Evolution of Dynamic Properties of Cross-Anisotropic Sand Subjected to Stress Anisotropy

Understanding the evolution of dynamic properties of sand subjected to induced anisotropy is indispensable for an accurate seismic analysis of geostructures. In this study, several bender element and hollow cylinder experiments along various anisotropic stress paths are performed on two types of sands to evaluate the soil dynamic properties over a wide range of small to large strain levels. Accordingly, the influences of both the major principal stress direction (α-direction) and the intermediate principal stress, b=(σ2-σ3)/(σ1-σ3), are examined. The data suggested that α-direction affects both stiffness and damping ratio, especially at higher confining pressures. However, b-parameter has little influence on stiffness and a fairly negligible impact on damping ratio. Based on the experimental results, an empirical model published in the literature is extended by introducing correction factors so as to incorporate the significant contribution of induced anisotropy into the predictions of shear stiffness and damping ratio of sands.