滤纸法测定非饱和膨胀土土水特征曲线试验

Determination of soil-water characteristic curve of unsaturated expansive soils using filter paper method

针对现实中土体含水量任意变化的情况,采用滤纸法测定非饱和膨胀土任意循环路径下对应的总吸力和基质吸力,得到了任意含水率变化下的总吸力曲线和土水特征曲线。将曲线进行拟合,利用毛细滞回内变量模型进行计算,通过与试验结果对比,验证了该模型对于膨胀土的适用性。结果表明:滤纸法测得的土水特征曲线与传统方法测得的曲线大致相同。含水量任意变化下的曲线不与完整脱、吸湿曲线重合,相同含水率下,脱、吸湿开始点之间含水率差值越小,脱湿后吸湿的曲线,基质吸力越高;吸湿后脱湿的曲线,基质吸力越低。毛细滞回内变量模型适用于非饱和膨胀土,计算结果与实际值能较好吻合。

The water content of the soil varies randomly in reality. In this paper, the filter paper method was used to measure the total and matric suction of the unsaturated expansive soil under any cycle path, and the total suction curve and soil-water characteristic curve （SWCC） under any moisture change were obtained. The curve was fitted, and the capillary hysteresis internal variable model was used to calculate and validate the model applicability for expansive soils through the comparison of test and ob served results. Results showed that SWCC determined by the filter paper method is similar to that measured by the traditional methods, and the curve under any change in moisture content does not coincide with the full curve. Under the same moisture content, the smaller the difference between the moisture contents at the starting point of moisture elimination and absorption, the higher the matric suction which is from desorption to moisture,and the lower the matric suction which is from moisture to desorption. Capillary hysteresis internal variable model is suitable for the unsaturated expansive soil, which generates similar results with the actual values.