A. Ayoubian et Pk. Robertson, VOID RATIO REDISTRIBUTION IN UNDRAINED TRIAXIAL EXTENSION TESTS ON OTTAWA SAND, Canadian geotechnical journal (Print), 35(2), 1998, pp. 351-359
Water-pluviated samples of Ottawa sand were tested in monotonic, undra
ined triaxial extension tests. The specimens exhibited similar ''limit
ed strain softening'' behavior, and they all experienced phase transfo
rmation from contraction to dilation at small axial strains. The tests
were stopped at different stages and the samples were frozen to obtai
n void ratio distribution along the length of the specimens. It was sh
own that void ratio redistribution can start at very low axial strains
in an undrained triaxial extension test. Before phase transformation,
void ratio redistribution was very small, but after phase transformat
ion void ratio redistribution started rapidly and continued until the
end of the tests at ultimate state. The location of the ultimate state
line in a void ratio - mean normal effective stress plot was shown to
be affected by localized failure at large strains in undrained triaxi
al extension tests. The actual ultimate state line with respect to voi
d ratios and effective stresses within the failure zone in the samples
can be located above the average ultimate state line obtained from av
erage measurements of void ratios and effective stresses of the entire
specimens.