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Uniaxial compressive strength and deformation of Beaufort Sea ice
Frederking, R. M. W.; Timco, G. W.
Ser
THl
N21d
'
*
National Research
Conseil national
Council Canada
de recherches Canada
.o.
1150
,
c. 2 ' I
BLDG
IUNIAXIAL COMPRESSIVE STRENGTH AND DEFORMATION OF BEAUFORT SEA ICE
by R. Frederking and G.W. Timco
Appeared in
VTT Symposium
27
The Seventh l nternational Conference on Port and
Ocean Engineering under Arctic Conditions Helsinki, Finland,
5
-
9
April,1983
Volume
1,
p.89
-
98
Reprinted with permission
Technical Research Centre o f Finland (VTT)
DBR Paper No.
1150
Division of Building
Research
Price
$1.00
OTTAWAI
N R C - C I S T I1
BLDG.
RES.
L I B R A R Y
1
Le comportement au p o i n t d e vue d e s di3ormations e t de l a r'es i s t a n c e d ' e ' c h a n t i l l o n s de g l a c e columnaire g r a n u l a i r e o r i e n t ' e s h o r i z o n t a l e m e n t a S t 6 m e s u r s i n - s i t u . Le s C c h a n t i l l o n s c y l i n d r i q u e s o n t dt'e plac'es e n t r e l e s p l a t e a u x d'une machine d ' e s s a i e t l e s d c h a n t i l l o n s e n forme d e prisme e n t r e d e s p l a t e a u x e n a c i e r de f q o n 3 o b t e n i r d i f f ' e r e n t e s r i g i d i t ' e s du mdcanisme d e l a machine d ' e s s a i . C e d e r n i e r a un e f f e t non n'egligeable s u r l e s mesures d e r'esistance l o r s q u e l e s r ' e s u l t a t s s o n t interpr'et'es e n f o n c t i o n d e s t a u x d e di3ormation nominale; mais, exprim& en t a u x d e c o n t r a i n t e s , c e t t e i n f l u e n c e a 'etg presque t o t a l e m e n t Climin'ee. La r ' e s i s t a n c e d e l a g l a c e g r a n u l a i r e (2,5
-
4
MPa) a CtS nettement sup'erieure 3c e l l e de l a g l a c e g r a n u l a i r e columnaire (1
-
2,5 MPa). M i s 3p a r t l a s t r i c t u r a - ~ . ~ -*A- ---y s o n t t o u s
R. F r e d e r k i n g , 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 C o u n c i l of Canada, Ottawa, Canada KIA OR6.
G.W. Timco, D i v i s i o n of Mechanical E n g i n e e r i n g , N a t i o n a l Research Council of Canada, Ottawa, Canada KIA OR6.
UNIAXIAL COMPRESSIVE STRENGTH AND
DEFORMATION OF BEAUFORT SEA ICE
A b s t r a c t
S t r e n g t h and deformation behaviour of h o r i z o n t a l l y o r i e n t e d specimens of g r a n u l a r and c o l u m n a r g r a i n e d i c e were measured i n
t h e f i e l d . C y l i n d r i c a l specimens were loaded on compliant
p l a t e n s and p r i s m o i d a l specimens on s t e e l p l a t e n s t o p r o v i d e a range of l o a d i n g system s t i f f n e s s . Loading system s t i f f n e s s proved t o have a s i g n i f i c a n t e f f e c t on s t r e n g t h when t h e r e s u l t s were i n t e r p r e t e d i n terms of nominal s t r a i n r a t e , but i n terms of
s t r e s s r a t e i t was l a r g e l y e l i m i n a t e d . The s t r e n g t h of t h e g r a n u l a r i c e (2.5
-
4 m a ) was s u b s t a n t i a l l y h i g h e r t h a n t h a t of columnar-grained i c e (1-
2.5 m a ) . R e g a r d l e s s of g r a i n s t r u c t u r e , t h e specimens a l l f a i l e d by y i e l d i n g a t a s t r a i n of about 3 x 1 INTRODUCTION I n c r e a s i n g i n t e r e s t i n A r c t i c r e g i o n s h a s r e s u l t e d i n expanding demands f o r knowledge of t h e mechanical p r o p e r t i e s of s e a i c e , i n f o r m a t i o n t h a t i s e s s e n t i a l i n e s t a b l i s h i n g d e s i g n i c e l o a d s on o f f s h o r e s t r u c t u r e s and i n t r a n s f e r r i n g performance e x p e r i e n c e on e x i s t i n g s t r u c t u r e s t o new l o c a t i o n s . Measured mechanicalp r o p e r t i e s a r e dependent on f a c t o r s t h a t c a n be d i v i d e d i n t o two c a t e g o r i e s t h e p h y s i c a l p r o p e r t i e s of t h e i c e and t h e
c h a r a c t e r i s t i c s of t h e t e s t system. P h y s i c a l p r o p e r t i e s of i c e i n c l u d e g r a i n s t r u c t u r e and s i z e , t e m p e r a t u r e , s a l i n i t y , p o r o s i t y and a i r c o n t e n t . T e s t system c h a r a c t e r i s t i c s i n c l u d e b a s i c
s t i f f n e s s of t h e l o a d i n g frame, l o a d i n g f i x t u r e s , and machine c a p a c i t y . A s has been p o i n t e d o u t by t h e IAHR I c e T e s t i n g Methods Working Group 111, i t i s n e c e s s a r y t o document a s
completely a s p o s s i b l e a l l f a c t o r s a f f e c t i n g measured r e s u l t s .
2 SAMPLE ACQUISITION AND SPECIMEN PREPARATION
The i c e used i n t h i s s t u d y was c u t 6 J a n u a r y 1982 from a r a f t e d block (- 5 m x 5 m x 0.8 m t h i c k ) i n a r u b b l e f i e l d a b o u t 20 m t o t h e w e s t of T a r s i u t , a c a i s s o n - r e t a i n e d i s l a n d about 40 km
o f f s h o r e i n t h e B e a u f o r t Sea. The r u b b l e had formed 4 J a n u a r y 1982 s o t h a t t h e i c e had only r e c e n t l y been exposed. Mean a i r t e m p e r a t u r e was a b o u t -35°C. F u r t h e r d e t a i l s of sample
a c q u i s i t i o n and t r a n s p o r t a t i o n a r e d e s c r i b e d i n a companion p a p e r i n t h e s e proceedings 131.
The upper 30 c m of t h e i c e cover comprised g r a n u l a r ice w i t h a g r a i n s i z e i n c r e a s i n g from 1 mm a t t h e t o p t o 3 mm a t a d e p t h of
, 30 cm. The lower 50 cm of t h e i c e cover comprised columnar g r a i n s of 5 t o 10 mm. A more complete d e s c r i p t i o n of t h e
p h y s i c a l c h a r a c t e r i s t i c s of t h e i c e i s a v a i l a b l e 141. H o r i z o n t a l c o r e s 7.56 cm i n d i a m e t e r were t a k e n from d e p t h s of 15-20 cm ( t o p specimens) and 60-65 cm (bottom specimens) t o make c y l i n d r i c a l specimens f o r u n i a x i a l compression tests. The i c e i n t h e t o p
. specimens showed a d i s c o n t i n u o u s columnar s t r u c t u r e , w i t h
columnar g r a i n s a b o u t 1 cm l o n g and 1-3 mm i n diameter. Columnar i c e , i n t h e bottom.specimens ( g r a i n d i a m e t e r 8 mm) showed a
tendency f o r a p r e f e r r e d a z i m u t h a l o r i e n t a t i o n of t h e c-axis i n t h e h o r i z o n t a l p l a n e a t an a n g l e of about 30 deg t o t h e a x i s of t h e specimen.
C y l i n d r i c a l specimens 23, 20, 15 and 10 cm l o n g were c u t t o o p t i m i z e u s e of t h e a v a i l a b l e p i e c e s of core. No f u r t h e r end p r e p a r a t i o n , o t h e r t h a n brushing o f f l o o s e snow, was c a r r i e d o u t . A s e t . o f 10 p r i s m o i d a l specimens from seven d i f f e r e n t l e v e l s i n
19.2 cm l o n g by 5.5 cm wide by 5.1 c m t h i c k and t h e ends were smoothed w i t h f i n e emery paper t o p r o v i d e a p o l i s h e d f l a t s u r f a c e . S a l i n i t y was i n t h e range 4.5 5 5X0, and i c e d e n s i t y
was 900 k 10 kg/m3.
3 TEST PROCEDURE
T e s t i n g was c a r r i e d o u t on a motorized 0.05
MN
c a p a c i t ycompression t e s t e r ( S o i l t e s t CT-405), a screw-drive machine w i t h a c t u a t o r r a t e s i n t h e range 0.2 t o 4 mmlmin. "Maraset" compliant p l a t e n s were used t o e l i m i n a t e t h e e f f e c t of i r r e g u l a r i t i e s and t o reduce r a d i a l s t r e s s e s a t t h e ends of t h e c y l i n d r i c a l
specimens. Two e x t e n s o m e t e r s were f i x e d d i r e c t l y t o t h e specimen, t h e i r o u t p u t averaged t o o b t a i n s t r a i n . Continuous r e c o r d s of l o a d v e r s u s t i m e and d i s p l a c e m e n t v e r s u s t i m e were made. A t y p i c a l r e c o r d i s p r e s e n t e d i n F i g u r e 1, and d e f i n i t i o n s of y i e l d s t r e s s ,
u,
l o a d i n g s t r e s s r a t e , 2 ' average s t r e s s r a t e , a s t r a i n a t y i e l d , E and s t r a i n r a t e a t y i e l d , E a r e av'
Y ' Y ' LOADING STRESS STRESS, RATE, bA,,STRAIN RATE AT YIELD, i
T I M E , s 1 - 5 1 1 I ! I I 1 Z 1 . 0
-
zI
V) V) W P: 8 = -11°C + V) 0 . 5 ~ s-
5 Olm Figcire 1. S t r e s s - t i m e and s t r a i n - t ime c u r v e s ' f o r test 1 on D $ y l i n d r i c a l specimen: D 1 2 3 4 5 %om = 2 x 10-4 s-1, S T R A I N . t e s t temperature -1 1 ° C-
92
-
.
i l l u s t r a t e d . Nominal s t r a i n r a t e , E i s nominal machine speed
nom
'
d i v i d e d by specimen l e n g t h . The p r i s m specimens were loaded on s t e e l p l a t e n s t o o b t a i n a s t i f f e r l o a d i n g system. Before
t e s t i n g , a l l specimens were s t o r e d i n a c h e s t f r e e z e r a t -11 2
1°C.
4 TEST RESULTS AND DISCUSSION
Complete test r e s u l t s a r e t a b u l a t e d i n Table 1 , and s t r e n g t h v e r s u s l o a d i n g s t r e s s r a t e i s p l o t t e d i n F i g u r e 2. The r e s u l t s from t h e t o p and bottom c o r e s f a l l i n t o d i s t i n c t l y d i f f e r e n t groups t h a t can be r e l a t e d t o g r a i n s t r u c t u r e . The l a r g e r g r a i n e d bottom specimens, w i t h p r e f e r r e d c-axis o r i e n t a t i o n a t 30
deg t o t h e specimen a x i s , had h a l f t h e s t r e n g t h of t h e more g r a n u l a r t o p specimens when t e s t e d a t comparable s t r e s s r a t e s . Also p r e s e n t e d on F i g u r e 2 a r e s t r e n g t h r e s u l t s a t a s i n g l e nominal s t r a i n r a t e of 2 x s-l f o r prism specimens a t d i f f e r e n t l e v e l s i n t h e i c e cover; t h e number i n b r a c k e t s
f o l l o w i n g each datum p o i n t r e p r e s e n t s t h e average d e p t h ( i n cm) of e a c h specimen. It may be s e e n t h a t t h e t e s t r e s u l t s f o r t h e prism specimens i n t h e upper p a r t of t h e i c e cover a g r e e w i t h t h e v a l u e s f o r t h e t o p c y l i n d e r s . S i m i l a r l y , t h e prisms a t d e p t h s between 40 and 60 cm have s t r e n g t h s s i m i l a r t o t h o s e of t h e bottom c y l i n d e r s . Specimens a t d e p t h s of 23 and 29 cm, where
6 I I I I I I I ~ I 1 1
----
0 TOP CYLINDERS lo+ , - I <("_< B r ,0-4 , - I
-
B o n o M cYLlNDERsI o 5 - PRISMS 2 nm 2 ,-
rn n E 4 - az
2-
F i g u r e 2. U n i a x i a l > compressive s t r e n g t h of h o r i z o n t a l l y Beaufort-
Sea, - l l ° C . ( ) Depth o i n cm of prism o r 1 1 1 I I I 1 1 1 1 1 ~ t I specimens; [I
Length 0.006 0.01 0.02 0.04 0.06 0.1 0.2 0.4 i n c m of c y l i n d r i c a lgrain structure is columnar but grain size smaller than at
greater depths, have strengths intermediate between those of the
top and bottom cylinders. This points to the importance of grain
TABLE 1 Uniaxial Compression Data Test Temperature: -11'
f1°C
a
Yield
Loading Strain Time
Strain
Nominal
Test No.
Stress Stress
at
to
Rate at
Strain
MPa
Rate
Yield
Yield
Yield
Rate
kPa s-l x lo3
.--Ilo4
,--I.lo4
Cylindrical Specimens
Prism Specimens
*
Specimen length, cm;
**
B for bottom specimens, T for top
specimens; ***No compliant platen;
+Mean depth of specimen
s t r u c t u r e and g r a i n s i z e i n d e t e r m i n i n g s t r e n g t h . It i s a l s o noteworthy t h a t s t r e n g t h r e s u l t s , on a s t r e s s r a t e b a s i s , a r e q u i t e s i m i l a r f o r simply prepared s p e c i m e n s ' o n compliant p l a t e n s and f i n e l y p r e p a r e d prism specimens on s t e e l p l a t e n s .
A power f u n c t i o n can be f i t t e d t o t h e s t r e n g t h v e r s u s l o a d i n g
stress r a t e r e s u l t s . The e x p r e s s i o n f o r t h e t o p specimens ( g r a n u l a r i c e ) i s
w i t h a c o r r e l a t i o n c o e f f i c i e n t r2 = 0.63. The e x p r e s s i o n f o r t h e
bottom specimens (columnar i c e ) i s
w i t h a c o r r e l a t i o n c o e f f i c i e n t r2 = 0.74. I n b o t h e q u a t i o n s ( 1 )
and ( 2 )
a
h a s u n i t s of MPa and MPa s-l. These s t r e n g t hR
e q u a t i o n s c a n be e x p r e s s e d i n terms of a v e r a g e stress r a t e oav u s i n g t h e r e l a t i o n
w i t h a c o r r e l a t i o n c o e f f i c i e n t r2 = 0.99. E q u a t i o n ( 3 ) i s determined from t h e s t r e s s r a t e d a t a of a l l t h e t o p and bottom specimens p r e s e n t e d i n T a b l e 1 and can be used t o c o n v e r t e q u a t i o n s ( 1 ) and ( 2 ) from a l o a d i n g s t r e s s r a t e b a s i s t o a n a v e r a g e stress r a t e b a s i s . The r e a d e r s h o u l d be c a u t i o n e d n o t t o e x t r a p o l a t e t h e p r e c e d i n g o r f o l l o w i n g e m p i r i c a l e q u a t i o n s beyond t h e r a n g e . o f t h e e x p e r i m e n t a l d a t a ; such e x t r a p o l a t i o n c o u l d l e a d t o absurd c o n c l u s i o n s .
Expressing y i e l d s t r e s s of columnar-grained i c e i n terms of a v e r a g e s t r e s s r a t e g i v e s
T h i s compares w i t h r e s u l t s of tests on h o r i z o n t a l l y o r i e n t e d specimens of c o l u m n a r g r a i n e d f i r s t - y e a r s e a i c e from Pond I n l e t
and Mould Bay which gave
121
A number of f a c t o r s such a s g r a i n s i z e and b r i e n t a t i o n , specimen p r e p a r a t i o n , t e s t machine, e t c .
,
d i f f e r (between t h e two d a t a s o u r c e s , e q u a t i o n s ( 4 ) and ( 5 ) ) , but over t h e average s t r e s s r a t e range of 1 0 ' ~ t o 10-1 MPa s'l s t r e n g t h r e s u l t s a r e comparable.It h a s been p o i n t e d o u t t h a t t h e s t r e n g t h r e s u l t s can be examined i n terms of time t o y i e l d o r f a i l u r e i n o r d e r t o v e r i f y t h e
s a t i s f a c t o r y performance of a t e s t machine
121.
T h i s h a s beendone i n Fig. 3, which shows t h a t t h e r e i s a t r e n d towards
d e c r e a s i n g time t o y i e l d w i t h i n c r e a s i n g s t r e n g t h , a s would be
expected. The curves drawn through t h e datum p o i n t s a r e
r e g r e s s i o n l i n e s , b u t s i n c e t h e c o r r e l a t i o n c o e f f i c i e n t s were
q u i t e low, no e q u a t i o n s a r e p r e s e n t e d . , .
I n F i g u r e 1 i t may be s e e n t h a t a l t h o u g h t h e t e s t .:ns r u n a t a
c o n s t a n t nominal s t r a i n r a t e of 2 x s-l, s t r a i n r a t e i s f a r
from c o n s t a n t . Over t h e range of
loe5
s-1 t o s-1 t h e s t r a i nr a t e a t y i e l d i s a b o u t 70% of t h e nominal s t r a i n r a t e . Also
shown ( F i g u r e l c ) i s a l i n e r e p r e s e n t i n g t h e dynamic e l a s t i c
modulus determined from b r i n e volume
151.
The h i g h e r measureds l o p e a t very s m a l l s t r a i n s s u g g e s t s e x p e r i m e n t a l e r r o r i n t h e s t r a i n measurements. Space l i m i t a t i o n s p r e c l u d e p l o t t i n g t h e s t r e n g t h r e s u l t s on a s t r a i n r a t e b a s i s , b u t c l o s e examihation of t h e d a t a i n T a b l e 1 i n d i c a t e s t h a t a t a given nominal s t r a i n r a t e t h e r e i s a s i g n i f i c a n t d i f f e r e n c e i n s t r e n g t h f o r compliant and s t e e l p l a t e n s . A t a nominal s t r a i n r a t e of 2 x 10'~ s'l t h e s t r e n g t h s
of g r a n u l a r i c e were 3.4 and 4.0 MPa f o r compliant and s t e e l
---
4 TOP CYLINDERS BOnOM CYLINDERS c . F i g u r e 3. U n i a x i a l compressive s t r e n g t h vs time t o y i e l d of f i r s t - y e a r s e a i c e from t h e o0
Beaufort Sea, -11°C. 2 0 30 40 5 0 70 l o o 2 0 0 300 400 ( ) Depth i n cm of Y I E L D T I M E , t y , s prism specimensp l a t e n s , r e s p e c t i v e l y , and f o r columnar ice, 1.6 and 2.1 MPa. D i f f e r e n c e s can be e x p l a i n e d i n terms of t e s t system s t l f f n e s s .
The r e s u l t s f o r c y l i n d r i c a l specimens were examined t o d e t e r m i n e t h e e f f e c t of specimen l e n g t h a t t h e nominal s t r a i n r a t e of
2 x s-l, but no s y s t e m a t i c i n f l u e n c e could be e s t a b l i s h e d . On t h e o t h e r hand, p l o t t i n g r e s u l t s on a s t r e s s r a t e b a s i s ( s e e datum p o i n t s i n s q u a r e b r a c k e t s , Fig. 2 ) confirmed t h e p a t t e r n of i n c r e a s i n g s t r e n g t h w i t h i n c r e a s i n g s t r e s s r a t e . Examination of y i e l d s t r a i n and s t r e n g t h showed c o n s i d e r a b l e s c a t t e r , w i t h no a p p a r e n t r e l a t i o n between them. The a v e r a g e s t r a i n a t y i e l d was 2.75
+
1.35 x f o r a l l t h e specimens; t h e r e was nos i g n i f i c a n t d i f f e r e n c e between g r a n u l a r and columnar ice.
An i n v e s t i g a t i o n was a l s o made of t h e s t i f f n e s s of t h e t e s t machine and l o a d i n g system. S t i f f n e s s f o r t h e whole system c a n . be q u i t e d i f f e r e n t from t h a t of t h e b a s i c t e s t machine owing t o t h e i n f l u e n c e of t h e l o a d c e l l , p l a t e n s , alignment j o i n t s , e t c . The c h a r a c t e r i s t i c s of t h e system were t h e r e f o r e determined by . l o a d i n g a specimen of known c o n s t a n t e l a s t i c i t y and measuring t h e l o a d , movement of t h e . s c r e w j a c k , and l o a d frame d e f l e c t i o n . The t e s t machine, i t s components, and t h e p o i n t s between which
d e f l e c t i o n s were measured a r e shown i n F i g u r e 4a ( a s c h e m a t i c of t h e specimen and l o a d i n g system i s p r e s e n t e d i n F i g u r e 4b).
L O A D I N G J A C K D E F L E C T I O N
I
I
L O A D I N G ' ( 1 3 S Y S T E M K S P E C I M E N a 1 L O A D I N G M A C H I N E b l T E S T S Y S T E M F i g u r e 4. Schematics of arrangements f o r d e t e r m i n i n g l o a d i n g system s t i f f n e s sLoading system stiffness, Kas, is defined as
AP
= - .
(6)
6
-6s
j
where AP is a load -increment,
6. is the corresponding
J
displacement increment of the screw jack, and 6s is the resulting
deformation increment of the specimen. 6s is defined as
AP
a
(7)
where
E is the elastic modulus of the specimen,
11is its length,
and
A
its cross-sectional area. Substituting equation (7) in
( 6 ) ,
the following equation.
for determining loadi~m
system
stiffness is obtained
J~~
Tests were conducted in a cold room at -lS°C with an aluminum
specimen
(a
=200 mm, diameter
=76.2 mm, and
E
=70 GPa) and
compliant platens. The basic frame stiffness measured between
the upper cross-head and screw-drive jack was about
200
xlo6 N/m. The actual stiffness of the loading system, as
calculated from equation
(8)and measurements of load and screw-
jack displacement, is presented in Figure 5. It may be seen that
the stiffness of the loading system with compliant platens is not
a constant, but a function of load and rate; loading system
stiffness is substantially less than load frame stiffness. In
tests with the aluminum specimen between steel platens, loading
system stiffness was nearly constant (100 MN/m) for loads up to
0.06 MN.
I I I
-
-
-
-
PLATEN DISPLACEhtNT RATE
-
0 - 2.5 x mmls
-
A---
1.2 x mmls 0-- -
- - -
-
-
2.5 x mmls-
t I \ LOAD. kNFigure 5. Loading
system stiffness
with compliant
platens as a
function of load and
platen displacement
rate, CT 405 test
machine at -15OC
D i r e c t a p p l i c a t i o n of l o a d i n g system s t i f f n e s s t o t h e
i n t e r p r e t a t i o n of t h e s e test r e s u l t s i s beyond t h e scope of t h i s paper. It may b e seen, however, t h a t f o r a g i v e n nominal s t r a i n r a t e a s t i f f e r l o a d i n g system w i l l impose h i g h e r s t r e s s r a t e s on
a specimen. T h i s c o u l d e x p l a i n t h e h i g h e r s t r e n g t h s measured f o r prism specimens on s t e e 1 p l a t e n s ( h i g h l o a d i n g system s t i f f n e s s ) t h a n f o r c y l i n d r i c a l specimens on compliant p l a t e n s (low l o a d i n g system s t i f f n e s s ) a t a g i v e n nominal s t r a i n r a t e of
2 x 10-4 s'l.
ACKNOWLEDGEMENTS
The a u t h o r s would l i k e t o thank Gulf Resources Canada and Dome Petroleum f o r t h e o p p o r t u n i t y t o perform t h e s e experiments. The l o g i s t i c s , t r a n s p o r t a t i o n and accommodation provided made t h e t e s t program p o s s i b l e . The a s s i s t a n c e of J. N e i l i n r e d u c i n g t h e d a t a and Mohamed Sayed i n d e t e r m i n i n g t h e t e s t system s t i f f n e s s
i s g r a t e f u l l y acknowledged. 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 b o t h t h e D i v i s i o n of B u i l d i n g Research and D i v i s i o n of Mechanical Engineering, N a t i o n a l Research C o u n c i l Canada.
REFERENCES
.l. IAHR Working Group on S t a n d a r d i z i n g T e s t i n g Methods i n I c e , S t a n d a r d i z e d T e s t i n g Methods f o r Measuring Mechanical
P r o p e r t i e s of I c e . J o u r n a l of Cold Regions S c i e n c e and
-
Technology 4(1981), pp. 245-253.2. Sinha, N.K., F i e l d t e s t 1 of compressive s t r e n g t h of f i r s t - y e a r s e a i c e . P r e s e n t e d t o Second Symposium on Applied G l a c i o l o g y , West Lebanon, N.H., 1982. To be p u b l i s h e d i n Annals of Glaciology.
3. Timco, G.W., and F r e d e r k i n g , R., Confined compressive s t r e n g t h of s e a i c e . The 7 t h I n t . Conf. on P o r t and Ocean
: Engineering under A r c t i c C o n d i t i o n s (POAC). H e l s i n k i 1983.
~4.
Timco, G.W., and F r e d e r k i n g , R., F l e x u r a l s t r e n g t h andf r a c t u r e toughness o f s e a i c e . Accepted f o r p u b l i c a t i o n i n J o u r n a l of Cold Regions S c i e n c e and Technology 1982.
5. Weeks, W.F., and Assur, A . , The mechanical p r o p e r t i e s of s e a i c e . Hanover, 1967. CRREL (Cold Regions Research and
Engineering L a b o r a t o r y ) Cold Regions S c i e n c e and E n g i n e e r i n g Monograph, P t . 2, Sec. C3.
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