Non-stationary anisotropy-dependent critical state for clays

In this paper, the effect of fabric anisotropy on the critical state behaviour of clays is investigated. An original concept of moving critical state is elaborated by a novel state parameter-based rotational hardening rule that is subsequently used to formulate a complete anisotropic elastoplastic constitutive model for clays. It is shown that some of the distinctive pre-failure and critical state responses of clays can be explained by adopting a non-stationary critical state line. Furthermore, an enhanced definition for the state of the soil is proposed that provides a more realistic correspondence between the shearing behaviour of an overconsolidated clay and its initial consolidation state. The proposed model is validated by simulating the experimental data from triaxial tests on a number of clays.