A soil freezing-thawing model based on thermodynamics

Abstract

The freezing-thawing behavior of soil plays a crucial role in frozen soil engineering. In this study, a soil freezing-thawing model is proposed from the perspective of statistical thermodynamics. First, the phase equilibrium relation for pore ice-water interface is deducted by applying statistical thermodynamics and the theoretical relationship is defined between the freezing temperature (i.e., the temperature at the ice-water interface) and the potential energy (i.e., total suction) of pore-water. This relation reveals that the matric suction of pore-water solely depends on the negative temperature at the pore ice-water interface for a given soil with constant osmotic suction and air pressure. Further, using the aforementioned relation and regarding the ice content of soil as an unknown variable, the thermo-hydraulic field in the soil freezing-thawing process can be solved by the mass and heat conversation. The governing equations related to this model are proposed in detail. Finally, to enhance the applicability of the proposed model, simplified forms in three typical conditions are provided, including the freezing process of saturated soil in artificial ground freezing technique, the capillary water migration coupled with freezing process of unsaturated soil in subgrade engineering and the vapor migration coupled with freezing process of semidry coarse soil under airport runways. Overall, the proposed model can be applied to various conditions and to other types of porous media (such as rock or concrete) that undergo freezing-thawing processes.