Critical state models for cyclic loading of K(o)-consolidated clay

An anisotropic critical state model for monotonic and cyclic loading of Ko-consolidated clay is presented, based on extension of an existing model. First, the performance of two existing critical state models is evaluated for anisotropic and cyclic loading. The first model is based on isotropic hardening, which incorporates a reduction of the yielding surface during elastic unloading in order to simulate a real soil behavior under cyclic loading. The second critical state model combines isotropic hardening with kinematic hardening, and is based on a two-surface concept. The proposed model adopts the two-surface concept, consisting of the consolidation surface and the inner yield surface, and the combined isotropic and kinematic hardening laws. To account for the effects of the anisotropy induced by the initial consolidation stage, the proposed model introduces a rotation of the consolidation and inner yield surface. The behavior of the new model is illustrated through numerical parametric investigations and comparisons with a limited number of existing test data