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

David Masin

ABSTRACT: 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.

Key words : clays, constitutive relations, elasto-plasticity, hypoplasticity, structure of soils (IGC: E13)