Experimental Study on the Thawing Characteristics of Frozen Clay Minerals and Frozen Sand–Mineral Mixtures

Abstract

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 frozen clay minerals, including Kaolin, Montmorillonite, and Illite, were assessed using nuclear magnetic resonance (NMR) spectroscopy. Three commonly utilized formulas from the literature, namely, the exponential formula, the Fredlund and Xing (FX)-type formula, and Wang’s formula, were employed to predict the STCCs of these frozen clay minerals. The effectiveness of these formulas was evaluated using the root mean square error, with findings indicating that both the FX-type formula and Wang’s formula demonstrate strong performance. Furthermore, the STCCs of frozen fine sand containing various proportions of clay minerals were also examined, revealing that both the FX-type formula and Wang’s formula still perform well in predicting these curves. The experimental results indicate that the unfrozen water content of frozen sand–mineral mixture increases with the clay mineral content under the same negative temperature during the thawing process. The underlying mechanism is analyzed, suggesting that the high surface energy and small size of clay minerals contribute to the retention of unfrozen water at negative temperatures.