A theoretical model of the soil freezing characteristic curve for saline soil

Soil freezing characteristic curve (SFCC) characterizes the relationship between liquid water content and tem-perature in frozen soils, which is of significance in simulating the heat, moisture, and solute migration process in the hydrological cycle in cold regions. Soil freezing process of saline soils includes various stages including ice or salt crystallization and ice-salt eutectic. However, most SFCC models ignored the eutectic stage. Based on the framework of chemical potential equilibrium, a theoretical model is developed considering the ice-salt eutectic phenomenon in this study. The model can well predict the change in unfrozen water content in various stages for both low and high initial concentrations from the soil-water characteristic curve (SWCC). The applicability and accuracy of the model are well verified by the published data of the measured phase diagrams of bulk salt so-lution and SFCCs for different types of soils. The effects of soil type, initial solute concentration, and initial water content on soil freezing process and eutectic temperature are further analyzed using the theoretical model, which is in agreement with reported experimental results. The work provides a comprehensive view to understand the freezing characteristic of saline soils.