汶川地震后公路边坡崩塌灾害发育规律
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摘要
震后崩塌是强烈地震造成的震裂山体在后期余震、降雨及重力作用下变形不断发展并再次发生的崩塌。基于对四川省省道S303线映秀-卧龙段震后公路边坡崩塌灾害的调查,通过空间分布、崩塌与物质组成、岩性、失稳斜坡坡度、坡高、坡形、坡向和崩塌形成机理的关系等方面的分析,得到了震后崩塌灾害的发育规律:1.震后崩塌分布规律与地震时引发的崩塌的规律一致,即地震时易发生崩塌的地段地震后仍然易发生崩塌。2.按照边坡物质组成,以岩质边坡崩塌占绝大多数,岩土组合体边坡次之;较坚硬岩石中发生的崩塌多而较弱岩石中发生崩塌少,沿线发生崩塌最多的是岩性为闪长岩、辉长岩和变质砂岩等坚硬岩石组成的斜坡。3.失稳斜坡坡度在36°～85°之间,主要分布在41°～60°之间,即震后崩塌灾害主要发生在40°以上的斜坡。映秀-耿达段和耿达-卧龙段发生崩塌的边坡坡度有明显的差别,映秀-耿达段集中在坡度为46°～60°的斜坡,而耿达-卧龙段集中在在坡度为41°～55°的斜坡。4.绝大多数崩塌发生在坡高150 m以内的斜坡上,映秀-耿达段和耿达-卧龙段发生崩塌的边坡高度有明显的差别,映秀-耿达段集中在高度为51～350 m的斜坡,而耿达-卧龙段集中在在高度<200 m的斜坡,尤以高度<100 m的最多。5.阳坡和阴坡的崩塌数量有明显的差异,阳坡发生崩塌的数量远远大于阴坡崩塌发生的数量。6.震后边坡崩塌的形成机理以滑移式崩塌和倾倒式为主。映秀-耿达段和耿达-卧龙段地处不同地质构造单元,由于岩性的差异,发生崩塌的斜坡的坡度、高度和主要形成机理具有差异性。
The post-earthquake rockfall refers to such rockfall that is formed in seismic-ruptured rocks caused by the earthquake and falls due to progressive deformation resulted in the later aftershocks,rain and gravity.Based on site investigation of the slope rockfall in the highway S303 from Wolong to Yingxiu in Sichuan province after Wenchuan earthquake,through the analysis of the space distribution,the relationship between rockfall and composition,lithology,and gradient,height,configuration and direction of slopes as well as the formation mechanism of the rockfalls,the development rules of the post-earthquake rockfalls are obtained:1)Distribution rule of rockfall after the earthquake is the same with that during the earthquake,that is,the place where rockfall occurs easily during the earthquake is still the same where rockfall occurs easily after the earthquake.2)According to the material composition of slope,most rockfalls are rock slope rockfalls,and then are rock-soil slope;the numbers of rockfalls in harder rocks is more than that in softer rocks,i.e.,most rockfalls are formed in diorite,gabbro and metasandstone.3)The gradient of rockfall slope is between 36°～85 °,mostly between 41°～ 60°,that is to say,post-earthquake rockfall occurs easily on slopes with gradient above 40°.What's more,there is an obvious difference in slope gradient between the highway from Yingxiu to Genda and from Genda to Wolong.The predominant slope gradient from Yingxiu to Genda is 46～60°,while that from Genda to Wolong is 41°～55°.4)Post-earthquake rockfall occurs easily on slope with height above 150m and there is an obvious difference in slope height between the highway from Yingxiu to Genda and from Genda to Wolong.The slope height from Yingxiu to Genda is mainly between 51～350 m,while the height of most of the rockfall slopes from Genda to Wolong is less than 200m,especially most less than 100 m.5)There is a remarkable difference in the number of rockfall between sunny and cloudy slope.6)The formation mechanisms of the post-earthquake rockfall are primarily sliding rockfall and dumping rockfall.Since the Yingxiu-Gengda and Gengda-Wolong lies in the different geological units which have difference in lithology,the gradient,height of slopes where rockfall occur and the rockfall mechanism is different.
The post-earthquake rockfall refers to such rockfall that is formed in seismic-ruptured rocks caused by the earthquake and falls due to progressive deformation resulted in the later aftershocks,rain and gravity.Based on site investigation of the slope rockfall in the highway S303 from Wolong to Yingxiu in Sichuan province after Wenchuan earthquake,through the analysis of the space distribution,the relationship between rockfall and composition,lithology,and gradient,height,configuration and direction of slopes as well as the formation mechanism of the rockfalls,the development rules of the post-earthquake rockfalls are obtained:1)Distribution rule of rockfall after the earthquake is the same with that during the earthquake,that is,the place where rockfall occurs easily during the earthquake is still the same where rockfall occurs easily after the earthquake.2)According to the material composition of slope,most rockfalls are rock slope rockfalls,and then are rock-soil slope;the numbers of rockfalls in harder rocks is more than that in softer rocks,i.e.,most rockfalls are formed in diorite,gabbro and metasandstone.3)The gradient of rockfall slope is between 36°～85 °,mostly between 41°～ 60°,that is to say,post-earthquake rockfall occurs easily on slopes with gradient above 40°.What's more,there is an obvious difference in slope gradient between the highway from Yingxiu to Genda and from Genda to Wolong.The predominant slope gradient from Yingxiu to Genda is 46～60°,while that from Genda to Wolong is 41°～55°.4)Post-earthquake rockfall occurs easily on slope with height above 150m and there is an obvious difference in slope height between the highway from Yingxiu to Genda and from Genda to Wolong.The slope height from Yingxiu to Genda is mainly between 51～350 m,while the height of most of the rockfall slopes from Genda to Wolong is less than 200m,especially most less than 100 m.5)There is a remarkable difference in the number of rockfall between sunny and cloudy slope.6)The formation mechanisms of the post-earthquake rockfall are primarily sliding rockfall and dumping rockfall.Since the Yingxiu-Gengda and Gengda-Wolong lies in the different geological units which have difference in lithology,the gradient,height of slopes where rockfall occur and the rockfall mechanism is different.
引文
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[9]Qi Shengwen,Xu Qiang,Liu Chunling,et al.Slope instabilities inthe severs disaster area of 5.12 Wenchuang earthquake[J].Journalof Engineering Geology 2009,17(1):39-49[祁生文,许强,刘春玲等.汶川地震极重灾区地质背景次生斜坡灾害空间发育规律[J].工程地质学报,2009,17(1):39-49]
[10]Huang Runqiu,Li Weile,Fault effect analysis of geohazard triggeredby Wenchuan earthquake[J].Journal of Engineering Geology,2009,17(1):19-28[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):19-28]
[11]Xie Heping,Deng Jianhui,Tai Jiajia,et al.Wenchuan large earth-quake and post-earthquake reconstruction related to geotechnicalproblems[J].Chinese Journal of Rock Mechanics and Engineer-ing,2008,27(9):1 781-1 791[谢和平,邓建辉,台佳佳,等.汶川大地震灾害与灾区重建的岩土工程问题[J].岩石力学与工程学报,2008,27(9):1 781-1 791]
[12]Feng Wenkai,Xu Qiang,Huang Runqiu.Deformation mechanics ofthe ruptures by earthquakes[J].Chinese Journal of Rock Mechan-ics and Engineering,2009,28(Suppl.):3 124-3 130[冯文凯,许强,黄润秋.斜坡震裂变形力学机制初探[J].岩石力学与工程学报,2009,28(增刊):3 124-3 130]
[13]Cheng Qiang,Wu Shigui,Su Yujie,Geological Hazards due to Wen-chuan earthquake along Yingxiu-Wolong highway[J].Journal ofEngineering Geology,2010,18(2):160-167[程强,吴事贵,苏玉杰.映秀-卧龙公路沿线汶川地震地质灾害研究[J].工程地质学报,2010,18(2):160-167]
[2]Keefer D V.Landslides Caused by Earthquakes[J].GerologicalSociety of America Bulletin.l984,95(4):406-421
[3]Wilson R C,Keefer D K.A real limits of earthquake-induced lands-liding[C]//Evaluating Earthquake Hazards in the Los Angeles Re-gion.U.S.Geol.Sur.Press,1985:316-345
[4]Abrahamson N A,Silva W J.Empirical response spectral attenuationrelations for shallow crustal earthquakes[J].Bulletin of the Interna-tional Association of Engineering Geology,1997,68(1):94-109
[5]Ding Yanhui,Wang Yuqing,Sun Jinzhong,et al.,Research on themethod for prediction of earthquake-induced landslides and its appli-cation to engineering projects.Journal of Engineering Geology,2000,8(4):75-80[丁彦慧,王余庆,孙进忠,等.地震崩滑预测方法及其工程应用研究[J].工程地质学报,2000,8(4):75-80]
[6]Yang Qinghua,Yao Lingkan,Ren Ziming,Centrifugal model test ondynamical characteristics of landslides of loose slope under seismicloading.Chinese Journal of Rock Mechanics and Engineering,2008,27(2):368-374[杨庆华,姚令侃,任自铭,等.地震作用下松散体斜坡崩塌动力学特性离心模型试验研究,岩石力学与工程学报,2008,27(2):368-374]
[7]Huang Runqiu,Li Weile.Research on development and distributionrules of geohazards induced by Wenchuan earthquake on 12th May2008[J].Chinese Journal of Rock Mechanics and Engineering,2008,27(11):2 173-2 183[黄润秋,李为乐.“5.12”汶川大地震触发地质灾害的发育分布规律研究[J].岩石力学与工程学报,2008,27(12):2 585-2 592]
[8]Yin Yueping,Researches on the geohazards triggered by Wenchuan,Sichuan[J].Journal of Engineering Geology,2008,16(4):433-444[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]
[9]Qi Shengwen,Xu Qiang,Liu Chunling,et al.Slope instabilities inthe severs disaster area of 5.12 Wenchuang earthquake[J].Journalof Engineering Geology 2009,17(1):39-49[祁生文,许强,刘春玲等.汶川地震极重灾区地质背景次生斜坡灾害空间发育规律[J].工程地质学报,2009,17(1):39-49]
[10]Huang Runqiu,Li Weile,Fault effect analysis of geohazard triggeredby Wenchuan earthquake[J].Journal of Engineering Geology,2009,17(1):19-28[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):19-28]
[11]Xie Heping,Deng Jianhui,Tai Jiajia,et al.Wenchuan large earth-quake and post-earthquake reconstruction related to geotechnicalproblems[J].Chinese Journal of Rock Mechanics and Engineer-ing,2008,27(9):1 781-1 791[谢和平,邓建辉,台佳佳,等.汶川大地震灾害与灾区重建的岩土工程问题[J].岩石力学与工程学报,2008,27(9):1 781-1 791]
[12]Feng Wenkai,Xu Qiang,Huang Runqiu.Deformation mechanics ofthe ruptures by earthquakes[J].Chinese Journal of Rock Mechan-ics and Engineering,2009,28(Suppl.):3 124-3 130[冯文凯,许强,黄润秋.斜坡震裂变形力学机制初探[J].岩石力学与工程学报,2009,28(增刊):3 124-3 130]
[13]Cheng Qiang,Wu Shigui,Su Yujie,Geological Hazards due to Wen-chuan earthquake along Yingxiu-Wolong highway[J].Journal ofEngineering Geology,2010,18(2):160-167[程强,吴事贵,苏玉杰.映秀-卧龙公路沿线汶川地震地质灾害研究[J].工程地质学报,2010,18(2):160-167]
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