书JournalofEngineeringGeology工程地质学报1004-9665/2007/15(Suppl.Ⅱ)006008高地应力条件下边坡岩体卸荷变形的两种表现形式研究室伍法权祁生文刘彤(中国科学院工程地质力学重点实验室北京100029)摘要本文简要介绍了高地应力地区水电高边坡工程中人们十分关注的两个工程地质与岩石力学问题:锦屏一级水电站边坡大范围岩体卸荷松动和小湾导致坝基(肩)岩体开挖快速卸荷问题。作者认为锦屏一级水电站左岸边坡大范围松动变形仍然是自重和构造复合应力场卸荷作用的结果,边坡的规模大、坡度陡,以及高水平构造应力是导致大范围卸荷松动变形的重要因素;小湾电站坝基(肩)岩体开挖过程中出现的坚硬完整岩体板裂、拱裂和“葱剥皮”等一系列新破裂现象是在高地应力作用下,由于开挖导致垂直坡面应力卸荷,增大边坡表面岩体主应力差和剪应力而引起的快速破裂行为,并通过破裂完成了顺坡面的最大主应力的卸荷,卸荷破裂主要集中在开挖面附近5~6m深度范围内。关键词高陡边坡坝基开挖快速卸荷大范围卸荷松动变形TWOTYPESOFUNLOADINGDEFORMATIONOFROCKSLOPESUNDERHIGHGEOSTRESSCONDITIONWUFaquanQIShengwenLIUTong(KeyLaboratoryofEngineeringGeomechanics,InstituteofGeologyandGeophysics,ChineseAcademyofSciences,Beijing100029)AbstractThepaperbrieflyintroducestwotypesofcommonlyconcernedengineeringgeologicalandrockmechanicalproblemsofhighslopesinhydropowerprojectsunderhighgeostress,i.e.,thebafflinglargescalerelaxdeformationofrockslopeattheJinpingNo.1hydropowerstationandthefastunloadingfracturescausedbydamfoundationexcavationattheXiaowanhydropowerstation.Thefollowingopinionsarepresented:①thelargescalerelaxdeformationoftheslopeatJinpingisactuallytheresultofunloadingofthecompositestressfieldofgravityandtectonicelements,andthelargescale,steepslopeandstronghorizontaltectonicstressarethemainfactorstoenlargetherangeofrelaxdeformation.②Thephenomenasuchasthintabulatefractures,arciformbrokenoffand"shallotskin"likefracturesoffreshhardrockattheexcavatedsurfaceofdamfoundationarecausedbyunloadingofσ3whichisalmostperpendiculartotheslopesurface,i.e.,theincreaseofthedifferenceofprincipalstressesleadstotherapidfailureofrock.Asafeatureofthiskindofrapidunloadingrelaxdeformation,thenewcracksconcentrativelydistributedinthede...