A deviatoric softening law for predicting the deformation of soft clays subject to anisotropic consolidation

ABSTRACT: The well-known Modified Cam-Clay (MCC) family of models employ an isotropic hardening law, where the size change of yield locus is governed only by plastic volumetric strain increment or decrement. However, reviewing the incremental anisotropic consolidation tests performed on soft clays at various stress ratios reveals the presence of deviatoric softening (DS). The anisotropic consolidation tests applied with higher stress ratios tend to result in higher compressibility of the investigated clays. This indicates that the deviatoric strain can cause the yield surface to contract. To address this issue, the volumetric hardening law has been modified to incorporate soil softening owing to plastic deviatoric strain increment. This new DS law is easy to implement and requires only one additional parameter to govern the yield surface contraction. The new DS model has incorporated this DS law into the rotational anisotropic hardening law of S-CLAY1. The model has been verified through simulations of a number of incremental anisotropic consolidation tests collected from the literature. It is demonstrated that the modified softening law can provide an improved prediction of deformation of soft clays subject to the anisotropic consolidation tests under different stress ratios.