2017 Volume 73 Issue 2 Pages 233-247
It is well known that partially saturated soils show higher strength and stiffness due to suction which works at meniscus water, however, they also exhibit more brittle failure with relatively large strain softening as well as clear shear bands than fully saturated soils and dry soils. It is important to understand the mechanism of brittle failure of partially saturated soils by investigating relation between macroscopic mechanical behavior and three-phase microstructural change such as progressive changes in suction and distribution of meniscus water with development of shear bands. In the present study, shear bands region generated in triaxial compression test of partially saturated sand specimen was observed by x-ray computed tomography. Image analysis provided the curvature, retention states and the number of pore water in order to evaluate the contributions of suction and meniscus water to the deviator stress. It was found that variation in suction due to the development of shear bands is very small. It was also found that relatively large number of meniscus water exists during strain hardening, while the decrease in the number of meniscus water seems to be one of the reason to cause strain softening. It seemed that lower number of meniscus water exists inside shear band so that the contribution to deviator stress is smaller than outside shear bands.