强降雨下基于Green-Ampt模型的边坡稳定性分析

降雨入渗分析方法直接影响降雨型滑坡的预测与防范。Green-Ampt(GA)模型物理意义明确、参数较少,在降雨型滑坡分析中逐渐得到了重视,但该方法忽略了湿润层非饱和层的存在以及饱和层渗流而影响计算精度。针对以上不足,基于GA模型,建立了适用于边坡并且能综合考虑湿润层土体含水率分布情况与饱和层内平行于坡面渗流作用的降雨入渗分析(LSGA)模型,并提出了该模型下边坡稳定性系数表达式。结果表明:对于不考虑分层的无限长边坡,LSGA模型可简化为GA模型,说明GA模型是LSGA模型的一个特例;与LSGA模型相比,GA模型在失稳深度和时间上有较大延缓;饱和层渗流作用对湿润层特性影响较小,对边坡稳定性影响较大;相反,坡体长度方向尺寸效应则对湿润层特性影响明显,而对边坡稳定性影响较小;利用LSGA模型和稳定性评价方法得到的结果与模型试验揭示的现象基本吻合,证明了该方法有较好的精确性和可靠性。

Stability analysis of slope based on Green-Ampt model under heavy rainfall

The method of rainfall infiltration analysis directly affects the prediction and prevention of rainfall-induced landslides. Green-Ampt (GA) model, which has clear physical meaning and few parameters, has been paid more and more attention in the analysis of rainfall-induced landslides. However, this method ignores the existence of the unsaturated layer of the wetting layer and the seepage of the saturated layer, which affects the calculation accuracy. In view of the above deficiencies, the LSGA model is established based on the stratified hypothesis and the saturated layer seepage, and the expression of slope stability coefficient is established. All results show that LSGA model can be simplified to GA model for infinite slope without considering the stratified hypothesis of wetting layer, which indicates that GA model is a special case of LSGA model. The slope infiltration depth and instability time of GA are obviously behind the LSGA model. The saturated layer seepage has slight effect on the characteristics of the wetting layer, but has a great influence on the stability of slope. On the contrary, the effect of slope length on wetting layer characteristics is important, but the effect on slope stability is slight. All results obtained by using LSGA model and the stability evaluation method are basically consistent with the phenomena revealed by the model test, which proves that the method has better accuracy and reliability than others.