非饱和膨胀土持水能力试验研究

Experimental research on water retention capacity of unsaturated expansive soil

利用压力板仪,进行不同干密度条件下非饱和膨胀土的土水特性试验,分析膨胀土土水特征曲线的基本特征,探讨干密度对膨胀土持水能力的影响,并根据试验得到的土水特征曲线推出其两个基本特征值。结果表明,不同吸力阶段干密度对持水能力的影响程度不同,对基质吸力低于进气值的边界效应阶段影响不大,基质吸力超过进气值进入转化阶段后,干密度增大明显增强了膨胀土的持水能力;膨胀土的进气值和残余含水率都比较大,并且随着干密度的增大均增大。应用数学模型描述不同干密度膨胀土的土水特征曲线,分析了干密度对数学模型参数的影响,给出了干密度、基质吸力和饱和度的函数表达式。

The experimental research on soil water characteristics of expansive soil with different dry density is carried out by the pressure plate.The basic characteristics are analyzed on the soil water characteristic curve（SWCC）.The effect of dry density is discussed on water retention capacity.The two basic eigenvalues are deduced according to the soil water characteristic curve.The results show that the effect is varied in the regime of SWCC.Dry density has little effect on the boundary effect stage when the matric suction is under the air-entry value.The water retention capacity is enhanced significantly on the transformation stage when matric suction is over the air-entry value.The air-entry value and resident water content are also high and increase as the dry density increases.The mathematic model is advanced to describe the SWCC of expansive soil.Then,the effect of dry density of expansive soil on the parameters of SWCC equation is analyzed.The relationship of dry density,matric suction and degree is described by a function expression.