Inclusion of expansive clay behaviour in coupled thermo hydraulic mechanical models

This paper discusses the development of a model for the coupled flow of heat, moisture and air in expansive clays. In particular, the results of recent research work on the inclusion of expansive behaviour exhibited by some clays are presented. Initially, a fully coupled thermal/hydro/mechanical (THM) simulation of a heating experiment is presented. The observed THM behaviour in unsaturated soil was predicted by the model, with the best correlation found in the thermal field. The influence of the osmotic potential on the soil via the effect of chemical solute concentration is explored in a non-linear elastic constitutive relationship. The ability of such a model to represent the large strains that can occur during free swelling of expansive soils has been demonstrated. Finally, the representation of the development of irreversible strains within an expansive soil has been investigated via a double structure elasto-plastic relationship. The ability of such an approach to simulate the accumulation of plastic strains during wetting–drying cycles has been shown.