毕业论文(数值模拟)

摘要高层建筑和地下工程的兴建，伴随着越来越多的深基坑开挖问题。深基坑开挖如果控制不力，往往容易引起较大的基坑变形，严重影响周围市政道路、管线和高层建筑物等的结构安全和正常使用。因此对基坑变形机理与影响因素以及其对周围环境影响的研究显得非常重要。本文在综合分析国内外研究成果的基础上，根据深基坑开挖特点，建立了有限元计算模型，对深基坑变形机理，地下水渗流对基坑的影响进行了数值模拟研究，主要取得的研究成果如下：1.结合广东佛山国际广场基坑的实际情况，通过MIDAS/GTS有限元软件,以水渗流作为讨论因素，分别建立考虑渗流和不考虑渗流两个计算模型，模拟基坑施工开挖过程,分析各开挖阶段渗流场的分布及变化规律。2.对渗流影响下的基坑变形性状(主要包括支护结构变形、坑外地表沉降变形和坑内地面隆起变形)进行分析研究，并将计算值和实测值作对比分析，得出在该工程条件下的基坑变形性状规律:(l)考虑渗流影响的支护结构最大水平位移计算值较不考虑渗流增大约30%，并与实际测值比较接近;(2)基坑地表最大沉降变形位置发生在距支护结构约为一倍的开挖深度处，考虑渗流影响的坑外地表沉降变形随开挖深度增加明显增大，且最大位移点向外移动;(3)坑内地面隆起变形曲线呈抛物线状，最大位移在基坑开挖面的中心点的位置。考虑渗流影响的坑内隆起变形，第一次开挖时基坑底部隆起量较大，随着开挖步而逐渐减小，至第四步开挖时的基坑底部隆起量小于非渗流作用下的情况。关键词：基坑开挖数值模拟有限元渗流基坑变形ABSTRACTIntheconstructionofhigh-risebuildingsandundergroundprojects,itisinevitabletoencountertheproblemofdeepfoundationpitexcavation.Ifthecontrolmeasurefail,pitexcavationwillinducelargedeformationofdeepfoundationpitandaffectsecurityandfunctionofthesurroundingstructuresseriously,suchasurbanroad,pipeline,high-risingbuildingandsoon.Soitisveryimportanttostudythedeformationmechanismoffoundationpit,theinfluenceofthedeepfoundationpitsonthesurroundingenvironment.Inthethesis,basedontheworldwideresearchachievements,thefinite-elementmodelwasestablishedaccordingtothebehaviorofdeepfoundationpitexcavation.Thedeformationmechanismoffoundationpit,theeffectofseepageflowtofoundationpit,theinfluencingfactorsofdeformationofdeepfoundationpitconsideringseepageweresimulatedandanalyzed.Themainachievementsareasfollows:1.FoundationofGuangdongFoshanInternationalPlazawiththeactualsituation,throughtheMIDAS/GTSfiniteelementsoftware.Theseepagewasconsideredtobeavariablefactor.Tostudythedistributionlawoftheseepage,3Dfiniteelementanalysismodelsthatinnoproeandproewereestablishedtosimulatetheprocessoffoundationpitexcavation,analysisthedistributionandvariationofexcavationstageseepage.2.Thebehavioroffoundationpitsuchassupportingstructuredisplacement,thesettlementdeformationofgroundandtheupheavealdeformationoflandwereanalysisedandresearched,anditwerecomparedwiththedateobtainedfromfieldobservation.Thebehavioroffoundationpitdeformationonthisconditionwereasfollow:(l)Thesupportingstructuremaximumdisplacementinporeis30%largerthanthatinnopore,andtheresultissimilartothevaluedataobtainedfromfieldobservation.(2)Thesettlementdeformationofgroundwasdeveloppingduringthestageofexcavation,themaximumisinsingleexcavatiomdepth.Thedeformationinporeincreasedsignificantly,andthemaximumdisplacementsiteoutwardmovement.(3)Theupheavaldeformationoflandshowedasaparabola,andthemaximumdeformationsiteisinthemiddleofthebottom.Consideringtheseepageoftheupheavaldeformationofland,theupheavaldeformationoflandatthefirstexcavationislarger.Graduallydecreaseswithfurtherexcavation,theupheavaldeformationoflandatthefourthexcavationissmallerthanthecaseinnopore.Keywords:Excavationoffoundationpitnumericalsimulationfiniteelementseepagedeformationoffoundationpit目录第一章绪论............................................................................................................................11.1课题研究背景及意义..................................................................................................11.2基坑渗流引起的问题..................................................................................................21.3国内外研究现状..........................................................................................................31.4本文的主要研究内容..................................................................................................7第二章基坑变形与渗流理论................................................................................................82.1基坑变形分析的基本理论..........................................................................................82.2基坑渗流分析的基本方法........................................................................................142.3基坑渗流研究概述....................................................................................................19第三章MIDAS/GTS有限元理论基础...................................................................................223.1MIDAS/GTS有限元软件..............................................................................................223.2非线性有限元分析....................................................................................................223.3数值模拟的实现........................................................................................................25第四章考虑渗流影响的基坑开挖工程实例分析..............................................................314.1工程概况....................................................................................................................314.2地质情况及水文地质条件........................................................................................314.3基坑支护方案以及降水方法....................................................................................314.4有限元模型的建立....................................................................................................314.5计算结果分析............................................................................................................354.6本章小结.......................................