Abstract
The study presented in this thesis focuses on an experimental/numerical analysis of physical properties (densities, porosity, particle size distribution) and hydrodynamic properties (desorption isotherm, soil-water characteristic curve, saturated and unsaturated permeabilities) of an arid soil from Burkina Faso and numerical simulation of water flow. The flow model is addressed through thermodynamic approach which provides a general framework to describe both the water state in the soil and the transport mechanisms : filtration of liquid, water vapor diffusion, liquid/vapor phase change. Experimental attempts of water flow in soil columns, sealed and placed into a controlled temperature chamber, have established the evolution of water content profiles over time. The experimental configuration is chosen so that only the water liquid phase filtration is taken into account. These experimental profiles were used to estimate, by inverse approach, the unsaturated permeability of soils at low water contents. Consideration of film flows in the relative permeability modelling corrects the shortcomings of capillary bundle models used to describe water flow from saturation to oven-dryness. The coefficients of phase change near and far from equilibrium modeled from experimental results prove non-equilibrium liquid/gas existence. It appears that the liquid/gas non-equilibrium at low water content is more pronounced with the capillary model with a frank drying front at the soil surface. Consideration of film flows extends liquid phase filtration into the soil until the hygroscopic state with a liquid water flux maintained at the soil surface for longer times.