四川某水库右坝肩滑坡成因机制及稳定性分析

拟建水库右坝肩处于由砖红色砂岩夹薄层或透镜状泥岩、粉砂质泥岩构成的斜向V形河谷中，无明显断层构造，雨水充沛且存在一古滑坡，经过调查，滑坡主要由滑坡堆积体和滑动面以及其下方的扰动带组成，滑坡区发育的纵向和横向结构面以及岩层面构成一楔形槽。认为滑坡的成因是暴雨下楔形槽内控制的滑移-拉裂破坏。经过定性分析，古滑坡天然状态是稳定的。采用极限平衡法计算古滑坡在天然状态、地震作用以及暴雨等工况下的稳定系数分别为1.45、1.39及1.27，由此可知滑坡在天然状态下是稳定的，地震作用对其稳定性影响不大，但暴雨作用下滑坡的稳定性有所降低。最后通过数值模拟再现了现阶段古滑坡的应力应变场和变形破坏特征。

MECHANISM AND STABILITY ANALYSIS |OF OLD LANDSLIDE AT PROPOSED RESERVOIR DAM SITE IN SICHUAN PROVINCE

A proposed reservoir dam stands in a V-shaped valley.  The ground is composed with the semi-longitudinal brick red sandstone and foliated or lenticular mudstone, silty sand mudstone intermediate layer. It has no evident fault structure.  It has an  old landslide.  The rain is plenty. Based on investigation, the old landside has  landslide debris accumulation, slipped surface and the bottom disturbed zone. The development of vertical and horizontal structure planes of the landslide area and bedding plane constitute a wedge-shaped slot. The cause of the landslide formation  can be due to the fact that the slippage-tension failure took place  at the wedge-shaped slot under heavy rain.  The limit equilibrium method is used to calculate the stability factors. The stability factors are 1.45 in the natural state, 1.39 in the seismic state and 1.27 in the heavy rain state, respectively. Therefore, the landslide is stable in the natural state.  The role of earthquake impact in the stability is not significant. But the stability of the landslide will be lower under the heavy rain. Finally, the stress-strain field and deformation failure features of the ancient landslide at this stage  are reproduced through  finite element simulation.