降雨入渗条件下非饱和土渗流特征试验

设计了一种可测量降雨入渗与底部排水条件下土体体积含水率与基质吸力变化规律的试验装置，开展不同降雨强度条件下砂土和粉质黏土的降雨入渗与排水过程室内模型试验，得到了不同土质在不同降雨强度下各高程处体积含水率与基质吸力的变化规律。结果表明：可将降雨入渗条件下不同土质的体积含水率变化划分为3个阶段，首先表面土体含水率上升，随着雨水的入渗，表面含水率保持不变，土体内部含水率由上至下依次上升，随后当浸润线达到装置底部后，土体的含水率开始逐渐增大，由非饱和状态过渡至饱和状态，最后当装置底部达到饱和后，土体中的水位开始逐渐上升，各个测点在降雨作用下由下至上依次达到饱和状态；不同土质土体的表面体积含水率均与降雨强度呈线性关系，在相同降雨强度下粉质黏土表面体积含水率大于砂土，不同土质浸润线的下降速度与降雨强度均呈对数函数关系，在相同降雨强度下砂土浸润线下降速度大于粉质黏土；土体基质吸力随着雨水的入渗由上至下逐渐减小，在水位上升过程中基质吸力变化幅度小于降雨入渗过程；在排水过程中，砂土与粉质黏土各高程处的含水率随排水时间的变化规律分别呈幂函数关系和指数函数关系，位置较高测点的含水率下降明显快于位置较低的测点。

Experiment on Seepage Characteristics of Unsaturated Soil Under Rainfall Infiltration

A experimental apparatus which was used to measure rainfall infiltration, the matric suction and volumetric water content of the soil under the condition of drainage from the bottom was designed. Indoor model test of rainfall infiltration and drainage on sand and silty clay under different rainfall intensity was carried out. The change law of volumetric water content and the matric suction of the different soil texture under different rainfall intensities were obtained. The results show that, firstly, variation of volumetric water content can be divided into three stages under the condition of rainfall infiltration.The water content at the soil surface increases first and remain unchanged with the infiltration of rainwater, and the water content inside the soil increases from the top to the bottom. When the phreatic line reaches the bottom of model, the water content of the soil begins to increase gradually and transforms from unsaturated state to saturated state. After the soil at the bottom reaches saturated, the water line rises up gradually and each measuring point becomes saturated from the bottom to the top under the action of rainfall. Secondly, volumetric water content of soil surface is proportional to the rainfall intensities. The volumetric water content at the silty clay surface is larger than that of the sandy soil under the same rainfall intensity. The decline rate of the wetting front has a logarithmic function to the rainfall intensity under the condition of rainfall. In specific, the decline rate of the wetting front of sandy soil is larger than that of silty clay under the same rainfall intensity. Thirdly, matric suction decreases gradually from top to bottom with the rainfall infiltration, but the variation of matric suction is not obvious in the process of underground water level rising. Last but not least, volumetric water content of each characteristic point of sandy soil can be fitted by power function, and the silty clay can be fitted by exponential function in the drainage process. The decrease rates of water content in a higher position is faster than that of a lower position.