Investigation and prediction on the freezing point of the clay under different salinity conditions

Freezing points play a crucial role in distinguishing between salt expansion and frost heave in frozen saline soil. Through a series of cooling experiments, the freezing points of sodium chloride and sodium sulfate saline soils were measured, considering various salt concentrations and ratios of c(Cl⁻)/2c(\({SO}_{4}^{2-}\)). The results revealed a three-stage cooling process: rapid cooling, constant cooling, and decreasing cooling. The freezing point of saline soil decreases with increasing salt concentration ranging from 1.5 to 4.9 times, attributed to the presence of more hydrated water molecules. Furthermore, influenced by the solubility of sodium sulfate, the freezing point of saline soil decreases with an increasing ratio of c(Cl⁻)/2c(\({SO}_{4}^{2-}\)) in the range of 0.7–4 times. The reduction of water content, on the other hand, enhances capillary action and soil particle adsorption, causing the freezing point of the soil to decrease by 0.5 to 1.7 times. To accurately predict the freezing point of saline frozen soil, a prediction model was proposed and validated, taking into account the effects of salt types, salinities, and water contents. This research serves as a valuable theoretical reference for predicting the freezing point of saline frozen soil.