土的冻结温度是使土体物理力学性质发生显著变化的关键温度，盐渍土中由于盐分存在使冻结温度的预测变得困难。本文提出了一种适用于硫酸盐渍土有盐分析出时的冻结温度计算模型，分别对硫酸钠自由溶液、硫酸钠盐渍土及石英砂的冻结温度变化规律展开了研究。首先，依据固液两相平衡时化学势的规律、冰晶表面曲率影响以及盐分结晶析出对溶液浓度的影响，构建了自由溶液、盐渍土及石英砂的冻结温度预测模型；然后，开展室内冻结试验得到了冻结温度测量值，通过计算测量值与计算值二者的均方根误差（RMSE）、显著性水平（α）及一致性系数（LA），验证了本文模型的精度与适用性。结果表明：土样中初始含水率越小，土样表面的毛细作用和吸附作用越强，使土样冻结温度越低。在土样孔隙中盐溶液有效浓度越大，冻结温度越小。由于盐分结晶的影响，有效浓度随盐浓度增大先增大后减小，然后保持不变。土样孔隙半径越小，冰晶表面曲率影响越大，冻结温度越低。该研究成果能为盐渍土盐冻胀变形及人工冻结中的温度参数分析提供一种新的方法。

Saline soils are widely distributed in the cold and arid regions of northwestern China. The freezing temperature of soil is a critical temperature at which the physical properties of soil undergo significant changes. This temperature determines whether the soil is in a frozen state or not， and it has an effect on frost heave deformation. Additionally， the freezing temperature is a crucial parameter in calculating the freezing depth and is closely associated with the formation of segregated ice and the migration of water and salt in the soil. But due to the presence of salt， predicting the freezing temperature is challenging in saline soils， and consequently， accurately predicting the freezing temperature of saline soil is of significant importance for engineering damage treatment and providing practical references in engineering construction. The soil particle size and salinity affect the freezing temperature of soil. This paper proposes a freezing temperature calculation model applicable to sulfate saline soils with salt analysis and different salinity. The study investigates the variations in freezing temperature for sodium sulfate free solution， sodium sulfate saline soil， and quartz sand. In the beginning， based on the principles of equal increments of chemical potential at the solid-liquid phase equilibrium， and the influence of the solute in pore solution on water activity and ice crystal interface curvature effect was considered， and a freezing temperature prediction model was developed for aqueous solution， saline soils and quartz sand， respectively. Then， the freezing temperature was obtained through the freezing process tests on the saline soil with different salt contents. The experimental equipment includes a metal container with a lid， containing an inner diameter of 2.5 cm and a height of 3.5 cm， a temperature sensor， a vertical precision incubator， and a data collector. Finally， the accuracy and applicability of the model are validated by the root mean square error， significance level and the coefficient of agreement.

Some conclusions were conducted in this paper. The results indicate that the lower the initial moisture content in the soil sample， the stronger the capillary and adsorption effects on the soil surface， resulting in a lower freezing temperature. Additionally， when the water content of quartz sand exceeds its saturation water content and the water content of the soil surpasses its liquid limit， the freezing temperature of the pore solution tends to stabilize as the water content increases. The higher effective concentration of pore salt solution leads to the lower freezing temperature， and due to the influence of salt crystallization， the effective concentration initially increases with initial concentration. Specifically， when the concentration is less than 0.53 mol⋅kg^-1， the freezing temperature decreases as the increasing of solution concentration. When the initial concentration is between 0.53 and 0.74 mol⋅kg^-1， the solution concentration results increasing in salt crystallization， reducing the effective concentration and increasing the freezing temperature. When the concentration is above 0.74 mol⋅kg^-1， salt precipitation is complete， the effective concentration remains constant， and the freezing temperature tends to stabilize. The smaller soil sample pore radius results in a greater influence of ice crystal interface curvature， which leads to a lower freezing temperature. Specifically， when the pore radius is less than 0.55 μm and greater than the critical pore radius of 0.003 μm， the freezing temperature of the soil sample decreases rapidly as the pore radius decreases. Above 0.55 μm， the extent of the influence of interface curvature on freezing temperature is greatest in clay， followed by silty clay， then silt， and least in quartz sand. This paper provides a practical model for temperature in saline heave deformation of saline soils and artificial freezing method， which provides theoretical basis for numerical simulation in hydro-thermal-saline coupling.