Investigating the Freezing-Thawing Hysteresis of Soils

The freezing-thawing characteristics of frozen soil are crucial for safe and reliable construction projects in cold regions. In this study, nuclear magnetic resonance (NMR) technology is employed to carry out freezing-thawing tests, aiming to explore the hysteresis behavior of soil during freezing and thawing. Three representative soil types (poorly graded sand, silt, and fat clay) are tested under different temperature modes to analyze their hysteretic characteristics of the soil freezing characteristic curve (SFCC). The results show that the hysteresis primarily occurs in the supercooling and rapid-decline stages, and the hysteresis loops of fat clay and silt are more distinct. The SFCC tests under different temperature modes reveal differences between the hysteresis of SFCC and that of the soil water characteristic curve (SWCC). Importantly, the supercooling phenomenon is identified as the main cause of this hysteresis. Based on this, we propose a theoretical model that incorporates the supercooling phenomenon into predictions of freezing-thawing hysteresis. By comparing with the measured data, this model can effectively capture all three stages of soil freezing-thawing hysteresis and particularly excel in predicting the supercooling and rapid freezing stages, with higher correlation coefficients and broader applicability. This study clarifies the critical role of supercooling in soil freezing-thawing hysteresis and builds a robust model for applications in cold-region engineering.