黄土地区高速铁路建设中的重大工程地质问题研究

1、黄土地区高速铁路建设中的重大工程地质问题研究    我国黄土面积约占全国陆地总面积的6.63,其中湿陷性黄土约占3/4。在黄河中游的陕、甘、青及山西、河南等省,地表几乎完全被黄土所覆盖,连续分布面积达44×104km2,形成了地层连续、厚度大、面积广的黄土高原地貌景观。由于黄土特殊的工程性质(水敏性、大孔性、结构性),黄土地区的铁路工程建设常常会出现多种工程病害,如路堤的不均匀沉降,高湿度黄土中隧道的塌方和既有线黄土隧道出现拱部裂缝,桩基因负摩擦力作用引起的变形和破坏等多方面的问题,给铁路运营和养护带来了较大的危害。我国高速铁路(客运专线)建设

2、起步晚,但发展速度很快,郑州至西安铁路客运专线设计时速350km/h,是我国也是世界上在湿陷性黄土地区建设的第一条高速客运专线铁路。沿线黄土分布广泛,约占全线总长度的80,其中湿陷性黄土区段占全线总长度的65,自重湿陷性黄土占线路总长度的27,湿陷程度从轻微(级)到很严重(级)在整个路段均有分布,涵盖了我国湿陷性黄土的全部类型。由于沿线湿陷性黄土的工程性质非常复杂,客运专线对黄土路基、桥梁和隧道的特殊要求以及可供借鉴的研究成果和工程经验不足,因此,以郑西客运专线为例研究黄土地区高速铁路建设中的重大工程地质问题具有极其重要的实践价值和理论意义。论文的总体研究思路、主要研究内容和成果如下:(1)从

3、勘察、设计、施工和检测方面论述了客运专线的技术要求,分析了黄土工程地质的研究进展,提出了通过黄土地区的郑西客运专线需要解决的重大工程地质问题。(2)按自然地理概况(地理位置、地形地貌、气候与水文、地震)、地层岩性、地质构造和水文地质特征等诸多方面阐释了郑西客运专线黄土区域工程地质环境。(3)深入进行了郑西客运专线黄土工程地质特性分析与湿陷性评价。总结分析了郑西客运专线沿线黄土的分布特征、物质成分、结构特征及物理力学性质等工程地质特性,通过现场试坑浸水试验研究了黄土的自重湿陷变形特性(发生发展变化规律、自重湿陷量及其沿深度的变化、湿陷土层下限深度、浸水湿陷影响范围)、黄土场地的湿陷类型和等级、因

4、地区土质而异的修正系数_0、黄土的湿陷敏感性及渗透性,在此基础上对郑西客运专线黄土的湿陷性进行了准确评价。(4)通过湿陷性黄土地基处理措施与改良土路基实体工程的质量检测与评价以及沉降观测试验研究,验证了郑西客运专线湿陷性黄土地基处理措施、填料改良技术与施工工艺的合理性和有效性,按照客专路基工后沉降15mm的标准要求,对路基工后沉降进行了分析评价和预测,为郑西客运专线铺设无碴轨道提供了基础依据。(5)结合大断面黄土隧道的工程地质特点和重点黄土隧道的工程地质条件及客运专线双线黄土隧道的支护设计参数,对大断面黄土隧道施工方法进行了综合评价,研究了支护结构的适用性及变形控制技术指标。(6)试验研究分析

5、了湿陷性黄土区桩基负摩擦力、中性点及沉降变形的影响因素、发展变化规律及桩顶附加浸水沉降、土桩相对沉降与负摩擦力、中性点深度的关系,提出了湿陷性黄土地区桩基施工需要关注的重点问题。(7)分析论述了路基、隧道、桥涵的修建对黄土地质工程环境的影响,研究提出了郑西客运专线黄土地质工程环境保护的对策和措施China'sloessareaapproximatelycomposes6.63ofthetotalnationallandarea,inwhichthecollapsibleloessaccountsforabout3/4.Theearth'ssurfacesofShaanxi,Ga

6、nsu,Qinghai,ShanxiandHhemiddlereachesoftheYellowRiverarealmostentirelycoveredbyloessandformcontinuousdistributionareaof440,000squarekilometers,whichcomposetheLoessPlateaulandscapewithacontinuousstratum,largethicknessandbroadarea.Becauseoftheloesswithspecialengineeringpropertiesof

7、watersensitivity,bigporeandstructure,thevariousengineeringdiseasesusuallyappearintherailroadengineeringconstructionofloessregion,suchasthedifferentialsettlementofembankment,thetunnelcollapseinhighhumidityloess,thearchringcrackofloesstunnelincurrentrailroadanddeformationorfailureofpilefoundationcause

8、dbynegativefriction,whichgivebiggerharmtotransportationandmaintenanceofrailroad.China'shighspeedrailway(passengerdedicatedline)constructionstartslatebutdevelopsveryquickly.ThedesignspeedofZhengzhou-Xi'anpassengerdedicatedlineis350km/h,itisthefirsthighspeedpassengerdedicatedlineconstructedint

9、hecollapsibleloessregionbothinChinaandtheworld.TheloessdistributeswidelyalongZhengzhou-Xi'anpassengerdedicatedline.Itaccountsforabout80ofthetotallengthofline,inwhichthelengthsofcollapsibleandself-weightcollapseloessarerespectively65and27.Thecollapsibleclassificationfromtheslight(Iclass)tothevery

10、serious(IVclass)isdistributedinthewholeline,whichcoversalltypesofcollapsibleloessesinChina.BecauseofthecomplexengineeringpropertiesofcollapsibleloessalongZhengzhou-Xi'anpassengerdedicatedline,thespecialrequirementsoftheloessroadbed,bridgeandthetunnelintheline,aswellastheshortageofprovidedresearc

11、hachievementsandengineeringexperiences,thestudyofmajorengineeringgeologicalproblemsofhigh-speedrailwayconstructioninloessregionillustratedwithZhengzhou-Xi'anpassengerdedicatedlinehaveextremelyimportantpracticevalueandtheorysignificance.Theoverallresearchideas,mainresearchcontentsandachievementso

12、fthethesisareasfollows:(1)Thetechnicalrequirementsofpassengerdedicatedlinearediscussedfromthesurvey,design,constructionandinspection.theresearchprogressofloessengineeringgeologyisanalyzed.ThegreatandimportantengineeringgeologicalproblemstoneedbesolvedarealsoproposedinZhengzhou-xi'anpassengerdedi

13、catedlinethroughloessarea.(2)TheregionalengineeringgeologicalenvironmentofloessrelatedtoZhengzhouxi'anpassengerdedicatedlineisresearchedfromseveralmainaspectsofphysicalgeographyoverview(geographicallocation,terrainandlandform,climateandhydrology,earthquake),formationlithology,geologicstructurean

14、dhydrologygeologicalfeature,etc.(3)ThethoroughanalysisofengineeringgeologicalcharacteristicsandtheexactevaluationofcollapsibilityofloessrelatedtoZhengzhouXi'anpassengerdedicatedline.Theengineeringgeologypropertiesareanalyzedandsummarizedsuchasdistribution,materialcomposition,structure,physicalan

15、dmechanicalcharacteristicsofloessalongtheline.Theseproblemsarealsoresearchedthroughthefieldpittestwithwaterimmersion,whichincludetheself-weightcollapsedeformationcharacteristicsofloess(i.e.thedevelopmentandchangelaw,self-weightcollapsesettlementandits'changewithdepth,thelowerlimitdepthofcollapsi

16、blesoillayerandthecollapsibleareainducedbywaterimmersion),thecollapsibletypesandgradesofloesssites,thecorrectioncoefficient_0varyingwithregionandsoil,thecollapsiblesensitivityandpermeabilityofloess.OnthisbasisofitthecollapsibilityofloessisaccuratelyevaluatedinZhengzhou-Xi'anpassengerdedicatedlin

17、e.(4)Thesuitabilityandeffectforthetreatmentmeasuresoncollapsibleloessfoundation,technologyofimprovedloessfillandconstructionmethodaretestifiedthroughthequalitytestandsettlementobservationofexpirementalroadbed.Thesettlementofroadbedafteracceptanceisanalyzedandpredictedaccordingto15mmstandardofpasseng

18、erdedicatedline.ThereforeitprovidesthefundamentalbasisfortheballastlesstrackapplicationinZhengzhou-Xi'anpassengerdedicatedline.(5)Theconstructionmethod,suitabilityofsupportingstructureandcontrolindexesofdeformationarestudiedcombiningwiththeoverallengineeringgeologicalcharacteristics,theengineeringgeologicalconditionsandsupportparametersdesignedforimportantloesstunnelswithdoublepassengerdedicatedlines.(6)Thesecontentsareexperimentallystudiedandanalyzedthatthe