Modelling the THM behaviour of unsaturated expansive soils using a double structure formulation

Paper presented at the 2nd International Conference on Unsaturated Soils. The study of Thermo-Hydro-Mechanical (THM) problems in porous media is generally dealt with assuming that they possess a continuous distribution of one type of voids. However, there are some media in which for a proper handling of the problem, it is crucial to consider the different structural levels involved in the material fabric. This work presents a coupled THM formulation developed to handle problems in porous media with two dominant structures of voids. The formulation is especially suitable for cases in which the material exhibits a strong coupling between the mechanical and hydraulic problem in both media. In its more general form, the proposed formulation allows the consideration of non-isothermal multiphase flows in both media, coupled with the mechanical and the thermal problems. Special attention has been placed on the mechanical constitutive model for non-saturated expansive clays. The double structure approach has been implemented in a finite element code and it has been used to analyze a variety of problems