Resumen de Thermo-hydro-mechanical coupled analysis in low permeability media
Thermo-Hydro-Mechanical (THM) analysis of engineering problems involving low permeability materials is a complex problem in which several factors make significant contributions. This Thesis is aimed mainly to the study of coupled THM process in engineered clay barriers and seals designed for the isolation of radioactive waste. Therefore, special attention has been placed on expansive clay behaviour. In the last few years, several laboratory investigations have shown the strong influence of pore structure on THM behaviour of swelling materials. Therefore, a main objective of this Thesis is the proposal of a THM framework which allows the inclusion of the effects of the material fabric on the analyses of real problems in geological media.
A general double structure THM formulation developed for porous media in which two distinctive types of voids are present has been proposed. This formulation expresses in a mathematical way the various THM phenomena deemed relevant in each structural level, and their main interactions. Concepts of double porosity theory have been used to extend a fully coupled THM single porosity formulation to the case of double structure media. The approach is able to handle non-saturated, non-isothermal multiphase flows coupled with the deformations of each medium. A central part of the approach is the mechanical constitutive law, a key point in the modelling of the expansive clay behaviour. The existence of two structural levels (a macrostructural one and the microstructural one) has been explicitly included in the model.
The macrostructure accounts for the large scale structure of the material, while the microstructure is associated with the active clay particles responsible for the swelling behaviour. The mechanical law is completed by establishing the interaction between the two structural levels. The model has been formulated using concepts of elasto-plasticity for strain hardening materials and generalized pl
