Résumé
The results of this research concern three aspects:<br />The theoretical aspect (part I) presents a general modelling of thermo-hydro-mechanical behaviour of unsaturated soils. The description takes into account skeleton deformation, liquid and gas phase's filtration, vapour diffusion, heat conduction and liquid-vapour phase change. This modelling is used to describe the water transport in unsaturated soils by favouring the three phenomena of liquid filtration, vapour diffusion and liquid-vapour phase change. <br />The instrumental aspect (part II) concerns the realization of sorption device and Richard's cell in temperature. These materials allow to realize desaturation experiments and to determine soil-water characteristic curve. Another aspect concerns the development of a thermal triaxial apparatus by adding a specific instrumentation more adapted to study the thermo-hydro-mechanical behaviour of unsaturated soils.<br />The experimental aspect is double. The first (part III), concerning desaturation study and characteristic curve determination of a plastic clay and a clayey silty sand at 20°C and 60°C, allows to determine a liquid phase transport coefficient. The second (part IV) is related to the representation of yield surfaces in the case of unsaturated clayey silty sand at different temperatures. This yield surface presents a thermo-extensive nature of which a modelling and a physical interpretation are proposed.