非饱和黄土土-水特征曲线与渗透系数Childs & Collis-Geroge模型预测

Soil-water characteristic curve and permeability perdiction on Childs &Collis-Geroge model of unsaturated loess

我国黄土厚度大,黄土地区地下水位深,降雨量少,黄土多处于非饱和状态,土-水特征曲线是非饱和黄土应力状态、强度及渗透性研究的基础。以陇东高原马兰黄土为试验对象,采用张力计法测定原状土样的土-水特征曲线,采用三种理论模型对试验数据拟合,其中Gardner模型简单、参数少,但Fredlund&Xing模型拟合效果最好。基于已测得的土-水特征曲线,采用Childs&Collis-Geroge预测非饱和渗透系数的模型,计算得到非饱和黄土渗透系数与基质吸力或含水率的关系,发现黄土从饱和到非饱和,其渗透系数急剧降低,黄土非饱和渗透系数与基质吸力或体积含水率的关系均可用指数函数表示。本文对典型黄土土-水特征曲线的研究及渗透性的预测为黄土工程问题,如降雨入渗的边坡稳定性评价、非饱和地基湿陷变形计算等提供理论基础。

Loess in China is thick, and groundwater levels are always very deep in loess area where is characterized by low precipitation, which makes loess always at unsaturated state. Soil-water characteristic curve is the foundation of researches on stress state, strength and permeability of unsaturated loess. This paper experiments on typical Malan loess in Longdong plateau, the soil-water characteristic curve of undisturbed sample is determined by tensionmeter, and the experimental data are then fitted with three theoretical models, of which Gardner model is the simplest with the least parameters, while Fredlund&Xing model has the best fitting effect. The relationship between permeability coefficient and matric suction or water content of unsaturated loess is built based on the measured soil-water characteristic curve by Childs& Collis-Geroge model which is commonly used to predict unsaturated permeability coefficient. The results show that the permeability coefficient decreases dramatically as saturated loess becoming unsaturated, the relationships between permeability coefficient and matric suction or volume water content of unsaturated loess can all be expressed in exponential form. Study of the soil-water characteristic curve and permeability coefficient prediction of typical loess provides loess engineering problems, such as the slope stability evaluation with the effects of rain infiltration and the computation of collapsible deformation of unsaturated foundation, with theoretical basis.