考虑体积变化的膨胀土土—水特征研究

Soil-water characteristics of expansive soil considering volume change

为研究考虑体积变化的膨胀土土—水特征,分析了体积含水率与重力含水率及孔隙比的理论关系,提出了考虑膨胀土体积变化的土—水特征曲线求解方法。以合肥膨胀土为研究对象,采用渗析法试验及滤纸法试验测定了重力含水率与基质吸力的关系,采用收缩试验测定了孔隙比与重力含水率的关系;根据本文方法,求得了考虑体积变化的合肥膨胀土土—水特征。结果表明:由渗析法及滤纸法可以分别获取土体在低吸力段及高吸力段的土—水特征曲线;收缩曲线可以用分段函数表示;膨胀土在吸水过程中体积发生了很大变化,不考虑这种体积变化将会高估膨胀土的体积含水率,且吸力越低,这种误差越大;采用van Genuchten模型对试验结果进行了曲线拟合,得到了试验土体考虑体积膨胀的土—水特征曲线拟合参数值:a=40.21,n=1.52,m=0.09;土样的初始干密度越大,同一吸力对应的含水率也越大。

In order to study the soil water characteristics of expansive soil taking into account of vol- ume change, the theoretical relationship between volumetric water content and gravity water content was analyzed, and a method to obtain the soil water characteristic curves （SWCC） considering vol- ume change was proposed. By taking Hefei expansive soil as a study object, the relationship be- tween gravity water content and matrix suction was measured with the osmotic method and filter pa- per method, and the relationship between void ratio and gravity water content was measured by the shrinkage test. The soil water characteristics of Hefei expansive soil considering volume change were obtained according to the method proposed in this paper. The results showed that SWCC in low and high suction sections could be obtained by the osmotic method and filter paper method, respectively. Volumetric shrinkage curve can be described by the piecewise function. The volume of expansive soil changed dramatically during the process of absorbing water. The volumetric water content can be overestimated if the volume change was ignored, and the error become larger in lower suction part. Fitting parameters a = 40.21, n = 1.5, and m = 0. 09 were obtained when the SWCC with considera- tion of volumn chang was fitted with the van Genuchten model. The water content under the same suction increased with the increase of initial dry density of the soil sample.