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学位论文独创性说明本人郑重声明：所呈交的学位论文是我个人在导师指导下进行的研究工作及其取得研究成果。尽我所知，除了文中加以标注和致谢的地方外，论文中不包含其他人或集体已经公开发表或撰写过的研究成果，也不包含为获得西安科技大学或其他教育机构的学位或证书所使用过的材料。与我一同工作的同志对本研究所做的任何贡献均已在论文中做了明确的说明并表示了谢意。学位论文作者签名：日期：学位论文知识产权声明书本人完全了解学校有关保护知识产权的规定，即：研究生在校攻读学位期间论文工作的知识产权单位属于西安科技大学。学校有权保留并向国家有关部门或机构送交论文的复印件和电子版。本人允许论文被查阅和借阅。学校可以将本学位论文的全部或部分内容编入有关数据库进行检索，可以采用影印、缩印或扫描等复制手段保存和汇编本学位论文。同时本人保证，毕业后结合学位论文研究课题再撰写的文章一律注明作者单位为西安科技大学。保密论文待解密后适用本声明。学位论文作者签名：指导教师签名：年月日论文题目：曹家沟黄土大断面隧道施工参数优化研究专业：结构工程硕士生：李保平（签名）指导教师：王小林（签名）摘要大断面黄土隧道断面面积大、围岩条件差导致设计、施工、运营遇到大量困难和问题。现阶段大部分黄土隧道多采用传统施工方法，施工工序繁杂、进度缓慢，而三台阶七步法在此类地质条件下具有独特的优势，但其施工参数的优化研究还不完善，这成为大断面黄土隧道工程中亟待解决的重要课题。本文通过研究黄土性质、黄土隧道变形特征、围岩压力、主要灾害，分析大断面隧道的界定和施工方法，比较国内黄土隧道传统施工方法，验证了曹家沟隧道采用三台阶七步法的可行性，并重点对三台阶七步法的施工过程和施工要点进行研究。在曹家沟大断面黄土隧道工程基础上，对三台阶七步法支护效果进行数值模拟研究，并优化三台阶七步法的各施工面错距，主要得到以下结论：（1）由于三台阶七步法台阶短、支护封闭及时，隧道围岩沉降得到较好控制，沉降主要发生在上台阶和中台阶开挖后，可以通过适当增加上台阶施工步距来控制围岩压力释放速率，提高施工安全性。（2）适当加大台阶施工面错距可以较好地控制地层沉降变形，上台阶与中台阶施工错距、中台阶左右导洞施工错距对围岩沉降变形影响较大。（3）建议各施工面错距合理范围如下：上台阶与中台阶施工错距范围为4～6m；中台阶左右导洞施工错距范围为2.5～3.5m；下台阶左右导洞施工错距范围为2.5～3.5m；下台阶与仰拱施工错距合理范围为6～8m。关键词：黄土；大断面隧道；工法；数值模拟；参数优化研究类型：应用研究Subject:StudyonConstructionParameterOptimizationofLargeCross-sectionLoessTunnelCao-jiagouSpecialty:structuralengineeringName:LiBao-ping(Signature)Instructor:WangXiao-lin(Signature)ABSTRACTThedesign,constructionandoperationoflargecross-sectionofloesstunneloftenencounteranumberofdifficultiesandproblemsduetoitslargeareaandunfavorableconditionsofsurroundingrocks.Theloesstunnelsatthepresentdayareoftenconstructedwithtraditionalmethodswhicharefeaturedbycomplexproceduresandslowprogress.Whereasthethree-benchseven-stepexcavationmethodcandisplayitsuniqueadvantagesundersuchgeologicalconditions.Butthestudyontheoptimizationofconstructionparametersisfarfromadequate,whichbecomesanimportanttopicforstudyintheprojectoflargecross-sectionloesstunnel.Thisthesissummarizesthepropertiesofloess,deformationfeatures,surroundingrockpressureandmajordisastersofloesstunnel.Apartfromthestudyonthedefinitionandconstructionmethodsofalargecross-sectiontunnel,itmakescomparisonofthetraditionalconstructionmethodsofloesstunnelandprovesthereliabilityofthree-benchseven-stepexcavationmethodappliedinCao-jiagouTunnelproject.Thenitfocusesontheprocessandmainpointsofthree-benchseven-stepexcavationmethod.Drawingtheexperienceofthelargecross-sectionloesstunneloftheongoingCao-jiagourailwayproject,ittakesnumericalsimulationanalysisonthesupportingeffectsofthree-benchseven-stepexcavationmethod.Moreover,itoptimizesthestaggereddistancesofconstructionsiteswiththree-benchseven-stepexcavationmethod.Themainconclusionsareasfollows:(1)Thesubsidenceofsurroundingrocksofthetunnelcaneffectivelycontrolledduetotheshortbenchesandtimelyenclosureoftimbering.Thesubsidencemainlyoccursaftertheexcavationoftheupperbenchandmiddlebench.Theunleashingspeedofthesurroundingrockpressurecanbecontrolledbyincreasingtheconstructionpaceoftheupperbench,thusimprovingtheconstructionsafety.(2)Thesubsidenceanddeformationofstratumcanbeeffectivelycontrolledbyaugmentingappropriatelythestaggereddistancesofthebenches.Thestaggeredconstructiondistancebetweentheupperbenchandthemiddlebench,aswellasthestaggereddistancebetweenthetwopilotsofmiddlebench,cangreatlyinfluencethesubsidenceanddeformationofthesurroundingrocks.(3)Thesuggestiononthereasonablerangesofstaggereddistancesisasfollows:thestaggereddistancebetweentheupperbenchandmiddlebenchis4~6m;thestaggereddistancebetweenthetwopilotsofthemiddlebenchis2.5~3.5m;thestaggereddistancebetweenthetwopilotsofthelowerbenchis2.5~3.5m;thestaggereddistancebetweenthelowerbenchandtheinvertedarchranges6~8m.Keywords:loess;largecross-sectiontunnel;constructionmethod;numericalsimulation;parameteroptimization.Thesis:Applicationresearch目录I目录1绪论........................................................................................................................11.1研究背景..........................................................................................................11.2研究意义..........................................................................................................21.3本课题研究现状..............................................................................................31.3.1大断面黄土隧道研究现状........................................................................31.3.2三台阶七步法研究现状............................................................................51.4本文研究内容..................................................................................................62黄土隧道特点........................................................................................................82.1黄土的性质......................................................................................................82.1.1黄土成因及分布........................................................................................82.1.2黄土分类...................................................................................................82.1.3黄土工程性质.........................................................................................102.2黄土本构模型..........................