Acta Polytechnica Hungarica Vol. 8, No. 4, 2011 – 91 – A Fully-coupled Thermo-Hydro-Mechanical Model for the Description of the Behavior of Swelling Porous Media Hanifi Missoum, Nadia Laredj, Karim Bendani, Mustapha Maliki Construction, Transport and Protection of the Environment Laboratory (LCTPE) Université Abdelhamid Ibn Badis de Mostaganem, Algeria hanifimissoum@yahoo.fr, nad27000@yahoo.fr, bendanik@yahoo.fr, mus27000@yahoo.fr Abstract: Although many numerical models have been proposed for unsaturated porous media, unrealistic assumptions have been made, such as the non-deformable nature of media, constant material properties, the neglecting of convection heat flow transfer, and static air phase. Most of these conditions are not justifiable for porous media with low hydraulic permeability and high swelling activity. In the present article, a fully coupled thermo-hydro-mechanical model is proposed that takes into account nonlinear behavior, including both the effects of temperature on dynamic viscosity of liquid water and air phase, and the influence of temperature gradient on liquid and air flows. Fully coupled, nonlinear partial differential equations are established and then solved by using a Galerkin weighted residual approach in space domain and an implicit integrating scheme in time domain. The obtained model is finally validated by means of some case tests for the prediction of the thermo-hydro-mechanical behaviour of unsaturated swelling soils. Keywords: multiphase flow; water transfer; unsaturated porous media; finite element; conservation; simulation 1 Introduction Swelling porous materials are commonly found in nature as well as developed in industry. They are studied in many disparate fields including in soil science, in hydrology, in forestry, in geotechnical, chemical and mechanical engineering, in condensed matter physics, in colloid chemistry and in medicine. This article specifically focuses on unsaturated swelling clays, which are widely distributed in nature. In agriculture, water adsorption by the clay determines the ability of soils to transport and supply water and nutrients. Compacted bentonites play a critical role in various high level nuclear waste isolation scenarios and in barriers for