任务精读：明挖法（双语）课件讲解

隧道施工技术明挖法TunnelConstructionTechnologyOpen-cutMethod明挖法目录TableofContentsOpen-cutMethod放坡明挖法1SlopingandOpen-cutMethod悬臂支护明挖法2MethodofOpen-cutwithCantileverSupport围护结构加支撑开挖法3MethodofOpen-cutwithEnclosureStructureplusSupport课程小结4Summary优点Advantages在覆盖层薄、人口稀少、车辆不多的地区采用最经济。缺点Disadvantages施工产生的噪声、振动等公害极大的干扰附近居民的生活和工作。明挖法Open-cutMethod基坑法foundationpitmethod明挖法又称基坑法Theopen-cutmethodisalsoknownasthefoundationpitmethod.施工作业面宽敞Spaciousconstructionworkingface施工速度快Fastconstructionspeed方法简单易行Asimpleandeasy-to-domethod主体结构受力条件较好GoodstressconditionsforthemainstructureItisthemosteconomicalmethodtobeadoptedinareaswiththinoverburden,sparsepopulationandfewvehicles.破坏地面Causesdamagetotheground中断交通Disruptionoftraffic拆迁工作量大HeavyworkloadofdemolitionPublichazardssuchasnoiseandvibrationgeneratedduringconstructiongreatlyinterferewiththelifeandworkofnearbyresidents.露天情况从地面向下挖出基坑，在基坑内进行结构施工，然后回填恢复地面。Itistodigafoundationpit

fromthegrounddowninanopen-airsituation,

constructthestructureinthefoundationpit,andthencarryoutbackfillingto

restoretheground.明挖法Open-cutMethod放坡明挖法SlopingandOpen-cutMethod悬壁支护明挖法MethodofOpen-cutwithCantileverSupport围护结构加支撑开挖法MethodofOpen-cutwithEnclosureStructureplusSupport放坡明挖法SlopingandOpen-cutMethod01放坡明挖法是指根据隧道侧向土体边坡的稳定能力，由上而下分层放坡开挖隧道所在位置及其上方的土体至隧道基底高程后，再由下而上顺作隧道衬砌结构和防水层，最后施作结构外回填土并恢复地表状态的施工法。明挖法Open-cutMethod放坡明挖法SlopingandOpen-cutMethod

Accordingtothestabilityofthelateralsoilslopeofthetunnel,thesiteofthe

tunnelandthesoilmassaboveitshallbesubjecttoslopingexcavationinlayersfromtoptobottomtotheelevationofthetunnelfoundationbase.

Then,thetunnelliningstructureandwaterprooflayerareconstructedsuccessivelyfrombottomtotop.

Finally,thesoiloutsidethestructureisbackfilled,andthegroundsurfaceisrestored.FoundationbaseelevationGradeIIIslopingGradeIIslopingGradeIslopingGroundelevation放坡明挖法SlopingandOpen-cutMethod优缺点Advantagesanddisadvantages主要适用于埋深较浅，边坡土体稳定性较好，且地表没有过多限制性条件的隧道工程。边坡稳定性较差时，可采用喷射混凝土进行边坡防护或采用锚杆加固边坡土体。适用条件Applicationconditions遇到受地下水影响的工程时，可采用井点降水的方法，以便提高边坡的稳定性及改善基坑内循工环境。明挖法Open-cutMethod放坡明挖法SlopingandOpen-cutMethod放坡明挖法SlopingandOpen-cutMethod开挖方量大Largeexcavationvolume机械化程度高Highlevelofmechanization施工速度快Fastconstructionspeed质量易于保证Easytoensurequality

Whentheprojectisaffectedbygroundwater,themethodofwellpointdewateringcanbeused,soastoimprovethestabilityoftheslopeandtheconstructionenvironmentinthefoundationpit.

Itisoftenusedfortunnelengineeringconstructionwheretheburialdepthisshallow,thestabilityofslopesoilmassisgood.andtherearenoexcessiverestrictiveconditionsonthegroundsurface.Whentheslopestabilityispoor,shotcretingcanbecarriedoutforslopeprotection,oranchorrodscanbeusedtoreinforcetheslopesoilmass.悬臂支护明挖法MethodofOpen-cutwithCantileverSupport02悬臂支护开挖法是将基坑围护结构插入基坑底部以下一定深度,然后在围护结构的保护下开挖基坑内的土体至设计隧道基底高程，再由下向上顺作隧道主体结构和防水层，最后施作结构外回填土并恢复地表状态的施工方法。明挖法Open-cutMethod悬臂支护明挖法MethodofOpen-cutwithCantileverSupport悬壁支护明挖法MethodofOpen-cutwithCantileverSupport

Thismethodistoinserttheenclosurestructureofthefoundationpitintothebottomofthefoundationpitatacertaindepthbelow,undertheprotectionoftheenclosurestructure,thesoilmassinthefoundationpitisexcavatedtothedesignedelevationofthetunnelfoundationbase,then,themainstructureofthetunnelandwaterprooflayerareconstructedsuccessivelyfrombottomtotop,andfinally,thesoiloutsidethestructureisbackfilled,andthegroundsurfaceisrestored.悬臂支护开挖ExcavationofbottomsurfaceUndergrounddiaphragmwallInsertiondepthExcavationdepthExcavationwithcantileversupport由于有围护结构的保护，开挖士方量小，且基坑内无支撑，便于基础开挖和主体结构施工的机械化，也易保证工程质量。围护结构较复杂，增加了造价及施工难度，此法有时也用在有支撑开挖基坑的上部。明挖法Open-cutMethod悬臂支护明挖法MethodofOpen-cutwithCantileverSupport悬壁支护明挖法MethodofOpen-cutwithCantileverSupport优点Advantages缺点DisadvantagesUndertheprotectionoftheenclosurestructure,theexcavationvolumeissmall,andthereisnosupportinthefoundationpit,whichfacilitatesthemechanizationoffoundationexcavationandconstructionofthemainstructureandalsohelpstoensurethequalityoftheproject.Theenclosurestructureiscomplex,whichleadstoanincreaseincostsandconstructiondifficulty.Thismethodissometimesusedintheexcavationoftheupperpartofthefoundationpitwithsupport.主要适于埋置较浅，边坡土体稳定性较差，且地表有一定限制性要求的隧道工程中。明挖法Open-cutMethod悬臂支护明挖法MethodofOpen-cutwithCantileverSupport悬壁支护明挖法MethodofOpen-cutwithCantileverSupport木桩Woodenpiles钢桩Steelpiles钢筋混凝土预制桩Precastreinforcedconcretepiles挖孔桩/灌注桩Boredpiles/cast-in-situpiles适用条件Applicationconditions

Methodofopen-cutwithcantileversupportismainlyusedfortunnelengineeringconstructionwheretheburialdepthisshallow,

thestabilityofslopesoilmassisgood,andtherearecertainrestrictiveconditionsonthegroundsurface.外因：Externalfactor:明挖法Open-cutMethod悬臂支护明挖法MethodofOpen-cutwithCantileverSupport内因：Internalfactor:常采用下列工程措施：Thefollowingengineeringmeasuresareoftenadopted:支护结构设计成刚度较大截面形式。Designthesupportingstructureintoasectionformwithhighrigidity.在支护结构顶部设圈梁等，以改善其整体受力状况，提高整体刚度。Setringbeamsatthetopofthesupportingstructuretoimproveitsoverallstressconditionsandoverallrigidity.基坑外一定范围内挖去表层覆盖土，以减少侧压力。Removethecoveringsoilwithinacertainrangeoutsidethefoundationpittoreducethelateralpressure.基坑外进行井点降水，采用压密注浆、搅拌桩或粉喷桩等方法加固。Outsidethefoundationpit,carryoutwellpointdewatering,andadoptcompactiongrouting,mixingpilesorcementinjectionpilesandothermethodsforreinforcement.基坑内用井点降水和加固土体方法，使坑底土体固结，增加土体抗力。Inthefoundationpit,adoptthemethodofwellpointdewateringandsoilreinforcementmethodstoconsolidatethesoilmassatthebottomofthefoundationpitandincreasetheresistanceofthesoilmass.基坑内设置护脚。Providetoeprotectioninthefoundationpit.施工中应经常检查支撑状态，必要时对其应力进行监控。Frequentlycheckthesupportstatusduringconstruction,andmonitorthestresswhennecessary.自身强度和刚度不够Insufficientstrengthandrigidity土体、地下水soilmassandgroundwater围护结构加支撑开挖法MethodofExcavationwithEnclosureStructureplusSupport03明挖法Open-cutMethod围护结构加支撑开挖法MethodofExcavationwithEnclosureStructureplusSupport施工工艺Constructionprocess明挖法Open-cutMethod围护结构加支撑开挖法MethodofExcavationwithEnclosureStructureplusSupport围护结构Enclosurestructure开挖至第一道支撑所需的高程、安装支撑并施加预应力Excavatetoelevationrequiredforfirstsupport,erectthesupport,andapplytheprestress挖槽法Trenchingmethod开挖支撑设计位置处土体(保留其两侧土体)挖至第二道支撑高程时，安装第二道支撑并施加预应力Excavatethesoilmassatthedesignpositionofthesupport(withthesoilmassonbothsidesretained).Afterexcavatingtotheelevationofthesecondsupport,erectthesupportandapplytheprestress由上向下开挖土体至适当高度Excavatethesoilmassfromtoptobottomtoanappropriatedepth继续用挖槽法安装下道支撑，重复以上方法，最后开挖至基底高程Continuetoerectthenextsupportusingthetrenchingmethod,repeattheaboveprocedures,andfinallyexcavatetothefoundationbaseelevation依次浇筑板底、下层侧墙、中板、上层侧墙、顶板Carryoutthepouringoftheslabbottom,lowersidewall,middleplate,uppersidewallandtopslabinsequence.明挖法Open-cutMethod围护结构加支撑开挖法MethodofExcavationwithEnclosureStructureplusSupport围护结构加支撑开挖法MethodofExcavationwithEnclosureStructureplusSupport支撑Support适用条件：基坑深度较大，侧压力较大的情况。Applicationconditions:Wherethedepthofthefoundationpitandthelateralpressureisrelativelylarge.斜支撑Diagonalsupport围护结构加斜支撑开挖法methodofexcavationwithenclosurestructureplusdiagonalsupport围护结构加水平支撑开挖法methodofexcavationwithenclosurestructureplushorizontalsupport围护结构加锚杆支撑开挖法methodofexcavationwithenclosurestructureplusanchorrodsupport锚杆Anchorrod水平支撑Horizontalsupport水平支撑Horizontalsupport明挖法Open-cutMethod围护结构加支撑开挖法MethodofExcavationwithEnclosureStructureplusSupport水平支撑开挖支护简图SketchofSupportforExcavationwithHorizontalSupportGroundFirstsupportSecondsupportExcavationfaceElevationDrawingAnglebraceTransversebraceEnclosure横撑Transversebrace角撑Anglebrace优点Advantages

墙体水平位移小；安全可靠，开挖深度不受限制。但要求围护结构的平面形状比较规则，以矩形为最佳。开挖基坑宽度较大时，支撑应加设中间支柱来保持其稳定性。中间支柱应在开挖前按设计位置做好。明挖法Open-cutMethod围护结构加支撑开挖法MethodofExcavationwithEnclosureStructureplusSupport

Horizontaldisplacementofthewallissmall.Themethodissafeandreliable,andtheexcavationdepthisnotlimited.However,itrequiresarelativelyregularplaneshapeoftheenclosurestructure,andrectangleispreferred.Whenthewidthoftheexcavatedfoundationpitisrelativelylarge,thesupportshallbeprovidedwithanintermediateposttomaintainitsstability.Theintermediatepostshallbemadeaccordingtothedesignpositionbeforeexcavation.施工工艺：采用中心挖槽法开挖基坑内土体至斜支撑基础底部高程,浇筑基础，及时安装支撑，使支撑端支撑在围护结构上，另一端支撑在已浇筑的基础上，并施加预应力，然后开挖其余土体。设有两道或多道斜支撑时，先安装外侧的长支撑,后安装内侧的支撑，并把所有斜支撑基础连为整体,形成结构板底。最后依次浇筑下层侧墙、中板、上层侧墙、顶板，并按要求的时序拆除支撑，完成结构体系转换。明挖法Open-cutMethod围护结构加支撑开挖法MethodofExcavationwithEnclosureStructureplusSupport斜支撑Diagonalsupport斜支撑立面图GroundElevationDrawingofDiagonalSupportExcavationfaceFoundationFirstdiagonalsupportSeconddiagonalsupportEnclosurestructureConstructionprocess:Itadoptsthecentraltrenchingmethodtoexcavatethesoilmassinthefoundationpittotheelevationofthefoundationbottomofthediagonalsupport,andthenthefoundationispoured.Thesupportsaretimelyerected,sothatoneendofthesupportissupportedontheenclosurestructure,andtheotherendissupportedonthepouredfoundation.Thentheprestressisapplied,andtheremainingsoilisexcavated.Whentwoormorediagonalsupportsareprovided,thelongsupportontheoutersideshallbeerectedfirst,andthenthesupportontheinnersideiserected,Afterthat,alldiagonalsupportfoundationsareconnectedtoformawholestructureof

thestructuralslabbottom.Finally,thelowersidewall,middleplate,uppersidewallandtopslabarepouredinsequence.Thesupportsareremovedaccordingtotherequiredsequence

tocompletestructuresystemtransformation.明挖法Open-cutMethod围护结构加支撑开挖法MethodofExcavationwithEnclosureStructureplusSupport斜支撑Diagonalsupport斜支撑立面图GroundElevationDrawingofDiagonalSupportExcavationfaceFoundationFirstdiagonalsupportSeconddiagonalsupportEnclosurestructure适用条件Applicationconditions适用于对沉降要求不严格，且基坑深度不大的情况。斜支撑基础及结构底板需分批施工，工序交错复杂，施工难度大。

Themethodisapplicabletosituationswheretherearelessstrictrequirementsforsettlement,andwherethedepthofthefoundationpitisnotlarge.Thediagonalsupportfoundationandstructuralbaseplateshallbeconstructedindifferentbatches,whichleadstothestaggeredandcomplexconstructionprocess,andgreatconstructiondifficulty.施工工艺：围护结构完成后，开挖至锚杆的设计高程，钻孔插入钢索后注浆，7-10d后对锚杆施加预应力。明挖法Open-cutMethod围护结构加支撑开挖法MethodofExcavationwithEnclosureStructureplusSupport锚杆anchorrod锚杆立面图ElevationDrawingofDiagonalSupportUndergroundconnectingwallExcavationfaceFreesectionAnchoragesectionAnchorrodhitintotheinclinedtopofthetunnelfaceMiscellaneousfillMuddysoilMediumsandSandgravelSandyloamStronglyweatheredrockConstructionprocess:Aftertheenclosurestructureiscompleted,Excavationshallbecarriedouttothedesignelevationoftheanchorrod,andgroutingshallbedoneafterdrillingandinsertingthewirerope.Prestressshallbeappliedontheanchorrodsafter7-10days.施工空间宽敞，有利于机械开挖和组织结构主体施工。能够较好的控制围护结构的水平位移，减少地面及建筑物的沉降量，并能适用于各种形状的围护结构。锚杆可设成单层或多层，开挖深度不受限制。工艺复杂，锚杆不易回收造价较高。当围护结构四周建筑物有密集的深基础时，不宜采用。锚杆的蠕变会降低其承载力。在流沙底层中若错头预留孔口与锚杆套简之间的空隙过大，易发生涌水涌砂，引起坑外地面和建筑物沉降。明挖法Open-cutMethod围护结构加支撑开挖法MethodofExcavationwithEnclosureStructureplusSupport锚杆anchorrod锚杆立面图ElevationDrawingofDiagonalSupportUndergroundconnectingwallExcavationfaceFreesectionAnchoragesectionAnchorrodhitintotheinclinedtopofthetunnelfaceMiscellaneousfillMuddysoilMediumsandSandgravelSandyloamStronglyweatheredrock优点Advantages缺点DisadvantagesSincetheanchorrodsaresetoutsidethefoundationpit,aspaciousconstructionspacecanbeprovidedwhichisconducivetomechanicalexcavationandorganizationoftheconstructionofthemainstructure.Thehorizontaldisplacementoftheenclosurestructurecanbebettercontrolled,sothatthesettlementofthegroundandbuildingsisreduced.Anchorrodscanbeusedforenclosurestructureswithvariousshapes,andtheycanbesetinsingleormultiplelayers.Moreover,theexcavationdepthisnotlimited.Theconstructionprocessismorecomplex,itisnoteasytorecycletheanchorrods,andtheconstructioncostsarehigh.Meanwhile,itshouldalsobenotedthat,Whenthebuildingsaroundtheenclosurestructurehavedense,deepfoundations,anchorrodsshouldnotbeused.Thecreepoftheanchorrodscanreducetheirbearingcapacity.Inthebottomlayerofquicksand,ifthegapbetweenthestaggeredreservedholeandtheanchorrodsleeveistoolarge,watergushingandsandgushingarelikelytooccur,causingsett