降雨条件下一维土柱垂直入渗模型试验研究及其渗透系数求解

Experimental study on one-dimensional vertical infiltration in soil column under rainfall and the derivation of permeability coefficient

为研究降雨条件下一维土柱的入渗规律及求解非饱和土体的渗透系数,开发一套模拟降雨条件下一维土柱垂直入渗模型试验装置,对非饱和重塑黄土土柱做了4组不同降雨强度下的一维垂直入渗试验,得到不同降雨强度下垂直土柱的入渗率时程曲线、浸润峰深度时程曲线及监测点体积含水率的变化规律;提出计算非饱和土体渗透系数的新方法,并结合试验结果,得到试验土样非饱和渗透系数与基质吸力的关系曲线。结果表明:(1)降雨强度对垂直土柱的入渗影响较大,当降雨强度小于土柱最小入渗能力时,入渗率等于降雨强度;当降雨强度大于土柱最小入渗能力时,入渗率时程曲线呈无压入渗、有压入渗和饱和入渗3阶段变化。(2)不同降雨强度下,土柱出现积水点和饱和点的历时不同,降雨强度越大出现积水点和饱和点的时间越短,有压入渗阶段越长。(3)在同一降雨强度下,监测点距土柱上表面越远,其体积含水率时程曲线越密集;而同一监测点,降雨强度越大,其体积含水率时程曲线越稀疏。(4)非饱和重塑黄土渗透系数随基质吸力的增大而减小,且渗透系数的对数与基质吸力呈线性变化。

A set of test system for studying the vertical infiltration in one-dimensional soil column under rainfall was developed. Four sets of tests were carried out to the unsaturated disturbed loess column under the different rainfall intensities. The time curves of the infiltration rate,the depth of the wetting front and the volumetric water content at the monitoring points were obtained.The formula of permeability coefficient was derived and the curve of the permeability coefficient varied with the matric suction of the disturbed loess was obtained. The rainfallintensity has great impact on the vertical infiltration in soil column. The infiltration rate equals to the rainfall intensity when the rainfall intensity is less than the minimum infiltration capacity of soil column. When the rainfall intensity is greater than the minimum infiltration capacity,the curve of infiltration rate can be divided into three stages,the non-compressive infiltration,the compressive infiltration and the saturated infiltration. The moment of occurrence of the dropsy point and the saturation point are different under different rainfall intensities,the greater the rainfall intensity,the earlier the dropsy point and saturation point appear,and the longer the stage of compressive infiltration. The permeability coefficient of the unsaturated remolded loess decreases exponentially with the increasing of matric suction.