The Soil Thawing Characteristic Curve (STCC), which delineates the relationship between unfrozen water content and temperature during the thawing process of frozen soil, is a critical factor with significant implications for heat and mass transfer dynamics. The STCCs of clay minerals, including Kaolin, Montmorillonite, and Illite, were evaluated using Nuclear Magnetic Resonance Spectroscopy (NMR). To predict the STCCs of these minerals, three formulas frequently cited in literature for describing unfrozen water content were applied. The efficacy of these formulas was assessed through metrics including the Sum of Squares due to Error (SSE),Coefficient of Determination(R-square), Adjusted R-square, and Root Mean Square Error (RMSE). Results demonstrate that the models proposed by Fredlund (1994)and Wang(2017) show remarkable accuracy. Furthermore, the STCCs of fine sand containing various proportions of clay minerals were examined, revealing that the formula by Fredlund (1994) outperforms others in predicting these STCCs. It is important to note that the unique properties of clay minerals, such as their high surface energy and diminutive size, lead to an increase in the unfrozen water content of sand- mineral mixtures as the proportion of clay minerals escalates at constant subzero temperatures.

frozen soil; unfrozen water; soil thawing characteristic; NMR; clay mineral