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3D FEM numerical simulation of infiltration of landslide considering runoff
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摘要: 现有数值模拟方法在模拟边坡降雨入渗时通常不能考虑径流流量补给对滑体渗流的影响，当滑床和滑带的渗透性相对于滑体极低时，会出现低估降雨入渗量、高估滑坡稳定性的现象。以Richards方程、运动波方程和有限元法为基础，提出了一种降雨时滑坡渗流数值模拟方法。该方法忽略滑床和滑带的渗流而只考虑滑体渗流过程，从而减小计算规模，也避免了因滑体与滑床(滑带)渗透性差异过大引起的数值计算困难；依据地形和滑体降雨入渗边界饱和情况，修正降雨入渗边界类型和流量，实现了考虑径流流量补给的滑坡降雨入渗简化数值模拟。对简单土质边坡降雨入渗进行数值模拟，从水量平衡与边坡渗流场两个角度，对比了考虑和不考虑径流流量补给的区别；结果表明，考虑径流流量补给时才能保证计算结果水量平衡，正确反映降雨入渗对基质吸力大幅降低的作用。Abstract: When the permeability of landslide bed and landslide zone is very low relatively to the sliding mass, the influences of the runoff from upper slope would not be considered by existing methods in the numerical simulation of rainfall infiltration, so that the feed of precipitation infiltration is underestimated, hence the stability of landslide is overestimated. In this paper, based on Richards's equation, the kinematic wave equation and FEM, a 3D simplified numerical method considering the runoff under the rainfall condition is proposed. In the new method, the calculation domain only contains the sliding mass, to decrease the computational scale and to avoid computational difficulty caused by a significant difference of permeability between the landslide bed (and slide zone) and sliding mass. And what's more, the rainfall boundaries are corrected according to the terrain and net rainfall including not only fluxes but also types (head boundary and flux boundary). The new method is suitable for numerical simulation of the landslide infiltration when the permeability of the landslide bed and landslide zone is very low relatively to the sliding mass, and it can consider the influences of water supply from the runoff to the infiltration of the sliding mass. In order to show the necessity in considering the water supply and the validation of the new method, the infiltration process of a simple soil slope is simulated by the new method and an existing method. The comparisons are made in the aspects of water balance and slope seepage field. The simulated results show that the calculation results, the water balance and the effects of rainfall infiltration on the matric suction can be guaranteed when the runoff supplement is taken into account.
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Key words:
- slope stability /
- rainfall infiltration /
- runoff supplement /
- FEM /
- numerical simulation
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表 1 土体SWCC与渗透性函数
Table 1. SWCC and permeability function of soil mass
θ 0.028 0.062 0.085 0.116 0.178 0.265 0.306 0.350 h/cm 200 100 80 60 40 20 10 0 kr 0.001 0.0085 0.010 0.018 0.050 0.886 0.995 1.000 注：θ为体积含水率；h为基质吸力；kr为相对渗透系数。 
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表 2 雨强和饱和渗透系数
Table 2. Values of R and ks
序号 雨强R/
(10-5cm·s-1)饱和渗透系数ks/
(10-5cm·s-1)R/ks 1 2.894 72.2 0.04 2 5.787 72.2 0.08 3 11.574 72.2 0.16 4 23.148 72.2 0.32 5 2.894 7.22 0.4 6 5.787 7.22 0.8 7 11.574 7.22 1.6 8 23.148 7.22 3.2
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