Numerical Modelling of Vapour-Ice Desublimation Process in Unsaturated Freezing Soils

Recent studies reveal that ice formation via vapour-ice desublimation in unsaturated freezing soils can lead to damage to infrastructures. Actually, the role of vapor flow in a freezing soils is unclear, and it is usually ignored when analyzing water migration process. In this study, a theoretical framework is established to formulate the coupled thermal and hydrological process, where the vapour diffusion governs the mass transfer process. The new model is designed to avoid using the local equilibrium assumption and the hydraulic relations that accounts for liquid water flow. This model contains 6 undetermined variables that are interacted in the 6 governing equations. In order to validate the numerical formulations/codes, a series of laboratory experiments are performed on a coarse sand which is not considered as frost susceptibility soil. The computed results show that the proposed model can indeed reproduce the unusual moisture accumulation observed in relatively dry soils, while the result agree well with the experimental date. This model provides an explanation for coupled movement of heat and moisture in cold and arid regions.