An anisotropic hardening rule for saturated clays

Abstract

The anisotropic hardening rule employs ϵ ij p as a hardening parameter rather than volumetric plastic strain ϵ v p (= ϵ ii p) , that is commonly used in geomechanics. Generalization of hardening in this manner provides a mechanism to take account of multiaxial response essential for modeling stress anisotropy. The ϵ ij p operates via the reference stress tensor, σ ij 0 , that retains the memory of the stress history and defines the yield function. As a state variable tensor, σ ij 0 is a dynamic quantity. The yield surface therefore can simultaneously expand, translate, and rotate in the principal stress space during loading, thereby providing a complete description of anisotropic behavior: inherent and induced anisotropy as well as changes in the degree of anisotropy as a part of updating stress history. The paper describes the model and compares its predictions with the field and laboratory test results to demonstrate the enhancements afforded by the anisotropic hardening over isotropic hardening.