硫酸钠盐渍土土-水特征曲线的试验与理论研究

土-水特征曲线（SWCC）在非饱和土力学中扮有重要的角色，是非饱和土力学研究的核心问题。以西北地区黄土中含有的典型硫酸钠盐为变化因素，采用滤纸法测得了兰州黄土及不同含盐量黄土状硫酸钠盐渍土的基质吸力并绘制土-水特征曲线，通过试验测试和理论分析来解释硫酸钠盐分对黄土状硫酸钠盐渍土基质吸力的影响规律，以期为工程实践提供一定的理论依据。结果表明：相同含水率下硫酸钠盐渍土的含盐量越高，基质吸力越大。以非饱和土力学理论和表面物理化学理论为基础，考虑了土中的盐分对基质吸力的毛细部分及吸附部分的影响，得到了土中含盐量与基质吸力关系的半经验公式。利用该公式计算得到不同含盐量硫酸钠盐渍土的土-水特征曲线，计算曲线与试验曲线吻合程度较高，表明该公式可以很好地描述盐渍土中不同含盐量与基质吸力的关系。

Experimental and theoretical study on soil-water characteristic curve of sodium sulfate saline soil

Soil-water characteristic curve （SWCC） is a curve describing the relationship between soil matric suction and water content， which is the core of unsaturated soil mechanics research. Matric suction is an important stress state variable of unsaturated soil， which controls the balance between soil structure and shrinkage membrane， and is an important factor affecting mechanical properties of unsaturated soil. Loess containing sodium sulfate is widely distributed in Northwest China， and has been widely used in engineering practice. The relationship between the matric suction of loess and the content of sodium sulfate is studied by experimental test and theoretical analysis， and the law of the matric suction of loess like sodium sulfate saline soil affected by sodium sulfate is obtained. Taking the typical sodium sulfate contained in loess in Northwest China as the variable factor， the matric suction of Lanzhou loess and sodium sulfate saline soil with different salt content was measured by filter paper method， and the soil water-characteristic curve was drawn. The results show that the existence and content of sodium sulfate have a great influence on the matric suction of loess， and the higher the salt content of sodium sulfate saline soil is， the greater the matric suction is. The influence of sodium sulfate on the matric suction of loess is different under different water content： when the water content is high， the influence of sodium sulfate on the matric suction of loess is small； when the water content is low， the influence of sodium sulfate on the matric suction of loess is great. Based on unsaturated soil mechanics theory and surface physicochemical theory， assuming that the salt solution in soil does not affect the pore structure of soil， considering the influence of salt solution in soil on the capillary part and adsorption part of matric suction， a semi empirical formula is obtained， which can be used to calculate the relationship between salt content in soil and matric suction. The Kelvin radius and the thickness of adsorbed water film corresponding to each suction in the formula are calculated by the method introduced in unsaturated soil mechanics. The measured data are used to fit the three parameters in the formula. The matric suction corresponding to each water content of sodium sulfate saline soil with different salt content is calculated by the semi empirical formula， and the soil-water characteristic curve is drawn. The results show that the calculated curve is in good agreement with the experimental curve， which shows that the formula can well describe the relationship between different salt content and matric suction in saline soil. In this paper， the law of the influence of sodium sulfate content on the matric suction of loess is obtained through experiments， and the law is expressed quantitatively by theoretical derivation and semi empirical formula， which provides certain theoretical basis and data support for the future engineering practice in this area. The semi empirical formula obtained in this paper can also be applied to the calculation of soil-water characteristic curve of other saline soils， but it should be noted that the formula will not be applicable when the concentration of salt solution in soil reaches the saturation concentration.