Measurement and correlations of <i>K</i> and <i>V</i>s anisotropy of granular soils

Abstract

The coefficient of lateral earth pressure at rest (K0) and stress-dependent shear wave velocity (Vs) of granular soils under one-dimensional compression loading were measured using a modified floating wall consolidometer-type bender element testing system. The Vs of the granular soils was monitored through paired bender elements installed in the floating wall and on top and base platens, and the Vs anisotropy of the soils was investigated by comparing the Vs values in three orthogonal directions. Granular materials such as glass beads (GB) and Ottawa sand with different shapes and sizes were adopted and the effects of particle shape and size and stress level on K0 and Vs anisotropy were discussed. From the laboratory observations, K0 was found to be dependent on the particle shape and surface roughness. The anisotropic stress state was found to play a major role in governing the Vs anisotropy of the GB; however, the Vs anisotropy of the sand resulted from the inherent geometry/fabric anisotropy and manifested by the anisotropic stress state. In addition, the degree of cross-anisotropy was defined and used to evaluate the cross-anisotropic properties of the geomaterials.