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1、第4卷第1期地下空间与工程学报Vol.42008年2月ChineseJournalofUndergroundSpaceandEngineeringFeb.20083偏压连拱隧道洞口仰坡失稳机制的数值分析1111向安田,朱合华,丁文其,贾明辉(同济大学地下建筑工程系,上海200092)摘要:以江西某高速公路一浅埋偏压连拱隧道为背景,用Marc有限元程序对其出口段进行了动态施工的三维数值模拟。从施工过程中的应力(剪应力和正应力)集中、塑性区的分布形态和发展规律、仰坡轴向和横向地表位移的分布特征等方面,系统研究了偏压连拱隧道强风化仰坡因施工而引起的失稳机制。结果表明:(1)塑
2、性区和应力集中区在模拟施工过程中只出现在洞体附近,可能的仰坡失稳往往是隧道施工失稳的累进性响应,机制是:隧道开挖引起近洞区的塌落和挤出破坏,从而扰动相对较远的仰坡,削弱甚至破坏其稳定性;(2)隧道上方和近山脊一侧仰坡轴向和横向位移比近山谷一侧的大,仰坡失稳往往从隧道上方和埋深较大一侧开始;(3)洞口仰坡的轴向水平位移前缘大,后缘小,垂直位移后缘大,前缘小,与圆弧型剪切滑移边坡的位移模式很吻合。关键词:洞口仰坡;塑性区;应力集中;失稳机制;累进性响应中图分类号:U453.1;TB115文献标识码:A文章编号:167320836(2008)0120073207MouthSl
3、opeFailureMechanismofShallowEmbeddedandDouble2archTunnelwithPartial2pressure(XIANGAn2tian,ZHUHe2hua,DINGWen2qi,JIAMing2hui(GeotechnicEngineeringInstituteofTongjiUniversity,Shanghai200092,China)Abstract:TakingoneexpresswayinJiangXiprovinceastheengineeringbackground,thisarticlesimulatesthe
4、constructioneffectonmouthslopeforoneshallow2embeddedanddouble-archtunnelwithpartial2pressure.Severalaspects,suchasstressconcentration,plasticzonedistribution,grounddisplacementalongtheaxialandtransverseslopeaxis,arestudiedparticularlyandsystematicallyanditisfoundthatthestressisconcentrat
5、edandtheplasticzonesaredistributedonlynearthetunnellining,theslopefailureisagradualandaccumulatedresponsetothetunnelfailureduringconstruction.Theresponsemechanismis:theexcavationcausestherockandsoilnearthetunneltobecavedin,disturbingtherelativelyfarslopeandimpairingitsstability.Theaxialo
6、rtransversedisplacementismoreprominentfortheslopebetweentunnelandmountainridge,whichmayfailfirstly,thenfollowstheonebetweentunnelandmountainvale.Fortheslopeatthetunnelmouth,thedisplacementmodealongmainslopeaxisissimilaroridenti2caltothatofaslopewhichisslippingorshearingoutalongacurvedsur
7、face.Theverticaldisplacementofbackslopeisbiggerthanthatofthefrontaloneandforhorizontaldisplacement,itisjusttheopposite.Keywords:mouthslopeoftunnel;plasticzone;stressconcentration;failuremechanism;gradualandaccumula2tedresponse力场和位移场的重分布以及边坡失稳机理、失稳模1研究背景式的研究已进行得很深入,取得了许多有用
