Review of the coupling of water and heat in the freeze-thaw process and its model of frozen soil

The coupling of water and heat in the freeze-thaw process is an important part of the hydrological cycle in cold regions, and it is an urgent problem that needs to be solved in the fields of agriculture, construction, and ecology in cold regions. We analyzed the freezing-thawing process of frozen soils and water-thermal coupling mechanism. At present, the driving force of water migration is mostly attributed to the soil water potential gradient, with the soil water characteristic curve used to solve the problem. However, this method does not consider the soil temperature, deformation, and physical properties. The hydrothermal coupling model achieves the coupling between water, temperature, and stress, but the feedback mechanisms of the changes in water, temperature, and stress on the soil characteristic parameters are not reflected. The mechanism for ice formation, under the action of multiple fields, is the key to solve the problem of soil frost heave. Meanwhile, we discussed the applicability and accuracy of the three types of current mainstream coupling models: The hydrodynamic, rigid ice, and thermodynamic models. Finally, we analyzed the current problems in the study of hydrothermal coupling in the freeze-thaw process.