Impact of freeze-thaw cycles on the hydro-thermal-deformation behavior of silty clay: An experimental study

The complex dynamic processes of moisture, temperature, and deformation in soil are crucial factors affecting its engineering performance in freeze-thaw environments. In this study, a unidirectional freeze-thaw cycle (FTC) experiment was conducted on silty clay. The variations in soil temperature (ST), unfrozen water content (UWC), heat flux, and vertical deformation were analyzed. The findings indicate significant differences in the variation rates of ST during freezing and thawing processes. UWC is notably impacted by ST, with the infiltration and redistribution of unfrozen water occurring due to the temperature gradient in the soil. During the thawing process, liquid water in the soil column near the top zone migrates downward under gravity, while during the freezing process, it migrates upward near the bottom zone. Moreover, the maximum value of UWC hysteresis degree occurs during the apparent transition from water to ice, with the corresponding ST approximately aligning with the freezing temperature. The hysteresis degree of UWC increases with repeated FTCs, and the increase in liquid water can enlarge the hysteresis degree near the freezing temperature. Additionally, changes in heat flux generally align with ST during FTCs; however, the heat flux gradually deviates and lags behind ST when the ST is below zero. Furthermore, the first FTC plays a crucial role in determining the vertical deformation of the soil column.