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Partially drained response of sands Gananathan, Nadarajah

Abstract

This study was carried out to improve our understanding of the behaviour of sands under different drainage conditions, especially the partially drained condition. The influence of aging on the stress-strain response of sands was also considered. The study was performed on two different sands, a Fraser River sand and a North Sea sand. As such, objectives of this study are (a) the effects of drainage conditions, (b) the partially drained response and (c) the influence of aging on the stress-strain response of sands. Identical soil specimens were aged under constant stresses for 1, 100 and 1,000 minutes and then sheared under undrained or partially drained conditions. Effects of the aging period on the stress-strain response were studied at k0 conditions and at different values of confining stress. A constant period of aging of 100 minutes was selected for the main laboratory program of tests. The shear response of aged (100 mins) sands, under drained and undrained conditions, was examined. Although aging positively influences the shear response of sands, in that shear strength increases, the general behaviour regarding the effect of confining stress and stress ratio is found to be the same. The effect of small imposed volumetric strains on the shear response of aged (100 mins) sands was studied. Imposed expansive volumetric strains negatively influence the shear response whereas the contractive strains influence positively. Certain imposed expansive volumetric strains results in continuous strain softening. Even though sands continuously strain soften for certain imposed expansive volumetric strains, the effect of confining stress and stress ratio are seen at small strain levels. The material with higher stress ratio and lower confining stress start to strain soften at smaller strain levels.

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