汶川地震触发大光包巨型滑坡基本特征及形成机理分析.pdf

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1、JournalofEngineeringGeology工程地质学报1004—9665／2008／16(6)-()730—12汶川地震触发大光包巨型滑坡基本特征及形成机理分析黄润秋裴向军李天斌(成都理工大学地质灾害防治与地质环境保护国家重点实验室成都610059)摘要大光包一红洞子沟巨型滑坡是汶川地震触发的最大规模滑坡，其体积达7．42亿ITl3，堰塞坝高达690m，是我国已知的最大规模地震滑坡和最高的滑坡堰塞坝，也是目前全世界已知的为数不多的几个方量在5亿ITI3以上的超大规模滑坡之一，其高达690m的滑坡堰塞坝为目前世界最高的滑坡坝。滑坡位于发震断层上盘，距发震断裂

2、——映秀一北川断裂不足7km。震前斜坡为三面切割的孤立型山脊，相对高差达1500m；斜坡岩层走向与坡面近于垂直，层面延展性极好，构成滑动面形成的基础。调查和分析表明，斜坡的临空条件和贯通性好的灰岩层面是滑坡产生的基础；而高强度和长持时强震地面运动是导致滑坡产生的根本因素。滑坡产生的机理和过程可分为以下4个阶段：即坡体震裂、松弛和解体阶段、高速溃滑阶段、震动堆积阶段、二次抛射和碎屑流堆积阶段。失稳高速下滑的坡体，形成了沿主滑方向长4．2km，宽2．2km的堆积体，高速流动的碎屑流越过下游侧风波岩山脊，沿红洞子沟形成了长lkm的碎屑流堆积区。关键词大光包滑坡形成机制溃滑震

3、动堆积中图分类号：P642．22文献标识码：ABASICCHARACTERISTICSANDFoRMATIoNMECHANISMoFTHELARGESTSCALELANDSLIDEATDAGUNGBAooCCURREDDURINGTHEWENCHUANEARTHQUAKEHUANGRunqiuPEIXiangjunLITianbin(StateKeyLaboratoryofGeo—HazardPreventionandGeo—EnvironmentProtection，ChengduUniversityofTechnology，Chengdu610059)Abstra

4、ctThelandslideatDaguangbaoandHongdongzigousiteisthelargestamongalllandslidesoccurredduringtheWenchuanEarthquake．Itsvolumeisupto742Mm，anditsdebrisdamheightreaches690m．Soitisalsothemostlargestscalelandslidetriggeredbyea~hquakeamongallinvestigatedlandslidesinChina．Additionally，ithasthehigh

5、estdebrisdamoriginatingfromlandslideinChina．Itisevenoneofafewsuperlarge—scalelandslidesknownallovertheworld，whoseindividualvolumeisover500Mm．Thedebrisdamformedbythislandslidecanbethehighestaroundtheworld．ThelandslideislocatedontheupperplateoftheCausativeFault．Itisnearly7kmawayfromthetri

6、ggeringseismicfractureofYingxiu—beichuanfault．TheslopewasanisolatedridgebeforetheEa~hquake．itgtheridgehadits3sidescut．Itsheightdiferencereaches1500m．Thestrikeofclinothenwasal—mostverticaltotheslopesurface．theclinothenhadperfectextension．Theycomposedtogetherthebasicconditionsofslidingsur

7、faceformation．Ourinvestigationandanalysisshowthatthefreesurfaceconditionsoftheslopeandthesurfaceconnectivityoflimestonebeddingplanewerethebaseoflandslideformation．Andthegroundmovementre—suhedfromtheintensivequakingwithlargeintensityandlongdurationwastheradicaltriggeringfactorof