P
Bulk density at lm.:
-
llqutdity Oraln Organtc index s ~ e c i f l c carbon
Water content Plastlclty Atterberg 1imitsb-i index (% dry weight)
0 N
100-
Liquidity Average Average index grain specific organic at Im.: gravity: carbon:
2 - 7 6 0 . 8 0 1
0
m
-
Carbonate (%dry weight)
Average carbonate:
2 . 1 4 at Im.: ptasticit y Averagl glastic index: limit: 10
50 fOO ~ ' " ' ~ ' " ' I
H r
Water content
150-
200
250
300-
Vane shear
50 1 1 1 F 1 1 -
Average
- b
L
L - - + - - - - . -
rtrsngth (kPa)
0 I 1 I I
Vane shear strength at lm.:
Average liquid limit: 34
r Q
go,
* Q O a 0 I w
E -3 b N
2 c . F 8 0 =z % 0~~1 g $5 g':
5 0 0 , > P k o
llcO C O O
Q a 0
u
b 22;l a 0 >" 5 a (3 ..a 0
CI g a r . O $ o
L *= . z r 4
S 2 a z 2 0 2 en
a h - > m Q
Station 647 Location 57 '59 - 8 ' ~ 154010.7 'W Water depth 22om
Depth (cm) -
5 0 -
Average lastic f5
index: limit: 3 1
Bulk den I t y Water content Plastlclty 8 (grntcrn 1 Atterberg I i m i t s H Index (% dry weight)
P 0 LC
1 0 0 -
1 5 0 -
200
250
300-
Llquldlt y Qraln Organtc Carbonate Vane shear Index speclflc carbon (%drywelght) strength
gravity (%dr wei ht) (kPa1 01.02.0 2.0 2.5 3.0 0 r 2 ! 4 0 1 2 3 4 0 1.0 1.5 2.0
l ~ ~ ~ l , ~ r ~ 7 ,
1 L - - - - m - - - - - - - - b -
Liquidity Average Average Average Vane shear index grain specffic organic carbonate: strength at tm.: gravity: carbon: at Im:
1.11 2 .58 8 -81 Average I! id iirnlt: 6p
Bulk density Water content Average at tm.: 1.57 atlm.: 76.4 ptasticity
0 50 700 l " ' r l " " l
I; -
1500 50
.- m E Q .: = E IS' 2;
Station 654 Water depth 232m
Depth
m aoL
100-
f50- L .
200 - - - - - 250 - - -
C
L
3 0 0 -
Bulk den i ty Water content Plasticity Liquidity Qraln 8 Organlc Carbonate Vans shear (grntcrn 1 At terberg I i m i t s H index index specific carbon (%dryweight) 8trsngth
(% dry weight) (!(Pa) 1 1.5 2.0
a
Bulk density Water content Average Liquidity Average Average Average Vane shear at lm.: at lm.: plasticity index grain specific organic carbonate:
Average plastic index: at Im.: gravity: carbon: 0 .870 at lm.: limit: 2 . 6 1 1 .006 Average liquid limit:
0 50 100 . 1500 50 0 50 I I f I
0 1 . 0 2 . 0 2.0 0 , 2 3 4 - 1 1
,o c -- f . ! g t $$
o O u C O O
0 ' .; c o , 2 ' a g;i ax 0.:@
E
$% $
$ E z . . . , C - $ r c g - r n - > E W E S m u = < =
Station 658 Location 58010.6 'N 1 ~ 3 ~ 3 2 . 6 ~ 1 ~ Water depth 190m
Grain slze (weight %I
Depth 0204080w ~ i r l f ~ l l f ' , silt. c l a y
(cm)
a0
- im
Bulk den I ty Water content Plastlclty Llqufdlty Graln # Organic Carbonate Vanashear (gm/crn 1 Atterberg I l m i t s H index index speclflc carbon (%dryweight) strength
(% dry weight) gravity (%dr wei ht) (kPa) 1.0 1.5 2.0 50 1W 150 0 50 0 1.02.0 2.0 2.5 3.0 0 1 2 8 4 0 1 2 3 4 0 50
T I I I I I
100-
150-
200
250
300-
1 - - - - - - - - - - - - - - - - - -
I I , I I I I
" f I '
Bulk density Water content Average Liquidity Average Average Average Vane shear at Im.: at lm.: plasticity index grain specific organic carbonate: ,trmgth
Average plastic index: at lm.: gravity: carbon: at 7m.: Ilrnit: 50 30 2 . 5 5
liqvid lim#:
I I I I I
Station 659 Location 58'01. B ~ N 153028.5 + W Water depth 112m
Depth
Graln sirs (weight %I
(cm)
50
02040806U
sand
L
-
-
Bulk den lty d (grn/crn 1
Bulk density at lm.:
P P w
100-
Water content Atterberg I h i t ~ H (96 dry weight)
0 50 100 150
-
Water content at tm.: Average plastic limit: 2 1
Plastlclty Index
150
Average plasticity
200
250'
index: 16
- - - - - L
b
Liquldft y index
r
300-
0 f .02.0
a
Liquid# y index at lm.:
Grain Organlc Carbonate speclflc carbon (%dry weight)
Average grain speclf)c organic carbonate: gravity : carbon: 0.340
2.47 0 - 2 2 8
Vane shear strength (kPa)
0 6Q I l l 1
i
Vane shear strength at lm.:
Average liquid limit: 37
Station 664 Location 5 8 " s ~ . o o ~ 1~3~36.901: ' Water depth 174m
Depth (cm) -
50 - P N P
1oopm -
Graln sire (weight 96)
150-
Bulk den I ty 8 (grn/cm 1
- - - -
1.0 1.5 2.0 1 " ~ ' " ' ~ ' '
i
Bulk density at lm.:
Water content At terberg l i m i t s ~ (% dry weight)
0 50 fOO 150 l ' l ' r T ' ' ' l ~
200
250
300 Water content at f m.: Average plastic limit: Average liquid limit:
- - - - - - - - - - -
Plastlcl ty Liquidity Index index
0 50 l r l ~ y r l
Average plasticity
0 1.02.0
Liquidity index
index: at lm.:
Orain Organlc spsclfic carbon
grain specific organic gravity : carbon:
2 09
Carbonate (%dry weight)
Average carbonate:
Vane shear strensth
Vane shear strength at lm.:
