舟曲磨里巨型滑坡基本特征及破坏模式

Characteristics and Failure Mode of Giant Moli Landslide in Zhouqu County,Gansu Province,China

甘肃省舟曲县是我国滑坡灾害最为严重的县区之一,分布着很多巨型滑坡。舟曲磨里滑坡位于白龙江一级支流大水坝河上游左岸,为典型的断裂带巨型滑坡,处于不稳定状态,严重威胁当地民众的生命财产安全。本研究通过无人机测绘、现场调查、变形监测、数值模拟等技术手段,对磨里滑坡的发育特征、变形趋势和破坏模式进行了分析研究。结果表明:(1)磨里滑坡形态、结构清晰,平面形态呈长条形,长度1500 m,宽度平均约385 m,厚度32~73 m,体积达2.12×10~7m~3,滑体由破碎千枚岩组成,为巨型超深层堆积层滑坡,在舟曲南部具有典型性;(2)滑坡复活主要受强降雨引发,其下段首先发生滑动,中上段受牵引影响产生蠕动变形,滑坡下段的移动速率大于中上段移动速率,滑动形式为典型的牵引式滑动;(3)不同工况下滑坡处于不稳定-基本稳定状态,不利工况下滑坡的破坏模式以整体的失稳变形或滑动为主。研究结果表明该滑坡规模宏大,不具备工程治理条件,建议对受磨里滑坡威胁的民众尽快采取避险搬迁措施。该防治措施已被当地政府采纳和实施,取得了良好的防灾减灾效益。本研究可为类似地区巨型滑坡复活破坏机制研究、应急处置及风险防控提供技术方法参考。

Zhouqu is one of the counties with the most serious landslide disasters in China. Moli landslide, located on the left bank of the upper reaches of the Dashuiba River, the first tributary of the Bailong River, is a typical giant landslide in a fault zone. This unstable landslide is seriously threatening households and properties in Guoye town, Zhouqu, China. In this study, UAV mapping, field investigation, deformation monitoring and numerical simulation were applied to analyze the development characteristics, deformation trend and failure mechanism of the Moli landslide. The results showed that:(1) Moli landslide has a clear shape and structure. Its planar shape is a long strip with a length of 1500 m, an average width of 385 m, a thickness of 32 ~ 73 m, and a volume of 2. 12 ×10~7m~3. The material of the landslide was composed of broken phyllite. This landslide was a giant ultra-deep accumulation landslide, which is a typical kind of landslides in south of Zhouqu.(2) The reactivation of the landslide was mainly triggered by heavy rainfall. The lower section of the landslide slid first, and the middle and upper sections crept and deformed under the effect of traction. The movement rate of the lower part was greater than that of the middle and upper parts. The sliding mechanism was a typical traction sliding.(3) The numerical simulation results illustrated that the landslide under different engineering conditions varied from unstable to basically stable, and the failure mode of the landslide under adverse engineering conditions was dominated by the overall instability deformation or sliding. Considering the large scale of the landslide and the lack of basic conditions for engineering constructions, it is suggested that residents threatened by the Moli landslide should be relocated in time. The suggestions have been adopted and implemented by the local government and achieved the benefits of geohazard mitigation. This study could be able to provide a technical and methodological reference for the research on the landslide reactive failure mechanism, emergency response and risk prevention and control in similar areas.