大型单斜层状基岩滑坡变形特征与失稳机制研究——以重庆石柱县龙井滑坡为例

Research on deformation characteristics and instability mechanisms of large monoclinal layered bedrock landslides:a case study of the Longjing landslide in Shizhu county,Chongqing

以重庆石柱县龙井滑坡为例,采用现场调查测绘、卫星遥感解译、无人机航测、工程地质钻探、深部位移监测、现场与室内试验等手段,详细分析该滑坡的变形特征、成因机制以及三维稳定性。该滑坡体积约142.83×10^(4)m^(3),为大型单斜层状岩质滑坡,具有复合性破坏特征。滑坡前后缘高差约50 m,前缘剪出口近陡立临空,为滑坡高位剪出提供了势能条件。斜坡内发育的2组优势构造裂隙与软弱夹层将中厚层基岩切割成碎裂块体,使岩体具有较好的离散性,为滑坡解体远程滑动提供了有利条件。底部软弱夹层经过长期演化蠕变,剪切强度逐渐降低形成滑带,为滑坡滑动提供了力学条件。运用力学矢量求解法,对龙井滑坡进行三维静力学解析。当滑带的抗剪强度处于饱和残余值时,滑坡安全系数为0.93,滑体将沿软弱夹层顺岩层的真倾向方向发生蠕滑变形,受到西侧稳定山体的阻挡后向SE方向发生小角度偏转滑动。本文采用多种手段较全面地分析龙井滑坡的变形特征以及失稳机制,可为此类受阻转向的楔形体滑坡早期识别与失稳模式判断提供有益的借鉴意义。

Taking Longjing landslide as an example,the deformation characteristics,genetic mechanisms and three-dimensional stability of the landslide are analyzed in detail by means of field survey and mapping,satellite remote sensing interpretation,UAV survey,engineering geological drilling,deep displacement monitoring,and field and laboratory tests. The landslide about 142.83×10^(4)m^(3) is a large monoclinal layered rock landslide with complex failure characteristics. The elevation difference between the front and the rear margins is about 50 m. The leading edge shear outlet is near a precipice,which provides potential energy for the high shear of the landslide. Two groups of dominant structural fractures and weak interlayers in the slope cut the medium-thick bedrock into fragmentation blocks,which makes the rock mass has good dispersion and provides favorable conditions for the long run-out landslide. After long-term evolutionary creep,the shear strength of the soft interlayer decreases gradually,forming a sliding zone,which provides the mechanical conditions for the landslide. The three-dimensional static analysis is carried out by using the method of mechanical vector solution. When the saturated residual shear strength is adopted,the safety factor of the landslide is 0.93. The slip body will creep along the true trend direction of the soft interlayer along the strata,and will slip in the SE direction at a small angle after being blocked by the stable mountain in the west. In this paper,the deformation characteristics and instability mechanisms of Longjing landslide are analyzed comprehensively by various means,which can provide useful reference for the early identification and instability mode judgment of wedge landslides with blocked steering.