A model of soils freezing with allowance for freezing zone

The solution of the moving-boundary problem, related to heat- and mass-transfer processes in freezing the fine-grained porous media is presented. It is assumed that a freezing zone, characterized by a wide temperature range of phase transitions, is formed. Therefore a three-zone model is developed. The preservation of the relaxation terms ∂I/∂t (I is the ice content) in the system of equations has made it possible to determine the ice distribution within the frozen and the freezing zones. For loamy soils the dependence of the freezing process on the characteristic parameters – Stefan and Lewis numbers, was analyzed. It was found that increasing the enthalpy of phase transition resulted in diminution of the frozen zone. Intensification of the migration process led to increasing the ice content and, consequently, the total moisture (including ice). When the water migration process is absent, in the course of freezing the redistribution takes place only between moisture and ice contents. The total moisture remains constant and equal to the initial water content. It is also shown that in coarse-grained soils (such as sand) the freezing zone is not formed. The theoretical conceptions and results derived from the solution are in agreement with experimental investigations.