Hypoplastic Modeling of Anisotropic Sand Behavior Accounting for Rotation of Principal Stress Direction

Abstract

The rotation of the principal stress direction has a significant influence on the stress–strain relation and deformation characteristics of sand. This study proposes a hypoplastic model to simulate the noncoaxial response of anisotropic sand subjected to the rotation of the principal stress direction. The densification effect of sand is considered through a properly defined function, enabling the model to simulate a gradually stabilized strain accumulation upon rotational shearing. A fabric tensor is used to describe the anisotropic microstructure of sand, and worked in conjunction with the stress in the form of a joint invariant–based state variable to simulate the impact of fabric anisotropy on the behavior of sand. The fabric tensor is integrated with the hypoplastic flow direction, making the model capable of generating a noncoaxial response. The model response was compared with the experimental data for rotational shear tests under various conditions.