强降雨下饱和平滑型滑坡坡体水流运动及其边坡稳定效应分析——以四川汉源二蛮山滑坡为例

Analysis of flow motion and its effect on the slope stability of plane sliding landslide saturated under heavy-rain——A case study of Ermanshan landslide in Hanyuan county of Sichuan province

分析强降雨饱和状态下平面滑动型(平滑型)滑坡的地下渗流的水流运动规律,同时考虑静水压力和动水压力的耦合作用,提出饱和状态下平滑型滑坡边坡稳定性分析新思路。运用地下水动力学原理,给出假设条件简化分析过程,导出强降雨下地下渗流水流运动方程。基于条分法理论,考虑坡体各点水流运动的不均匀性,改进传统的边坡稳定性系数计算公式,并给出边坡失稳的临界条件。以四川省汉源县万工集镇二蛮山滑坡为例,验证计算公式的合理性。研究表明,强降雨饱和状态下平滑型滑坡的稳定性主要取决于岩土体饱水内摩擦角、渗透系数K、滑体规模(厚度、长度等)和坡顶相对坡脚水位差Δh。该研究成果可用于指导抢险救灾工作,具有一定的工程实用意义。

The flow motion law of the underground seepage of plane sliding landslide saturated under heavy-rain is studied; and then a new improved method for slope stability analysis of such landslide is presented, considering the coupling effect of hydrostatic pressure and hydrodynamic pressure. Using the principle of groundwater dynamics, on the basis of some assumptions to simplify the analysis process, the underground seepage flow equation under heavy-rain is derived. Based on the slice method theory, taking the non-uniformity of the flow activity at each point into account, the traditional calculation formula for slope stability coefficient is improved; and the critical condition of failure is also given. The proposed formulas are applied to Ermanshan landslide occurred in Hanyuan county of Sichuan province; and the obtained results prove the rationality of the method. The research indicates that the stability of plane sliding landslide under the heavy rain mainly depends on the internal friction angle of saturated rock and soil, the permeability coefficient, the scale of sliding mass （thickness and length） and the relative water-head between the slope crest and the toe. Such research results have a certain practical significance that can be used to guide the emergency rescues and disaster relief work.