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Testing ice in the High Arctic
Ser
TH1
,,,,
c
National Research
Conseil national
Council Canada
de recherches Canada
no.
1118
c . 2TESTING ICE I N THE HIGH ARCTIC
by
N.K. Sinha
Appeared in
Proceedings of the 9th. Canadian Congress of
Applied Mechanics (CANCAM 83)
University of Saskatchewan, Saskatoon, Sask.,
May 3 0
-
June 3,1983
p. 899
-
900
Reprinted with permission
DBR Paper No. 11 18
Division of Building Research
This publication i s being distributed by the Division of
Building Research of the National Research Council of Canada. I t should not be reproduced in whole or in p a r t
without permission of the original publisher. Tha Di-
vision would be glad to be of assistance in obtaining such permission.
Publications of the Division may be obtained by mail- ing the appropriate remittance (a Bank, Express, o r Poet Office Money Order, o r a cheque, made payable to the Receiver General of Canada, c r e d i t NRC) to the
National Research Council of Canada, Ottawa. K1A OR6.
Stamps a r e not acceptable.
A l i s t of allpublications of the Division i s available and may be obtained f r o m the Publications Section, Division of Building Research, National Research Council of Canada, Ottawa. KIAOR6.
ABSTRACT
The paper d i s c u s s e s t h e procedures u s e d f o r
s t r e n g t h a n d d e f o r m a t i o n s t u d i e s o f s e a i c e ,
and
t h e extremely c o n s i s t e n t f i e l d r e s u l t s o b t a i n e d
i n
t h e High A r c t i c .
Emphasis
i s
on t h e l o v i n
c a r e t o be g i v e n t o specimen p r e p a r a t i o n .
Cette
6 t u d e p o r t e s u r l e s m6thodes u t i l i s ' e e s
d a n s
les t r a v a u x de r e c h e r c h e p o r t a n t s u r l a
r g s i s t a n c e e t l a dgformation d e l a g l a c e marine
e t
l e s r b u l t a t s e x t r b e m e n t homoghes o b t e n u s
dans l e Haut Arctique.
L ' a c c e n t e s t
m i s
s u r
l ' a t t e n t i o n t o u t e s p 5 c i a l e q u ' i l f a u t a p p o r t e r
3
T e s t i n g i c e i n t h e High A r c t i c D r . N.K. S i n h a Geotechnical 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 Research N a t i o n a l Research Council o f Canada Ottawa, O n t a r i o K I A
OR^
The q u a l i t y o f i c e , i t s t h i c k n e s s , and t e m p e r a t u r e a r e e s s e n t i a l i n f o r m a t i o n i n s o l v i n g most e n g i n e e r i n g problems i n v o l v i n g f l o a t i n g i c e . S a l i n i t y , a i r p o r o s i t y , g r a i n s t r u c t u r e , and c r a c k s a r e important f a c t o r s determining i c e q u a l i t y and have been d i c t a t e d by p a s t a s w e l l a s p r e v a i l i n g c l i m a t o l o g i c a l c o n d i t i o n s . A l l i n f l u e n c e b o t h p h y s i c a l c h a r a c t e r i s t i c s and mechanical p r o p e r t i e s . It i s d i f f i c u l t , and o f t e n i m p o s s i b l e , t o o b t a i n such i n f o r m a t i o n f o r d e s c r i b i n g t h e p h y s i c a l s t a t e o f a f l o a t i n g i c e b l o c k o r an i c e s h e e t . Most working t e m p e r a t u r e s w i t h i c e a r e , i n r e a l i t y , v e r y h i g h a s f a r a s i t s m a t e r i a l r e s p o n s e s a r e concerned because t h e working t e m p e r a t u r e s a r e s o c l o s e t o i t s melt- i n g p o i n t . High t e m p e r a t u r e deformation and f a i l u r e mechanisms p l a y a dominant r o l e i n i c e mechanics, and r a t e s e n s i t i v i t y o f s t r e n g t h a n d . o t h e r mechanical p r o p e r t i e s become p r e - dominant. The t e s t c o n d i t i o n s a r e complicated f u r t h e r by t h e f a c t t h a t n e i t h e r t h e e x p e r i - mentor n o r most e x p e r i m e n t a l t o o l s a r e "comfort- a b l e " a t t h e sub-zero ambient t e m p e r a t u r e s r e q u i r e d i n any s t u d i e s o f i c e . I n s p i t e o f e x t e n s i v e e f f o r t s i n l a b o r a - t o r i e s and i n t h e f i e l d t o overcome t h e s e t e c h n i c a l d i f f i c u l t i e s i n i n v e s t i g a t i n g s t r e n g t h and deformation q u a l i t i e s o f i c e , d i s c r e p a n c i e s i n t h e r e s u l t s a r e s t i l l t o o l a r g e . There i st o o much s c a t t e r , and t h e r e i s t o o much d i s - agreement among d i f f e r e n t s e t s o f r e s u l t s . There i s t h e r e f o r e a requirement t o develop b e t t e r t e c h n i q u e s f o r t e s t i n g i c e , b o t h i n t h e c o n t r o l l e d environment o f t h e well-equipped l a b o r a t o r y , and under t h e a d v e r s e c o n d i t i o n s encountered i n t h e f i e l d .
The a u t h o r t w i c e s p e n t a month a t t h e High A r c t i c Weather S t a t i o n a t Mould Bay,
P r i n c e P a t r i c k I s l a n d , N.W.T. ( 7 6 O ~ ; 1 1 9 ° 2 0 ' ~ ) , i n September-October 1981 and i n June-July 1982. Both t r i p s were made on b e h a l f o f a Canada-U.S.A. j o i n t program known a s t h e R a d a r s a t I F i r e x P r o j e c t . The primary o b j e c t i v e s were t o determine micro- wave p r o p e r t i e s o f f i r s t - y e a r and m u l t i - y e a r s e a i c e i n n a t u r a l c o n d i t i o n s i n t h e A r c t i c , i n f o r - mation t h a t was t o be a p p l i e d i n a remote-sensing s a t e l l i t e . Extensive ground-truth o b s e r v a t i o n s were c a r r i e d o u t t o determine 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 o f t h e v a r i o u s t y p e s o f i c e encountered and u l t i m a t e l y t h e i n v e s t i g a t i o n s were extended t o i n c l u d e t h e mechanical proper- t i e s o f t h e s e t y p e s o f i c e a s w e l l . Observations were made on r a t e s e n s i t i v i t y o f u n i a x i a l , un- c o n f i n e d compressive s t r e n g t h of f r e s h l y recov- e r e d f i r s t - y e a r s e a i c e from Mould Bay and m u l t i -
y e a r s e a i c e from a l a r g e f l o e o f about 1 5 km
d i m found n e a r t h e j u n c t i o n o f C r o z i e r Channel and McClure S t r a i t .
The t e s t s were conducted i n a p o r t a b l e
room on t h e s h o r e of Mould Bay. A commercial t e s t machine ( S o i l t e s t ~ ~ 4 0 5 ) designed f o r a l o a d c a p a c i t y o f 50 kN was used. Large p r i s - matic samples 50 x 100 x 250 mm were used t o t e s t i c e o r i e n t e d h o r i z o n t a l l y w i t h r e s p e c t t o t h e i c e cover. The samples were c a r e f u l l y machined w i t h r e s p e c t t o t h e o r i e n t a t i o n s o f t h e g r a i n s . T e s t s were conducted o v e r a wide range o f displacement r a t e s and t e m p e r a t u r e s , l o a d was determined by a c a l i b r a t e d l o a d c e l l , and s t r a i n was measured i n t h e c e n t r a l a r e a o f t h e specimens, away from t h e end p l a t e n s , w i t h a p a i r o f s p e c i a l l y designed d e v i c e s ( 1 ) mounted d i r e c t l y on t h e specimens ( F i g . 1 ) .
The r a t e s e n s i t i v i t y o f s t r e n g t h , o r t h e maximum s t r e s s , was analyzed on t h e b a s i s o f average s t r e s s r a t e a s w e l l a s t h e average s t r a i n r a t e t o peak s t r e s s because o f e a r l i e r s u c c e s s i n p r e s e n t i n g r e s u l t s i n t h i s manner ( 2 ) . Time and s t r a i n a s p e c t s o f t h e t e s t r e s u l t s i n d i c a t e d t h a t extremely c o n s i s t e n t r e s u l t s can a l s o be o b t a i n e d under f i e l d c o n d i t i o n s . References ( 1 ) S i n h a , N.K. (1981) Rate s e n s i t i v i t y o f com- p r e s s i v e s t r e n g t h o f columnar-grained i c e . Experimental Mech. 2 1
( 6 )
p. 209-219. ( 2 ) S i n h a ,N.K.
(1982) Constant s t r a i n - and s t r e s s - r a t e compressive s t r e n g t h o f columnar- g r a i n e d i c e . J. M a t e r i a l s S c i e n c e , 1 7 ( 3 ) , p. 785-802. S T R E S S vs S T R A I N T r r t Y 35 B 80 oC M o u l d Bey. J u n r 1992 l o r t y p o . F i r r t Y r o r S r a I o r . H o r i r o n t o l S r o t i o m R a t - S - t t i n g m 3. 0 T - m p r r a t u r r a -18 'C F i g . 1 S t r e s s - s t r a i n r e l a t i o n s h i p s o b t a i n e d on h o r i z o n t a l l y o r i e n t e d samples o f f i r s t - y e a r s e a i c e from Mould Bay, w i t h t h e i r l o n g a x i s p a r a l l e l and 45O t o t h e d i r e c t i o n o f t h e t i d a l w a t e r c u r r e n t i n t h e Bay. Both t e s t s were performed under t h e same900 cross-head displacement r a t e . A 0
