地震边坡破坏机制及其破裂面的分析探讨
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摘要
地震作用下边坡破坏机制是边坡动力稳定性分析的前提,目前主要采用拟静力与动力有限元时程分析的方法进行分析,认为地震边坡破坏机制为剪切破坏,并以极限平衡法计算得到的剪切滑移面作为地震动力作用下的破裂面,而不考虑地震荷载作用下的拉破坏,从而使地震边坡稳定性分析失真。汶川地震边坡调研发现,滑坡上部多数发生拉破坏,甚至有些岩土体被抛出,这是一个很好的启示,为此,采用FLAC动力强度折减法,结合具有拉和剪切破坏分析功能的FLAC3D软件对地震边坡破坏机制进行数值分析。计算表明,地震边坡的破坏由边坡潜在破裂区上部拉破坏与下部剪切破坏共同组成,而不是剪切滑移破坏,通过多种途径给出地震边坡破裂面位置的确定方法,为边坡动力稳定性分析提供更加准确的基础。
The failure mechanism of slope under earthquake is the premise of slope′s dynamic stability analysis. Presently,pseudo-static method and dynamic time-history analysis method are commonly used,which regard the failure mechanism of slope under earthquake as shear failure,and take the shear sliding surface obtained by limit equilibrium method as failure surface under dynamic effect of earthquake without considering the tension failure under seismic load. It may lead to inaccuracy in the stability analysis of slope under earthquake. Investigation of the slopes during Wenchuan earthquake shows that tension failures mostly appear in the upper part of the landslides,and even some rock and soil masses are thrown out,which is an obvious enlightenment. So the FLAC dynamic strength reduction and program of FLAC3D with the function of tensile and shear failure analysis are adopted to study failure mechanism of slope under earthquake numerically. The study shows that the failure of slope under earthquake is made up of the tension failure in the upper part of the fracture zone and the shear failure in the lower part instead of shear sliding failure. A method of locating the fracture surface of slope under earthquake through several ways is provided,which is an accurate foundation for dynamic stability analysis of slopes.
The failure mechanism of slope under earthquake is the premise of slope′s dynamic stability analysis. Presently,pseudo-static method and dynamic time-history analysis method are commonly used,which regard the failure mechanism of slope under earthquake as shear failure,and take the shear sliding surface obtained by limit equilibrium method as failure surface under dynamic effect of earthquake without considering the tension failure under seismic load. It may lead to inaccuracy in the stability analysis of slope under earthquake. Investigation of the slopes during Wenchuan earthquake shows that tension failures mostly appear in the upper part of the landslides,and even some rock and soil masses are thrown out,which is an obvious enlightenment. So the FLAC dynamic strength reduction and program of FLAC3D with the function of tensile and shear failure analysis are adopted to study failure mechanism of slope under earthquake numerically. The study shows that the failure of slope under earthquake is made up of the tension failure in the upper part of the fracture zone and the shear failure in the lower part instead of shear sliding failure. A method of locating the fracture surface of slope under earthquake through several ways is provided,which is an accurate foundation for dynamic stability analysis of slopes.
引文
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[10]LI X P,SIMING H E.Seismically induced slope instabilities and the corresponding treatments:the case of a road in the Wenchuan earthquake hit region[J].Journal of Mountain Science,2009,6(1):96–100.
[11]许强,黄润秋.5.12汶川大地震诱发大型崩滑灾害动力特征初探[J].工程地质学报,2008,16(6):721–729.(XU Qiang,HUANG Runqiu.Kinetics characteristics of large landslides triggered by May12th Wenchuan earthquake[J].Journal of Engineering Geology,2008,16(6):721–729.(in Chinese))
[12]ZHENG Y R,DEN C J,TANG X S,et al.Development of finite element limiting analysis method and its application to geotechnical engineering[J].Engineering Sciences,2007,3(5):10–36.
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[14]Itasca Consulting Group,Inc..Fast Lagrangian analysis of continua in three dimensions(version3.0)user′s manual[R].[S.l.]:Itasca Consulting Group,Inc.,2003.
[15]赵尚毅,郑颖人,张玉芳.极限分析有限元法讲座——II有限元强度折减法中边坡失稳的判据探讨[J].岩土力学,2005,26(2):332–336.(ZHAO Shangyi,ZHENG Yingren,ZHANG Yufang.Study on slope failure criterion in strength reduction finite element method[J].Rock and Soil Mechanics,2005,26(2):332–336.(in Chinese))
[16]LIN M L,WANG K L.Seismic slope behavior in a large-scale shaking table model test[J].Engineering Geology,2006,86(2):118–133.
[2]CRESPELLANI T,MADIAI C,VANNUCHI G.Earthquake destructiveness potential factor and slope stability[J].Geotechnique,1998,48(3):411–419.
[3]WRIGHT S G,RATHJE E M.Triggering mechanisms of slope instability and their relationship to earthquakes and tsunamis[J].Pure and Applied Geophysics,2004,160(11):1865–1877.
[4]HAVENITH H B,VANINI M,JONGMANS D.Initiation of earthquake-induced slope failure:influence of topographical and other site specific amplification effects[J].Journal of Seismology,2003,7(3):397–412.
[5]祁生文,伍法权,刘春玲,等.地震边坡稳定性的工程地质分析[J].岩石力学与工程学报,2004,23(16):2792–2797.(QI Shengwen,WU Faquan,LIU Chunling,et al.Engineering geology analysis of stability of slope under earthquake[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(16):2792–2797.(in Chinese))
[6]CHEN T C,LIN M L,HUNG J J.Pseudostatic analysis of Tsao-Ling rockslide caused by Chi-Chi earthquake[J].Engineering Geology,2004,71(1):31–47.
[7]BAKER R,SHUKHA R,OPERSTEIN V,et al.Stability charts for pseudo-static slope stability analysis[J].Soil Dynamics and Earthquake Engineering,2006,26(9):813–823.
[8]刘汉龙,费康,高玉峰.边坡地震稳定性时程分析方法[J].岩土力学,2003,24(4):553–556.(LIU Hanlong,FEI Kang,GAO Yufeng.Time-history analysis method of slope seismic stability[J].Rock andSoil Mechanics,2003,24(4):553–556.(in Chinese))
[9]WANG F W,CHENG Q G,LYNN H,et al.Preliminary investigation of some large landslides triggered by Wenchuan earthquake in2008,Sichuan Province,China[J].Landslides,2009,6(1):47–54.
[10]LI X P,SIMING H E.Seismically induced slope instabilities and the corresponding treatments:the case of a road in the Wenchuan earthquake hit region[J].Journal of Mountain Science,2009,6(1):96–100.
[11]许强,黄润秋.5.12汶川大地震诱发大型崩滑灾害动力特征初探[J].工程地质学报,2008,16(6):721–729.(XU Qiang,HUANG Runqiu.Kinetics characteristics of large landslides triggered by May12th Wenchuan earthquake[J].Journal of Engineering Geology,2008,16(6):721–729.(in Chinese))
[12]ZHENG Y R,DEN C J,TANG X S,et al.Development of finite element limiting analysis method and its application to geotechnical engineering[J].Engineering Sciences,2007,3(5):10–36.
[13]郑颖人,赵尚毅,张鲁渝.用有限元强度折减法进行边坡稳定分析[J].中国工程科学,2002,4(10):57–62.(ZHENG Yingren,ZHAO Shangyi,ZHANG Luyu.Slope stability analysis by strength reduction FEM[J].Engineering Science,2002,4(10):57–62.(in Chinese))
[14]Itasca Consulting Group,Inc..Fast Lagrangian analysis of continua in three dimensions(version3.0)user′s manual[R].[S.l.]:Itasca Consulting Group,Inc.,2003.
[15]赵尚毅,郑颖人,张玉芳.极限分析有限元法讲座——II有限元强度折减法中边坡失稳的判据探讨[J].岩土力学,2005,26(2):332–336.(ZHAO Shangyi,ZHENG Yingren,ZHANG Yufang.Study on slope failure criterion in strength reduction finite element method[J].Rock and Soil Mechanics,2005,26(2):332–336.(in Chinese))
[16]LIN M L,WANG K L.Seismic slope behavior in a large-scale shaking table model test[J].Engineering Geology,2006,86(2):118–133.
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