三峡水库区奉节县典型岩质斜坡变形破坏模式及成因机制分析

Deformation and failure modes and genetic mechanisms of typical rocky slopes in Fengjie County, Three Gorges reservoir region

从奉节地区所处的区域地质构造背景出发,充分分析研究该地区斜坡的物质成分组成、结构特征、岩层组合特点,同时考虑长江河谷的发育变迁对该地区地形地貌变化的影响,将研究区斜坡结构划分为以下6种类型:顺倾坚硬岩层斜坡、顺倾软弱岩层斜坡、顺倾软硬岩互层斜坡,反倾坚硬岩层斜坡、反倾软弱岩层斜坡、反倾软硬岩互层斜坡。论文从斜坡变形破坏形态入手,归纳、总结了以上6种类型斜坡的变形破坏模式和特点:总体上看,坚硬岩层组成的斜坡以断裂、崩塌变形破坏为主,而软弱岩层组成的斜坡以弯曲、滑动、塑性流动变形破坏为主。由于岩性本身存在强度差异,而且由于不同的岩层组合,及其与不同坡向的组合,造成各类斜坡的变形破坏又独具特点。通过分析研究,认为重力作用、降雨及地下水作用、河流冲刷作用是造成研究区斜坡发生变形破坏的主要原因。对于所划分的不同结构类型的斜坡,以上3种动力地质作用的效果也不尽相同,最终在各种作用相互影响下,形成了奉节地区复杂多样的斜坡变形破坏模式。

Considering the regional geologic tectonic background and the influence of Yangtze River, with the material composition, features of structure and strata of the slopes, six different structure types of slope are proposed, which are consequent hard strata, consequent soft strata, consequent interlayer strata, bending-forward hard strata, bending-forward soft strata and bending-forward interlayer strata. Deformation and failure modes of various structure slopes mentioned above are analyzed in detail in this paper. Generally, the slopes with the hard rock show the failure modes of falling and topping mainly, but the slopes with the soft rock present the failure modes of bending, sliding and flowing. Deformation and failure modes of different slopes have their own characters because of diversity of rock intensity, distinct combination of terrane and different assembly of terrane combination and incline. Genetic mechanisms of different failure modes are explained with the consideration of the functions made by gravity, rainfall and erosion of Yangtze River. Different type slopes are affected by various geological mechanics, which result in different slope deformation and failure modes. Finally, complicated and various modes in Fengjie County are formed by common concentration of kinds of dynamic geological functions.