考虑软弱夹层控滑机制及其空间不确定性的顺层岩质滑坡易发性评价: 万州区铁峰乡应用研究

顺层岩质滑坡突发性强, 破坏性大, 是危害山区城镇安全的重要灾害类型之一。发育软弱夹层的顺向斜坡是顺层岩质滑坡的高发区, 区域顺层岩质滑坡易发性评价应融入软弱夹层的控滑机制和空间分布不确定性分析。以万州区铁峰乡为研究区, 在软弱夹层物质结构及空间分布详细调查的基础上, 分析了原生沉积、构造变形和表生改造作用下区内页岩和泥岩两类软弱夹层发展为滑动面的演化机理, 总结了顺层岩质滑坡的变形破坏机理。考虑软弱夹层空间分布的不确定性, 提出了软弱夹层垂向分布和有效控滑深度范围内软弱夹层控滑贡献度的计算模型。提取了软弱夹层类型和控滑贡献度等表征顺层岩质滑坡控滑结构的关键指标, 结合地形地貌、斜坡结构、水文地质及人类工程活动4类要素, 构建了顺层岩质滑坡易发性评价指标体系。针对万州区铁峰乡河谷南侧的顺向坡区段, 以斜坡为评价单元, 采用层次分析法对研究区顺层岩质滑坡开展了易发性评价。结果显示研究区内侏罗系珍珠冲组泥化夹层和自流井组页岩层是顺层岩质滑坡的主要控滑层位, 极高易发区和高易发区占比分别为9.7%和25.8%, 岩质斜坡单元下伏软弱夹层分布情况和斜坡前缘开挖情况是影响滑坡灾害易发性的主要因素, 建房和道路开挖等人类工程活动极易诱发顺层岩质滑坡灾害。与不考虑软弱夹层相关指标的易发性评价结果相比, 本文方法的结果更符合实际情况。 

Susceptibility assessment of a translational rockslide considering the control mechanism and spatial uncertainty of a weak interlayer: Application study in Tiefeng Township,Wanzhou District

Translational rockslides are an important disaster that endangers the safety of mountain towns. The dip slopes with weak interlayers are the areas prone to translational rockslides. The regional translational rockslide susceptibility assessment should consider the sliding mechanism and spatial distribution uncertainty analysis of the weak interlayer. Taking Tiefeng Town of Wanzhou District as the study area, based on the detailed investigation of the material, structure and spatial distribution of weak interlayers, this paper analysed the evolution mechanism of shale and mudstone developing into sliding surfaces under the action of primary deposition, tectonic deformation and supergene transformation and summarized the deformation and failure mechanism of translational rockslides. Considering the spatial distribution uncertainty of the weak interlayer, a calculation model of the vertical distribution of the weak interlayer and the contribution of the weak interlayer to slip control in the effective control depth are proposed. The key factors that characterize the sliding structure, including the type of weak interlayer and the contribution degree of the weak interlayer, are selected as susceptibility assessment factors. In addition, four elements, topography, slope structure, hydrogeology and human activities, are considered. The susceptibility of translational rockslides in the study area was assessed with slope units adopting the analytic hierarchy process. The investigation and assessment results show that the mud interlayers of the Jurassic Zhenzhuchong Formation and the shale layer of the Ziliujing Formation are the main potential slip surfaces of the translational rockslide in the study area. The extremely high susceptibility area and high susceptibility area accounted for 9.7% and 25.8%, respectively. The distribution of the underlying weak interlayer and the excavation of the slope units are the main factors affecting the susceptibility to landslide disasters. Human activities such as house building and road excavation are the main triggering factors of translational rockslides.Compared with the susceptibility assessment results without considering the factors of the weak interlayer, the results of the method proposed in this paper are more consistent with the facts.