冻结特征曲线（SFCC）是指冻土中温度和未冻水含量之间的关系，采用核磁共振系统和低温恒温冷浴获得了采用不同浓度NaCl溶液饱和的黏土的冻结特征曲线。根据试验结果分析不同浓度的孔隙溶液对冻结特征的影响规律，结果表明：随着溶液浓度的增大，冻结特征曲线向上移动，也就是说在相同未冻水含量下，浓度越大，冻结温度越低。这主要是因为盐溶液引起了渗透势能，使得孔隙水中总势能降低，从而降低了孔隙水的冰点。在冻土中，孔隙水的冻结温度与能量状态有关，其中孔隙水的势能包括基质势能和渗透势能，而基质势能部分又分为毛细部分和吸附部分，渗透势能与孔隙溶液的浓度有关。当土体中未冻水含量较低时，主要是吸附效应在起作用。此时未冻水是以吸附膜的形式吸附在土颗粒的周围，将非饱和土的概念引入到冻土中，采用分子间作用力和吸附水膜厚度之间的关系，以描述处于吸附状态的冻结特征曲线。结合渗透势能来模拟不同浓度下的冻结特征曲线，与试验数据拟合结果较好。

Soil freezing characteristic curve (SFCC) represents the relationship between the freezing temperature and unfrozen water content. The SFCCs of clay samples saturated by different concentrations of NaCl solution are obtained using the nuclear magnetic resonance (NMR) and the cold bath. The effect of pore solution at different concentrations on the SFC is analyzed. It is shown that with the increase of the solution concentration, the freezing characteristic curve moves upwards, that is, at the same unfrozen water content, the freezing temperature decreases with the increase of the concentration. It is mainly because the osmosis potential induced by salt solution lowers the total potential of soil water, which in turn depresses the water freezing point. The freezing temperature is related to the energy status of liquid water in frozen soils. The total pore water potential includes the matric potential and the osmosis potential, where the matric potential includes capillary and adsorption and the osmosis potential depends on the concentrations of pore solution. When the unfrozen water content of the sample is very low, the adsorption effect is available. At this time, the unfrozen water is adsorbed on the soil particles in the form of adsorbed film. Similar to the unsaturated soils, a relationship between intermolecular forces and adsorbed water film is used to describe the soil freezing characteristic curve at low water potential. Combined with osmotic potential, the freezing characteristic curves at different concentrations are simulated, and the fitting results are in good agreement with the experimental data.