边坡降雨入渗问题中两种边界条件的处理及应用  

Treatment of two boundary conditions for rainfall infiltration in slope and its application

作　　者：年庚乾 陈忠辉[1] 张凌凡 包敏 周子涵 NIAN Geng-qian;CHEN Zhong-hui;ZHANG Ling-fan;BAO Min;ZHOU Zi-han(School of Mechanics and Civil Engineering,China University of Mining and Technology,Beijing 100083,China)

机构地区：[1]中国矿业大学(北京)力学与建筑工程学院,北京100083

出　　处：《岩土力学》2020年第12期4105-4115,共11页Rock and Soil Mechanics

基　　金：国家重点研发计划(No.2016YFC0801602,No.2017YFC1503103)。

摘　　要：基于饱和-非饱和渗流的Richards方程,以COMSOL Multiphysics有限元数值计算软件为平台,针对边坡降雨入渗问题中的入渗边界条件和渗流(溢出)边界条件,以孔隙水压力为控制条件,推导了二者的控制方程,并以二维土柱模型及已有文献中的实例模型为基础,探讨了控制方程中边界耦合长度尺度L的取值,结果发现L为0.001 m时较为合理。建立简单二维边坡模型,应用上述边界条件的控制方程,分析了不同降雨强度(长而弱、短而强)下,边坡降雨的入渗及渗流规律。结果表明:4 mm/h的降雨强度下,实际入渗率始终等于降雨强度,表层土体的体积含水率从0.29增至0.35,降雨75 h时坡脚处发生表面渗流,降雨200 h时研究区域总入渗量为39.068 m3;40 mm/h的降雨强度下,实际入渗率首先等于降雨强度,然后逐渐减小,表层土体的体积含水率从0.29增至0.415(饱和),降雨4h时坡脚处发生表面渗流,降雨20h时研究区域总入渗量为26.908m^3,降雨量相同但其值远小于前者。该结论与已有研究的边坡降雨入渗规律相符,进一步证明了上述边界条件控制方程的可靠性,为边坡降雨的有限元数值分析中边界条件问题提供了一种可行方法。Using the Richards’ equation of saturated-unsaturated seepage, the commercial Multiphysics finite element software COMSOL is adopted to deduce the governing equations of two boundary conditions with the pore water pressure as the control variable for the infiltration and seepage(overflow) boundary conditions in the rainfall infiltration problem of slope. Based on the two-dimensional soil column model and the published models, the value of the boundary coupling length scale L in the governing equation is discussed, and L equal to 0.001 m is found reasonable. A simple two-dimensional slope model is then established, and the governing equations of the above boundary conditions are applied to analyze the infiltration and seepage law of rainfall with different intensities(long and weak, short and strong). The results show that when the rainfall intensity is 4 mm/h, the actual infiltration rate is always equal to the rainfall intensity, and the water content of the surface soil has increased from 0.29 to 0.35. When the surface seepage has occurred for 75 h at the foot of the slope, the total infiltration of the study area at 200 h is 39.068 m^3;when the rainfall intensity is 40 mm/h, the actual infiltration rate first equals the rainfall intensity, and then gradually decreases, and the water content of the surface soil increases from 0.29 to 0.415(saturated). When the surface seepage has occurred for 4 h at the foot of the slope, the total infiltration of study area at 20 h is 26.908 m^3, which is far less than the former. This conclusion is consistent with the existing rainfall infiltration law in slope, which further proves the reliability of the above boundary condition governing equations that provides a feasible method for the boundary condition problem in finite element analysis of rainfall in slope.

关 键 词：边坡 降雨入渗 RICHARDS方程 边界条件 控制方程 

分 类 号：TU42[建筑科学—岩土工程]