Abstract
The purpose of this paper is to explain the shear behavior of sand under various three-dimensional stress paths. In the stress-strain model under shear proposed here, the direction of strain increments is analyzed by considering the sliding mechanism on a spherical surface in the principal value space of the mechanical quantity tij which has been introduced to describe uniquely soil behavior in three-dimensional stresses. The magnitude of strain increments is calculated with reference to the idea by Prévost where the properties of isotropic and kinematic hardenings in plasticity are combined. The validities of this model are then confirmed by the true triaxial tests on Toyoura sand not only under radial straight stress paths on the octahedral plane but also under rotational stress paths that the direction of shear stress on the octahedral plane is changed continuously.
