Characterization of cross-anisotropic soil deposits from isotropic compression tests

Abstract

Isotropic compression tests have been performed on two fine sands. Specimens of Nevada sand were prepared by air pluviation and by funnel deposition followed by tapping to relative densities of 30, 50, 70, and 90%. Specimens of Santa Monica Beach sand were prepared by air pluviation to a relative density of 90%. All specimens exhibited cross-anisotropic behavior, both in terms of total strains and in terms of unloading strains. Small pressure cycles performed during loading and unloading were used to study elastic behavior. The inclination angles of the total and plastic strain increment vectors relative to the hydrostatic axis in the principal stress space were used to express and to study the evolution of cross-anisotropy in the sand deposits. In the context of elasto-plastic constitutive modeling, the variation of the inclination of the plastic strain increment vector was further characterized by a rotation of the plastic potential surface as a means to capture the inherent cross-anisotropic behavior observed in such sand deposits.