考虑倾角的土质边坡Green-Ampt改进入渗模型

Improved Green-Ampt infiltration model of soil slope considering inclination

针对传统Green-Ampt入渗模型忽略坡角和土体非饱和区对边坡降雨入渗的影响这一情况,利用倾角对土体入渗势能梯度进行修正,并将入渗时边坡土体按含水率划分为饱和层、过渡层和未湿润层,建立考虑倾角的土质边坡分层假定入渗模型,推导边坡降雨入渗深度与降雨历时的关系,并通过入渗实例将新模型与传统模型进行比较。研究结果表明:分层假定模型预测的坡面产流时间及湿润锋深度与降雨历时的关系较传统Green-Ampt入渗模型(简称为GA模型)更接近实测值;自由入渗阶段,分层假定模型的湿润锋扩展深度与GA模型一致,但入渗速率低于GA模型;积水入渗阶段,分层假定模型的湿润锋扩展深度及入渗速率均大于GA模型,湿润锋扩展深度的差值随着降雨历时的增大逐渐增大,而入渗速率差值的变化呈相反趋势。根据新模型,分析了倾角和雨强对边坡降雨入渗的影响,发现随着边坡倾角的增大或雨强的减小,雨水入渗到坡体内相同深度所需的降雨历时增加,这种现象在倾角大于60°或雨强小于20 mm/h时尤为明显。

In view of the fact that the traditional Green-Ampt infiltration model ignores the influence of slope angle and unsaturated zone of soil on the rainfall infiltration of slope,the gradient of infiltration potential energy of soil was modified by using the slope angle,and the soil was divided into saturated layer,transition layer and non humid layer during infiltration.Then a new model based on stratified assumption considering inclination was established.The relationship between infiltration depth and rainfall duration was ascertained and the new model was compared with the traditional GA model through an infiltration example.The results show that the surface runoff initiation time and the relationship between wetting front depth and rainfall duration predicted by the new model are closer to the measured values than those by the GA model.In the stage of free infiltration,the wetting front depth of the new model is the same as that of GA model,but the infiltration rate of the new model is lower than that of GA model.In the stage of ponding infiltration,the wetting front depth and infiltration rate of the new model are higher than those of GA model,and the difference of wetting front depth increases gradually with the increase of rainfall duration,while the change of difference between infiltration rates shows the opposite trend.According to the new model,the influence of slope inclination and rainfall intensity on rainfall infiltration is analyzed.It is found that the rainfall duration required for rainwater infiltration into the same depth of slope increases with the increasing slope inclination or the decreasing rainfall intensity,which is especially obvious when the inclination is more than 60°or the rain intensity is less than 20 mm/h.