三峡库区白杨湾含多级软弱滑带滑坡变形特征与成因机制分析

Deformation Characteristics and Formation Mechanism of Baiyang Bay Landslide Containing Multistage Weak Slip Zones in Three Gorges Reservoir Area

三峡库区白杨湾滑坡是典型的含多级软弱滑带的滑坡,通过航拍和现场勘查,采用钻探、物探、位移监测、数值模拟相结合的手段,查明了滑坡变形特征和多级滑带的位置,滑坡的形成和发展受外部诱发因素与内部地质条件共同控制。钻探和物探解译揭示该滑坡为包含软弱夹层和多级滑带的深层岩土混合滑坡,分为2个滑动带。地表变形特征及位移监测表明滑坡中前部变形量相对较大,日变形量1.3~4.0 mm,处于均速变形状态,深部位移曲线显示有两处凸起位移突变点,主、次滑面特征明显,与钻孔勘探结果相互印证。数值模拟结果反映出,该滑坡在现状工况下处于欠稳定状态,在暴雨工况下滑坡安全系数显著降低,处于不稳定状态。滑坡区的地形地貌、地质构造、地层岩性为滑坡的形成提供了物源和场地条件,人类工程活动和降雨加剧了滑坡的变形。

The Baiyang bay landslide in the Three Gorges Reservoir area is a typical landslide with multistage weak slip zones.Through aerial photography and site surveys,we identified the deformation characteristics of the landslide and the location of the multistage slip zone by drilling,geophysical prospecting,displacement monitoring,and numerical simulation.The formation and development of the landslide are controlled by external inducing factors and internal geological conditions.Drilling and geophysical interpretation manifest that the landslide is a deep-seated rock-soil mixed landslide with multi-level slip zones with weak interlayers,divided into two sliding zones.Surface deformation and displacement monitoring reveal large deformation in the middle and front part of the landslide,with the daily deformation reaching 1.3-4.0 mm uniformly.The deep displacement curve shows two abrupt change points of bulge displacement with notable characteristics of primary and secondary sliding surfaces,which is verified by survey data.Moreover,numerical simulation results reflect that the landslide is in an under-stable state under current working conditions;in particular,the safety factor of the landslide under heavy rain condition declines remarkably,indicating an unstable state.The topography,geomorphology,geological structure,and stratum lithology of the landslide provide the source and site conditions for the formation of the landslide.Human engineering activities and rainfall have also exacerbated the deformation of the landslide.