A novel model of heat-water-air-stress coupling in unsaturated frozen soil

The accurate prediction of frost heave in unsaturated frozen soil is crucial for the construction and protection of projects in cold regions. The occurrence of frost heave in unsaturated frozen soil is accompanied by an extremely complicated process of heat and mass transfer, which is closely related to the temperature gradient, water migration, air transfer, latent heat, deformation, overburden pressure, and so on. Based on thermodynamics and continuum mechanics, a comprehensive coupling model is proposed to describe the temperature variation and liquid water/vapor redistribution in unsaturated frozen soil. The Clapeyron equation was used to establish the relationship between the ice pressure and the water pressure during phase equilibrium. The initial water content of the frost heave, frozen fringe, and consolidation compression deformation are also introduced into the model to calculate the frost heave in unsaturated frozen soil. The proposed model was validated through a comprehensive experiment wherein a unidirectional freezing test was performed on a soil column in a closed system in our lab. The well-known experiment conducted by Mizoguchi and the simulation of this test by other study were also considered to validate the feasibility and adaptability of the model. The results reveal that the temperature variation, total water content distribution, and frost heave obtained by the proposed model are consistent with the measurement results.