Abstract: The freezing point and freezing characteristic curves of saturated remolded silt with solution (NaCl, Na2CO3) were measured by thermocouple and nuclear magnetic resonance method. Upon comparing the NaCl and Na2CO3 solutions, the effects of initial salt content on freezing temperature and unfrozen water content were studied. The results show that the freezing temperature of soils decreases with the increase of initial salt content; the freezing temperature of saturated soils with NaCl solution is lower than that of the corresponding pure solution with the same concentration. But the freezing temperature of saturated soils with Na2CO3 solution (<0.6 mol/L) is higher than that of the pure solution. At the same temperature, the content of unfrozen water in soils increases with the initial salt content of NaCl, but does not change obviously with the initial salt content of Na2CO3. The mechanism analysis shows that the salt type and salt content have different effects on soil water potential. Based on the improved generalized Clapeyron equation, the freezing temperature of salt-bearing soil was introduced into the prediction model of unfrozen water content. The quantitative expression of unfrozen water content of soil was obtained, and compared with the measured data with considering the effect of salt content. It is verified that the model can reasonably predict the unfrozen water content of saline soils at different temperatures.

Key words: freezing temperature, unfrozen water content, salt solution concentration, nuclear magnetic resonance(NMR), Clapeyron equation