泸定县四湾村滑坡的地质成因与稳定评价
摘要
四湾村古滑坡体位于在建的大渡河泸定水电站下游约1 km处,其稳定性对电站的设计、建设和运营均存在较大影响。为评价滑坡的稳定性,对其进行详细的地质勘察和测试分析工作,并在此基础上分析其形成与演变过程,建立地质结构模型。该滑坡为一由地震诱发形成的高速滑坡,ESR法测年揭示其形成年代为17.2±2 ka B.P.,即晚更新世晚期。滑坡曾堵塞大渡河,滑坡坝溃决后滑坡堆积体发生过3次次级滑移。残留的滑坡堆积体呈帚形,长约700 m,宽约800 m,最大厚度137.62 m,体积约5.0×107 m3。堆积体前缘延伸至大渡河河床,临河为40°的陡坎,中后缘整体平缓。物质成分为花岗岩和闪长岩块石,夹块碎石土,透水性良好。勘察期间没有发现滑坡存在有宏观变形迹象。采用三维强度折减法和极限平衡法对滑坡的稳定性进行评价,安全系数分别为1.49和1.42。滑坡稳定性良好。
Siwancun landslide locates at 1 km downstream of the dam site of Luding Hydropower Station and its stability has great influence on the dam design,construction and operation.In order to evaluate its stability,detailed geological investigation and tests are carried out;geological origin and evolution are analyzed,and a geological structural model is established.The landslide is a high-speed one induced by earthquake dated back to 17.2±2 ka B.P.,i.e.the late period of Late Pleistocene by ESR method.The landslide dammed Dadu River experienced at least 3 secondary slides after dam break.The present landslide fills is of broom-shaped,around 700 meters long,800 meters wide and the maximum depths of 137.62 m.The total volume is about 5.0×107 m3.Its toe extends into the bed of Dadu River.At its front,the bank slope is steep with a slope of 40°,while the middle and rear parts of the slope are gentle.The slide fills are mainly composed of boulders and granular soils of granite and diorite origin,with good permeability.No deformation is evidenced during site investigation.Three-dimensional stability evaluation is carried out using the strength reduction technique and limit equilibrium method;and the factors of safety are 1.49 and 1.42,respectively.It is shown that the landslide is stable.
Siwancun landslide locates at 1 km downstream of the dam site of Luding Hydropower Station and its stability has great influence on the dam design,construction and operation.In order to evaluate its stability,detailed geological investigation and tests are carried out;geological origin and evolution are analyzed,and a geological structural model is established.The landslide is a high-speed one induced by earthquake dated back to 17.2±2 ka B.P.,i.e.the late period of Late Pleistocene by ESR method.The landslide dammed Dadu River experienced at least 3 secondary slides after dam break.The present landslide fills is of broom-shaped,around 700 meters long,800 meters wide and the maximum depths of 137.62 m.The total volume is about 5.0×107 m3.Its toe extends into the bed of Dadu River.At its front,the bank slope is steep with a slope of 40°,while the middle and rear parts of the slope are gentle.The slide fills are mainly composed of boulders and granular soils of granite and diorite origin,with good permeability.No deformation is evidenced during site investigation.Three-dimensional stability evaluation is carried out using the strength reduction technique and limit equilibrium method;and the factors of safety are 1.49 and 1.42,respectively.It is shown that the landslide is stable.
引文
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[4]邓建辉,张嘉翔,闵弘,等.基于强度折减概念的滑坡稳定性三维分析方法(II):加固安全系数计算[J].岩土力学,2004,25(6):871–875.(DENG Jianhui,ZHANG Jiaxiang,MIN Hong,et al.3D stability analysis of landslides based on strength reduction(II):evaluation of reinforcing factor of safety[J].Rock and Soil Mechanics,2004,25(6):871–875.(in Chinese))
[5]陈菲,邓建辉.岩坡稳定的三维强度折减分析[J].岩石力学与工程学报,2006,25(12):2 546–2 551.(CHEN Fei,DENG Jianhui.Three-dimensional stability analysis of rock slope with strength reduction method[J].Chinese Journal of Rock Mechanics and Engineering,2006,25(12):2 546–2 551.(in Chinese))
[6]冯树仁,丰定祥,葛修润.边坡稳定性的三维极限平衡分析方法及应用[J].岩土工程学报,1999,21(6):657–661.(FENG Shuren,FENG Dingxiang,GE Xiurun.3D limit equilibrium method for slope stability and its application[J].Chinese Journal of Geotechnical Engineering,1999,21(6):657–661.(in Chinese))
[7]姜清辉,王笑海,丰定祥,等.三维边坡稳定性极限平衡分析系统软件SLOPE3D的设计及应用[J].岩石力学与工程学报,2003,22(7):1 121–1 125.(JIANG Qinghui,WANG Xiaohai,FENG Dingxiang,et al.SLOPE3D—a three-dimensional limit equilibrium analysis software for slope stability and its application[J].Chinese Journal of Rock Mechanics and Engineering,2003,22(7):1 121–1 125.(in Chinese))
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