It is widely known that the principal stress directions rotates in foundations subjected to the cyclic loading due to wheel traveling, tidal wave, earthquake, etc. Besides, it has been indicated that the direction and the magnitude of inelastic deformation of soils depend on the stress rate much more than those predicted by elastoplastic constitutive equation with the smooth plastic potential surface. In this article the deformations in test results for sands subjected to the principal stress rotation process keeping the magnitudes of principal stresses and to the stress rates with various directions are predicted appropriately by the subloading surface model with the anisotropy due to the rotation of yield surface and the tangential stress rate effect which lead to the non-coaxiality of directions of inelastic strain rate and stress.
