ABSTRACT
S t r e s s c r a c k i n g i s d e f i n e d by ASTM as "an e x t e r n a l o r i n t e r - n a l r u p t u r e i n a p l a s t i c caused by a t e n s i l e s t r e s s l e s s than i t s s h o r t - t e r m m e c h a n i c a l s t r e n g t h " . For geomembranes t h e r e are a number o f p o s s i b l e c o n t r i b u t o r s t o t h i s u n d e s i r a b l e phenomenon:
• e f f e c t s o f s u r f a c e w e t t i n g agents (e.g., e n v i r o n m e n t a l s t r e s s c r a c k i n g )
• e f f e c t s o f r e s i d u a l s t r e s s • s t r e s s c r a c k s o r i g i n a t i n g from s c r a t c h e s o r o t h e r
d e f e c t s • s t r e s s c r a c k s o r i g i n a t i n g from i r r e g u l a r geometry • f a t i g u e , o r c y c l i c , i n d u c ed c r a c k i n g • combinations o f the above
While not e x c l u s i v e l y the case, the above mechanisms o f t e n o c c u r at geomembrane f i e l d seams. Here, l i q u i d s are i n cont a c t w i t h the s u r f a c e , r e s i d u a l s t r e s s e s o f t e n occur due t o the extreme h e a t i n g and r a p i d c o o l i n g , g r i n d marks are o f t e n p r e s e n t due t o s u r f a c e b u f f i n g t o remove o x i d e l a y e r s , t h e geometry c r e a t e s s t r e s s r a i s i n g v i a a l o a d e c c e n t r i c i t y , and th e r m a l s t r e s s e s due t o temperature expansion and c o n t r a c t i o n can oc c u r .
