Modeling Evaporation, Shrinkage and Cracking of Desiccating Soils

ABSTRACT: 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 a constrained kinematics, which is three times higher than during free drying.