降雨作用碎石土堆积层滑坡变形规律

Effect of Rainfall on Deformation Regularity of Debris Landslide

降雨诱发碎石土堆积层滑坡十分普遍,野猫面滑坡则是典型的碎石土堆积型滑坡,也是三峡库区内距三峡大坝最近的特大型滑坡体,研究其在不同降雨条件下的变形规律具有示范性和实用价值。首先,在滑坡区域地质分析的基础上,研究了碎石土堆积层滑坡的组成结构;然后应用Modflow软件建立了滑坡地下水渗流场数值模型,对不同降雨强度和降雨历时条件下,降雨入渗补给地下水的规律进行了模拟;最后,运用FLAC3D软件对不同降雨工况条件下,渗流场变化引起的滑坡变形规律进行了模拟。研究结果表明:①野猫面滑坡碎石土堆积层表现为三层结构,上部为碎块石土,中下部为块石土、钙质胶结碎块石,下部滑面为碎石土和黏土夹碎石;②降雨强度和降雨历时增加均使滑坡地下水头抬升,在斜坡前缘临近库岸部分的水力坡度明显增大;③降雨作用下,滑坡位移量增加,变形由地表向深部、由前缘向后缘发展,在滑面处剪应变集中;极端大暴雨条件下,前缘存在整体变形区;④碎石土堆积层滑坡地表径流疏导与生态防渗可有效防治滑坡。

Rainfall-induced debris landslides are widely distributed in China. Yemaomian landslide is a typi-cal debris landslide, and is also the largest landslide nearest to the Three Gorges Dam. To investigate its deformation regularity under different rainfall conditions has an important practical merit and could con-tribute to the understanding the deformation of other similar type landslides. Firstly, the structure of Yemaomian debris landslide has been investigated based on the geological analysis of landslide. Secondly, the groundwater flow model was established by Modflow code, and the process of the rainfall infiltration to the groundwater under different rainfall intensities and durations was simulated. Lastly, the regularity of landslide deformation caused by the groundwater seepage change was simulated with FLAC3D software. The results indicated that： （1） The deposit of Yemaomian debris landslide consists of three layers with broken-rock soils in the top layer, rock soils and calcite-cemented broken-rock in the middle-low layer, and gravel soil and pebbly clay in the bottom layer. （2） The increase of rainfall intensity and duration would lead to the increase in the groundwater head in the landslide and the hydraulic gradient greatly increased in the fore part of the slope near the reservoir bank. （3） Rainfall induced the increase of landside displace- ment, the development of the deformation from surface to deep ground and from front to back of slope, and the concentrations of the shearing stress on the slip surface. The global deformation area has been formed under dramatically rainfall condition. （4） Grooming surface runoff and ecological anti-seepage can effectively prevent debris landslide.