金沙江某水电站上下坝址岩体卸荷差异研究.pdf

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1、JournalofEngineeringGeology工程地质学报1004—9665／2009／17(3)-0313-04金沙江某水电站上下坝址岩体卸荷差异研究张勇①李天鹏②聂德新①刘彬①(①成都理工大学工程地质研究所成都610059)(②中国水电顾问集团昆明勘测设计研究院昆明650051)摘要在河流下切、斜坡成坡过程中，斜坡应力场不断调整和适应坡体的变化，表浅部岩体在应力变化过程中往坡外发生卸荷，在同一地区岩体卸荷深度应当相差不大。而在西南某水电站相隔仅1．4km上下坝址勘察过程中发现，两坝址岩体卸荷深度却存在较大差异，

2、上坝址岩体卸荷深度在20m以上，最大深度达到90m；下坝址岩体卸荷深度仅为5～20m。，通过现场调查及数值模拟成果表明，上下坝址岩层方位是两坝址岩体卸荷差异的决定性因素，上坝址为顺向坡，岩层走向与边坡走向平行，倾角较陡的岩层形成拉裂面，易于风化营力的侵入，岩体卸荷深度大；下坝址为横向坡，岩层走向与边坡走向近于垂直，岩体强度远大于岩层面的强度，且平行坡向的结构面数量少，岩体卸荷深度在20m以内。关键词卸荷顺向谷横向谷应力中图分类号：P642文献标识码：AUNLoADINGoFTHERoCKMASSATTHEUPANDDoWN

3、TREAMDAMSOFHYDRoPoWERSTATIoNINJINSHARIVERZHANGYong~LITianpeng~NIEDexinO)LIUBin~(①ChengduUnwe~i@ofTechnology，Chengdu610059)(~KunmingHydropowerInvestigation，DesignandResearchInstitute，CHECC。Kunming650051)AbstractTheprocessofstreamtrenchingandslopeformationcauseacont

4、inuouschangeinthestressfieldoftheriverbankslopes．Thesuperficialrockmassisunloadedinthechangeofstressfield．Thedepthofunloadingshouldbeindifferentinthesamearea．AninvestigationiscarriedonthestressfieldatahydropowerstationinsouthwestChina．Thestationhastwodams．Theupand

5、downtreamdamshaveadistanceof1．4kin．Theinvestigationdetec—tedthatunloadingdepthsoftherockmassesatthetwodamsiteshavewiderdifferences．Attheupstreamdamsite，theunloadindepthismorethan20m，anditsextremedepthcanreachto90m．Atthedownstreamdamsite，theunloadingdepthisonly5～20

6、m．Fieldsurveyandnumericalsimulationindicatethatorientationoftherockforma—tionisthekeyfactorforthediferenceintheunloadingdepthsattheupanddownstreamdams．Trendsofrockfor-mationandriverbankslopesattheupstreamdamareparalleled．Therockmassofsteepdipangleiseasytobecracked

7、．Theweatheringisinvaded．Thedepthoftherockmassunloadingisdeep．Atthedownstramdam，thetrendsoftherockformationandriverbankslopesarenearlyareperpendicular．Thestrengthoftherockmassisgreaterthanthebeddingplanes．Thestructuralsurfacesthatparalleltotheriverbankslopesareless

8、．Therefore。theunloadingdepthofrockmassiswithin20m．收稿日期：2008-08-01；收到修改稿日期：2008—11—27．基金项目：国家自然科学基金资助项目(编号40372127)．第一作者简介：张勇，地质工程专业．Email：zhangenhuall@1