COMPARISON OF PREDICTIVE CAPABILITIES OF SELECTED ELASTO-PLASTIC AND HYPOPLASTIC MODELS FOR STRUCTURED CLAYS

This paper compares different approaches to constitutive modelling of natural structured clays by means of experimental data on natural Pisa and Bothkennar clays. The models evaluated are a hypoplastic model for structured clays, its simple elasto-plastic equivalent that requires parameters with similar physical meaning, and advanced elasto-plastic models based on kinematic hardening approach. Hypoplasticity predicts non-linear stress-strain response in the pre-failure region and different stiffness in different loading directions, it thus provides a clear qualitative advance with respect to the simple elasto-plastic model. It gives qualitatively similar predictions with the kinematic hardening models. The structure degradation and the large-strain response are predicted similarly by both the hypoplastic and elasto-plastic models, which show that the critical state soil mechanics theories can be treated successfully within the framework of the theory of hypoplasticity.