Hydrothermal Interaction Properties of Unsaturated Frozen Soil Studied Using a Modified Soil Freezing Characteristic Curve

Frost heave, which is related to the variation in the hydrothermal interaction properties of soil, is the main factor causing the inhomogeneous deformation of structures in cold regions. The relevant requirement for describing frost heave is to obtain the soil freezing characteristic curve, which contains fundamental information for describing the hydrothermal behavior of frozen soil. In this study, the unknown parameters of the van Genuchten equation and the hydraulic conductivity of partially frozen soil were indirectly derived using the pulsed nuclear magnetic resonance (P-NMR) technique based on the soil freezing characteristic curve and Clapeyron equation. Based on continuum mechanics, a hydrothermal coupling model combined with the unknown parameters obtained from a P-NMR experiment was applied to quantify the hydrothermal performance of the frozen soil. The mathematical module of COMSOL Multiphysics was employed to solve the coupling equation numerically. To validate the proposed coupling model, water transfer experiments were conducted on silty clay in closed and open systems under freezing conditions in our laboratory. The measured experimental data were consistent with the prediction results, confirming the applicability of the coupling model of the frozen soil in predicting the hydraulic parameters based on the new soil freezing characteristic curve.