Rotational hardening with and without anisotropic fabric at critical state

The question of zero or non-zero anisotropic fabric at critical state for clays is a debatable issue. The present note addresses a way to model either eventuality by proposing a novel rotational hardening rule for clay plasticity constitutive modelling. Various conditions are derived on the model constants such that some basic requirements are satisfied, among them the uniqueness of the critical state line and prevention of excessive rotation of the plastic potential and yield surfaces in stress space. Schematic and real data simulations illustrate the performance of the new rotational hardening rule.