Modeling evaporation, shrinkage and cracking of desiccating soils
Room temperature drying tests on silt slurry with free and constrained boundaries, reveal an initial phase with a significant shrinkage at full saturation. Hence, this shrinkage is linked to a mass loss of pore fluid through the external boundary. Shrinkage in the unsaturated phase is much smaller. A simultaneous porosimetry reveals a bi-modal pore size distribution with a distinct evolution. In a microscopic model a bundle of deformable capillary vessels represent the modal size pores. Larger mode pores dominate the deformation, the smaller ones contributing little. A transition to an unsaturated phase occurs when the negative pore fluid pressure at the vessel exit reaches the pressure of fluid cavitation in large, then small vessels. Further desaturation is a result mainly from migration of the evaporation interfaces. Cracking arises due to an excess of radial tensile stress due to aconstrained kinematics, which is three times higher than during free drying.
