奉节县曾家棚滑坡时空差异性变形特征与成因机制分析

Characteristics and mechanism of spatio-temporal difference deformation of Zengjiapeng landslide

研究库水位波动和降雨影响下滑坡的位移变形特征并分析其破坏机制,对了解三峡库区滑坡的演化过程具有重要意义。以奉节曾家棚滑坡为例,基于GPS地表监测位移分析了滑坡在不同特征库水位运行阶段的变化规律,结合灰色关联度模型确定了滑坡不同部位的变形在不同阶段的主要控制因素,借助GEO-Studio软件模拟了曾家棚滑坡在历史降雨和库水位波动耦合作用下的稳定性变化,并与定量分析结果进行了交叉检验。结果表明:曾家棚滑坡的运动状态随时间变化,从缓慢蠕变状态进入阶跃变形状态。平面上,中东部坡体与西部坡体相比,运动更加强烈;剖面上,前缘变形早且变形量大。曾家棚滑坡变形失稳过程为初期蓄水启动了曾家棚古滑坡,前缘首先发生变形;降雨作为中后期主控因素,和库水位波动联合作用共同诱发了滑坡多次阶跃变形,使滑坡前中后部形成贯通裂缝;最终由二十年一遇的暴雨诱发滑坡发生整体破坏。

It is of great significance to understand the evolution of the landslide in the Three Gorges Reservoir area.This paper studies the landslide deformation characteristics under the influence of reservoir water level fluctuation and rainfall and analyzes its failure mechanism.According to the GPS surface displacement monitoring data,the deformation characteristics of the landslide at different water level operation stages are detailed analyzed.Then,the grey correlation model is used to identify the main controlling factors of landslides displacement of different parts at different water level operation stages.Finally,GEO-Studio software was used to simulate the stability variation of Zengjiapeng landslide under the coupling effect of historical rainfall and reservoir water level fluctuation.The cross-check with quantitative analysis shows that:The kinematic state of Zengjiapeng landslide is time-varying,changes from slow creep state to step-like deformation state.In surface,more intense movement is observed in the east-central part of the slope than in the west part.In profile,the deformation is initiated in the front part,and then extends to the trailing part.The deformation and instability process are determined:the Zengjiapeng ancient landslide was first activated by the initial impoundment,and the leading edge deformed at first.Rainfall,as the main controlling factor in the middle and late stage,coupled with the fluctuation of reservoir water level and induced multiple step-like deformations of the landslide.Hence,a series of penetrating cracks are formed in the whole body of the landslide.Eventually,the overall failure was triggered by a strong rainfall once in 20 years.