Numerical Modelling of desiccation processes in clayey soils

Desiccation processes in clayey soils involve a gradual moisture content loss induced by evaporation from the soil surface. The desiccation process, mainly governed by very nonlinear hydraulic properties, has an influence on the mechanical behaviour of the soil because the material tends to shrink, thus inducing changes in the stress fields. To understand this process one needs to solve the coupled hydraulic-mechanical problem. In this paper, the formulation (including the unsaturated soil equilibrium and the mass balance equations) and some initial results of a numerical finite element code that solve the boundary value problem are presented. The state variables used in the model are the net stress (total stress) and the suction (negative pore water pressure). For the mechanics part, a non-linear elasticity model based on the state surface concept is chosen, while for the hydraulics problem, Darcy’s law, including unsaturated flow, is used. To relate negative pore water pressure to the degree of saturation the van Genuchten equations are used.