强降雨作用下堆积层滑坡稳定性分析

Stability analysis of colluvial landslide due to heavy rainfall

强降雨作用易造成堆积层滑坡发生,带来严重的生命财产损失。基于Green-Ampt(GA)模型,同时考虑湿润锋以上饱和带渗流作用,推导了一种新的滑坡降雨入渗函数,弥补了GA模型只适用于无限长坡的不足。为考虑降雨入渗对土体条块强度的影响,采用整体抗剪强度准则评价滑坡稳定性,并在受力分析时考虑了湿润锋以上饱和带渗透力作用,建立了滑坡稳定性系数表达式。研究结果表明:滑坡降雨入渗的尺寸效应非常明显,湿润锋扩展速率随着坡长的增大而增大,当滑坡无限长时新降雨入渗模型与GA模型计算结果相同,说明GA模型是新模型的一个特例。此外,降雨初期,滑坡稳定性下降较快;随着降雨的持续,稳定性下降速率逐渐放缓。与模型试验结果对比表明,提出的降雨入渗模型和评价方法计算结果与试验揭示的现象一致,证明了该方法的可靠性。

Disastrous failures of shallow residual soil slopes, which result in great loss of lives and properties, are mostly attributed to heavy rainfall. To evaluate the stability of colluvial landslide during rainfall, a new analytical infiltration model for slope is derived from the traditional Green-Ampt（GA） model. The new model assumes the pore water flow parallel to slope surface in saturated layer above the wetting front, and overcomes the deficiency of GA model which is only applicable to the infinite slopes. In addition, a new method is proposed to calculate the safety factor for soil slice based on the shear strength criterion related to the depth of saturated layer, and in this method the safety factor is deduced by taking the seepage force into account. The results show that the size effect of rainfall infiltration is significant, and the movement rate of wetting front increases with the increase of slope length. The proposed infiltration model is identical with GA model in analyzing infinite slope, demonstrating that the GA model is a special case of the proposed model. It is shown that the stability of slope decreases sharply at the initial time of rainfall, but the rate of decrease slows as rainfall continues. The predicted results of the new infiltration model show a high consistency with that of slope model test, showing the reliability of the proposed method.