Abstract
A series of triaxial compression tests is carried out on the unsaturated silty kaolin clays. Specimens are subjected to undrained compressive shear under the conditions of constant air pressure. The pore water pressure and volume change during shear are monitored. The pore water pressure develops with compression and then turns to decrease with expansion when the degree of saturation is relatively high. On the contrary to it, when the degree of saturation is low, the pore water pressure monotonically increases independent of volume change. These experimental facts can be explained from the effects of the bulk stress. Thus, throughout experimental investigations, it is revealed that the behaviors of unsaturated soils are consistently explained in terms of the meniscus and the bulk stresses. Particularly, it is found that the failure criterion on unsaturated soils can be uniquely described using the suction stress, which is defined as the summation of meniscus and bulk stresses.
