大型阶地型地震滑坡的成因机制和三维稳定性分析
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摘要
以陈家坝场镇滑坡为例,通过对都坝河阶地的调查,概化出了都坝河阶地模型;根据对陈家坝滑坡的地貌学分析,结合水文地质调查和剖面对比,发现陈家坝滑坡位于都坝河的二级阶地上,是大型阶地型地震滑坡;通过陈家坝阶地地震滑坡的地形地貌、物质组成和岩土体力学性质室内试验分析,对其成因机制进行深入研究,发现陡倾的地形条件、松散的物质条件以及滑坡区前后缘高差大构成了滑坡的基本条件,而地震波反复剪切作用下饱和滑带土的残余剪切强度低和距离断裂带较近的强地震动是滑坡形成的主要原因;在对滑坡阶地模型概化的基础上,考虑滑坡的三维空间效应,采用有限差分强度折减法对其在自然状态、暴雨、地震等工况下进行了三维稳定性分析评价,并得到了不同工况下滑坡潜在三维不稳定的区域。这些分析对阶地型地震滑坡失稳机制的研究及稳定性评价具有一定的意义。
Through in-situ investigation,the terrace model of Duba river is generalized.According to the geomorphic characteristics and hydrogeological investigation,Chenjiaba seismically induced landslide is located on the terrace the river;sliding surface is formed by long-term immersion of groundwater.Geological structures of sliding mass and the residua on terrace as well as the attitude of bedrock exposed at the front and posterior margin of the landslide are compared respectively;so failure mode of this landslide is determined;while the severe earthquake occurred,silty clay of the sliding surface are weakened by groundwater,which resulted in the sliding of unconsolidated accumulative formation on the terrace.The finite-difference and strength-reduction method is adopted to compute its stability factors under natural,rainstorm,seismic conditions.And three dimensional shapes of potential unstable body under different conditions are put forward.
Through in-situ investigation,the terrace model of Duba river is generalized.According to the geomorphic characteristics and hydrogeological investigation,Chenjiaba seismically induced landslide is located on the terrace the river;sliding surface is formed by long-term immersion of groundwater.Geological structures of sliding mass and the residua on terrace as well as the attitude of bedrock exposed at the front and posterior margin of the landslide are compared respectively;so failure mode of this landslide is determined;while the severe earthquake occurred,silty clay of the sliding surface are weakened by groundwater,which resulted in the sliding of unconsolidated accumulative formation on the terrace.The finite-difference and strength-reduction method is adopted to compute its stability factors under natural,rainstorm,seismic conditions.And three dimensional shapes of potential unstable body under different conditions are put forward.
引文
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[14]GRIFFITHS D V,LANE P A.Slope stability analysis by finite elements[J].Geotechnique,1999,49(3):387-403.
[15]DAWSON E M,ROTH W H,DRESCHERA.Slope stability analysis by strength reduction[J].Geotechnique,1999,49(6):835-840
[16]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[J].岩土力学,2004,25(6):871-875.DENG Jian-hui,ZHANG Jia-xiang,MIN Hong,et a1.3D stability analysis of landslides based on strength reduction[J].Rock and Soil Mechanics,2004,25(6):871-875.
[2]姚鑫,徐冲,戴福初,等.四川汶川Ms8级地震引发的滑坡与地层岩性、坡度的相关性[J].地质通报,2009,28(8):1156-1163.YAO Xin,XU Chong,DAI Fu-chu,et al.Contribution of strata lithology and slope gradient to landslides triggered by Wenchuan Ms8 earthquake,Sichuan,China[J].Geological Bulletin of China,2009,28(8):1156-1163.
[3]张永双,石菊松,孙萍,等.汶川地震内外动力耦合及地质灾害实例[J].地质力学学报,2009,15(2):131-141.ZHANG Yong-shuang,SHI Ju-song,SUN Ping,et al.Coupling between hedonic and exogenic geological processes in the Wenchuan earthquake and example analysis of geohazards[J].Journal of Geomechanics,2009,15(2):131-141.
[4]殷跃平.汶川八级地震滑坡特征分析[J].工程地质学报,2009,17(1):29-39.YIN Yue-ping.Features of landslides triggered by the Wenchuan earthquake[J].Journal of Engineering Geology,2009,17(1):29-39.
[5]殷跃平.汶川八级地震地质灾害研究[J].工程地质学报,2008,16(4):433-444.YIN Yue-ping.Researches on the geohazards triggered by Wenchuan earthquake,Sichuan[J].Journal of Engineering Geology,2008,16(4):433-444.
[6]孔纪名,崔云,田述军,等.地震碎裂滑动型滑坡发育特点及典型实例分析[J].四川大学学报(工程科学版),2009,41(3):119-125.KONG Ji-ming,CUI Yun,TIAN Shu-jun,et al.Typical case study on the development characteristics of fragmentation-sliding seismic landslide[J].Journal of Sichuan University(Engineering Science Edition),2009,41(3):119-125.
[7]胡卸文,黄润秋,施裕兵,等.唐家山滑坡堵江机制及堰塞坝溃坝模式分析[J].岩石力学与工程学报,2009,28(1):181-189.HU Xie-wen,HUANG Run-qiu,SHI Yu-bing,et al.Analysis of blocking river mechanism of Tangjiashan landslide and dam-breaking mode of its barrier dam[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(1):181-189.
[8]祁生文,徐强,刘春玲.汶川地震极重灾区地质背景及次生斜坡灾害空间发育规律[J].工程地质学报,2009,17(1):39-49.QI Sheng-wen,XU Qiang,LIU Chun-ling.Slope instabilities in the severest disaster areas of 5·12 Wenchuan earthquake[J].Journal of Engineering Geology,2009,17(1):39-49.
[9]黄润秋,李为乐.汶川大地震触发地质灾害的断层效应分析[J].工程地质学报,2009,17(1):19-29.HUANG Run-qiu,LI Wei-le.Fault effect analysis of geohazard triggered by Wenchuan earthquake[J].Journal of Engineering Geology,2009,17(1):19-29.
[10]李秀珍,孔纪名,邓红艳,等.5·12汶川地震滑坡特征及失稳破坏模式分析[J].四川大学学报(工程科学版),2009,41(3):72-77.LI Xiu-zhen,KONG Ji-ming,DENG Hong-yan,et al.Analysis on characteristics and deformation failure mode of large-scale landslides induced by 5·12 Wenchuan earthquake[J].Journal of Sichuan University(Engineering Science Edition),2009,41(3):72-77.
[11]DUCAN J M.State of the art:Limit equilibrium and finite element analysis of slopes[J].Journal of Geotechnical Engineering,ASCE,1996,122(7):577-596.
[12]宋二祥.土工结构安全系数的有限元计算[J].岩土工程学报,1997,l9(2):1-7.SONG Er-xiang.Finite element analysis of safety factor for soil structures[J].Chinese Journal of GeetechnicalEngineering,1997,19(2):1-7.
[13]连镇营,韩国城,孔宪京.强度折减有限元法研究开挖边坡的稳定性[J].岩土工程学报,2001,23(4):407-411.LIAN Zhen-ying,HAN Guo-cheng,KONG Xian-jing.Stability analysis of excavation by strength reduction FEM[J].Chinese Journal of Geotechnical Engineering,2001,23(4):407-411.
[14]GRIFFITHS D V,LANE P A.Slope stability analysis by finite elements[J].Geotechnique,1999,49(3):387-403.
[15]DAWSON E M,ROTH W H,DRESCHERA.Slope stability analysis by strength reduction[J].Geotechnique,1999,49(6):835-840
[16]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[J].岩土力学,2004,25(6):871-875.DENG Jian-hui,ZHANG Jia-xiang,MIN Hong,et a1.3D stability analysis of landslides based on strength reduction[J].Rock and Soil Mechanics,2004,25(6):871-875.
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