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Source:StandardHandbookforCivilEngineersLarsChristianF.Ingerslev,ArthurG.BendeliusParsonsBrinckerhoff20NewYork,NewYorkTUNNELENGINEERINGunnelengineeringmakespossiblemanyotherrequirementsforthetunnelmustfirstbevitalunderwaterandundergrounddefined.GeologicalandenvironmentaldatamustTfacilities.Uniquedesignandconstruc-thenbecollected.Criticaldesignloadingcon-tiontechniquesareinvolvedbecauseofditionsmustthenbeestablished,includingthenecessityofprotectingtheconstructorsandacceptableconditionsofthetunnelfollowingusersofthesefacilitiesfromalienenvironments.extremeevents(forexample,howlongbeforetheThesefacilitiesmustbebuilttoexcludethetunnelisreusable).Appropriateconstructionmaterialsthroughwhichtheypass,includingmethodsarethenevaluatedtodeterminethemostwater.Often,theyhavetowithstandhighappropriatetomeettheestablishedcriteria,pressures.Andwhenusedfortransportationorconditions,andcost.Themethodsunderconsider-humanoccupancy,tunnelsmustprovideadequateationshouldincludebothtemporaryandperma-lightingandasafeatmosphere,withmeansfornentexcavationsupportsystemsaswellastheremovingpollutants.structuresitself.DesignstandardsandcodesofTunnelsareconstructedusingmanymethods,practiceapplyprimarilytoabove-groundstruc-dependinguponthekindofsoiland/orrocktures,sothatcareshouldbeusedintheirthroughwhichtheywillpass,theirsize,howdeepapplicationtoundergroundandunderwatertheyneedtobe,andtheobstructionsthatmaybestructures.encounteredalongtheroute.Thesemethodsincludecut-and-coverconstruction,drillandblast,tunnelboringmachine(TBM),immersionofprefabricatedtunnels,andsequentialexcavationmethods(SEM).Morespecializedmethods,suchas20.1Glossarygroundfreezingandtunneljacking,areusedlessAdit.Ashort,transversetunnelbetweenparallelfrequentlyandoftenunderverydifficultcon-tunnelsortothefaceoftheslopeinasidehillditions.Compressedairworkinghasbecometunnel.uneconomicalbecauseofworkinghourrestric-AirLock.Acompartmentinwhichairpressuretions,timefordecompressionthatresultsfromcanbevariedbetweenthatofthecompressedairhighworkingpressures(over40psiisnotusedinshieldtunnelingandthatoftheoutsideair,unusual),unionlaboragreementsforworkundertopermitpassageofworkersormaterial.compressedair,andhighworkmen’scompen-sationandhealthbenefitrates.OccasionalentryBench.Topofpartofatunnelsection,withundercompressedairmaystillberequired,suchashorizontalornearlyhorizontaluppersurface,toclearobstructionsaheadofatunnelboringtemporarilyleftunexcavated.machine,ortoperformessentialmaintenanceonBlowout.Asuddenlossofalargeamountofpartsofsuchamachine.compressedairatthetopofatunnelshield.ThedesignapproachtoundergroundandunderwaterstructuresdiffersfromthatofmostBreastBoards.Timberplankstoholdthefaceofotherstructures.Internalspace,designlife,andtunnelexcavationinloosesoil.DownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.2nSectionTwentyDryPacking.Fillingavoidwithastiffmortar,20.2ClearancesforTunnelsplacedinsmallincrements,eachrammedintoplace.ClearanceinatunnelistheleastdistancebetweentheinnersurfacesofthetunnelnecessarytoEvase´Stack.Anair-exhauststackwithacrossprovidespacebetweentheclosestapproachofsectionincreasinginthedirectionofairflowatavehiclesortheircargoorpedestriantrafficandratetoregainpressure.thosesurfaces.MinimumtunneldimensionsareFace.Thesurfaceattheheadofatunneldeterminedbyaddingtheminimumclearancesexcavation.Amixedfaceisaconditionwithmoreestablishedforatunneltothedimensionsselectedthanonetypeofmaterial,suchasclay,sand,gravel,forthetypeoftraffictobeaccommodatedinthecobblesorrock.tunnelandthespaceneededforotherrequire-ments,suchasventilationductsandpipelines.Grommet.AringofcompressiblematerialinsertedundertheheadandnutofaboltClearancesforRailroadTunnelsnIndi-connectingtunnellinerstosealthebolthole.vidualrailroadshavedifferentstandardstosuitHeading.Asmalltunnel,ortunnels,excavatedtheirequipment.Butontangenttracks,clearanceswithinalargetunnelcrosssectionwhichwillbeforsingle-anddouble-tracktunnelsshouldnotbeenlargedtothefullsection.lessthanthoseshowninFig.20.1.(Clearancesshownarethoseinthe“AREMAManual”Jumbo.AframethatrollsontracksorrubberAmericanRailwayEngineeringandMaintenance-wheelsandcarriesdrillsforexcavationofrocktunnels.of-WayAssociation,8201CorporateDrive,Suite1125,Landover,MD20785,(www.AREMA.org).Lagging.TimberplanksorsteelplatesinsertedInrailtunnels,clearancesforpersonnelareabovetunnel-supportingribstoholdbackrocksrequiredonbothsideswherenichesarenotorsoil.provided.Theseclearancesshouldbeatleast6ftLinerPlate.Asteelsegmenttosupportthe8inor2mhighand30inwideeachsideoftheinteriorofatunnelexcavation.vehicleclearancediagram,althougha24-inminimumispermittedonsomelines.InhighwayLining.Atemporaryorpermanentstructuretunnels,a3ftor0.9mclearancefromfaceofcurbmadeofconcreteorothermaterialstosecureandisusedwherewalkwaysareprovided.Inbothfinishthetunnelinteriorortosupportanroadandrailtunnels,itiscommonpracticetoexcavationprovideawalkwayalongthecommonwallMucking.Removalofexcavatedorblastedbetweenadjacentductstofacilitateemergencymaterialfromfaceoftunnel.evacuationbetweenductsandtopreventpeoplefromemergingdirectlyintothepathofoncomingPilotTunnel.Asmalltunnelexcavatedoverparttraffic.ortheentirelengthtoexploregeologicalconditionsOncurvedtracks,theclearancesshouldbeandassistinfinalexcavation.increasedtoallowforoverhangandtiltingofan85-PioneerBore.(SeePilotTunnel.)ft-longcar,60ftctocoftrucks,andaheightof15ft1inabovetopofrail.(DistancefromtopofrailstoPolingBoards.Timberplanksdrivenintosofttopoftiesshouldbetakenas8in.)soil,overtimbersupports,toholdbackmaterialThetrackshouldbesuperelevatedatcurvesduringexcavation.accordingtoAREMAstandards.Scaling.RemovaloflooserocksfromtunnelClearancesforpantograph,third-rail,orcaten-surfaceafterblasting.aryconstructionshouldconformtodiagramspublishedbytheElectricalSection,EngineeringShield.AsteelcylinderofdiameterequaltothatDivisionoftheAssociationofAmericanRail-ofthetunnel,forexcavationoftunnelsinsoftroads.materialtoprovidesupportatthefaceofthetunnel,ThelatestclearancestandardsofAREMAtoprovidespaceforerectingsupports,andtoshouldbecheckedfornewconstruction.Localprotectworkersexcavatinganderectingsupports.legalrequirementsshouldgoverniftheyexceedSpiling.(SeePolingBoards.)thesestandards.DownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.3Fig.20.1ClearancesspecifiedbyAREMAforrailwaytunnelsonatangent.Circulartunnelsshouldbefittedtotheclearancerapid-transittunnels.Requirementsvarywithsizediagrams,withsuchmodificationsasmaybeofrollingstockusedinthesystem.permissible.Figure20.2showsthenormal-clearancedia-gramoftheNewYorkCityBMTandINDDivisionClearancesforRapid-TransitTunnelsn267ftcars.Figure20.3givestheclearancesTherearenogeneralstandardsforclearancesinestablishedfortheSanFranciscoBayAreaRapidDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.4nSectionTwentyFig.20.2Clearancediagramfor670car(BMT&INDDivisions).NewYorkCitySubwaySystem.TransitSystem,whichhascars10ftwideand75ftSinceconstructioncostsoftunnelsarehigh,longona5-ft6-ingagetrack.Theclearancesallowclearancerequirementsareusuallysomewhatnotonlyforoverhangofcars,tiltingduetoreduced.Althoughsomeolder2-lanetunnelshavesuperelevation,andsway,butforabrokenspringusedroadwaywidthsof21ftbetweencurbsforordefectivecarsuspension.unidirectionaltrafficand23ftforbi-directionaltraffic,usuallywithspeedrestrictions,thesewidthsClearancesforHighwayTunnelsnThenolongermeetcurrentstandardsfor12ftor3.6mAmericanAssociationofStateHighwayandlanes.FullwidthshouldersarerarelyprovideddueTransportationOfficials(AASHTO)hasestablishedtocost,butatleastanadditional1ftisprovidedstandardhorizontalandverticalclearancesforadjacenttoeachcurb.Widershouldersorsightvariousclassesofhighways.ThesehavebeenshelvesmayberequiredaroundhorizontalcurvesmodifiedandexpandedfortheInterstateHighwaytocomplywithsightdistancerequirements.ASystemunderthejurisdictionoftheFederalminimumdistancebetweenwallsof30ftisaHighwayAuthority(FHWA)(Fig.20.4).commonrequirement.ResurfacingwithintunnelsForruralandmosturbanpartsoftheInterstateisrarelypermittedwithoutfirstremovingtheoldHighwaySystem,a16-ftverticalclearanceissurfacing,sonoallowanceforresurfacingisrequired.requiredforoverheadclearance.ItisusualinDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.5Fig.20.3ClearancediagramforSanFranciscoBayAreaRapidTransitSystem.tunnelstoprovideoverheadlanesignalstoshowoverheadsigns,jetfansforventilation,andanywhichlanesareopentotrafficinthedirectionofotherceiling-mounteditems.Minimumoverheadtravel,soextraoverheadallowanceisrequiredfortrafficclearancesdependuponwhichalternativethese,andwhenappropriatealsoforlighting,routesareavailableforover-heightvehiclesandtheclassificationofthehighway,butacceptedvaluesusuallyliebetween14ftand5.1m.Additionalheightmayberequiredonverticalcurvestoallowforlongtrucks.Additionalspacemayberequiredforventilation,ventilationequip-ment,andventilationducts.20.3AlignmentandGradesforTunnelsAlignmentofatunnel,bothhorizontalandvertical,generallyconsistsofstraightlinesconnectedbyFig.20.4Clearancediagramforinterstatehigh-curves.Minimumgradesareestablishedtoensurewaytunnels.adequatedrainage.MaximumgradesdependonDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.6nSectionTwentythepurposeofthetunnel.Constructionofatunnel500ft.Maximumlinegradeis3.0%and1.0%inintheupgradedirectionispreferredwheneverstations.Toensuregooddrainage,gradeshouldpossible,sincethispermitswatertodrainawaypreferablybenotlessthan0.50%.fromthefaceunderconstruction.AlignmentandGradesforHighwayAlignmentandGradesforRailroadTunnelsnFortunnelsundernavigablewaterTunnelsnStraightalignmentsandgradesaslowcarryingheavytraffic,upgradesaregenerallyaspossible,yetprovidinggooddrainage,arelimitedto3.5%;downgradesof4%areacceptable.desirablefortrainoperation.Butoverallconstruc-Forlightertrafficvolumes,gradesupto5%havetioncostsmustbetakenintoaccount.beenusedforeconomy’ssake.BetweengoverningGradesincurvedtunnelsshouldbecompen-navigationclearances,gradesarereducedtoasatedforcurvature,asisdoneforopenlines.Inminimumadequatefordrainage,preferablynotgeneral,maximumgradesintunnelsshouldnotlessthan0.25%longitudinallyandacrossslopeofexceedabout75%oftherulinggradeoftheline.1.0%.Forlongrocktunnelswithtwo-waytraffic,aThisgradeshouldbeextendedabout3000ftbelowmaximumgradeof3%isdesirabletomaintainand1000ftabovethetunnel.reasonabletruckspeeds.AdditionalclimbinglanesShort(under2500ft),unventilatedtunnelsforslowertrafficmayberequiredwhengradesshouldhaveaconstantgradethroughout.Long,exceed4%.ventilatedtunnelsmayrequireahighpointnearRadiiofcurvatureshouldmatchtunneldesignthecenterforbetterdrainageduringconstructionifspeeds.Shortradiirequiresuperelevationandworkstartsfromtwoheadings.somewideningofroadwaytoprovideforRadiiofcurvesandsuperelevationoftracksareoverhangandsightdistance.governedbymaximumtrainspeeds(Art.19.9).20.4PavementsandAlignmentandGradesforRapid-TransitTunnelsnRadiiofcurvatureandlimitinggradesEquipmentforaregovernedbyoperatingrequirements.TheHighwayTunnelsNewYorkCityINDSubwayhasa350-ftminimumRoadwaybaseisareinforcedconcreteslab;onthisradius,withtransitioncurvesforradiibelowisplacedarenewablepavement.Well-designed2300ft.Maximumgradesforthissystemare3%bitumasticconcretehasgivengoodserviceandhasbetweenstationsand1.5%forturnoutsandgoodridingqualities.crossovers.TheSanFranciscoBARTsystemisAveragedailytrafficcapacityofatwo-lanetwo-designedfortrainspeedsof80mi/h.Relationofdirectionaltunnelisabout20,000vehicleswithaspeedtoradiusandsuperelevationoftrackformaximumof1200to1500vehiclesperlaneperhorizontalcurvesisdeterminedbyhour.Forsingle-directiontrafficinbothlanes,4:65V2capacitiesare10to15%higher.E¼U(20:1)RRed-amber-greentrafficlightsareinstalledatabout1000-ftintervals,oratsuchspacingthatthewhereE¼superelevation,indriveralwaysseesatleastonelight.TelephonesareR¼radius,ftplacedinrecessesabout500ftapartforserviceandV¼trainspeed,mi/hemergencycalls.Mosttunnels,particularlythoseunderwater,U¼unbalancedsuperelevation,whichareequippedwithfiremainsandhoseoutlets3shouldnotexceed24inoptimumorevery300ft.Boosterpumpsinventilationbuild-4inasanabsolutemaximumingsraisesupplypressureto120psiforuseofFor80mi/hdesignspeed,theradiuswithanfoam.Fireextinguishersaremountedinrecessesofoptimumsuperelevationwouldbe5000ft.Forahoseoutlets.Fire-alarmstationsandphonesareat1maximumpermissiblesuperelevationof84in,athesamelocations.Emergencytruckswithheavyminimumradiusof3600ftwouldberequired.Thehoists,firehose,foamequipment,andemergencyabsoluteminimumradiusforyardsandturnoutsistoolsarekeptinreadinessateachportal.DownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.720.5Preliminarydesignation(RQD),isanindicatorofrockproblemstobeencountered.InvestigationsGroundwaterlevelsshouldbeloggedinallSurveysshouldbemadetoestablishalltopogra-borings.Presenceofanynoxious,explosive,orphicalfeaturesandlocateallsurfaceandsubsur-othergasesshouldbenoted.facestructuresthatmaybeaffectedbythetunnelWhereloweringofgroundwatermaybeconstruction.Forunderwatertunnels,soundingsemployedduringconstructionofcut-and-coverorshouldbemadetoplotthebedlevels.boredtunnelsonland,thepermeabilityoftheKnowledgeofgeologicalconditionsisessentialgroundshouldbetestedbypumpingtestsindeepforalltunnelconstructionbutisofprimarywellsatselectedlocations.Rateofpumpingandimportanceforrocktunnels.Explorationsbydrawdowncheckedinobservationwellsatvariousboringsandseismicreflectionforsoftgroundanddistancesshouldberecorded;aswellasrecoveryofunderwatertunnelsarereadilymadetotheextentthewaterlevelafterstoppingthepumps.necessary.Forrocktunnels,particularlylongones,Geophysicalexplorationtodeterminehowever,possibilitiesforboringsareoftenlimited.elevationsofdistinctivelayersofsoilorrockAthoroughinvestigationshouldbemadebyasurfaces,density,andelasticconstantsofsoilmaygeologistfamiliarwiththearea.Thisstudyshouldbeusedforpreliminaryinvestigations.Thefind-bebasedonacarefulsurfaceinvestigationandingsshouldbeverifiedbyacompleteboringexaminationofallavailablerecords,includingprogrambeforefinaldesignandconstruction.recordsofotherconstructioninthevicinity,suchasprevioustunnels,mines,quarries,opencuts,shafts,andborings.Thegeologistshouldprepareacomprehensivereportfortheguidanceof20.6TunnelVentilationdesignersandcontractors.TunnelswillberequiredtobeventilatedtodiluteForsoftgroundandunderwatertunnels,orremovecontaminants,controltemperature,boringsshouldbemadeatregularintervals.Theyimprovevisibilityandtocontrolsmokeandheatedshouldbespaced500to1000ftapart,dependinggasesintheeventofafireinthetunnel.onlocalconditions.Closerspacingshouldbeusedinareasofspecialconstruction,suchasventilationbuildings,portals,andcut-and-coversections.20.6.1VentilationRequirementsSpoonsamplesshouldbetakenforsoilclassifi-forConstructioncation,andundisturbedsamples,wherepossible,forlaboratorytesting.SamplesnotneededintheOccupationalSafetyandHealthAdministrationlaboratory,boringlogs,andlaboratoryreports(OSHA)establishesstandards,regulations,andshouldbepreservedforinspectionbycontractors.proceduresnecessarytomaintainsafe,sanitaryDensity,shearandcompressivestrength,andconditionsforallworkersonconstructionsites.plasticityofsoilsareofspecialinterest.EmployersarerequiredtoinitiateandmaintainAllboringsshouldbecarriedbelowtunnelprogramsthatwillpreventaccidents.Also,invert.Forpressurefacetunnels,boringsshouldbeemployersareadvisedtoavailthemselvesofsafetylocatedoutsidethetunnelcrosssection.andhealthprogramsprovidedbyOSHAandareForrocktunnels,asmanyboringsaspracticablerequiredtoinstructandtrainemployeestoshouldbemade.Holesmaybeinclined,tocutasrecognizeandavoidunsafe,unsanitaryconditions,manylayersaspossible.Holesshouldbecarriedincludingpreventionandspreadoffires.OSHAbelowtheinvertandmaybestaggeredoneitherrequirementsalsocoverundergroundconstruc-sideofthecenterline,butpreferablyoutsidethetion.Followingaresomeoftherequirementstunnelcrosssectiontopreventannoyingwaterapplicabletoventilation.leaks.WhereformationsstrikingacrossthetunnelFreshairshouldbesuppliedtoallundergroundhavesteepdips,horizontalboringsmaygivemoreworkareasinsufficientquantitiestopreventinformation;borings2000ftinlengtharenotdangerousorharmfulaccumulationofdusts,uncommon.Allcoresshouldbecarefullycatalogedfumes,mists,vapors,orgases.Unlessnaturalandpreservedforfutureinspection.Theratioofventilationmeetsthisrequirement,mechanical3corerecoverytocorelength,calledtherockqualityventilationshouldbesupplied.Atleast,200ftofDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.8nSectionTwentyfreshairshouldbeprovidedforeachemployeeAventilationsystemdilutesandpurgessmokeunderground.Theairflowshouldbeatleast30ft/andcombustionandexhaustgases.Itscapacityminwhereblastingorrockdrillingisconductedormustbeadequatetopreventirritatingsmokeorgaswherepollutedairislikelytobepresentorconcentrationswhileatrainpassesthroughandtodeveloped.Thedirectionofairflowshouldbecleartheairbetweentrainpassages.Dieselcontentreversible.Afterblasting,smokeandfumesshouldofnitrogenoxidesmayformcorrosiveacidsinbeimmediatelyexhaustedtooutdoorsbeforeworklungswheninhaledforlongperiods.Thefollowingisresumedinaffectedareas.systemsareusedbyAmericanrailroads:UndergroundoperationsareclassifiedasgassyInjectingastreamofairathighvelocityintheifairmonitoringdisclosesforthreeconsecutivedirectionoftrainmovementtokeepsmokeaheaddays10%ormoreofthelowerexplosivelimitforofthetrain.methaneorotherflammablegases,measuredabout12infromwork-areaenclosuresurfaces.Injectingahigh-speedhigh-volumeairstreamWheresuchconditionsoccur,operationsetherfromtheoppositeendagainstthetrainmotiontothanthosenecessaryforcorrectingtheconditionsdilutesmokeandclearthetunnel.shouldbediscontinued.VentilationsystemsshouldAdditionofportaldoorswiththefirstinjectionbemadeoffire-resistantmaterials.Controlssystem,toincreaseefficiencyandpreventbackflowforreversingairflowshouldbelocatedaboveincaseofastalledtrain.Doorsareinterlockedwithground.signalsystems(MoffatTunnel).Atnormalatmosphericpressureunderground,theairshouldcontainatleast19.5%butnotmoreBecauseofabsenceofsmokeorexhaustgasthan22%oxygen.Testshouldbemadefrequentlywhenelectrictractionisused,ventilationbyfirstforoxygen,thenforcarbonmonoxide,pistonactionoftrainsisadequatefortunnelsfornitrogendioxide,hydrogensulfide,andotherelectrictrainsexceptunderemergencyconditions.pollutants.IfhydrogensulfideconcentrationAuxiliaryexhaustfansshouldbeinstalledtoreaches20ppmor20%ormoreofthelowerremovesmokeincaseoffireandtodrawfreshairexplosivelimitforflammablegasesisdetected,intothetunnelfromthestationsorportals.Fansprecautionsshouldbetakentoprotectorevacuatemaybeinstalledinexhaustshaftsbetweenpersonnel.stationsorinseparateventilationbuildingsinMobilediesel-poweredequipmentusedunder-longunderwatertunnelsequippedwithexhaustgroundinatmospheresotherthangassyoperationsducts.High-speedrapid-transittunnelsrequiremusteitherbeapprovedbyMSHAortheemployerair-reliefshaftsaheadofstationstopreventairmustdemonstratethatitisfullyequivalenttosuchblastsfromenteringthestations.Inhotclimates,MSHA-approvedequipment.(30CFRPart32heatdissipationintunnelsandstationsrequiresMSHA).specialventilationcapacityandairconditioning.Forconstructionincompressedair,seeAcomputerprogram,theSubwayEnvironmentArt.20.16.Simulation(SES),forsystemdesignhasbeen[“ConstructionIndustry:OSHAStandardsfordeveloped.(“SubwayEnvironmentalDesigntheConstructionIndustry(29CFR1926/1910),”Handbook,”UrbanTransportationAdminis-SuperintendentofDocuments,GovernmentPrint-tration,Washington,DC20590.)ingOffice,Washington,DC20402(www.gpo.gov)].20.6.2VentilationforRailroad20.6.3EmissionContaminantsandRapid-TransitTunnelsinRoadTunnelsShorttunnelsgenerallyhavenoforcedventilation.ExhaustgasesofgasolineinternalcombustionLongertunnelsfordieseltrainsmayneedenginescontaindeadlycarbonmonoxideandventilationtopurgesmokeandexhaustgases.irritatingsmokeandoilvapors.DieselenginesTunnelsforelectrictractionareadequatelyself-willalsoproducedangerousnitrogenoxidesandventilatedbypistonactionbutmayrequirealdehydes.Thecomponentsofexhaustgasesvaryemergencyventilation.overawiderange.DownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.9TheventilationsystemalsomustbecapableofCarbonMonoxide(CO)hasbeenproventobecontrollingsmokeandhotgasesincaseoffire(seetheumbrellapollutantinmostroadtunnels.ThatVentilationSystemsforRoadTunnelsfollowing).is,whentheCOlevelinanygivenroadtunnelisTheFederalgovernmentorhealthauthoritiesofmaintainedatorbelowthelevelsshowninTablestatesplacerestrictionsonpermissiblecarbon20.1,alloftheothervehiclepollutantswillbemonoxide(CO)content.Withnewstandardswithinappropriatelevels.Theonlyexceptiontolimitingcontaminantsinvehicleexhaustgases,thisisthecaseofparticulatematteremittedbyhowever,itmayeventuallybepossibletomeettheDieselenginedvehicleswhenthetunneltrafficCOlimitationswithoutextensiveincreaseinstreamcontainsonanaveragemorethan15%ventilation.EngineersshouldcheckcurrentrulesDieselenginedvehicles.attimeofdesign.ThecurrentmethodofdeterminingthevehicleHazefromvehicleexhaustgases,particularlyemissionstobeconsideredforaroadtunnelfromDieselenginedvehicles,doesreducevisibilityventilationsystemdesignistoapplytheUnitedinthetunnel.Inpractice,whentheCOlevelwithinStatedEnvironmentalProtectionAgency’sMOBILthetunnelismaintainedatlevelsasproposedinseriesofcomputerprograms.Mobil5BistheTable20.1,adequatedilutionoftheirritatingpartscurrentversioninusetoday.ofexhaustgasesandadequatevisibilityisassured.NewroadtunnelsbuiltintheUnitedStatesmustcomplywiththetime-weightedlimitsfor20.6.4VentilationSystemsforconcentrationofCOestablishedbytheU.S.RoadTunnelsEnvironmentalProtectionAgencyandtheFederalInstraighttunnelsuptoabout1000ftinlength,HighwayAdministration.Theselimitsarelistedinnaturalairflowisusuallysufficient,particularlyTable20.1.withtrafficinonedirection.IfatunnelisexposedOthercountriesmaysetotherstandardsfortoheavytrafficcongestionattimes,installationofcarbonmonoxide(CO)concentrationswithintheirexhaustfansinashaftoraditnearthecenterfortunnels.TheWorldRoadAssociation(PIARC)emergencyventilationisadvisableifthelengthpublicationsprovidedocumentationontheexceeds500ft.subject.Fortunnelsinwhichtrafficmayincorporateahighpercentage(10%ormore)ofdieselvehicles,NaturalVentilationnNaturallyventilatedtheventilationrequirementsfordilutionofNOxtunnelsrelyprimarilyonatmosphericconditionsparticlesofnitrogenandparticulates(smoke)tomaintainairflowandasatisfactoryenvironmentbecomesignificant.TheNOxemittedbyvehiclesinthetunnel.Thepistoneffectoftrafficprovidesconsistsmainlyofnitricoxide(NO),whichadditionalairflowwhenthetrafficismoving.oxidizesintheatmospheretoformnitrogenNaturallyventilatedtunnelsover1,000feet(305dioxide(NO2).Basedonexposurelimitsrec-meters)longrequireemergencymechanicalventi-ommendedbytheAmericanConferenceoflationtoextractsmokeandhotgasesgeneratedGovernmentalIndustrialHygienistsandatypicalduringafireasdefinedbyNFPA502“Standardfor4-to-1ratioforNOtoNO2,themaximumRoadTunnels,Bridges,andOtherLimitedAccesspermissibleconcentrationofNOxisabout10ppm.Highways”.Tunnelswithlengthsbetween800and1,000feet(240and305meters)willrequiretheperformanceofanengineeringanalysistodeter-minetheneedforemergencyventilation.BecauseTable20.1LimitsonCOinRoadTunnelsoftheuncertaintiesofnaturalventilation,especiallytheeffectofadversemeteorologicalandExposuretime,MaximumCOoperatingconditions,relianceonnaturalventi-minconcentration,ppmlation,tomaintaincarbonmonoxide(CO)levels,fortunnelsover800ft(240m)longshouldbe0–15120thoroughlyevaluated.Ifthenaturalventilationis16–3065demonstratedtobeinadequate,theinstallationofa31–4145mechanicalsystemwithfansshouldbeconsidered46–6035fornormaloperations.DownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.10nSectionTwentySmokefromafireinatunnelwithonlynaturaltudinalsystems,suchasexcessiveairspeedintheventilationmovesupthegradedrivenprimarilybyroadwayandsmokebeingdrawntheentirelengththebuoyanteffectofthehotsmokeandgases.Theoftheroadwayduringanemergency,becomesteeperthegradethefasterthesmokewillmoveapparent.thusrestrictingtheabilityofmotoriststrappedThelongitudinalformofventilationisthemostbetweentheincidentandtheportalatthehighereffectivemethodofsmokecontrolinaroadtunnelelevationtoevacuatethetunnelsafely.withunidirectionaltrafficaswasdeterminedintheMemorialTunnelFireVentilationTestProgram.AlongitudinalventilationsystemmustgenerateMechanicalVentilationnAtunnelthatissufficientlongitudinalairvelocitytopreventthesufficientlylong,hasheavytrafficflow,orbacklayeringofsmoke.Backlayeringisthemove-experiencesadverseatmosphericconditionsmentofsmokeandhotgasescontrarytotherequiresmechanicalventilationwithfans.Mech-directionoftheventilationairflowinthetunnelanicalventilationlayoutsinroadtunnelsareeitherroadway.Theairvelocitynecessarytopreventofthelongitudinalortransversetype.backlayeringofsmokeoverthestalledmotorvehiclesistheminimumvelocityneededforsmokeLongitudinalVentilationnThistypeofcontrolinalongitudinalventilationsystemandisventilationintroducesorremovesairfromtheknownasthecriticalvelocity.tunnelatalimitednumberofpoints,thuscreatingalongitudinalflowofairalongtheroadway.TransverseVentilationnTransverseventi-Ventilationiseitherbyinjection,orbyjetfans.lationincludessystemsthatdistributesupplyairInjectionLongitudinalVentilationisfre-andcollectexhaustairuniformlyalongthelengthquentlyusedinrailtunnelsandisalsofoundinofthetunnel.Thereareseveralsuchsystemsroadtunnels.Airinjectedatoneendofthetunnelincludingthefulltransversesystemwhichmixeswithairbroughtinbythepistoneffectoftheincludesbothsupplyandexhaustairuniformlyincomingtraffic.Thistypeofventilationismostdistributedandcollected.Thesemi-orpartialeffectivewheretrafficisunidirectional.Theairtransversesystemsincorporateonlyone,eitherspeedremainsuniformthroughoutthetunnel,andsupplyorexhaustair.theconcentrationofcontaminantsincreasesfromSemitransverseventilationcanbeconfiguredzeroattheentrancetoamaximumattheexit.aseitherasupplysystemoranexhaustsystem.InjectionlongitudinalventilationwiththesupplySemitransverseventilationisnormallyusedinatalimitednumberoflocationsinthetunneltunnelsuptoabout7,000feet(2,000meters);iseconomicalbecauseitrequirestheleastnum-beyondthatlengththetunnelairvelocityspeedberoffans,placestheleastoperatingburdenneartheportalsmaybecomeexcessive.onthesefans,andrequiresnodistributionairSupplysemitransverseventilationappliedtoducts.atunnelwithbi-directionaltrafficproducesaJetFanLongitudinalVentilationhasbeenuniformlevelofcontaminantsthroughouttheinstalledinasignificantnumberoftunnelsworld-tunnelbecausetheairandthevehicleexhaustwide.Longitudinalventilationisachievedwithgasesentertheroadwayareaatthesameuniformspeciallydesignedaxialfans(jetfans)mountedatrate.Inatunnelwithunidirectionaltraffic,thetunnelceiling.Suchasystemeliminatestheadditionalairflowisgeneratedintheroadwaybyspacesneededtohouseventilationfansinathemovementofthevehicles,thusreducingtheseparatestructureorventilationbuilding;however,contaminantlevelinportionsofthetunnel.itmayrequireatunnelofgreaterheightorwidthtoBecausethetunnelairflowisfan-generated,thisaccommodatejetfanssothattheyareoutofthetypeofventilationisnotadverselyaffectedbytunnel’sdynamicclearanceenvelope.Thisenvel-atmosphericconditions.Thesupplyairtravelstheope,formedbytheverticalandhorizontalplaneslengthofthetunnelinatunnelductfittedwithsurroundingtheroadwaypavementinatunnel,supplyoutletsspacedatpredetermineddistances.definethemaximumlimitsofpredictedverticalIfafireoccursinthetunnel,thesupplyairinitiallyandlateralmovementofvehiclestravelingonthedilutesthesmoke,whichwasshownintheroadatdesignspeed.AsthelengthofthetunnelMemorialTunnelFireVentilationTestProgramtoincreases,however,thedisadvantagesoflongi-beanineffectivemethodforcontrollingsmokeDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.11fromlargerfires.Supplysemitransverseventi-exhaustduct.Theseopeningsincludedevicesthatlationshouldbeoperatedinareversedmodeforcanbeoperatedduringafireemergencytoextracttheemergencysothatfreshairentersthetunnelalargevolumeofsmokeasclosetothefiresourcethroughtheportalstocreatealongitudinalflowaspossible.Testsconductedasapartoftheofairequivalenttothecriticalvelocity.ItalsoMemorialTunnelFireVentilationTestProgramprovidesatenableenvironmentforfire-fightingconcludedthatthisconceptisextremelyeffectiveeffortsandemergencyegress.inreducingthetemperatureandsmokeintheExhaustsemitransverseventilationinstalledintunnel.Thesizeofopeningstestedrangedfrom10022aunidirectionaltunnelproducesamaximumto300ft(9.3to28m).contaminantconcentrationattheexitportal.InaOversizedexhaustportsaresimplyanexpan-bi-directionaltunnel,themaximumlevelofcon-sionofthestandardexhaustportinstalledinthetaminantsislocatednearthecenterofthetunnel.exhaustductofatransverseorsemi-transverseInafireemergencyboththeexhaustsemiventilationsystem.Twomethodsareusedtocreatetransverseventilationsystemandthereversedsuchaconfiguration.Oneistoinstalloneachportsemitransversesupplysystemcreatealongitudi-expansionadamperwithafusiblelink;theothernalairvelocityinthetunnelroadwaythususesamaterialthatwhenheatedtoaspecificextractingsmokeandhotgasesuniformlyalongtemperaturemeltsandopenstheairway.Severalthetunnellength.testsofsuchmeltablematerialwereconductedaspartoftheMemorialTunnelFireVentilationTestProgrambutwithlimitedsuccess.FullTransverseVentilationnFulltrans-verseventilationhasbeenusedinextremelylongtunnelsandintunnelswithheavytrafficvolume.20.6.5ElementsofRoadTunnelFulltransverseventilationincludesbothasupplyductandanexhaustducttoachieveuniformVentilationSystemsdistributionofsupplyairanduniformcollectionofMajorcomponentsofventilationsystemscom-vitiatedairthroughoutthetunnellength.Duringamonlyusedforroadtunnelsaredescribedinthefireemergencytheexhaustsystemintheincidentfollowing.zoneshouldbeoperatedatthehighestavailablecapacitywhilethesupplysystemintheadjacentincidentzoneisoperated.ThismodeofoperationVentilationBuildings(Figs.20.5and20.6)nFans,electricaltransformersandswitch-createsalongitudinalairflow(achievingthecriticalvelocity)towardstheincidentzoneandallowsthegear,controlboard,andauxiliaryequipmentaresmokeandheatedgasestobeextractedascloseashousedinventilationbuildings.Inshort-andpossibletothefireandkeeptheupstreamstoppedmedium-lengthtunnels,onebuildingateithertrafficclearofsmoke.portalissufficient.Longertunnelsshouldhaveabuildingateachportal.Afewofthelongesthavethreeorfourbuildings.Forunderwatertunnels,OtherVentilationSystemsnThereareventilationbuildingsmaybeatthewater’sedge,manyvariationsandcombinationsofthesystemseachbuildingcontrollingalandandariversectiondescribedpreviously.Mostofthehybridsystemsofthetunnel.areconfiguredtosolveaparticularproblemfacedFreshairistakeninthroughlargelouverareasinthedevelopmentandplanningofthespecificinthewallsofthebuilding.Thelouversshouldbetunnel,suchasexcessiveaircontaminantsexitingprotectedbybirdscreens.Louversareusuallyattheportal(s).aluminumandarrangedforsheddingwater.AdequatedrainsshouldbeprovidedinthefanVentilationSystemEnhancementsnAroomtoremoverainwater,whichmayblowinfewenhancementsareavailableforthesystemsthroughthelouvers.Vitiatedairisdischargeddescribedpreviously.Thetwomajorenhancementsthroughverticalstacks,whichalsoshouldbearesinglepointextractionandoversizedexhaustcoveredbyscreens.ports.TunnelDuctsareusuallyofconstantareaSinglepointextractionisanenhancementtoathroughouttheirlength.Concretesurfacesshouldtransversesystemthataddslargeopeningstothebesmoothforminimumfriction.Obstructions,DownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.12nSectionTwentyFig.20.5SectionsthroughHamptonRoadsTunnelVentilationBuilding.(a)Fresh-airsupplysystem.suchasceilinghangers,shouldbestreamlinedorat1938,andvaneaxialfans,alaterdevelopment.leastrounded.TurnsinductsandshaftsleadingtoCentrifugalfanshavebackward-curvedbladesandthetunnelshouldbeequippedwithnoncorrosivearenonoverloading.Theefficienciesofwell-turningvanesforsmoothairflow.designedfansofeithertypeareaboutthesame.Fluesspacedabout15ftapart,extendedfromForunderwatertunnels,withverticalairshaftsintheducts,supplyfreshairslightlyaboveroadwaytheventilationbuildings,thevaneaxialfanslevel.Ceilingportsareslantedat458intherequireconsiderablylessspaceandavoidthedirectionofairflowintheducts.Allairopeningsefficiencylossthroughthefanchambersusuallyshouldprovidethemeanstoadjustsizetobalanceassociatedwithcentrifugalfans.Bladesforvanetheairflowoverthelengthofthetunnel.axialfansmayhaveafixedpitchormaybeadjustableduringoperation.Whenreversed,theformertypeprovides80%ofmaximumcapacity.FansnTwotypesoffansareavailable:Thelattertypemaybeadjustedfrom0to100%ofcentrifugalfans,usedinalltunnelsuptoaboutcapacityforsupplyandexhaust,thuspermittingDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.13Fig.20.5(Continued)(b)Exhaust-airsystem.adjustmentstomeetvariabledemandsforventi-Chainsareenclosedinsolidhousings;beltsarelationwithfewerfans.Thenoiselevelofvaneprotectedbywireguards.axialfansatmaximumspeedissomewhatForflexibility,theloadisdividedbetweenhigherthanthatforcentrifugalfansbecauseofseveralfans—atleasttwo,sometimesasmanyasgreatertipspeed.Insensitivesurroundings,thesix—foreachsystem.Fourisagoodnumberfor3noisefromsupplyandexhaustfanscanbedemandsexceedingabout600,000ft/min.dampenedbysoundbaffles.VaneaxialfansmayTofurtheradjustsupplytovariabledemand,fanhaveexternaldrivesormotorsbuiltintothehubofmotorsareequippedwithtwo-speedwindings.theimpellers.ThreespeedswithtwomotorshavebeenusedinCentrifugalfansareoperatedbysquirrel-cageearlierinstallationsbutarenotnecessarywithanmotorsthroughchainormultipleV-beltdrives.adequatenumberoffans.SparefansmaybeThelattereliminatelubricationproblemsandwearprovidedasprotectionagainstbreakdown,ortotalonamultiplicityofparts(inherentinchaindrives),fancapacitymaybeincreasedby10or15%.Withgiveexcellentservice,andcanbeeasilyreplaced.goodmaintenance,fansareseldomoutofDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.14nSectionTwentyFig.20.6SectionthroughventilationbuildingoftheHollandTunnel.commission,andtheextracapacityofthesystemisareinuse;thelattertakelessspaceandtimetosufficienttomaintainacceptableconditionsforoperate.limitedperiodswithoneunitoutofservice.ToprotecttheexhaustfansincaseofaseriousFanControlnInshort,unattendedtunnels,fireinthetunnel,automaticdelugesprinklerfanscanbecontrolledautomaticallywithcarbonsystemsshouldbeinstalledtocooltheexhaustair.monoxideanalyzers.LargertunnelswithheavytrafficmayhaveoperatorsstationedinthecontrolDampersnAllfansshouldbeequippedwithroom.Theyoperatethefanstocontrolconditionsinshutoffdamperstopreventshortcircuitingofair.thetunnel.AtleasttwoindependentsourcesofTheiroperatingmotorsshouldbeinterlockedwithelectricpowermustbeavailable,usuallythroughthecontrolofthefanmotorsforautomaticopeningfeedersfromdifferentpartsoftheutilitysystem.Ifandclosing.Trapdoor-typeormultibladedampersthesearenotavailable,adiesel-engineemergencyDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.15generatorsufficientforminimumrequirementsControlofmanynewertunnelsisprogrammedshouldbeinstalled.forcomputeroperation.Thecomputers,however,maybebypassedformanualoperationinanemergency.CarbonMonoxideAnalyzersnThesetakeTopermitsurveillanceoftunneltrafficbycontinuousairsamplesfromthetunnelandpersonnelinthecontrolroom,monitorsmaybeanalyzethemforCOcontent.Theresultsareinstalledinthatroomtodisplayviewsoftheentirevisuallyindicatedandalsorecordedonpapertape,lengthoftheroadwaysastransmittedbytelevisionwithtimegradations.Therecordersaremountedcamerasmountedinthetunnel.Inashorttunnel,onthefaceofthecontrolboard,toguidetheeachcameracoversaspecificstretchofroadwayoperatorinselectionofnumberoffansandspeedandtransmitstoaspecificmonitor.Foralongnecessary.tunnel,tolimitthenumberofmonitorsrequiredtoInalongitudinalorsemitransversesupplyaconvenientnumber,groupsofcamerasmaybesystem,airsamplesaretakenfromthetunneloperatedinsequencetotransmittotheirmonitors.properatpointsofmaximumconcentration.Inanemergency,thesequencecanbeinterruptedIntransversesystems,thesamplesmaybetakentopermitaspecificcameratofocusontheregionoffromtheexhaustducts.concern.HazeControlnTomeasurevisibilityinTrafficControlnSignallightsgenerallyaretunnelsaffectedbyhazefromexhaustgases,mountedattheportalsofatunnelandatintervalsinstrumentshavebeendevelopedthatgiveaintheinteriorsuchthatatleastonetrafficlightisreliableindicationwithoutexcessivemaintenance.plainlyvisiblewithinasafestoppingdistance.InaEquipmentmanufacturedforthePortAuthorityoftunnelwithtwo-waytraffic,thesignalsfacingNewYorkandNewJerseyusesthescatteringoftrafficmayincorporatered,amber,andgreenultravioletlightbydustparticles.Instrumentslights.Lightsonthereversesideofthosesignalsprotecttheopticsbyrecessingthemintubesmayberedandamber,topermitlanealternationthroughwhichfilteredairisexhausted.Anotherinanemergency.Inatunnelwithtwo-lane,one-typeofinstrumentcomparestheintensitiesoftwowaytraffic,thesignalsfacingtrafficcarryred,branchesofasplitlightbeampassingthroughtheamber,andgreenlights,whereaslightsonthesameoptics,onegoingthroughatubefilledwithreversesideofsignalsfortheleftlanemaybecleanair,theotherthroughtunnelair.amberandred,topermittwo-waytrafficinanemergency.TrafficflowmaybemonitoredbypairsofVentilationPowerRequirementsnTheelectricinductioncoilsthatareembeddedinthepowerrequirementsandpressurelossesarebestpavementofeachlaneandthatreporttheflowonevaluatedusingtheprodedurescontainedintheindicatorsinthecontrolroom.IftrafficvelocityisTunnelEngineeringHandbook(J.O.Bickelandtooslow,forinstance,lessthan5to10mi/h,theT.R.Kuesel,‘‘TunnelEngineeringHandbook,’’trafficlightsarechangedtoamber,forcaution.IfKluwerAcademicPublishers,NewYork).trafficstops,thelightsarechangedtored.Ifnecessary,forslowtraffic,thetrafficlightsmaybealternatedbetweenstopandgotospacetrafficflow20.7TunnelSurveillanceintothetunnel.andControlEmergencyexhaustventilationssystemsinshortFireControlnAutomaticfiredetectorsmaybetunnelsortunnelswithverylighttrafficmaybeinstalledintheceilingthroughoutatunnel.Whenaactivatedbysuchinstrumentsinthetunnelasfireoccurs,theyindicatethelocationandsendancarbonmonoxideanalyzersorfire-alarmoralarmtoanoperatorwhoalertsanemergencytelephoneboxesconnectedtothenearestfireandcrew.Iftheoperatorverifiesthealarm(whichpolicedepartments.Emergencyoperationforothermighthavebeenactivatedbytheheavyexhaustoftypesoftunnelsshouldbesupervisedbypersonneladieselengineratherthanbyafire),anemergencyincontrolcenters.programcanbestarted:TheemergencycrewandDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.16nSectionTwentyvehiclesaremobilized.Fortrafficmovingtowarda10ft-c—batchandscreeningplants,mechanicalfire,signallightsareturnedtored,whilefortrafficandelectricalrooms,indoorworkrooms,riggingmovingawayfromthefire,signalsremaingreen,tolofts,indoortoilets,andtunnelandshaftheadingspermitevacuation.Andtheventilationsystemforduringdrilling,mucking,andscaling.theaffectedpartofthetunnelisconvertedtoexhaust.Forotherareas,followilluminationrecommen-Hydrantsgenerallyareinstalledabout300ftdationsin“PracticeforIndustrialLighting,”IESapart,innichesinthetunnelwalls,toprovideRP7,theIlluminatingEngineeringSocietyofNorthwaterforfirefighting.WatermaybeobtainedfromAmerica.municipalwatersupplies,ifavailable.Otherwise,Foremergencyuse,everyemployeeunder-thewatermainsmaybeconnectedtotanksgroundshouldbeequippedwithaportablehandprovidingabout10,000galofstorage.Thetanksorcaplampunlesssufficientnaturallightoranmaybelocatedneareachportalandsuppliedbyemergencylightingsystemprovidessufficientpumpsfromlocalsourcesorfromgroundwater.illuminationalongescapepaths.OnlyportableBoosterpumpsmaybeinstalledtoprovideatlightingmeetingOSHArequirementsmaybeusedleast125-psipressureforapplicationofwaterwithin50ftofanyheadingduringexplosiveonfires.Firealarmsandfireextinguishersforhandling.(SeealsoArt.20.16.)controlofminorfiresmaybeinstallednexttothe[“ConstructionIndustry:OSHASafetyandhydrants.HealthStandards29CFR1926/1910,”Superinten-dentofDocuments,GovernmentPrintingOffice,Washington,DC20402.]CommunicationsnEmergencytelephonesmaybeplacedalongthetunnelsidewallsforcommunicationwithanoperatorinthecontrolLightingforTunnelsinServicenSinceroom.Anaerialinthetunnelwillpermitthelocomotivesareequippedwithstrongheadlights,operatortotransmitmessagestomotoriststhroughrailwaytunnelsaregenerallynotlightedexceptfortheircarradiosandallowthemtoreceiveotheremergencyevacuation.Subaqueoustunnelsandbroadcastswhileinthetunnel.othertunnelsonelectrifiedlines,particularlyincities,areequippedwithanominalamountofPowerSupplynPowershouldbesuppliedlights,especiallyinrefugeniches.fromtwoindependentsources,forexample,fromRapid-transittunnelsarelightedsufficientlytotwodifferentutilitiesorindependentsubstationsmakeobstructionsontracksvisibleandtofacilitateofoneutility.Analternativeisastandbydieselmaintenancework.Thelightsareinstalledand/generatingplantcapableofsupplyingpowerorshieldedtopreventglareinthemotorman’satleastforventilationandemergencylightingeyes.Luminairesareinstalledintunnelsfortokeepthetunnelinoperation.Thisequip-emergencyuse.mentshouldbesupplementedbystoragebat-Forhighwaytunnels,themosttroublesometeriestosupplyinstantpowerfortheemergencylightingconditionisthetransitionfrombrightlightlighting.intheapproachtothetunnel,theentrance(thresholdzone)luminance,totheluminanceintheinterior.Guidelinesforalleviatingthiscon-20.8TunnelLightingditionhavebeenissuedbytheAmericanAssoci-ationofStateHighwayandTransportationTheOccupationalSafetyandHealthAdminis-Officials(AASHTO)andtheIlluminatingEngin-trationsetsminimumrequirementsforillumina-eeringSocietyofNorthAmerica.Thresholdzonetiononconstructionsites:illuminationvariesgreatlywithtopography,orien-tation,sunexposure,andseasonandshouldbe5ft-c—generalconstruction-arealighting,ware-evaluatedforthemostcriticalcondition.Daylighthouses,corridors,exitways,tunnels,andshaftspenetrationthroughtheportalintothethreshold3ft-c—concreteplacement,excavationandwastezonemayassistthetransition.Inadditiontotheareas,accessways,activestorageareas,loadingthresholdzone,twoorthreetransitionzonesplatforms,refueling,andfieldmaintenanceareasgraduallyreducetheluminancetothatoftheDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.17interior.Thelengthofeachofthesezonesshouldgoodconcretecontrol,thenumberoftheseshouldbeapproximatelyonesafe-stoppingsight-distancebesmall.Itisgoodpracticetodesigntunnels(SSSD)atdesignspeed.Reductionbetweenzonesassumingthattheywillleakandthereforeprovideshouldnotexceed3:1.appropriatedrainagepaths.2Atnight,apavementluminanceof2–5cd/mIfwaterappearsinconsiderablequantityduringminimumisrecommendedfortheentirelengthofrocktunnelingoperations,tightsteellaggingoverthetunnel.Theapproachandexitroadwaysshouldthetunnelsupportsandgroutingmaypreventhavealuminancelevelofnolessthanonethirdtheleakage.Inseriouscases,itmaybenecessarytotunnelinteriorlevelforadistanceofaSSSD.dry-packbetweentherockandthetunnellaggingTherearefourviabletypesoflightsourcesusedtodrainwater.Thisisaslow,costlymethodintunnels,fluorescent,low-pressuresodium(LPS),requiringmuchmanuallabor.Drypackbehindthehigh-pressuresodium(HPS),andmetalhalidesidewallscaneasilybeplacedandiseffectivein(MH).TheadvantagesanddisadvantagesofeachpreventingthebuildupofahydrostaticheadarediscussedingreaterdetailinANSI/IESNARP-behindthelining.Longitudinaldrainpipesshould22-968.1.Theseincluderestriketimeintheeventofbeinstalledbehindthebaseofthesidewalls,withmomentarypowerinterruption,linearityofsourcethelateralsatregularintervalsleadingtothemaintoreduceflicker,cost,colorrendering,lampsize,drain(thisisalargedraininstalledunderthelampefficacy,controloflightdistribution,effectsofroadway,forroadwaydrainage).Waterwillflowairtemperature,lumendepreciationwithtime,throughthedrypackingandintothebasedrains.glare,theriskoflamprupture,andkeepingInarocktunnel,heavyflowofwatercomingenclosuresdust-tightandwatertight.Florescentthroughadrillholeindicatesawater-bearingfaultlampsfrequentlyprovidethelowerilluminationorseam.Theflowmaybestoppedbydrillinglevels,combinedwithLPSatthresholdandadditionalholesandinjectingcementgrout.Sometransitionzones.LowerwattageLPSsourcesareholesshouldbeslantedtoreachbeyondthealsousedininteriorzones.HPSandMHlampsperiphery.Ifdensesandorrockflourinthefaultcomeinawideselectionofsizes,betterlamplife,preventsproperpenetrationofcementgrout,compactsizeandareeasilyopticallycontrolled.chemicalgroutingmaygivesatisfactoryresults.Inspecialcases,itmaybenecessarytodrillapilotholewellaheadofthefacetodetectseverewaterconditions,especiallysubstantialquantitiesunder20.9TunnelDrainageheavypressure.ThismustbedoneforrockMosttunnelsthroughhillsandmountainshavetunnelingunderdeepbodiesofwater.waterproblems.SurfacewaterpenetratesthroughInhighwaytunnels,drainageinletsshouldbefissuresandpercolatesthroughpermeablesoils.installedatregularintervalsalongthecurbs,withAttemptstosealofftherockbygrouting,withcrossconnectionstothemaindrain.Thelattereithercementorchemicals,usuallyarenotshouldbeofgeneroussize,inlongertunnelscompletelysuccessfulsinceveryhighpressurespreferablylargeenoughtoprovidecrawlspacemaybuildupevenifflowsarelow.Cast-in-placetoremovesiltaccumulations,particularlywhenconcreteliningsmaynotbecompletelywatertight.gradesarenearhorizontal.TrapsatdrainageinletsWatermayfinditswaythroughshrinkagecracksinareundesirable,becauseofthedangerintheeventtheliningsintotheinterioroftunnels.There,itmayofafuelspill.freezeincoldweatherandproduceanunsightlyLeakageinwell-constructedunderwatertun-appearance,objectionableinhighwaytunnels.nels,eithershield-drivenorimmersed,isusuallyConsequently,provisionmustbemadetodrainminor.Itcanbecontrolledbycalkingjointsinwaterfromtunnels.segmentallinersorbyinjectingcrackswhereleaksFirefighting,washingoftunnelinteriors,andappear.Mainsourcesofwaterarewashingofflushingofpavementsalsointroducewaterthattunnelinterior,firefighting,drippingsfrommustbedrained.vehicles,andraincollectedinopenapproaches.Althoughcut-and-covertunnelscanbewater-Pumpsareusuallysizedtohandlethefullflowproofed,thisisdifficultwithboredtunnels.Ifthefromonefirehydrant.waterproblemisnotserious,themosteconomicalContinuousopenguttersrecessedintothecurbssolutionistosealcracksintheliningthatleak.Withhavebeenusedinmanysubaqueoustunnels.TheDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.18nSectionTwentyguttersleadwatertoalowpoint,whereitisperiod.Theymayalsodischargeexcesswateraftercollectedinasump.Drainageinlets,spacedaboutthereservoirhasbeenfilled,orbeconvertedto50ftapartalongeachcurbandconnectedtointaketunnelstoapowerhouselocatedinthesidelongitudinaldrainlinesembeddedintheconcreteofthevalleybelowthedam.Iftheyarenotneededbelowthecurbs,aredesirablebecausetheypreventaftercompletionoftheproject,thediversionpropagationoffirebyburningfuelincaseofatunnelsareclosedwithconcreteplugs.Extensiveseriousaccident.Drainlinesshouldbeatleast8indiversiontunnelshavealsobeenbuilttocollectindiameter.Theyshouldbeequippedwithwaterfromseveralwatershedsforacentralpowercleanoutsevery500ft.plant.Instraight,openapproaches,transverseinter-Intaketunnelsbringwaterfromreservoirstoceptorsabout300ftapartaremosteffectiveinturbinesortheheadsofpenstocks.Thetunnelsarepreventingwaterfromenteringatunnel.Theyaremostlyinrockandoperateunderapositive18inwide,extendfromcurbtocurb,andarehydrostatichead.Inperviousandfissuredground,coveredwithgratings,withslotsparalleltothetheyarelinedwithreinforcedconcreteorsteelcenterlineoftheroadway.Aninterceptorisplacedplate;insoundrock,asprayed-concreteliningmayinfrontofthetunnelportalandanotherabout10ftbeadequatetoprovideasmoothsurfaceaslongasinside.thereissufficientoverburdentoexceedtheinternalIncurved,superelevatedapproaches,drainagepressure.inletsshouldbeinstalledatregularintervalsalongManymilesofaqueducttunnelshavebeenbuiltthelowcurb.formunicipalorareawater-distributionsystems.AlldrainagefromopenapproachesshouldbeThesetunnelsare,forthemostpart,inrockbutcollectedinsidetheportalsinsumpsbelowthemayalsocontainstretchesofsoft-groundtunnel-roadway.Eachsumpshouldbedividedintoaing.Theymaybeunderlargehydrostaticpressure,settlingbasinandasuctionchamber.EasyaccesssuchastheNewYorkCityaqueduct,whichcrossesmustbeprovidedforcleaningoutsediments.AtheHudsonRiver600ftbelowsealevel.minimumofthreeelectricallydriven,large-Tunnelswithsmallornointeriorpressureclearancedrainagepumpsshouldbeinstalled,onegenerallyhaveahorseshoesection;pressureasastandby.Alternatingautomaticcontrolsrotatetunnelsarecircular.Liningisconcrete,6to36inthepumpsinservice.High-water-levelalarmthick,dependingonsize,pressure,andnatureofcircuitsshouldbeextendedtothecontrolroom.rock.WeldedsteeltubesmaybeneededwhenSumpandpumpcapacity,withtwopumpspressuresareparticularlyhigh.Gradetunnelsmayoperating,shouldbedesignedformaximum,belinedwithplainconcrete,pressuretunnelswithshort-durationrainfallforthelocality.Anintensityreinforcedconcrete.Diametersrangefrom7ftforof4in/h,basedona15-mindownpouratarateofsmallaqueductsto50ftforHooverDamdiversion8in/h,isampleformostareas.tunnels.Inverysoundrock,sprayed-concreteAsmallersumpshouldbelocatedatthelowlininghasbeenused.PartsoftheColoradoRiverpointofthetunnel.Thissumpalsoshouldbeaqueductarelinedwithcontinuoussteelshellsdividedintoasettlingandasuctionchamber.Twoagainstconcretebacking,andtheinsideisautomaticallycontrolleddrainagepumps,withaprotectedby2inofreinforcedsprayedconcrete.capacityof250gal/mineach,maybeadequate.Toexpediteconstruction,longtunnelsareTheirdischargeshouldbecarriedtooneofthesubdividedintoseveralheadingsbyshaftsorportalsumps.adits,about2to5miapart.20.10WaterTunnels20.11SewerandDrainageTunnelsThesemaybediversionorintaketunnelsforhydropowerplants,oraqueductsbringingwatertoLargecitiesrequiremilesoftunnelstocarryoffcityandmunicipaldistributionsystems.stormrunoffandtoconductwastewatertoDiversiontunnelscarryriverwaterarounddamtreatmentplants.Thesetunnelsarebuiltinasitesduringconstruction.Theyaredesignedtovarietyofsoils.Someareconstructedasboxcarrythemaximumexpectedrunoffduringthisculvertsbythecut-and-covermethod,butmostareDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.19tunneledwithtunnelboringmachines(TBMs).Sizevariesfromabout7to15ft.Drainagetunnelsforstormwaterareusuallylessextensivesincetheycandischargeintonearestopenwaters.Thecrosssectionofseweranddrainagetunnelsisusuallyhorseshoeorcircular,withconcretelining.Qualityofconcreteisofspecialimportancetoresistthedetrimentaleffectofwastewater.Generally,theyaregradetunnels,exceptforsiphonsunderrivers,whichareunderpressure.Acircularoregg-shapedsectionmaintainsvelocityatlowflowtopreventexcessivesettlingofsolids.Alignmentisdictatedbylocationoftreatmentplants,soilconditions,andthestreetplanofthecity.Continuousgradesshouldbemaintainedexceptforsiphons.Aminimumgradeshouldbemaintainedforgravityflow.20.12Cut-and-CoverTunnelsShallow-depthtunnels,suchasrapid-transitlinesundercitystreets,underpasses,landsectionsofunderwatertunnels,andendsectionsoftunnelsthroughhills,arebuiltbycut-and-covermethods.Atrenchisexcavatedfromthesurface,withinwhichaconcretetunnelisconstructed.Withbottom-upconstruction,thecompletedtunneliscoveredup,andthesurfacereinstated.Withtop-downconstruction,thewallsareconstructedfirst,Fig.20.7TaipeiMetroCut-and-Cover.perhapsusingbentoniteslurryinnarrowtrenches.Theroofisconstructednext,backfilledandthesurfacereinstated.Excavationandconstructionofexcavationsthatare4ftormoredeep,astairway,thefloorsbelowrooflevelthenfollow,usingaccessladder,orrampshouldbeprovidedforegresssoasfromtheendsorfromgloryholes.Bothbottom-uptorequirenomorethan25ftoflateraltravelforandtop-downconstructionalmostalwaysusecast-workers.inplaceconcrete.DepthofinvertonsubwaysandAmongthemeasuresthatOSHAspecifiesforunderpassesusuallydoesnotexceed35to40ft.Forsafeguardingpersonnelinexcavationsaretheconnectionstosubaqueoustunnels,cutsuptofollowing:Precautionsshouldbetakentoprevent100fthavebeenusedunderspecialcircumstances,exposureofpersonneltoharmfullevelsofanddepthsto60ftarenotuncommon.atmosphericcontaminants(Art.20.6).IfnaturalTheOccupationalSafetyandHealthAdminis-lightingisinadequateforsafeworkingconditions,tration(OSHA)setsstandards,regulations,andilluminationtomeetOSHArequirementsforproceduresforprotectionofpersonnelduringexcavationshouldbeprovided(Art.20.8).Person-excavation.OSHArequiresthatallsurfaceencum-nelshouldnotbeallowedtoworkinexcavationsinbrancesandundergroundutilityinstallations,suchwhichwateraccumulatesunlesstheworkersareassewers,electricalandtelephoneconduits,andprotectedbysafetyharnessesandlifelines,wateriswaterpipes,beprotected,supported,orremovedbeingremovedtocontrolthewaterlevelwithinasnecessarytosafeguardtheworkers.Also,safelimits,andspecialsupportsorshieldsareusedstructuralrampsusedforaccessoregressshouldtoprotectagainstcave-ins.bedesignedbyastructuralengineerandcon-Toavoidexposuretofallingobjects,personnelstructedinaccordancewiththedesign.FortrenchshouldnotbepermittedbelowloadscarriedbyDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.20nSectionTwentyFig.20.863rdStreetTunnelStruttingandTie-backs.liftingordiggingequipment.Unlessexcavationsalongtheface.Ifthelowerportionoftheareentirelyinstablerockorarelessthan5ftdeepexcavationhasverticalsides,thatregionshouldinstablesoil,protectionshouldbeprovidedbeshieldedorsupportedtoaheightatleast18inagainstcave-ins.Retainingdevicesmaybeabovetheverticalsides.requiredtopreventexcavatedorothermaterialsGroundwatermaybelowered,asneeded,byorequipmentfromfallingorrollingintothetiersofwellpoints.Thismaylowertheground-excavation.wateroutsidetheexcavationconsiderablyandWherespaceanddepthofexcavationpermitcausesettlements.Theloweringoftheexternalandthegroundissufficientlyfirm,openslopesgroundwatercanbereducedbytheuseofslurrymaybeusedalongthesidesoftheexcavation.Forwalls,contiguousoroverlappingboredpiles,orexcavationsupto20ftdeep,OSHAlimitstheslopesteelsheetpiling.Adjacentstructureswithariskof1toamaximumof1:12(348withthehorizontal),settlementmayrequireunderpinning.Further-unlesssoiltestsandanalysesindicatesteepermore,whereloweringofgroundwaterexposesslopeswillbestable.Aregisteredprofessionalwoodenpilestoair,deteriorationmayfollow.engineermustdesignexcavationsdeeperthanWherespacepermits,thesidesofthetrench20ft,andexcavationsmustbemonitoredbyamaybeslopedbacktoreducetheneedtoprovidecompetentpersonasdefinedbyOSHA.Personnelsupporttothem.Inconfinedordeepareas,supportshouldbeprotectedfromlooserockorsoilfallingofexcavationmayberequired.Theexcavationorrollingfromtheexcavationface.Forthesupportmaybetemporarywallsthatarenotpartpurpose,loosematerialmayberemovedbyscalingofthefinalstructure,ortheymayformpartoftheandprotectivebarriersmaybeinstalledatintervalsfinalstructure,especiallywhenexcavationsareDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.21andeliminateorreducegroundwaterlowering.Sectionsoftrenchesabout20ftlongareexcavated.Thetrenchesarekeptfilledwithbentoniteslurry.Then,reinforcingcagesareloweredintothem,andconcreteisplacedtofillthetrenches,displacingtheslurry.Keysectionsareformedattheendsofthetrenches.Thewallsserveaspartofthefinalstructureorasimperviousbulkheads.SPTCorCaliforniaWall,acombinationofsoldierpilesandslurrywall.ThiswasusedonsomestationsofBART,andaspartofthefinalstructureformuchoftheCentralArteryProjectinBoston.Largewide-flangesteelbeamsareinsertedinslurry-filledboredholes,thespacebetweenthebeamsisexcavatedunderslurry,andexcavationandpipeholesarefilledwithconcrete.Caremustbeusedinexcavationtohavetheconcretesolidlykeyedintothespacebetweentheflanges.Thesteelpilesinthecompositewallactasreinforcingandpermiteasyattachmentofinteriorbracing.Thefundamentalbasisforthedesignofexcavationsupportsystemsisconsiderationofhowthesoilbeingsupportedbehaves,andperhapsalsohowthefloorofthetrenchbehaves,sincesubstantialheavecanoccurunderadversecon-ditions.AnymovementofthesupportsystemcanFig.20.9TangentPiles.causesoilmovementandhencesettlementofadjacentstructures.Itistheamountofmovementthatcanbetoleratedattheadjacentstructuresthatdeep.Theeaseandsimplicityofconstructingtheoftendictatesthetypeandstiffnessofthefinalstructurewithintemporarywallsmustbeexcavationsupportsystem,withcontrolofbalancedagainstcostsavingswhentheyareground-waterlevelsoftenbeingcrucial.Structuresincorporatedintothefinalstructure.Temporarymayhavetobedesignedforbothshort-termandexcavationsupportmaybesteelsheetpiles,soldierlong-termeffects.Oneoftheprimarytoolsforpilesandlagging,andtangentorsecantpiles.Forthispurposeissoil-structureinteractionanalysis.deeperexcavations,concreteslurrywallsmaybeFramestructuressupportedbybeam-on-an-constructed,usually2ft,3ft,or4ftthick,some-elastic-foundationanalysisarealsocommonlytimesincorporatingsoldierpilesorbeams(SPTCused.Inmostcases,atwo-dimensionalanalysisiswalls),andmayformpartofthefinalstructure.sufficient,althoughcomplexareasmayrequireSteelsheetpilewalls,fordepthstoabout30tothree-dimensionalmodeling,perhapsusingfinite40ft,supportedbywalesandcrossbracing.Theelementanalysis.wallskeeplossofgroundtoaminimum.ManysubwayandhighwaystructureshaveSoldierpilesandlagging,madeofsteelHbeenbuiltusingsteelcolumnsandbeamswithjackbeamswithwoodorconcretelagging.Thesearearches,butthisisuncommontoday.Newstruc-usedforgreaterdepth.Laggingmustbeblockedturesaregenerallyreinforcedconcreteboxstruc-tightagainsttheearthtocontrollossofground.turesbutwhentheexcavationsupportsystemalsoSoldierpilesmaybecombinedwithsheetpiles,formspartofthefinalstructure,itmayinpracticeinsteadofwoodlagging,iftightbulkheadsarebedifficulttoobtainfullfixitybetweenthewallsrequired.Walesandcrossbracingsupporttheandtheslabs.Partialfixitymaythenbespecified,walls.andperhapsshearconnectionsalsoprovided.ForConcreteslurrywallsbuiltinbentonite-slurryhighloadontherooforlargespans,thecompositetrencheshavebeenusedtopreventlossofgroundactionofathinconcreteslabontopofsteelbeamsDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.22nSectionTwentyhasbeenused.Haunchesmayhelptoreducefillingortheplacementofreinforcement),andeffectivespans.Archedtunnelroofsareraretoday.againstnoxiousgases(vehicleexhaust,forexample)Designloadsincludeweightofoverburden,selfandfirewithinthetunnel.Protectionmethodshaveweight,liveloadsurcharge,potentialfutureincludedalayerofconcrete,plywoodboards,construction,horizontalearthpressure,hydrostaticandbrick(againstverticalfaces).Heatresistingloadsifbelowthewatertable,andseismicloads.materialsandcoverplateswithgasketshavebeenWeightofsubmergedstructuresmustbeadequateusedtoprotectjointswithintunnels.topreventfloatationexcludingallremovableitemsTosaveonexcavationwidth,waterproofingforfromwithinthetunnelandaboveitwhileignoringwallsmaybeappliedtotrenchbulkheadsandfrictiononthesides.concreteplacedagainstit.TunnelWaterproofingnTunnelsindrysoilneednowaterproofingonbaseandwalls,butroofslabsshouldhaveatleastminimumwaterproofing.20.13RockTunnelingTunnelsbelowgroundwaterlevelshouldbewaterproofedallaround.Standards,regulations,andproceduresoftheTunnelsthatarenotwaterproofedshouldbeOccupationalSafetyandHealthAdministrationdesignedassumingthattheywillleak,andpathsshouldbeadheredtoinrockexcavations,asinallprovidedtoremoveanyleakagewater.Manyconstructionoperations.(SeeArts.20.6,20.8,andtunnelshavedrainagechannelsadjacenttoexterior20.12.)wallsandasecond“false”wallafewinchesfromTunnelinginrocktodayisprimarilybydrill-thefirstontowhichthefinaltunnelfinishesareand-blastorbyusingaTBM(tunnelboringattached.Jointsaremorelikelytoleakthanothermachine).Drill-and-blasttunnelscanbeanyshape,locations,sothatspecialattentionshouldbepaidtowhereasmostTBMsareonlycapableofdrillingwaterproofingjointsevenifsurfacewaterproofingcircularholes.Aruleofthumbisthatatunnelisnotapplied.requiresatleastonediameterofcover,althoughMethodsofsurfacewaterproofingincludelessmaybepossible.Whererockqualityismembranessuppliedinrollformwithoverlappingparticularlygood,thetunnelmaybeunlinedororweldedjoints,spray-appliedmembranes,blind-mayonlyneedmesh,sprayedconcreteandrocksidewaterproofingdesignedfortheoutsidefaceofboltsordowels.Morefracturedrockmayrequirewallscastagainstexistinggroundorthesupportsignificanttemporarygroundsupportsuchassteelsystem,clay-basedpanelsthatswelloncontactwithsetsandlatticegirdersuntilafinalliningiswater,andchemicaladditivestotheconcrete.Somecompleted.Fracturezonesmaybeparticularlymethodsofwaterproofingrequiresafetyprecau-difficulttocrossduetohighflowsofwaterundertionsduringapplication,suchasventilation.Water-highpressure,andduetothequantitiesoflooseproofingmembranesthatadheretothesurfacetomaterial.Forsomepurposes,liningmaybewhichtheyareappliedhelptopreventthespreadrequiredtopromoteflowortopreventingressofbeneaththemembraneofanywaterthatcouldleakwater.throughapuncture.Therepairofleaksappearing(Kuesel,T.R.,TunnelStabilizationandLining,ontheinsideofthetunnelmaythenbeassimpleasin‘‘TunnelEngineeringHandbook,’’Bickel,J.O.,injectingoffendingcrackslocally,otherwisenewKuesel,T.R.,andKingE.H.,Editors,Chapman&leaksmayappearaspreviousleaksarerepaired.Hall,1996.U.S.ArmyCorpsofEngineersManual,Forjoints,alargenumberofextrusionsare1997,DesignofTunnelsandShaftsinRock,EMavailablethataredesignedtobeburiedinthe1110-2-2901.)concrete,halfeachsideofthejoint,someofwhichForrockexcavation,themostimportantcanbeinjectedlaterifleaksstilloccur.Jointsmaygeologicalconditionstobeanticipatedarethealsobewaterproofedusinghydrophilicmaterials,presenceoffaults,usuallyinvolvingareasofbadlygasketsincompressionwithinthejointorboltedfracturedrock;directionanddegreeofstratifica-tothesurfaceeachsideofthejoint,andsurfacetion;fissuresandseams;presenceofwater,whichappliedinjectableandreinjectabletubes.maybecoldorhotorcontaincorrosiveorirritatingMostwaterproofingmustbeprotectedagainstingredients;pocketsofexplosiveortoxicgas;andmechanicaldamage(forexample,duringback-rockstrain.ThepetrographyisoflesserimportanceDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.23unlesstherockishighlyabrasive,causingeitherusedasaseperateservicetunnel,orexcessivewearofdrills.abandoned,orenlargedtoformthefinaltunnel.ToomuchinformationcanneverbeprovidedInthesepilottunnels,internalrockstressescanbefortheengineer,toproducearealisticdesign,andmeasuredbypressurecellsandstraingagesforthecontractors,topreparesoundbids.Evenatinsertedintransversedrillholes,andthenaturebest,unforeseendifficultiesmustbeexpected.oftherock,foliation,blockiness,andpressureofInadditiontogeologicalsurveysandboringsfaultsandwatercanbeinspected.(Art.20.5),engineersmayuseelectric-resistivitymeasurementsandgamma-rayabsorptionforinformationondepthandcharacteristicsofrockTunnelBoringMachines(TBM)nThehighformations.Informationalsomaybeobtainedfrominitialcostofhard-rockTBMstendstorestricttheirtheU.S.GeologicalSurvey,whichhasextendeditsusetolongertunnels.Althoughideallysuitedtoscopeandgeophysicalstudiesbeyondtheminingcirculartunnelsduetotherotarymotionofthefield.Wheregeologicalconditionsareparticularlycuttingheads,variationsoftheexcavatedshapehardtoevaluateorareespeciallysevere,explora-maybetechnicallyfeasible,ashavebeendonewithtorypilottunnels,about1010ft,maybedrivenafewsoft-groundTBMs.Largegrippersarejackedpartwayfromeachendorfortheentirelengthofaoutwards,eithertoeachsideortopandbottom,tunnel,priortofinaldesignandadvertisingofandholdthemainpartofthemachineandtransferconstruction.TBMsmaybeusedforpilottunnelstheappliedthrusttotheadjacentfirmrock.DiskTable20.2LoadHpinFeetonRockonSupportinTunnel*RockconditionHp,ftRemarks1.HardandintactZeroLightliningonrockboltsonlyifspallingorpoppingoccurs2.Hard,stratified,orschistose0to0.5BLightsupports.Loadmaychangeerraticallyfrompointtopoint3.Massive,moderatelyjointed0to0.25B†4.Moderatelyblockyandseamy0.35(BþHt)toNosidepressure1.10(BþHt)5.Veryblockyandseamy0.35(BþHt)Littleornosidepressureto1.10(BþHt)6.Completelycrushed,chemically1.10(BþHt)Considerablesidepressure.Requires†intactcontinuoussupportoflowerendsofribsorcircularribs7.Squeezingrock,moderatedepth1.10(BþHt)toHeavysidepressure;invertstrutsrequired.2.10(BþHt)Circularribsrecommended.8.Squeezingrock,greatdepth2.10(BþHt)toSameasforType74.50(BþHt)9.SwellingrockUpto250ft,Circularribs.Inextremecases,useyieldingregardlessofsupportsvalue(BþHt)*Ifdepthofrockovertunnelismorethan1.5(BþHt),whereBiswidthandHtisheightoftunnel.FromR.V.ProctorandT.L.White,“RockTunnelsandSteelSupports,”CommercialShearing&StampingCo.,Youngstown,Ohio.†Ifroofoftunnelispermanentlyabovethewatertable,valuesforTypes4and6canbereducedby50%.DownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.24nSectionTwentycuttersmountedinthecutter-headfacerollathighAcenterheadingmayalsobeusedinlargerockpressureontheexposedrockfaceandcrushthetunnels.Fromit,thesectionisenlargedtofullsizerock,thetailingsfromwhicharemechanicallybyradialdrilling.removed.Afteranadvanceofuptosixfeetorso,thegrippersmustberetracted,movedforwardsFull-FaceTunnelingnTosavetimeandandjackedoutagain.Advanceratesareverylabor,full-facerockexcavationisusedwhereverdependentonthehardnessoftherockanditsfeasible,forefficientmechanizationoftheoper-integrity,andthewearandtearthattherockmayation.Largetrackorrubber-wheel-mountedjumbocause.Inswellingrock,extraprecautionsmustbeframescarryhigh-speeddrills.Asanalternativetotakentoensurethatthemachinedoesnotgetstuck.drillandblast,roadheadersaresometimesusedonAstherockqualitydiminishes,themachinewillweakerrock.TheyaresmallerexcavatorsequippedneedtoresembleasoftgroundTBMmoreandwithripperorpoint-attackteethmountedonmore.RockTBMstendtobelaunchedfromarotatingballsattachedtoslewingandelevatingminedchamberinwhichthewholemachinecanbearms.Beingmoremaneuverable,roadheaderscanassembled.excavateopeningsofalmostanyshape.Mucking(removalofexcavation)isdonebylarge,mechan-izedloaders.Muckiscarriedindieseltrucks,wherepermissible,orintrainsoflargeminecarsHeadingsnInthepast,whenmuckingwaspulledbybattery-poweredlocomotivesiflawsdonebyhandloadingintominecars,anddrillprohibituseofinternalcombustionengines.equipmentwascumbersome,excavationwasadvancedindriftsorheadings.InweakrockorExcavationLimitsnContractplansprescribeforverywidetunnels,thismethodisstillused.Aexcavationprofiles.AninnerAlineisthetopheadingmaybeadvancedfirst.Thispermitsminimumtheoreticalsectiontobeexcavated;toinstallationofcrownsupportsifneeded.Therestisthisisaddedatolerance,usually6intotheBlineorexcavatedbybenchingdownfromthetopheading.paymentline.AnyoverbreakbeyondthisisattheThesedifferentlevelsmaketransportationofcontractor’sriskandhastobefilledattheexcavatedmaterialinconvenient.Inwidetunnels,contractor’sexpense.sideheadingsmaybeadvanced.Inthatcase,legsofsteelsets(supportsforsidewallsandroof)areplaced,wherenecessary.ThesideheadingsareBlastingnDrillingpatternandblastingfollowedbyatopheadinganderectionofthearchchargesaregovernedbytherockcharacteristics,supports.Theremainingblockcanbeattackedfragmentationdesiredformucking,andexternalfromthefaceorfromthesidedrifts.conditions,suchasproximityofsensitivestruc-Abottomheadingorpilottunnelmaybeusedtures.Theprocedureshouldbeworkedoutbyaninstead.Enlargementproceedsatseveralplacesexperiencedblastingexpertandmayhavetobealongtheheadingsimultaneously.Thepilottunnelmodifiedduringconstruction.Thecentergroupofhastobelargeenoughtoallowinandouttrafficholes,firedfirst,aredrilledconvergent,sothataandshouldbetimberedtoprotectit.conicalshapeisblasted.BlastingproceedstowardInverylongtunnels,aparallelheading,40ftortheperipherywithshort-timedelays.A6-or8-in-morefromthetunnelaxis,expeditesexcavationbydiametercenter,or“burn”hole,withoutcharge,providingaccesstoseveralworkingfacesthroughactsasareliefopening,improvingblastingeffect.crossdrifts.Fromthispilottunnel,transverseRoundsareusuallyabout10ftdeepbutmaybeheadingsaredrivenatseveralpointstothemainmoreorless,dependingontherock.Linedrilling,tunnelaxis,fromwhichtunnelexcavationcanaringofstraightholes,fairlycloselyspacedproceedinbothdirections.Theparallelheadingaroundtheperiphery,isusedifassmoothasectioncarriesalltraffictothedifferentfacesandservesasaspossibleisdesired.adrainageandventilationtunnel.Thismethodwasusedinthe12-miSimplontunnel,wheretheTemporarySupportsnPracticallyallrockparalleldriftwaslaterenlargedtoafull-sizedtunnelsneedsometemporarysupports.Timbersingle-trackrailroadclearance,andintheMoffatmaybeusedinpilottunnelsandsmallheadings.andNewCascadetunnels.Forlargertunnelcrosssections,steelsetsareDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.25Fig.20.10DrillandBlast(TARP).moreeconomicalbecauseoftheirstrengthandofinterlockingchannels.Thespacebetweenpanseaseofinstallation.ThesearemadeofIbeamsandrockshouldbedry-packedtoallowwatertocold-rolledintoshape.Forsmalltunnelswithrunoffintothedrainagesystem.circulararches,thesetsmaybecontinuousTheconcentratedloadsonthesetsatblockingframes.Inlargertunnelsorforflatarches,thepointsproducebendingmomentsintheframes.setsconsistofseparatepostsandarches(Fig.20.11).Table20.2presentsformulasforloadsonsupportsWhereroofsupportsonlyarenecessary,theinrocktunnels(R.V.ProctorandT.L.White,“RockarchesmaybesupportedonplatesrestingonTunnelsandSteelSupports,”CommercialShearingrockledges.SteelsectionsareusuallyuniformforandStampingCo.,Youngstown,Ohio).theentiretunnel,andspacingofsetsisvariedThroughbadlyfaultedrockorpressureareas,accordingtorockloads.Normalspacingis4ft.circulartunnelsectionsandringsupportsarebutspacingmaybereducedto2ftorincreasedtopreferable,particularlyinseismicareas(Fig.20.12).asmuchas6ft.Thesetsshouldbeerectedassoonasscalingoflooserockhasbeencompleted.BlockingshouldRockBoltsnIngoodrock,butalsoforsomeimmediatelybewedgedbetweenthesteelandtherockthatmaybeclassifiedaspoor,rockboltsmayrocksurfaceat3-to5-ftintervalstopreventrockbeusedtosecuretheexcavation.Theyareusuallymovementfromstarting.Thesteelframesshould1inindiameterand8ftlong.Theymaybeallowspaceatthecrown,betweenthelowerflangecoupled,however.Theboltsprovideanchorageinandtheconcretesurface,forapipeforplacingsoundrock,wheretheyareheldbywedgesdrivenconcrete.intosplitendswhentheboltsareinsertedorbyTimberorsteellaggingshouldbeplacedexpansionsleevesgrippingthesidesoftheholebetweenthesets.Theamountoflaggingdependswhentheboltsarethreadedin.Theboltsaretestedonrockconditions.Laggingmaybepracticallyforpull-outandprestressedbynutsbearingsolid,ortheremaybegapsofvariouswidthsagainstfaceplatesontherocksurface.Unten-betweenthesheets,asrequiredbycircumstances.sioneddeformedbars,bolts,orsteelorglass-fiberBadlyfragmentedrockmayrequiremetalpanningtubesareusedasrockreinforcementandfullybetweensetsifwaterispresent.Thepansaremadegroutedwithcementorhigh-strengthresingrout.DownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.26nSectionTwentyFig.20.11TypicalcrosssectionthroughtheLehighTunnelonthePennsylvaniaTurnpikeExtension.HalfsectionBshowsthebracing,orsets.Theyarestressedbydeformationoftherock,concreteissprayedontheroof.Theconcreteis3whichismonitoredbyextensometersandconver-madewithawell-gradedaggregate,upto4-insize,gencemeasurementuntilequilibriumisreached.Ifwhichisfrequentlydry-mixedwithcementandannecessary,additionaluntensionedortensionedacceleratingagent.Themixtureisejectedthroughaboltsareinserted.Allrockboltsinpermanentnozzleunderpressurebyspecialpumps.Mixinginstallationsshouldbegroutedasprotectionwaterisaddedatthenozzle.Initialsettakesplaceagainstcorrosion.inabout30to120s,finalsetin12min.Anothertypeofbolthasaperforatedsleeve,Alsooftenusedisawetmix,forwhichwhichisplacedinaholeintherockandfilledwithaggregate,cement,andwaterareplacedinthegrout.Astheboltispushedintothehole,thegroutmixerandadditiveisinjectedasaliquidattheissqueezedthroughtheperforationsandagainstnozzle.Additionofabout5%byvolumeoftherock.Bondbetweenbolt,grout,androckmicrosilicategreatlyimprovesadherenceofshot-providestheholdingforce.cretetotherockandreducesreinforcingsteel1=1=requirements.Additionof2-to12-insteelfiber1ShotcretenUseofsprayedconcrete(guniteortoamixintheamountof2to1%byweightshotcrete)aspreliminarytunnelsupportforrockconsiderablyincreasestheultimatestrengthandtunnelswasdevelopedinEuropeandhasalsobeentoughnessoftheshotcrete.successfulinNorthAmerica.AssoonaspossibleThicknessoftheinitiallayermayvaryfrom2toafterblasting,whilemuckingisgoingon,alayerof4in,dependingonrockconditions.AdditionalDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.27Fig.20.12TypicalsectionthroughBerkeleyHillRockTunnel(heavilyfaultedrock)fortheSanFranciscoBayAreaRapidTransit.layersmaybesprayedonasneeded.TotalStrengthofconcreteinplacereaches200tothicknessmaybeasmuchas8in.250psiin2h,1400to1500psiin12h.TheultimateThenozzlemaybehelddirectlybyanoperatorcompressivestrengthof4000to5500psiisaboutorattachedtoaboommanipulatedbyaworker15%lessthanthatofthesameconcretewithoutstationedundertheprotectiveroofofthejumbo.accelerator.Automaticapplicationhasbeensuccessfulinamachine-boredtunnel(HeitersbergTunnelinSwitzerland).Robots,controlledbyanoperatorWaterproofingnAbovethegroundwateronthejumbo,canbeusedtoapplyeitherdryortable,waterproofingisusuallyappliedtoceilingswetmixshotcrete.intransportationtunnelstopreventdripping.ShotcreteissprayedonthesidewallsafterDrainagepathsmaybeprovidedalongthebasecompletionofmucking.Heavywaterinflowmustofthewallstohandleanywaterthatdoesappear.beinterceptedanddrainedthroughinsertsintheFalsewallswithfinishesareoftenusedtohideshotcrete.Well-trainedoperatorsandcarefulwallswhereleakageisexpected.Formosttunnelssupervisionandcontrolareessentialforgoodbelowthegroundwatertable,awaterproofingresults.Properlyexecuted,themethodcanbeusedmembraneenvelopingthetunnelisusedbetweensuccessfullyforfracturedrock.theinitialgroundsupportandthefinallining.IftheDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.28nSectionTwentytunnelliningisundrained,thefinalliningwillcarrythefullgroundwaterpressureandshouldbedesignedaccordingly.Wheredrainageisprovidedoutsidethewaterproofingmembrane,thefinalliningmaybedesignedforareducedgroundwaterpressure.Waterproofingmembranesmayalsoneedtoresistdeleteriousgasesorliquidsexpectedtobepresent.LeakagenSeeArt.20.13.(J.O.BickelandT.R.Kuesel,“TunnelEngineeringHandbook,”VanNostrandReinholdFig.20.13TimberbentssupportpolingboardsCompany,NewYork.)inbasicearthmining.Steelsupportsareoftenusedinsteadoftimber,20.14TunnelsinFirmparticularlyforlargeheadings.Steellances,madeMaterialsofsmallwide-flangebeamswithwedge-shapedpoints,maybeusedinsteadofwoodpolingboards.OccupationalSafetyandHealthAdministrationThelancesarelongenoughtobesupportedontworequirementsshouldbesatisfiedinundergroundframesanddrivenbyjacksorairhammersintotheexcavations.(SeeArts.20.6,20.8,and20.12.)softfaceforadistanceequaltothesupportspacing.Materials,otherthanrock,thatmaybeInloosesoilorrunningsand,thefaceisencounteredintunnelingaresandsofvarioussupportedbybreastboards.Ashallowslotaboutdensitiesandgrainsizes;sandsmixedwithsiltor2ftdeepandoneortwopolingboardswideisclay;clays,eitherpureorcontainingsiltorsand,excavatedinthetopoftheface,andashortverticalandvaryingfromrelativelyplasticwithhighwaterbreastboardisplacedimmediately,toholdthefacecontenttofirmanddry;andalluvialmixturesofandsupporttheforwardendofthepoling.Aftersandandgravelorglacialtill.Toimprovethethisslothasbeenexcavatedacrosstheheadingandpropertiesofpoorerground,ortoreducewaterallverticalbreastboardsset,acapisinstalled,infiltration,groundimprovementpriortominingsupportedbyshortposts.Therestofthefacemaymaybeundertaken.Thismaytaketheformofthethenbeexcavateddownwardandheldbyinjectionofcementitiousorchemicalgrout,orithorizontalbreastboards(seeFig.20.14).mightphysicallymixsoilwiththesematerials.ThesizeoftheheadingshouldbeaslargeassoilBentonitehasalsobeenused;environmentalissuescharacteristicsallow,butnotlessthan5ftwidebyassociatedwiththeuseoftheselectedmaterial7fthigh.Steelbentsshapedtothetunnelarchareshouldbeconsidered.Ifnotsubjecttohydrostaticpreferabletotimberframing,ifeconomical,pressureoffreewater,materialsmaybeexcavatedconsideringbothpriceandspeedofoperation.bymining.TemporarysupportisgivenbytimberPolingmaybetimberorsteel.orsteelframinginheadingswhosesizeandnumberdependonlocalconditions.Miningofheadingsinallthesematerialsrequiresthedrivingofpolingboards,supportedbycrosstimbersandpoststoholdtheroof.Asexcavationisadvancedonafaceassteepasthematerialwillstand,theseboardsaredrivenfurther,withtherearsupportedbytheframe,thefrontbythesoil.Anewsupportissetundertheforwardendofthepolingboardsandtheprocessrepeated.Thesidesoftheheadingareheldbyboardssupportedbytheposts,asrequired.Figure20.13illustratesthebasicprocedureforthistypeofFig.20.14Mininginrunninggroundrequiresexcavation.breastboards.DownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.29Steellinerplatesareavailableinvariousshapesconditions.ThustheapplicationofSEMwouldandsizes.Theymaybeusedtosupportthegroundbelimitedeconomicallytovariablegeometryifalimitedexcavatedareaoftherooforarchwillstructures.Howeverforshallowtunnels,suchstandlongenoughforinsertionofthelinerplates,structurescouldprobablybemoreeconomicallystartingatthetopofthearchandworkingdown.constructedusingcut-and-covertechniques.TheflangeofeachplateisboltedtothepreviouslySEMrequiresextremelydryconditions;de-erectedliner.wateringisoftennecessarybeforetheexcavationInsmalltunnels,ribbedorcorrugatedlinercanproceed.SEMinvolvescarefulsequencingofplatesmaygiveadequatesupport.Inlargetunnelstheexcavationaswellasinstallationofsupports.orunderheavierloads,theplatesarebackedupbyShotcrete(akindofconcretesprayedfromhigh-steelribs,againstwhichtheyareblocked.Linerpoweredhoses)maybeusedtolinethetunnelorplateswithoutflangesmayalsobeusedaslaggingsupporttheface,andgrouting(theinjectionofaorpoling.SeealsoArt.20.17.cementingorchemicalagentintothesoil)maybeTopreventsettlementorunbalancedload,allusedtoincreasethesoil’sstrengthandreduceitsvoidsbehindthelinerplatesshouldbefilledbypermeability.Becauseoftherequirementsofthisinjectionofpeagravelorcementgrout.method,therateofexcavationisslow.UseofthisSmalltunnelsmayconsistofasingleheading.methodinsaturated,non-cohesivegranularsoilsForlargetunnels,variouscombinationsofhead-wouldrequiretheuseofgroundwatercontrolandingsareused.Someoftheseareknownbythegroundimprovementtechniques.Onerealconcerncountryoftheirorigin,asAmerican,Austrian,withtheuseofSEMingranularsoilsissuddenBelgian,English,German,orItalianmethods,butuncontrollablegroundloss,oftenresultinginareusedinmanyvariations.Originally,thesurfacesinkholes.Thiscanhappenwhenthemethodsrequiredwoodsupports,butnowsteelselectedgroundimprovementmethodisunsuc-supportsarefavored,whereeconomical.cessfulbecauseoflocalizedvariationingroundconditions.OnemethodoftenusedtocontrolgroundwaterSequentialExcavationMethod(SEM)niscompressedair.However,thehighairpressuresAlsoknownastheNewAustrianTunnelingoftenrequiredmightmaketheuseofcompressedMethod(NATM),SEMwasdevelopedinAustriaairtunnelinguneconomicalincomparisontootherbutisnowusedworldwide.Itisatunnelingpossiblemethods.Itisforsimilarreasonsthatshieldmethodadaptedtotheexcavationofvariableandtunnelingusingcompressedairhasbeenreplacednon-circularcross-sectionreachesoftunnel,suchbytunnelingwithpressurizedfacetunnelboringashighwayrampsandsubwaystations.Thismachines.Anothercommonlyusedmethodofundergroundmethodofexcavationdividesthecontrollinggroundwaterisdewatering.However,space(cross-section)tobeexcavatedintosegments,unrestricteddewateringcanhaveasignificantthenminesthesegmentssequentially,oneportioneffectonadjacentfoundations.Anapproachthatatatime.ExcavationsequencingbytheAmericanhasbeenusedwithvariablesuccessoverseashasmethod,AustriansystemandBelgianmethodarebeentoinstallgroundwatercut-offwalls(slurryoutlinedbelow.walls,etc.)alongbothsidesoftheright-of-wayandTheexcavationcanbecarriedoutwithcommonthendewateringinsidethecut-off.Whendewater-miningmethodsandequipment(oftenabackhoe),ingsands,runningorfast-ravelingground,con-chosenaccordingtothesoilconditions;tunnel-ditionsmayresultsothatsomeformofgroundboringmachinesarenotused.Groundconditionsimprovement,suchascloselyspacedgroutableareassessedatthefaceofthetunnelorfromthespilesorhorizontaljetgroutingabovethecrownofsideofasmalltunnel,whichhelpstodecidehowtotheexcavationcouldberequired.Twoothergroundproceedinthebestwayanddeterminesthechoiceimprovementmethodsthatcouldbeusedarejetofequipmentandlining.Itshouldbenotedthatthegroutingandchemicalgrouting.EachmethodcombinationofgroundtreatmentandSEMforthewouldbeusedtocreateablockofstabilizedgroundexcavationofuniformcross-sectiontunnelswouldthroughwhichthetunnelscouldbeexcavated.generallybemoreexpensivethantheuseofpressurizedfaceTBMconstructionunderAmer-AmericanMethodnAsshowninFig.20.15a,icanundergroundconstructionlaborandeconomicexcavationstartswith(1)atopheadingattheDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.30nSectionTwentyFig.20.15Someexcavationproceduresforlargetunnels:(a)Americanmethod.(b)Austrianmethod.(c)Belgianmethod.tunnelcrown,whichissupportedbypoling,posts,Thesearesupportedbylongitudinaltimbers,inandcaps.Next,theexcavationiswidenedbetweenturnsupportedbystrutsextendingfanlikefromatwobentsandthetoparchsegmentsadjoiningthesillinthecenterheading.(2)Next,acentercutiscrownareset,supportedbyextrapostsorstruts.excavatedtotheinvert(3),leavingbenchesto(2)Theexcavationthenisbencheddownalongthesupportthearchofthetunnellining.Slotsarecutsides,andanothersegmentofribsissetoneachintothebenchesatintervalstounderpinthearches.side.(3)and(4)ThesearedoweledtotheupperTherestofthebenchthenisremovedtocompletepartandsupportedbytemporarysills.Thisthesidewalls(4),afterwhichtheinvertisconcreted.processisrepeatedtotheinvertsill.ThebenchTheexcavationmaybeadvancedaconsiderablefinallyisexcavatedtofullsection.(5)Grounddistancebeforethetunnelliningneedbeinserted.betweenribsisheldbylagging,andvoidsare(J.O.BickelandT.R.Kuesel,“Tunnelpacked.ThismethodissuitableinreasonablyfirmEngineeringHandbook,”VanNostrandReinholdmaterial.Company,NewYork.)AustrianSystemnAsshowninFig.20.15b,afull-heightcenterheadingisadvanced.Iteither20.15ShieldTunnelinstartswithatopheadingandiscutdowntotheFreeAirinvertinshortlengthsorstartsasseparatebottomThissectiondescribesshieldtunnelingwheretheandtopheadings.(1)and(2)Inthelattercase,thefaceisessentiallyopenandexposedatambientaircorebetweenthetwoisexcavatedforshortpressure,andSection20.16whenexposedunderdistances,andtheshortpostsreplacedwithlongcompressedair.Boththesemethodsarelessones.(3)Thearchsectioniswidenedinshortcommontodaythantunnelingbythetunnelboringlengthsandisheldbysegmentalarchribsandmachines(TBM)describedinSection20.19,nowlongitudinalpolingboards.(4)Thearchribsarewidelyused.supportedbystrutsfromthecenter-cutframingShieldtunnelingisgenerallyusedinnoncohe-andsillsatthespringline.Therestoftheexcavationsive,softgroundcomposedofloosesand,gravel,isadvancedtofullfaceinshortincrements,andorsiltandinalltypesofclay,orinmixturesofanypostsaresettosupportthesills.(5)Thismethodisofthese.Itisindispensablefortunnelinginthesesuitableforreasonablystablesoil.materialsbelowthewatertable.RequirementsoftheOccupationalSafetyandBelgianMethodnAsshowninFig.20.15c,inHealthAdministration(OSHA)forundergroundfirmground,theupperhalfofthetunnelisconstructionshouldbecompliedwithinoper-excavated,startingwithacenterheadingfromtheationswithshields.OSHArequiresthefollowing,crowntothespringline.(1)Thisiswidenedtobothinparticular:Lateralorotherhazardousmovementsides,thegroundbeingheldbytransversepolings.ofashieldwhensubjectedtoasuddenlateralloadDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.31shouldberestricted.PersonnelaccessingshieldedDependingonthediameterandloads,theareasshouldbeprotectedagainstcave-ins.Person-girdersarebracedbyhorizontalandverticalsteelnelshouldnotbepermittedinshieldswhentheystruts.Thecuttingedgeisbeveledandreinforcedarebeinginstalled,removed,ormovedvertically.byweldedsteelplatestoathicknessofupto3orExcavationsmayextendupto2ftbelowashield4in.Forlooseground,theupperhalfofthebottom,iftheshieldisdesignedtoresisttheforcesshieldisextendedforward12to18intoformafromthefulldepthofthetrenchandifsoilwillnotprotectivehood.belostfrombehindorbelowthebottomoftheThetailoftheshieldoverlapsslightlytheendofshield.(SeealsoArts.20.6and20.8.)thefinishedliningandprovidesspaceforatleastTheshieldisacylindermadeofweldedsteelonelinerring,andforunderwatertunnelsisplate(Fig.20.16).Ithasadiameterslightlylargerusuallylongenoughtoaccommodatetworings.thantheoutsideofthetunnellining.TheplateisTheinsideofthetailclearstheliningbyabout1instiffenedbytwointeriorringgirders,thefirstoneallaround.Forworkinginsoftclay,thefrontoftheinstalledashortdistancebehindthecuttingedge.shieldmaybeclosedbyasteelbulkheadwithdoor-Fig.20.16Longitudinalsectionthroughashieldusedfortunnelingthroughsoftgroundinfreeair.DownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.32nSectionTwentyequippedopeningsthroughwhichmaterialistoexactlineandgradetosupporttheshieldasitexcavated.Softclaymaybeextrudedthroughtheadvances.Asimilarbottomheadingmaybeusedopeningswhiletheshieldadvances.inafullrockfaceifthefullcrosssectioncannotbeWorkingplatformsthatcanbeadvancedandexcavated.Then,therockmaybeblastedaroundretractedbyhydraulicjacksaremountedonthetheperipheryoftherestofthecuttingedgetoshieldbracing(Fig.20.16).Theygiveaccesstoallpermitadvancingtheshield.Progressinmixedpartsofthefaceand,bykeepingincontactwithit,faceintheQueensMidtownTunnelaveragedsupportitifnecessaryduringshoving.Additionalabout3to4ftper24-hday.breastingjackscanbemountedinthebracingtoBestprogressismadeinplasticmaterialholdbreastboardsagainstthefaceifitneedsthroughwhichtheshieldmaybeshovedblind,extensivesupport.thatis,withouttakinganysoilintotheinside,thevolumebeingdisplacedbycompressingorheavingofthesurroundingmaterial.Tocounter-ShieldAdvancementnHydraulicjacks(Fig.actthetendencyofthetunneltoheavebehindthe20.16)foradvancingtheshieldaresetonthewebsshield,becauseofbuoyancy,enoughsoilmaybeoftheringgirdersclosetotheperipheryoftheadmittedthroughsmallopeningsinthefaceshield.Theshovejacksareevenlyspacedaroundbulkheadandleftintheinverttobalancethetheperimeterandexertpressureagainsttheforcesuntiltheinteriorliningisplaced.Thisforwardringgirder,whichisstiffenedbybracketsmethodiscalledshovinghalf-blind.Inthefirstweldedtotheskinofthecuttingedge.JacktubeoftheLincolnTunnel,NewYorkCity,aboutplungersareequippedwithshoesbearingagainst20%ofthematerialwastakenin.Ifdisplacementthetunnellining.Thestrokeofthejacksisslightlyorheavingofthesoilmaycausedisturbanceofmorethanthewidthofalinerring.adjacentstructures,suchasbuildingsoranotherArotatingerectorarmismountedinsidethetailtubenearbyalreadyinplace,theopeningsshouldtopickupandplacelinersegments.Hydraulicbeadjustedtoadmitnearlyallthedisplacedpumpsmountedbehindtheshieldsupply5000-tomaterial.Thiswasdoneinthesecondandthird6000-psipressuretothejacks,erectorarmmotor,tubesoftheLincolnTunnel,throughopeningsandotherhydraulicallyoperatedequipment.aggregating5to20%ofthefacearea.AverageControlvalvesforthesedevicesaremountedonadailyprogresswasabout30ft.panelintheshield.ShieldsareusuallystartedfromshaftssunktoThemethodofoperation,excavation,andspeedtheinvertgrade.Theseshaftsmaybespeciallyofadvancevarygreatlyaccordingtothetypeofconstructedforthisormaylaterbepartofasoil.Insandandgravel,thefaceusuallyhastobeventilationbuilding.Anopeningisprovidedintheheldbybreastboards(Fig.20.16),whicharebracedshaftwalltofittheshieldandisclosedbyatimberbytelescopingstruts,breastingjacks,orthebulkheadduringsinkingoperations.Theshieldisworkingplatforms.Thebreastingmayhavetobeerectedonaconcretecradleatthebaseoftheshaft.carrieddowntotheinvertoftheface,whichisTheoppositeshaftwallformstheabutmentfortheexcavatedtothecuttingedgeofthehood.Ifjackingforces.Afewringsareerectedbehindthecompressedairisused,thebreastingmaybeshield,whichisadvancedthroughtheopeningcarriedpartwaydowntowheretheairpressureafterremovalofthebulkhead.balancesthehydrostatichead,thelowerpartoftheTheshieldissteeredbyvaryingthepressureoffacetakingitsnaturalslope.Infirmmaterials,siltytheshovingjacksaroundtheperiphery.Onlargesand,orstiffclay,thefullfacemaybeexcavatedtunnels,thetotaljackingforcemaybe3000towithoutbreasting.Averageprogressforthe31-ft-5000tons.Iftheshieldhasatendencytorise,morediameterQueensMidtownTunnel,NewYorkCity,pressureisappliedatthetopthanatthebottom.inthesematerialswasbetween7and8ftin24h.Similarcorrectionsaremadeforotherdirections.Shieldsarenotwell-suitedforrocktunneling,Ifthesoilisrelativelyloose,itisexcavatedatthebutrockormixedfaces,partlyrockandpartlysoil,facebyhandtools.Inhard-packedsiltysandsormaybeencounteredinpartsofsoft-groundverystiffclay,airspadesareused.Relativelysofttunnels.Iftherockishighenough,abottomclaymaybecutbyclayknives.Themuckmaybeheadingmaybeexcavatedaheadoftheshieldandshoveledbyhandonashortconveyorintheshield,aconcretecradleplaced,withsteelrailsembedded,butmorecommonly,alargehydraulicscraperorDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.33hoeisusedtoloosenthesoilandscoopitontothePackingnSincetheshieldhasalargerconveyor.Fromthere,itisdischargedonaloadingdiameterthanthelining,avoidexistsaroundtheconveyormountedonamovablecarriagebehindlinerrings.Thismaypermitacave-inandcausetheshield.Theloadingconveyordumpsitintosettlement.Theusualpracticewhensegmental3minecars,usuallyofabout4-ydcapacityinlargelinersareusedistoinjectpeagravelintothisvoidtunnels.Themucktrainsarerolledbackthroughthroughgroutholesinthelinersimmediatelyafterthetunnelstoanaccessshaft.Theindividualcarstheshieldhasbeenadvanced(Fig.20.16).Cementarehoisteduptheaccessshaftanddumpedintogroutislaterinjectedintothegraveltosolidifyit.Inhoppersfordischargingintotrucks.asectionoftheVictorialineoftheLondonsubwayindeep,verystiffclay,anarticulatedcast-ironliningwasinstalledandexpandedagainsttheclaybehindtheshield.TheadjacentringswerepressedTunnelLiningsnExceptinverystifforintocontactbythejackingforcesbutwerecompactsoils,segmentalringlinersareusedinnotbolted.Expansionofsteelribswithwoodshieldtunnels.Theseusedtobeofcastironbutlagginghasalsobeenusedtoachievetightfittodaysteelorprecastconcreteisused.Theagainstthesoil.segmentsarebroughtinbyminecars,unloadedSemicircularorsemiellipticalshieldshavebyhoistsmountedontheconveyorcarriage,andbeenusedastemporarysupportsfortheroofordepositedwithinreachoftheerectorarm.Thisisaarchofexcavations,mostlyindryordewateredtelescoping,counterweightedarmpivotedonthesoils,forexample,fortunnelsatshallowdepthcenterlineofthetunnelforfullrotationbyawhereopen-cutoperationsareprohibitedbyhydraulicmotor(Fig.20.17).Agripperatitscircumstances.Theyareadvancedinamannerouterendengageslugsorbarsinthesegmentssimilartothatforcircularshields.andplacesthese,startingatthebottom.A(J.O.BickelandT.R.Kuesel,“Tunnelshort,taperedsegmentformsthekey.SeealsoEngineeringHandbook,”VanNostrandReinholdArt.20.17.Company,NewYork.)Fig.20.17Sectionthroughaconventionalshield(usedin1930fortheDetroit,Mich.—Windsor,Ont.,Tunnel)fortunnelingwithcompressedair.DownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.34nSectionTwenty20.16Compressed-Airmaterial,theblanketwouldhavetomakeupthe23deficiencyof1370lb/ft.At60lb/ftsubmergedTunnelingweight,23ftofclaywouldberequired.NavigationAlthoughtunnelshieldsinfreeairareeffectiveinrequirementsmaymakeitnecessarytoremovethenaturallydrysoilorgroundthatcanbedewateredblanketaftercompletionofthetunnel.Clayforthis(Art.20.15),compressedairisneededwhileblanketshouldberelativelysoftsothatitwilltunnelingbelowthewatertable,particularlyinreadilycoalesceintoanimperviouslayer.subaqueoustunnels.Theairpressurecounteractsthehydrostatichead.Also,thepressurereducestheBulkheadsnWhentheshieldisstartedfromawatercontentofthesoilattheface,makingitmoreshaft,anairtightdeckisbuiltabovethetunnel,tostableandsafertoexcavate.holdthepressureuntiltheshieldisadvancedsomeLegalissuessurroundingsafetyandhealthdistance.Anairtightbulkheadisthenbuiltintotheissuesofcompressedairtunnelinghavereducedtunnelasufficientdistancebehindtheshieldtouseofthismethod.Itstillhastobeusedfromtimeprovidespacefortheloadingconveyorandafewtotimetoremoveobstructionsinfrontoftunnelminecars.Tokeepthevolumefilledwithboringmachinesthattheycannothandle,andtocompressedairwithinreasonablelimitsandtocarryoutmaintenanceandrepairsonsomeofthecomplywithsafetylaws,newbulkheadsarebuiltmachines.asthetunneladvancesandtheoldbulkheadsareremoved.Usually,regulationspermitamaximumAirPressurenTheoretically,theairpressuredistanceof1000ftbetweenthefaceandtherequiredtobalancethehydrostaticheadis0.43psibulkhead,whichmaybeconstructedofsteelorforfreshwaterand0.44psiforseawaterperfootofconcrete.depth.Actually,thepressuredependsonthepropertiesofthesoilaswellasonthemethodofAirLocksnWorkerandmateriallocksareexcavation.Inopenmaterial,suchasperviousbuiltintotheairtightbulkhead.Thelocksarecoarsesandandgravel,thefullairpressurewouldairtightcylindersatleast5ftindiameterandhaveberequired,whereasinimpervioussoils,suchasgasketeddoors(Fig.20.17).Workerlocksshouldstiffclay,nopressureatallmaybeneeded.A3provideatleast30ftofairspaceperoccupant.carefulanalysisofthesoilatregularintervalsalongCompressedairisadmittedtothelockfromthethealignmentisneededtoestimatethemaximumhigh-pressuresideorfromthecompressed-airlineairpressureandairquantitiesrequired.Closedandisexhaustedthroughaconnectiontothefree-shieldsfortunnelsintheHudsonRiversiltairside.Valvesoftheseconnectionsarecontrolledoperatedwithaslittleas16-psiairpressureinfromtheinsideinworkerlocksandgenerallyfromdepthsupto100ft.Inthesandandgravelundertheoutsideinmateriallocks.Thedooratthehigh-theEastRiverinNewYork,thehydrostaticheadpressuresideopensfromthelockintothetunnel;wasbalancedforaboutone-quarterorone-thirdthedooratthefree-airendopensintothelockthediameterabovetheinvert.Toreducelossofairchamber.Doorsareheldtightbytheairpressureatthetopoftheface,breastboardswereplasteredandcannotbeopeneduntilpressuresonbothsideswithclay.areequalized.Pressuregagesareprovidedinthelocksaswellasinthetunnel.BlowoutPreventionnWiththeairpressureThemateriallockisatthelevelofthemine-carbalancingtheheadatthebottomoftheface,thereistrack.Thelockshouldbelargeenoughtoanexcessofpressureatthetop.Iftheweightofaccommodateseveralminecars.coveroverthetunnelisinsufficienttoholdtheTheworkerlockisatahigherlevelandmustexcessairpressuresafely,aheavyclayblanketmayhavenotlessthan5ftclearheadspace.Thislockisbeplacedontheriverbottomoverthetunnelequippedwithbenchesforworkerstositdownon.headingtopreventablowoutatthetopoftheface.Inlargetunnels,twosetsoflocksmaybeusedtoIftheairpressureequalsthewaterpressureatthespeedupoperations.Ifthereisdangerofrapidinvert,theexcesspressureatthetopofa30-ft-flooding,anextraworkerlockmaybeplacedasdiameterfacewouldbe13psiinseawater,orhighaspossible,andahangingsafetywalk231870lb/ft.Fora10-ftnaturalcoverof50-lb/ftextendedatthislevelfromthelocktotheshield.DownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.35Asafetyscreenplacedintheupperpartofthefromtheworkingchamberandfree-airsideoftunnelneartheheadingwilltrapairabovethisthelock.3safetywalkincaseoffloodingandpermitworkersOSHArequiresalsothatatleast30ft/minoftoescape.Somesafetylawsrequireinstallationofventilationairbesuppliedperworkerinthetwoworkerlocks.workingchamber.Inaddition,OSHAspecifiesthatAspecialdecompressionchambercapableofatleast10ft-cbeprovidedbyelectriclightsonaccommodatinganentireshiftofworkersshouldwalkways,ladders,stairways,orworkinglevels.beavailablewhendecompressiontimerequiredisTwoindependentsupplysourcesshouldbeused,morethan75min.Apassagewayshouldbeincludinganemergencysourcethatbecomesprovidedtogiveworkersinamanlockaccesstooperativeiftheregularsourceshouldfail.Externalthespecialchamber.partsofelectricalequipment,includinglightingfixtures,wheninstalledwithin8ftofthefloor,shouldbemadeofgroundedmetalornoncombus-tible,nonabsorptive,insulatingmaterial.SafetyandHealthnForallcompressed-airOSHAalsorequiresthatsanitary,comfortablework,awell-equippedfirst-aidstationanddressinganddryingroomsbeprovidedfordecompressionchamberarerequired,staffedbyaworkersemployedincompressedair.Facilitiestrainedattendantatalltimes.Aphysicianmustbeshouldincludeatleastoneshowerforevery10availableatalltimesforemergencycallswhileworkersandatleastonetoiletforevery15workers.workisinprogress.Fire-fightingequipmentshouldbeavailableatallMoststatesandcountrieshavelawsregulatingtimesinworkingchambersandworkerlocks.theworkinghoursandlockingratesforcom-OSHArequirementsfortotaldecompressionpressed-airwork.RegulationsoftheU.S.Occu-time,whichdependsontheairpressureinthepationalSafetyandHealthAdministrationforworkingchamberandthetimeofworkerexposureworkincompressedairaswellasforconstructiontothatpressure,arelistedinTable20.3.Decom-ingeneralandallundergroundoperationsshouldpressionshouldtakeplaceintwoormorestages,beobserved.(SeealsoArts.20.6,20.8,and20.15.)butnotmorethanfour.(FourstagesarerequiredOSHArequiresthatarecordbekeptoutsideforpressuresof40psigormore.)InStage1,workerlocksofthetimeineachshiftthatworkerspressuremaybereducedatarateupto5psi/minspendincompressionanddecompression.Acopyfrom10to16psi,butnottolessthan4psig.Inlatershouldbegiventothesupervisingphysician.stages,therateofpressurereductionmaynotDuringthefirstminuteofcompressioninalock,exceed1psi/min.Localrules,however,alsopressuremaybeincreasedupto3psigandshouldshouldbechecked.Limitsofunioncontracts,beheldatthatlevel,andagainat7psig,longthough,aresometimesmorestringentthanlegalenoughtodetermineifanyoneinthelockisbeingrequirements.adverselyaffected.Afterthefirstminute,pressureTheamountofairrequiredforcompressed-airmayberaisedgraduallyatarateupto10psi/min.tunnelingdependsonsomanyvariablesthatexactIfpersonnelexperiencediscomfort,pressurerulescannotbegiven.Todeterminethesizeoftheshouldbereducedtoatmosphericanddistressedcompressorplantforagivenjobrequiresagreatpersonnelshouldbeevacuatedfromthelock.dealofjudgmentbytheengineer,basedonpastExceptinemergencies,pressureinalockshouldexperience.Low-pressuremachinesareinstallednotexceed50psi.Temperatureinalockshouldbeforthetunnelairandhigh-pressureunitsforairatleast708Fbutnotmorethan908F.,whereastools.Adequatestandbycapacitymustbeprovidedtemperatureincompressed-airworkingareasbyusinganumberofcompressors.High-pressureshouldnotexceed858F.airmaybeusedasanemergencytunnelsupplybyUnlessairpressureintheworkingchamberisinterconnectingthecompressorsthroughreducinglessthan12psig,decompressioninaworkerlockvalves.shouldbeautomatic.Manualcontrols,however,shouldbeprovidedinsideandoutsidethelocktooverridetheautomaticmechanisminemergencies.ShieldlessTunnelingnSometunnelshaveThelockshouldhaveawindowatleast4ininbeenbuiltinwater-bearinggroundbyusingdiametertopermitobservationoftheoccupantscompressedairinconjunctionwithlinerplates,DownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.36nSectionTwentyTable20.3TotalDecompressionTime,Min,afterConstructionWorkinCompressedAir*Working-Workingperiod,hchamber,11psig21122345678Over89to1233333333333146666666616163316777777173348486218777811174863637387207781515436373831031132299162438689310311312813324111223275292117122127137151261314293469104126141142142163281523314198127143153153165183301728386210514316516817818820432193543851261631781932032132263421395898151178195218223233248362444631131701982232332432532733828497312817820322323825326327840314984143183213233248258278288423756102144189215245260263268293444364118154199234254264269269293464474139171214244269274289299318485189144189229269299309319319505894164209249279309329*Fornormalconditions,asspecifiedbytheOccupationalSafetyandHealthAdministrationin“ConstructionIndustry:OSHASafetyandHealthStandards(29CFR1926/1910),”revised1991.withoutashield.Considerablelengthsof7-to12-Unlinedwatertunnelsinrockaresusceptibletoft-diameterinterceptorsewersinNewYorkwereleakageeitherintooroutofthetunnel,dependingconstructedthisway.AfewmilesofChicagoupontherelativepressures.Thereisthereforeasubwaywerebuiltinsoftclaywithsteelribsandriskthatmaterialcouldbewashedoutofweaklinerplatesundercompressedair.zonesandfissures,potentiallyleadingtoinstability[J.O.BickelandT.R.Kuesel,“Tunnelunlesslined.However,NorwegianhydropowerEngineeringHandbook,”VanNostrandReinholdtunnelsingoodcrystallinerockareoftenunlinedCompany,NewYork;“ConstructionIndustry:formostoftheirlength.OSHASafetyandHealthStandards(29CFR1926/1910,”SuperintendentofDocuments,ShotcreteLiningnWhererockisstructurallyGovernmentPrintingOffice,Washington,DCsoundbutmaydeterioratethroughcontactwith20402(www.gpo.gov).]wateroratmosphericconditions,itcanbeprotectedbycoatingwithsprayedconcrete,reinforcedwithwirefabricorfibers,orunrein-forced(Art.20.13).Suchaliningmayalsobeused20.17TunnelLiningsinwatertunnelsingoodrocktoprovideasmoothsurface,reducingthefrictionfactorandturbulence.UnlinedTunnelsnTunnelsinverysoundrock,notaffectedbyexposuretoair,humidity,orCast-in-PlaceConcretenMosttunnelsinfreezing,andwhereappearanceisimmaterial,arerock,andalltunnelsinsofterground,requirealeftunlined.Thisisthecasewithmanyrailroadsolidlining.Highwaytunnelsofanyimportancetunnels.arealwayslinedforappearanceandbetterlightingDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.37conditions.Stoneorbrickmasonryhasbeenusedto(RecommendationsinRespectoftheUseofagreatextentinthepast,butcurrentlyconcreteisPlainConcreteinTunnels,AFTESc/oSNCF,17preferred.ThethicknessofthepermanentconcreteRued’Amsterdam,F75008Paris,France.)liningisdeterminedbythesizeofthetunnel,loadingconditions,andtheminimumrequiredtoReinforcedConcreteLiningnInmostembedthesteelribsofanyprimarylining.Theliningisplacedinsections20to30ftlong.cases,reinforcingsteelwillberequiredtowith-Segmentalsteelformsareuniversallyusedandstandtensionandbendingstresses.Reinforcementmustbeproperlybracedtosupporttheweightofisusuallyrequiredatleastontheinsidefacetothefreshconcrete.Thewallsareusuallyconcretedresisttemperaturestressesandshrinkage,althoughfirst,uptothespringline.Nextcomethearchreinforcementelsewheremaybeneededtoresistpours.Itisimportantthatthespacebetweenthemoments.formsandtherockorsoilsurfacebecompletelyfilled.GroutpipesshouldbeinsertedinthearchLiningsforShieldTunnelsnLiningsforconcretetopermitfillinganyvoidswithsand-and-shieldtunnelsmaybeone-passortwo-pass.Aone-cementgrout.passliningsystemiswhenthefinalliningisalsoConcreteisplacedthroughportsinthesteeltheinitiallining,usuallyfortunnelsinsoil.Withaliningorpumpedthroughapipeintroducedinthetwo-passliningsystem,aninitialliningisinstalledcrown,aso-calledslickline.Placementstartsatthebehindtheshieldjustsufficienttoallowtheshieldbackofthepour,andthepipeiswithdrawnslowly.toadvancewhileawaterproofingmembraneisAcombinationofbothmethodsmaybeused.installedandthefinalcast-in-placereinforcedConcreteiseitherpumpedorinjectedbyslugsofconcreteliningisprepared.Theadvancerateiscompressedair.Admixturesareaddedtogetanthususuallyfasterandcostsfall.Theinitialliningeasilyplacedmixwithlowwatercontentandtomaybesegmentalringswithminimalboltingforreduceconcreteshrinkage.Ifthereisleakageeaseoferection(Fig.20.18),orsteelribswithofwater,itusuallyoccursatshrinkagecracks,lagging.Precastconcretesegmentsarenowwidelywhichmaybesealedwithaplasticcompound.Orusedandtheuseofcastironandfabricatedsteelthewatermaybecarriedoffbycopperdrainagearerareduetotheirhighcost.Althoughtheinitialchannelsinstalledinchasescutintheconcreteliningmaybedesignedaspartofthefinallining,(Art.20.9).anyleakagethroughthesealswouldresultintheFootingsforsidewallsinrocktunnelsarecutfullhydrostaticpressureactingontheinsidefinalintotherockbelowgrade.Theygiveadequateliningforwhichitshouldbedesigned.stabilityunlesssqueezinggroundisencountered,inwhichcaseaconcreteinvertliningisplaced.Insoftground,aconcreteslabisplaced,toserveasPipeinTunnelnWaterandsewertunnelsuppavementinhighwaytunnels.Ifheavysideto14ftdiameterareoftenprovidedwithanpressureexists,thisslabmayhavetobemadeinternalpipethatformstheinnerlining.Aftertheheaviertopreventbuckling.pipeissecuredagainstmovement,thespacebetweentheinitialgroundsupportandthepipeisfilledwithcellularormassconcrete.SewerpipesmayrequireafurtherinteriorliningtoprotectUnreinforcedConcreteLiningnAcon-againstcorrosiveliquidsandgases.Watertunnelscreteliningisplacedtoprotecttherockandwithahighinternalpressureexceedingtheprovideasmoothinteriorsurface.Wheretheexpectedexternalpressuresareusuallyprovidedconcreteliningisexposedtocompressionstresseswithasteelliningifareinforcedconcreteliningisonly,itmaybeunreinforced.Mostshaftsnotinsufficientlystrong.Sincethepipemaybesubjecttointernalpressurearelinedwithdewatered,itmustalsobedesignedfortheexternalunreinforcedconcrete.Shrinkageandtemperaturepressure,which,ifthepipehasleaked,mayequalcracksareprobableandmaycauseleakage.Wheretheinternalpressure.thereisariskofnon-uniformloading,unreinforced(U.S.ArmyCorpsofEngineersManual,1997,linersarenotused,suchasinsqueezinggroundDesignofTunnelsandShaftsinRock,EM1110-andthroughsoiloverburden.2-2901.)DownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.38nSectionTwentyFig.20.18Crosssectionshowstypicalsegmentalcast-ironliningforatunnel(LincolnTunnelundertheHudsonRiver).Instiffsoils,steelribs,usually4-inHbeams,andSegmentsaremadetoclosetolerancesonallwoodlaggingmaybeusedasprimarylining.Thesides.Theyareconnectedbyhigh-strengthbolts.ribsareusuallyspaced4ftctocandareerectedinLongitudinaljointsareoffsetinsuccessiverings.thetailoftheshield.PrecutanddressedwoodTheflangeshaverecessesalongtheirmatchinglaggingisplacedsolidlyaroundthecircumferenceedgesforcalking.Thesegroovesusedtobefilledbetweentheflangesoftheribs.Thislaggingalsowithleadorimpregnatedasbestoscalkingstrips,transfersthejackingforcestothetunnellining.poundedinmanually.Syntheticsealers,suchasPrecast-concretelagginghasalsobeenusedsiliconerubberandpolysulfides,canbeinjectedsuccessfully.intothegroovesbycalkingguns.ThesecompoundsSegmentsaremadeaslongasconvenientadheretothemetalsufficientlytoformaneffectivehandlingpermits,usually6to7ft.Thewidthofsealunderpressuresusuallyencounteredintheringsdependsonthedistancethefacecanbeunderwatertunnels.safelyexcavatedaheadoftheshieldandweighttoEachcast-ironsegmentisprovidedwitha2-inbehandled.Thewidertherings,thelongerthetailgroutplugforinjectionofpeagravelandgroutintooftheshieldandhencethemoredifficultthethespacebetweentheliningandthesoil.Boltholessteeringoftheshield.Earlytunnelshad18-in-widearesealedwithgrommetsofimpregnatedfabricorrings.Recenttunnelshavegoneto30or32in.plasticgrommets,thelatterbeingparticularlyDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.39effective.Boltsaretightenedwithhydraulicorverydifficult.Itisnotuncommonformostboltstopneumaticwrencheswherepossibleotherwiseberetrievedoncethegroutisset.Secondaryliningswithhandwrenches.arenotessential.Weldedsteelsegments,similarinshapetocast-Heavy,interlockingconcreteblockshavebeenironsegments,havebeenusedforeconomicusedsuccessfullyinrelativelydryorimperviousreasonsinsomesubaqueoustunnels.Theyweresoil.Theypresentdifficultieswhenexposedtoweldedinjigstotolerancesascloseaspracticable,waterpressureduetoleakage.butflangeswerenotmachinedandnocalkingExceptwheresteelringsandlaggingorconcretegrooveswereprovided.Difficultieswereexperi-blocksareusedasprimarylining,nosecondaryencedinmakingthemwatertightwithgaskets.concreteliningisused,unlessrequiredforAnimproveddesignincludescalkinggroovesappearanceandinteriorfinishofhighwaytunnels.andfabricationtolerancessimilartothoseforInthiscase,aconcreteliningoftheminimumcastiron.thicknesspracticableisplaced.Whenthetunnelistobefacedwithtile,provisionshouldbemadeforattachingit.(TofacilitatemaintenanceandimprovePrecastConcretenPrecastsegmentsarelighting,wallsandceilingsofhighwaytunnelsareessentialtoincreasingthespeedofmachineusuallyfinishedwithceramictiles.)Toprovidetunneling.Acompromisemustbereachedbetweengoodadherenceofthescratchcoat,scoringwiresthesegmentsizeandthenumberofsegmentstobemaybeweldedlongitudinallyonthesteelformsinstalled,directlyaffectingtheweightofthefortheliningtoprovidearoughconcretesurface.segments,thesizeoftheequipmentneededtoCoatingofsmoothconcretesurfaceswithepoxyhandlethesegments,andthenumberofoperationscompoundmayresultinsatisfactoryfinishesattobecarriedout.Thewidthofthesegmentsislesscost.governedbythestrokeofthejackspushingtheSeealsoArt.20.18.headoftheshield,usuallyintherangeofthreetofivefeet.Taperedrings,narrowerononeside,areusedonbends.Atleastthreesegmentsperringarerequired,withfivetoeightbeingmorecommon.Theclosingsegmentinaringisusuallysmallerand20.18DesignofTunnelwedgeshapedtofacilitateinsertion.JointsinLiningsadjacentringsareusuallystaggeredsothatalljointsarediscontinuous,helpingtostiffentheArticle20.17discussesthetypesofliningsusuallyrings.usedfortunnels.ThefollowingparagraphsConnectiondetailstoadjacentsegmentsvarydescribedesignofalinerring.widelyandcanbeflanged(Fig.20.19).StraightAlinerringisstaticallyindeterminate.Aone-boltswithnuts,washersandgrommetsarethepassliningisdesignedfortransportanderectionmostcommon,buttheuseofcurvedrecessedboltsloads,loadsduringgrouting,andgroundloadsresultinsmallerpockets.Gainingpopularityareincludingseismic.Inlieuofcomputeranalyses,straightboltsplacedatanangletominimizewhichmightbeassimpleasatwo-dimensionalrecesses;theboltscoupleintosocketscastintotheanalysisofagridframeworksupportedonsprings,adjacentsection.Dowelsmayalsobeusedbetweenorascomplexasfiniteelementorfinitedifferenceadjacentrings.Theboltsensurethattherubberorthree-dimensionalanalysesusingsoil-structureneoprenesealsbetweensegmentsarecompressed.interactionforeachstepoftheconstructionTheadditionofahydrophilicsealneartheoutsideprocess,stressesinthelinerringmaybecomputedfacemayreduceleakageevenfurther.Duetotheaftertheringismadestaticallydeterminatebyaveryclosetolerancesneededtoensuresealsremaincutatthetopandoneendisfixed(Fig.20.20).watertightandthatthediameterremainsconstant,ForacircularringofconstantcrosssectionahighdegreeofmechanizationwithsteelformsissymmetricallyloadedthethrustatthecrownCisused.Thesegmentsmustbeinstalledwithintheshieldtailandthespacebehindthem(thetailvoid)ð2pgroutedatapressureatleastequaltotheexternalTc¼Mcosfdf(20:2)pressure,makinglateralalignmentmodificationspR0DownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.40nSectionTwentyFig.20.19Typicallinersegmentsusedforrapid-transittunnels.DownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.41loadscarriedbythesecondarylining.Compressionofcompetentrockduetooutwarddisplacementofthetunnellininginapressuretunnelmayalsoneedtobeconsidered.Oftenthoseliningsmustbedesignedtotakethefullinternalpressure.Beyond100psiinternalpressure,reinforcedconcretelinersmaynolongerbesufficientandsteellinersmaybeneeded.Ifatunneliswatertight,theinteriorliningisusuallydesignedtocarryatleastthefullexternalwaterpressure,sinceleaksinanyouterliningswilleventuallyleadtofulltransferofthehydraulichead.Ifthetunnelisdrained,atleastsomeofthehydrostaticheadshouldbeconsidered.Blastingmayalsodisturbtherocklocally,leadingtoloadsdifferenttothoseofaboredtunnel.Fig.20.20StressesinlinerringmaybeFollowingthederivationofmoments,axialcomputedbyassumingitcutatcrownC.thrustandshears,theconcretecrosssectioncanbedesignedaccordingly,andsteelorfiberreinforce-Theverticalshearatthecrowniszero,andthementplacedaccordinglyasneeded.Tensioncracksmomentisinthemselvesdonotnecessarilyresultinfailure,ðpwhereasthrough-cracks(oftencausedbyshrink-1Mc¼RTcMdf(20:3)age)cancauseleakageandcorrodeexposedsteel.Itp0isusuallyundesirableforcrackstoextendmorewhereR¼radiusofringthanhalfwaythroughthesection.TypicalsteelM¼bendingmomentatanypointUduetoreinforcementforcrackcontrolmayreach0.28%orloadsonCUmoreofthesectionarea.Restraintsattheexteriorfaceduetokeyingintoanirregularrocksurfacef¼anglebetweenUandcrownCmaychangethecalculatedbehavior.LiningswithWiththethrustandmomentatthecrownknown,irregularwidtharemorelikelytocrackatthethestressesatanypointontheringcanbethinnestsectionsoratinitialgroundsupportcomputed,asforanarch(Art.6.71).embedments.Waterstopsareusedatconstruction(AsetofequationsispresentedinChapter15Bjointstoreduceleakage.‘‘TunnelStructures,StructuralEngineeringHand-Becauseofflexibility,tunnellinerringscanofferbook,’’2000UpdateforENGnetBASE,EditedbyonlylimitedresistancetobendingproducedbyWai-FahChenandLianDuan,CRCPress,2000unbalancedverticalandhorizontalforces.The(www.crcpress.com).)liningandsoilwilldistorttogetheruntilastateofLoadsonaliningincludeitsownweightandequilibriumisobtained.Ifthedeflection,in,internalloads,weightofsoilabovethetunnelexceedsmorethan1.5D/10,whereDisthetunnel(submergedsoilfortunnelsbelowwaterlevel),diameter,ft,theliningmayhavetobetemporarilyreactionduetoverticalloads,uniformhorizontalbracedwithtierodswhenitleavestheshielduntilpressureduetosoilandwaterabovethecrown,thefinalloadingconditionsandpassivepressuresandtriangularhorizontalpressureduetosoilandhavebeendeveloped.Incertainsoftmaterials,waterbelowthecrown.whenshieldswereshovedblind(withoutmaterialMagnitudeofloadsontunnellinersdependsonbeingexcavated),initialhorizontalpressurestypesofsoil,depthbelowsurface,loadsfromexceededtheverticalloads,sothattheverticaladjacentfoundations,andsurfaceloads.Thesewilldiameterlengthenedtemporarily.Ultimately,therequirecarefulanalysis,inwhichobservationssectionrevertedtoapproximatelyitsinitialcircularmadeonprevioustunnelsinsimilarmaterialswillconfiguration.bemosthelpful.Whenaliningisinrock,determinationoftheInrock,thequalityoftherockwillaffecttheloadsimposedontheliningneedtobedonewithloadsthatarecarriedbythetunnel,andloadscare.Stablerockmaydistributethestressesaroundcarriedbyanyinitialrocksupportmayeffectthethetunnel,andifimpervious,mayleaveanyDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.42nSectionTwentytunnelliningvirtuallyunloaded.Followingexca-[Kuesel,T.R.,TunnelStabilizationandLining,vation,rockthathasnotyetreachedstabilitycanin‘‘TunnelEngineeringHandbook,’’Bickel,J.O.,stillbemoving,extremeexamplesofwhichareKuesel,T.R.,andKingE.H.,Editors,Chapman&squeezingandswellingrock.Furtherdisplace-Hall,1996(www.wkap.nl)][U.S.ArmyCorpsofmentsmaybelittleaffectedbythepresenceoftheEngineersManual,1997,DesignofTunnelsandlininginsuchcases,ormaydependupontheShaftsinRock,EM1110-2-2901(www.USACE.relativestiffnessesofthetwo,sothattheliningARMY.MIL/inet/USACE-docs/eng-manuals).](Themustbedesignedaccordingly.Concretecastdesign,sizingandconstructionofprecastconcreteagainstirregularrockmayalsobekeyedintothesegmentsinstalledattherearofatunnelboringrockandresultincompositeaction.Iftherockismachine,1997,translatedintoEnglish1999,Frenchanisotropic,materialpropertiesandmovementsTunnelingAssociationAFTESc/oSNCF,17Ruemaydependupondirection.Someexternalloads,d’Amsterdam,F75008Paris,France.)suchasgroundwaterpressureandsomeclays,areindependentofdisplacements.Dependingupon20.19MachineTunnelingtheporosityofthesurroundingmaterial,waterpressurecaneventuallybuilduptothefullToreducecostsandincreasethespeedoftheever-hydrostaticloadeveninarocktunnel.increasingamountoftunnelconstruction,aPotablewatersupplytunnelsmayneedtobenumberoftunnel-boringmachines(TBM)forrockmadewatertightwhenpassingthoughareaswhereandsoftgroundhavebeendeveloped.Universaltheinflowofgroundwaterisnotacceptable.Wheremachinesformixedgroundofrockandsoftgroundwatercontainsfinesiltorchemicalsthatmaterial(mixedface)aredesignedforeachspecificcouldclogdrainagefacilitiesonwhichthetunnellocationandhaveopenedupnewpossibilitiesfordesignisbased,regularmaintenanceisrequiredtomachinetunneling.keepdrainagepathsclear,orelsenewdrainagepathsmustbeprovidedorthetunneldesignedasHardRockTBMsnRock-boringmachineswatertight.Sewagetunnelsfrequentlygenerateconsistofarotatinghead,eithersolidorwithhydrogensulfideandsorequireextraprotectionspokes,onwhicharemountedcuttingtoolsagainstcorrosion,suchasusinganinternalPVCorsuitableforthetypeofrock.ThemachinesareHDPEmembranecastintotheinternaltunnelmountedonlargeframes,whichcarrythedrivinglining.machineryandauxiliaries,includingaseriesofhydraulicjackstoexertheavypressureagainstthePrecastLiningSegmentsnAnalysisandface.Chiselcuttersserveforsoftrock,diskcuttersdesignmustcoverallaspectsoffabrication,breakharderrockbywedgeaction,andtoothedstorage,transportation,installation,jackingloads,rollercutterswithtungstencarbideinsertscuttheandexpectedloadsinservice.Allowanceforcreephardestrocks.Acriticalfactorinevaluatingandshrinkageduringallstagesisrequired.Itisnotproductionistheamountofdowntimeforuncommonforsegmentstobeinstalledslightlymaintenanceandreplacementofcuttersandaskew,resultinginextraboltingforcesandnon-theircost.Mostlongtunnelsinrockusehard-rockuniformloads.CurvedboltsalthougheasiertoTBMs.install,requireextrareinforcement.AttentiontoreinforcementdetailsatcornerscanhelptoreduceSoftGroundTBMnTwomaintypesoftunneldamage.Compressedgasketstendtocreatetensileboringmachine(TBM)areusedinsoftground,astressesthatmayrequirereinforcement.DurabilityslurryTBMandanearthpressurebalance(EPB)ofthetunnelliningishighlydesirable,andmaybeTBM.Bothtypesoperatewithasealedfrontenhancedbyusinglowpermeabilitycrack-freecompartmentthatiskeptundersufficientpressureconcrete,theuseofpozzolanstoresistsulfatetostabilizethefaceandminimizegroundmove-attackandmicrosilicatoimprovestrength,protect-ment.EPBTBMshavebeenlimitedtodiametersingtheboltsandreinforcementagainstcorrosionunder33ftduetothehightorqueneededtodrivesuchasbyapplyingepoxycoatingtothefabricatedtherotatingcutterhead,althoughotherformsofreinforcement,andbytheuseofexternalwater-drivemayovercomethislimitation.SlurryTBMsproofing,includingqualitygroutandabitumenhavebeenbuiltupto50ftdiameter,andlargercoatingtotheexteriorface.sizesareplanned.SettlementsatthesurfaceinsoftDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.43Fig.20.21PreparingtheCairoMetroShieldforAssembly.groundaredirectlyrelatedtothepercentagelossofequilibriumwiththesoilandgroundwatermaterialoutsidethetunnel.Typicallossofmaterialpressuresactingattheface.Theequilibriumisliesbetween0.5%and2.5%.Factorsaffectingtheoftenbalancedbyacompressedairreservoirandlossincludethepropertiesofthematerialflowcontrols.Theslurryalsoactsasalubricantandtraversed,thefacepressureused,thedesignoftheholdsloosenedsoilinsuspension.Themainshield,andtherateofadvance.TunnelsexistwheredisadvantageofaslurryTBMisthattheslurrythelosshasbeenzero.SoftgroundTBMsaremustbecontinuouslycirculatedthroughasepara-generallylaunchedfromarelativelysmallshaft,tor,oftenlocatedonthesurface,toremovethewithsubsequentpartsofthemachinebeingaddedexcavatedmaterialbeforereturningtherecondi-asprogressismade.tionedslurrytotheface.OnemainadvantageisThesealedfrontcompartmentofaslurryTBMisthattheundergroundoperatorsnevercomeintousuallyfilledwithabentoniteslurryheldincontactwiththeexcavatedmaterial.TheslurryDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.44nSectionTwentyTBMalsohasbetterfacecontrol,especiallyinsoimmersedtunnelscanbedesignedtosuitdesignmixed-faceandboulderyground.Manyslurryspeeds,existinglanduses,topography,andTBMsalsoincorporateaboulder-crushingunit.connectionstoexistingroadorrailsystems.Soilexcavatedbytherotatingcutterheadofan(L.C.F.Ingerslev,“WaterCrossings—theEPMTBMfallsbehindtheheadandisremovedbyOptions,”TunnelingandUndergroundSpaceTechnol-screwconveyorthatdischargeseitherontoaogy,Vol.13,No.4,pp.357–363,ElsevierScienceconveyorbeltordirectlyintomuckcars.TheLtd.,1998.)excavatedmaterialmaybeconditionedbytheImmersedtunnelsconsistofverylargeprecastadditionofwater,clayorbybiodegradableconcreteorconcrete-filledsteeltunnelelements.additivestoassistinlubricationandtoprovideTheyarefabricatedinconvenientlengthsonbetterpressuredropthroughthescrewconveyor,shipways,indrydocks,orinimprovisedfloodablethuspreventingthedirectexitofgroundwater.Thebasins,sealedwithbulkheadsateachend,andthenrateofadvancemustbecloselycoupledtotheratefloatedout.Theymayrequireoutfittingatapierofadvancetoavoidexcessivegroundmovement.closetotheirfinaldestinationbeforebeingtowedtotheirfinallocation,immersed,loweredintoapreparedtrench,andjoinedtopreviouslyplacedFlowingGroundnTunnelingmachineshavetunnelelements.Afteranyfurtherfoundationbeendevelopedforuseinflowingground,toworkshavebeencompletedasdiscussedbelow,confinethepressuretoasmallspacebetweentheimmersedtunnelsarebackfilledandthebedfaceandabulkheadbehindthecuttingwheel.Theyreinstated(Fig.20.22).Whereintrusionintotheuseapressurizedslurrycomposedofbentoniteorwatercolumnispermitted,thefinalbedlevelmayofexcavatedmaterial,tobalancethepressure.Thebehigherthantheoriginal.Thesideslopesofthesolidsaresettledoutoftherecirculatedslurry,andexcavatedtrenchdependuponthesoilcharacter-theirvolumeisaccuratelymeasuredtodetermineistics;oftenaslopeof1:1.5isfeasibleundertheadvanceofthemachine.temporaryconditions,althoughflattergradesandInverysoftmaterials,thevolumeofmaterialanallowanceforpossiblesloughingmaybeexcavatedmustmatchtheadvanceofthemachine,requiredinsoftermaterials.orelsesinkholesmayappearormoundsmaybepushedup,inbothcasescausingunacceptablylargegroundmovements.FloatingTunnelsnForparticularlydeepafter-crossingsatanumberoflocations,designs20.20ImmersedTunnelshavebeenproposedfortunnelsthatremaintotallyImmersedtunnelsshouldbeconsideredforallexposedwithinthewatercolumn.These“floating”watercrossings.Theyaretheshallowestformoftunnelsmaybesupportedbelowthewatersurfacetunnel,requiringonlyminimalprotectionagainstonpiersrisingfromthebed,unsupportedifthesinkingshipsanddroppinganchors,with5ftofdistancebetweenendsisshort,supportedfromgranularmaterialandscourprotectionoftenbeingfloatingpontoons,orevenhelddownbycablesadequate.Becausetheyaresoshallow,theyresultifpositivelybuoyant.ThetextinSection20.20intheshortestcombinedlengthoftunnelandappliestofloatingtunnelsaswellasimmersedapproaches,andbecausetheymayservetheirtunnels,exceptforfoundationsandbackfilling.functionbetterthanotherchoices,theoverallcostWhereasimmersedtunnelsneedonlyconsidercanbeless.Approachgradientscanalsobeflatter.dynamicloadsuptotimethattheyarefinallyImmersedtunnelscanbeconstructedingroundplaced,floatingtunnelshavetobedesignedforconditionsthatwouldmakeboredtunnelingdynamicloadsthroughouttheirlife.Theyappeardifficultorexpensive,suchasthesoftalluvialtobeparticularlyattractivefordeepnarrowdepositscharacteristicoflargeriverestuaries,butwaterways,sincetheoveralllengthoftunnelmaywhenrockhastobeexcavatedunderwater,besignificantlyshortenedcomparedtootherformsimmersedtunnelingmaybelesscosteffective.oftunnel.WhilemostimmersedtunnelsarebuiltConsequently,theidealalignmentforanimmersedforwaterdepthsofbetween5mand20m,tunnelmaynotcoincidewiththeidealalignmentconceptsfor100mdepthhavebeenprepared.forabridge.Alignmentsdonotneedtobestraight,FloatingtunnelscouldavoidtheneedtobesoDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.45Fig.20.22Immersedtunnelsaresetinatrench,whichisthenbackfilled.deep,aslongasrisksfromshipandsubmarinetraffic,butafuelfireusuallygoverns.Permittedcollisioncanbehandled.classesofvehiclesmayberestrictedbylegislation(“InternationalTunnelingAssociationorownerrequirementstolimititthepotentialsizeImmersedandFloatingTunnelsWorkingGroupofthefire.Finally,additionalairspacemaybeState-of-the-ArtReport,”SecondEdition,Perga-neededforthetunnelelementstobeabletojustmon,April1997.)floatwhencompletedwithbulkheadsinplace,andperhapsspaceforadditionalballast,eitherinsideorout,tostaysubmergedwhencompletedandInternalDimensionsnHighwaydesignorbulkheadsremoved.Floatingtunnelsthatrelyonclientrequirementsshoulddeterminetherequiredbuoyancymusthavesufficientcompartmentalizednumberoftrafficlanes,tracks,orinternalspaces.Itbuoyancytostayafloatincaseofaccidentalisusualtoavoidclimbinglaneswithinimmerseddamagetotwoadjacentcompartments.tunnelselementsthemselves,andnominalwidths[L.C.F.Ingerslevetal,Chapter15BTunnelofemergencylanesorshouldershavealmostStructures,‘‘StructuralEngineeringHandbook,’’alwaysbeenusedtominimizecosts.Iftunnelsare2000UpdateforENGnetBASE,EditedbyWai-Fahparticularlylong,extrawidthmayhavetobeChenandLianDuan,CRCPress,2000(www.providedatintervalstopermitemergencystop-crcpress.com).]ping.Curbs,ormoreusuallybarriers,areprovidedtoprotectthewallsfromtrafficimpact.Barriersover2fthighmaymakethelanewidthseemConstructionnThetechniqueofimmersednarrowerandslowmotorists.Emergencyaccesstunnelingisoftenlessriskythanboredtunneling,intoanadjacenttunnelshouldbeavailable,sayatsincetunnelelementmanufacturecanbebetter300ftintervals,whichwouldrequireanemergencycontrolledduetotheconstructionoftheelements“walkway”atleast2ftwideontopoftheadjacentinacontrolledenvironmentinthedry.Asaresult,barrier.Suchemergency“cross-passages”mayimmersedtunnelsarenearlyalwaysmuchmoreneedtobeprovidedatintervalsofsay100meters.watertightandthereforedrierthanboredtunnels.ExtraspacemaybeneededfortunnelandotherTwomaintypesoftunnelhaveemerged,knownutilities,constructionandmisalignmenttolerances,assteelandconcrete.Steeltunnelsusestructurallighting,lanesigns,andhighwaysigns,whilesteel,usuallyintheformofstiffenedplate,workingkeepingtheclearanceheightaslowaspossible.compositelywiththeinteriorconcrete,whereasEscapeducts,whenprovided,shouldbeslightlyconcretetunnelsdonot,relyingonsteelreinforcingover-pressurizedrelativetoadjacentductstobarsorprestressingcables.Thenumberofconcreteprevententryofnoxiousfumes.Withtheminimumtunnelsisaalmosttwicethatofsteeltunnels.Steelspacesdetermined,spaceallowancesforanytunnelscanhaveadraftofaslittleasabout8ft,necessaryventilationsystem(suchasforjetfanswhereasconcretetunnelshaveadraftofalmosttheoradditionalducts)canthenbeevaluated.Thefulldepth.Tunnelcross-sectionsmayhaveflatcriticaldesigncasemaybeformovingorstalledsidesorcurvedsides.Historically,concretetunnelsDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.46nSectionTwentyhavebeencircular,orcurvedwithaflatbottom,butConcreteTunnelsnAllbutfourofthethepredominantshapehasbeenrectangular(Fig.concretetransportationtunnelsbuilthavebeen20.23),whichisparticularlyattractiveforwiderectangular(Fig.20.23).Theyareforroad,rail,orhighwaysandcombinedroad/railtunnels.Steelforbothroadandrail.Anumberofothertunnelstunnelshavebeencircular,curvedwithaflatcarryingpedestrians,utilities,sewageorwaterbottom,andrectangular(particularlyinJapan),buthavealsobeenbuilt.RoadandrailtrafficarethepredominantshapeinthepastintheUShascarriedinseparateducts.Ofalltheroadtunnels,beenacircularshellwithinanoctagonalshape,onlyonecarriesfourlanesinasingleduct.Allthewithventilationductsaboveandbelowtheroad-othershavethreeorlesslanesperduct.Inordertoway,eitherinsingletubeorbinocularversions.Thiskeepprofilesasshallowaspossible,anyairductsarrangementofventilationductsmaychange,sinceareusuallylocatedatthesides,ratherthanabovecurrenttechniquespermittheuseoflongitudinalorbelowthetrafficduct.Becauseconcretetunnelsventilationinmuchlongertunnels,oftenobviatingaremuchheavierthansteeltunnelswhentheyaretheneedforseparateventilationducts.Steellaunched,theyareusuallyconstructedwithindrytunnelscanbecategorizedintothreesub-types:docksorpurpose-builtcastingbasins(gravingdocks)capableofbeingfloodedforremovaloftheelements.Formanynarrowertunnels,someform†Singleshell,wherethestructuralshellplateofcatamaranlaybargehasbeenusedtosupportworkscompositelywiththeinteriorreinforcedthemduringtheirimmersionandplacing,whereasconcreteandtheshellplaterequirescorrosionsomewidertunnelshavehadapontoonplacedonprotection(Fig.20.25).topneareachendfromwhichthetunnelwaslowered.Inmostcases,watertightnesshasbeen†Doubleshell,wherethestructuralshellplateassuredbysomeformofexteriormembrane,whichworkscompositelywithinteriorreinforceditselfmayrequireprotection.Ideally,themem-concreteandisprotectedbyexternalconcretebraneshouldadheretotheconcretetolimittheplacedwithinanon-structuralformplate(Fig.spreadofanyleakagethroughit.Anoutersteel20.26).Thisshapehasalsobeenusedinpairsformembranecanyieldandstillremainwatertightseveraltunnels,themostrecentbeingTeddespitesignificantdeformations.WilliamsinBoston,Massachusetts.DoubleshellAnelementisalengthoftunnelthatisfloatedtunnelsareonlyfoundintheUS.andimmersedasasinglerigidunit.Forafew†Sandwich,wherestructuralsteelplates,bothDutchtunnelsandtheØresundtunnel(betweeninternalandexternal,areconnectedbydia-DenmarkandSweden),therigidityhasbeenphragmsandtheinternalspaceisfilledwithtemporaryandwaslaterreleased,elementsunreinforcedself-compactingconcrete.consistingofanumberofdiscretesegmentsFig.20.23Box-sectionconcreteimmersedtunnel(DeasIslandTunnel).DownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.47Fig.20.24WesternHarbourCrossing,Hongkong.stressedtogetherlongitudinallyforeaseoftrans-threeareforrailinTokyo,Japan,andthreeareforportationandplacing.AfterplacingandreleaseofrailintheUSincludingtheuniquetwoovertwordthesegments,eachmayactasamini-elementfreeconfigurationofthe63StreetTunnelinManhat-tomoveatthesegmentjoints.Theabilitytousetan.TheBaytowntunnelinTexaswascircularwithdiscretesegmentscandependuponsubsurfacetwolanesforhighway,andtheCrossHarbourconditions,acceptabledisplacements,andsuffi-TunnelinHongKongissimilarbutbinoculartocientcapacitytoresistseismiceffects.givetwolanesineachdirection.TheDetroitRiverMosttunnelelementsarecastinbays,similartotunnel(1910)andtheHarlemRivertunnel(1914)segments,butcontinuousacrossthejoints.Typi-maynotquitefitintothiscategory,beingthefirstcallythefloorslabiscastfirst.Thewallsandrooftwoimmersedtransportationtunnelseverbuilt,maybecastineitheroneortwooperations.Specialbutdohavesimilaritiestosingle-shelltunnelsandeffortsmustbemadetoreduceorpreferablycarryrail.eliminatecrackingintheconcreteduringfabrica-Figure20.25showsthecross-sectionoftheSantion.TestingandrepairofleaksshouldbeFranciscoBayAreaRapidTransit(BART)trans-baycompletedbeforesubmergingelements.tubewithonetrackineachdirection,separatedby(L.C.F.Ingerslev,“ConcreteImmersedTunnels:anexhaustairductandaservicepassage.The57TheDesignProcess,”ImmersedTunnelTechniques,elementshaveatotallengthofabout19,000ft.TheTheInstitutionofCivilEngineers,Telford,UK,1989.)steelshellisweldedtomakeitcontinuousacrossthejoints,asisthereinforcedconcretelining,toSteelSingle-ShellTunnelsnOftheeightprovidesecurityagainstmajorearthquakeloading.single-shelltunnelswithsomeexternalcurvature,AtthelandfalljunctionswiththeventilationDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.48nSectionTwentyFig.20.25TransbayTubeoftheSanFranciscoRapidTransitSystem(steelsingleshell).buildings,specialearthquakejointspermitrelativefloatingatafitting-outpier,bypumpingconcretemovementinalldirections.Theshellplateisthroughhatchesinthetopoftheshellintoprotectedagainstcorrosionbyacoatingandasegmentalsteelforms.Pouringsequenceswerecathodicprotectionsystem.regulatedtocontrolincrementsofwaterpressureAlleightrectangularsingle-shelltunnelsareontheshellplateandlongitudinalbendinglocatedinJapan.Theyareverysimilarinlayouttomoments.Thehatcheswereclosedwithweldedconcretetunnels,thedifferencebeingthattheouterplates,andtheexteriorconcretecapwascastandsteelshellworkscompositelywiththeconcrete,enoughtremieconcreteplacedinthesidepocketswhereasevenifanoutersteelplateispresentasatoreducefreeboardtoabout1ft.Most,ifnotall,ofwaterproofingmembraneinasimilarconcretethesetunnelshavebeenimmersedusingatunnel,itisnotconsideredinthestrengthdesign.catamaranlaybargeconsistingofabargeeachsideofthetunnelelementconnectedbytwotransversebeamsfromwhichtheelementisSteelDouble-ShellTunnelsnFifteenofsuspended(Fig.20.28).Additionaltremieconcretethesetunnelshavebeenbuilt,ofwhichfivearecanthenbeaddedtogivetherequirednegativebinocular,themostrecentbeingtheTedWilliamsbuoyancyforimmersing,placing,andjoining.TunnelisBoston.Figure20.26showsatwo-laneMoretremieconcretemaybeneededtoachievethetunnelwithacircularinteriorsection.Thesteelshellfinalfactorofsafetyagainstfloating.platewas31ftdiameterandabout300ftlong.Figure20.27showsacombinationoftwosuchExteriordiaphragms,approximatelyoctagonal,arecylindricalsectionsforoneofthetwofour-lanespacedabout15ftapart,andlongitudinalribsofthetubesoftheFt.McHenryTunnelunderBaltimorebarsandTsectionsstiffentheshell.OutsideformHarbor.plateswereattachedtothediaphragmsandsuppor-tedbyanglestrutsextendedfromtheshellstiffeners.Thetubeswereerectedonshipways.AllweldsSteelSandwichTunnelsnAlthoughpos-weretestedforwatertightnesswithacompressed-tulatedelsewheremanyyearsearlier,steelsand-airstreamandsoapsolution.BeforetheendswerewichtunnelshavebecomearealityinJapan.closedwithweldedwatertightbulkheads,theRectangularinshape,theprinciplebehindthisreinforcingsteelfortheinteriorconcreteliningformofconstructionisthatthereisasteelskinwasplaced.Thekeelconcreteinthespacebetweeninsideandoutsidethetunnel,bothactingtheoutsideformplatesandthebottomoftheshellcompositelywiththeconcretebetweenthem.Thewascastbeforelaunching.TheconcreteliningandplateisstiffenedwithflatandL-shapedribs,androadwayslabwerecastwhiletheelementwastheinteriorisdividedupintocellsbydiaphragmsDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.49Fig.20.26Cylindricalsteeldouble-shellimmersedtunnel(HamptonRoadsTunnel).intwodirections.Self-compactingnon-shrink“AITES-ITA2001,WorldTunnelCongress:Pro-concreteispumpedintoeachcellthoughoneholegressinTunnellingafter2000,”Proceedingsppwhileairisreleasedthroughothers.OsakaSouth209–216,Milan,June2001.)PortandKobePorttunnelsarebeingconstructedWithascreededfoundation(Fig.20.22),thebythismethod,thelatterbeingtheonlysteeltunnelisfoundedonaleveledbedofsandorstonetunnelsofartocarrythreelanesperduct.2ftto3ftthick,placedpriortotheimmersedtunnel.ThelevelinghasbeendonebydraggingeitheraheavygridofsteelbeamsorasteelboxFoundationsnTherearetwobasicsystemsinfilledwiththefoundationmaterialalongtheuseforsupportingimmersedtunnelsonlineandalignment,suspendingthemfromacarriageongrade,ascreededfoundation,andapumpedsandrailssetparalleltotherequiredgrade.Thematerialfoundation.Inaddition,afewtunnelsarefoundedhasalsobeenplacedinnarrowpassestransversetoonpileswheresoilsareparticularlysoftorspecialthealignmentusingapipe,theelevationofwhichconditionsprevail.Suchconditionscanincludewascomputercontrolled.earthquakewherestonepilesmayhelptodissipateForapumpedsandfoundation,thetunnelisexcessporewaterpressureandpreventsoilfoundedonasandormortarfoundationofsimilarliquefaction.thickness,placedafterthetunnelelementis(LC.F.Ingerslev,“ImmersedTunnelFoun-temporarilysupportedinplace.Theelementcandations,”ComitatoOrganizzatoredelCongresso,besetontwolightpilebentsthathavebeenDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.50nSectionTwentyHalfofsteelimmersedtunnelcombinestwocylindricalsections(Ft.McHenryTunnel).Fig.20.27DownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.51constructedtothecorrectgrade.Thesandcanbeimmersiongasketorsoftnosedgasket(Gina-placedthroughmovablepipesinsertedandwith-type)incompression,attachedtotheendofonedrawnfromthesidesbeneaththestructure(sandoftheelementsandmatingwithaflatsteelfacejetting),orthroughfixedpipesembeddedwiththeontheother.Theuseofasecondaryindependentstructure(sand-flow)withconnectionseitherexter-flexibleseal,capableofbeingreplacedfromnalontherooforsides,orinternalthroughvalves.withinthetunnel,iscommonpractice(oftenanOnemethodofsandjetting,inventedbytheomega-shapedseal).EachsealshouldbecapableDanishfirmofChristiani&Nielson,isparticularlyofresistingtheexternalhydrostaticpressureandeffective:Asandslurryisinjectedthroughashouldallowforexpectedfuturemovements.movablenozzle,andthesurpluswaterispumpedJackspullthetubesintocontacttoprovideanoffbyanothernozzle,therollingmotiondepositinginitialseal.Thejointisthendrained,activatingthesandinacompactlayer.Withsandflow,thethefullhydrostaticpressureontheoppositerollingcurrentdepositsthesandaroundtheendofthetube.Thepressurecompressesthedischargepointinafirmcircularlayer(pancakes),gasketscompletely,providingasecureseal.Then,oftenallowedtogrow20–26ftradius.Dischargethebulkheadsbetweentheconnectedtubescanpointsarebuiltintotheundersideoftheelementbeopenedandthejointcompletedfromtheandareconnectedtopipesleadingtoconvenientinside.pointsatwhichthepumpedsandsupplymaybeDependingupontheconstructionsequence,connected.thelastelementmayneedtobeinsertedintheAswellaspilebents,elementshavebeenremainingspace,ratherthanappendedtotheendtemporarilysupportedbyjacks,penetratingofthepreviouselement.Inordertoachievethis,athroughthebaseofthesection.Thejacksbearonsmallfinalgapwillremain.Thisclosureorfinalpreviouslyplacedconcreteblocks.Byadjustingthejointcorrespondstoashortlengthoftunnelthatjacks,thesectionisbroughttoexactgrade.Then,willneedtobeconstructedinaspecialway.thesandfoundationcourseisflushedin.Methodsusedhaveincludetremieconcretetosealarigidjoint,andforflexiblejoints:Immersion,PlacingandJoiningnLooselytermedthe“sinking”operation,thesethree†dewateringtocompletethejointinthedryfromoperationsareperformedwithahighdegreeoftheinside;controlandthereforeofaccuracy.Immersionand†terminalblockwhereashortclosuresectionisloweringofeachelementisregulatedbywinchesslidoutfromwithinonesideuntilitmeetstheonspecialbargesorpontoons,orbycranes,fromotherandanyremaininggapisclosedwithawhichtheyaresuspended.Alignmentiscontrolledrubbergasketincompression;byinstrumentssetonfixedpointsandsightingontargetsmountedontemporarytowersattachedto†wedge-shapedblockdroppedintotheremain-theendsofthesectionsorbysonartopre-installedinggapuntilitissealedagainstbothsides.targetstoavoidusingtemporarytowers.Steel-shellBackfillnUptoabouthalftheheightoftheelementshavehistoricallybeenconnectedwithelement,thetrenchisbackfilledwithwell-gradedshortlengthsofshell,whichprojectbeyondtheendself-compactingmaterialtolocktheelementsbulkheads.Thegapbetweentheendswascoveredsecurelyintoplace.Ordinarybackfillisplacedtobyhoodplatesextendedfromthelowerandupperadepthofatleast5ftoverthetopofthetunnel.Ifhalfoftheshellextensions.Formplateswereanypartofthetunnelprojectsabovethenaturalinsertedintoguidesontheverticaledgesofthebottom,dikesshouldbebuiltatleast50ftawayonbulkheads.Thespacearoundthejointwasfilledbothsidestoaheightof5ftabovethetunnel.Thewithtremieconcreteasapreliminaryseal.Thespacebetweenthedikesshouldbefilledwithinsideofthejointwasdrained,andclosureplatesbackfill,coveredwithastoneblankettopreventwereweldedtointeriorribsoftheshellextensions.scourwherenecessary.Finally,theconcreteliningwascompleted.Makingrigidimmersionjointstodayusingtremieconcreteisunusual,withrubber-gasketDesignnTunnelelementsaredesignedasrigidjointsbeingalmostuniversallyused.Flexiblestructurestoresistdeadloads,liveloads,excep-jointsaregenerallysealedwithatemporarytionalloadsandextremeloads.DeadloadincludesDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.52nSectionTwentymeanwaterlevel.Liveloadincludesseabedshafts.Enclosuresofverticalsteelsheetpiling,forerosionandsiltation,andvariationsinwaterlevel,roundorrectangularshafts,aresuitableforwater-current,stormloadsandearthquakes,eachwithabearingground.returnperiodof5yearsorless.ExceptionalloadsWheregroundconditionsarepoorandwater-includelossofsupport(subsidence)belowthebearing,shaftsmaybeconstructedwithacaissontunnelortooneside,andstormsandextreme(hollowbox),withcompressedairasneededtowaterlevelswithaprobabilityofbeingexceededexcludewater.Gravitypullsthecaissondownasonceduringthedesignlife.Extremeloadsincludeexcavationproceeds.Sinceitsweightisrelativelysunkenships,shipcollision,water-filledtunnel,small,thecaissonmayhavetobetemporarilyexplosion(e.g.vehicular),fire,thedesignseismicballastedorjettedforsinking.Thedepthtowhichaeventpredictedforthelocation,andtheresultingcaissonmaybesunkislimitedbythehighcostofmovementofsoils.Conditionstobeinvestigatedcompressed-airwork,whichresultsfromtheshortshouldincludenormal,abnormal,extreme,andworkinghourspermittedunderhighpressure.construction.Open-bottomshaftswithheavywalls,oftencircularorsubdividedintocompartments,maybebuiltonthegroundandsunkbyexcavatingthegroundunderneath.Indrysoil,theexcavationmay20.21Shaftsbedonedirectly;ifwaterispresent,clamshellIntunnelwork,shaftsarestartingpointsforbucketsandhigh-pressurejetsmaybeusedtoexcavationinrockorfirmmaterialorshields.Forloosenthesoilandremoveit.Onreachingthelongtunnels,suchasaqueducts,severalshaftsproperdepth,thebottomoftheshaftisclosedbyareusedtodivideconstructionintoshortertremieconcrete.sectionsthatcanbeworkedsimultaneously.ForAsanalternativemethodforshaftconstruction,vehiculartunnels,especiallysubaqueousshieldwater-bearinggroundmaybefrozeninacirculartunnels,theshaftsareusedasbasesforringaroundtheshaftlocationandtheexcavationventilationbuildings.Inconstructionofshafts,madeinthedry.Closed-endpipesaredrivenregulationsoftheOccupationalSafetyandHealthverticallyintothegroundaroundtheperiphery,Administrationshouldbeobserved(Arts.20.6,andopen-endsmallerpipesinsertedintothem.A20.8,and20.12to20.16).refrigerant,usuallybrine,iscirculatedattempera-Timbershaftsareminedandbracedinthesameturesaslowas2308Ffromtheinterconnectedmannerastunnelsinsimilarmaterial.Usually,innerpipesintothelargeronesandfromthempolingboards5to6ftlongaredrivenintothereturnedtotherefrigerationplant.Severalmonthsgroundandbracedatregularintervalsbymayberequiredtofreezeadeepringsolidly.Therectangulartimberframes.Then,thesoilisventilationshaftoftheScheldtRiverTunnelinexcavatedtotheendsofthepolingsandanewAntwerpwasbuiltinthismanner,aswereaframeinstalledatthislevel.numberofmineshaftsinGermanyandFrance.Arelativelyshallowshaftmaybestarted(J.O.BickelandT.R.Kuesel,“Tunneloversizewithsheeting10to20ftlongdrivenEngineeringHandbook,”VanNostrandReinholdverticallyontheoutsideoftheframebracing.Company,NewYork.)Intermediateframesareinstalledastheexcavationproceeds.Atthebottomofthetierofsheeting,thesidesaresteppedintomakeroomforthenexttierofverticalsheeting.20.22SeismicAnalysisandInrockshafts,timberingisusedtopreventlooseDesignrocksfromfallingoffthewalls.Itsplacementusuallylagsanappreciabledistancebehindtheexcavation.Earthquakeloads,ormorecorrectlyseismicloads,Steellinerplatesalone,orincombinationwithareincludedamongtheloadsonastructurethathorizontalribs,maybeusedinsoftgroundwherearerequiredtobeconsideredbymostcurrentexcavationcanbemadeinincrementsequaltothedesigncodes.Seismiceffectscanoccurduringthewidthofthelinerplates.Hbeamsdrivenverticallyconstructionphaseandshouldthereforealsobeassoldierpiles,withwoodorsteellaggingandconsideredduringthatperiod;anappropriatelevelhorizontalbracing,maybeusedforrectangularofriskshouldbeagreedwiththeowner.TheDownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.53seismichazardatatunnelsitecanbequantifiedbyapproximatetogrounddeformations,aconserva-aproject-specificseismichazardassessment.Typi-tiveassumption.Foratunnelinrock,tunnelcally,afunctionalevaluationearthquake(FEE),deformationswillmatchthoseoftherock,butinlikelytooccurnotmorethanonceduringthedesignsoftersoils,thetunnelwillresistsoilpressures.Thelife,isusedfirsttodesignthestructureforeitherresponseofthetunneltothefree-fieldsoillimitedorfullperformancefollowingaseismicdisplacements(asifthetunnelwereabsent)willevent,asagreedwiththeowner.Nextasappro-dependuponboththestiffnessofthetunnelandpriate,eitherthesafetyevaluationearthquake(SEE)thatofthesoil.Whilethecomplexseismicanalysesorthemaximumcredibleearthquake(MCE),bothmaybesolvednumericallyusingcomputers,someconcernednotonlywithlifesafetybutalsowiththesimplifiedprocedureshavebeenpublished.Sim-survivabilityofthestructureunderthemostsevereplifiedbeam-on-elastic-foundationanalysiscanseismiceventconsideredatthelocation,ischeckedalsobeusedtoaccountforthesoil-structuretoensurecompliancewithminimumperformance.interactioneffectsofsoildeformations,especiallyIfnecessary,thestrengthofsomepartsoftheinsoftsoils.HorizontalshearS-waves,dependingstructuremayhavetobeenhancedtocomply.upontheangleofapproach,causetransverseStructuresburiedinsoilaregenerallycon-bendingoraxialwavesandproducethelargeststrainedtofollowtheseismicdeformationsofthestrainsthatareusuallygoverning.CompressionP-groundinwhichtheyarelocated.Thestiffnessofwavesshouldalsobeconsidered.Atsiteswherethetunnelisgenerallysmallrelativetothesoil,sotherearedeepdepositsofsoil,RayleighR-wavesthatinallbutsoftsoils,tunneldeformationswillmaygoverntheinducedstrains.Racking(ovaling)Fig.20.28LayBarge.DownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERING20.54nSectionTwentydeformationsintheplaneofthecross-sectioncanobtained,forlongitudinal,lateralandverticaloccurintunnels,butnotusuallyinverticaleffects.Internalelements,notincontactwiththeshafts,andiscausedprimarilybyseismicsoilandwithanaturalfrequencyapproachingthatwavespropagatingperpendiculartothetunneloftheseismicwaves,mayneedtobedesignedtolongitudinalaxis.Verticallypropagatingshearsubstantiallylargerseismiccoefficients.Thever-wavesaregenerallyconsideredthemostcriticalticalseismiccoefficientcanbereasonablyassumedtypeofwavesforthismodeofdeformation.Axialtobetwo-thirdsofthedesignpeakhorizontalandcurvaturedeformationsareinducedbyaccelerationdividedbythegravity.componentsofseismicwavesthatpropagatealongSpecialprecautionsareneededfortunnelsinthelongitudinalaxis.soilsthatmightliquefyorslip,especiallysoifTheeffectsofaseismiceventonatunnelasacrossingactivefaults.Liquefactionmaycausewholecanbeintegratedtogiveaneffectivetunnelstofloatup.Sinceitisvirtuallyimpossibleaccelerationatthetunnellocation,expressedasatodesignagainsttheseconditions,thebestpolicyseismiccoefficienttimestheaccelerationduetoiseithertoimproveorreplacethesoilinquestiongravity.Threeseismiccoefficientsareusuallyortoavoidit.Faultsarebestavoided,butifthatFig.20.29TARPCalumetShaft.DownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
TUNNELENGINEERINGTunnelEngineeringn20.55isnotanoption,thenthetunnelmustbeParsonsBrinckerhoffMonographNo.7,1993.)(St.designedtoaccommodateexpecteddisplace-John,C.M.,andZahrah,T.F.,AseismicDesignofments,andperhapsthesurroundingmaterialUndergroundStructures,TunnelingandUnder-mayalsoneedtopermitrelativemovementofthegroundSpaceTechnology,Vol.2,No.2,1987.)tunnel.Locationsofespeciallycriticaldesignina(Chapter15BTunnelStructures,‘‘Structuraltunnelareatchangesofinertiaandsoilproper-EngineeringHandbook,’’2000Updateforties(wheretherewillbecontrastingresponses),ENGnetBASE,EditedbyWai-FahChenandLianandatjointsthatmightopenupandcauseDuan,CRCPress,2000(www.crcpress.com).)flooding.Ductilityinstructuresisparticularly(EarthquakeAnalysis,L.C.F.IngerslevandimportantforstructurestosurviveandforlifeO.Kiyomiya,InternationalTunnelingAssociationsafety.ImmersedandFloatingTunnelsWorkingGroup,(Wang,J,‘‘SeismicDesignofTunnels—A‘‘State-of-theArtReport,’’SecondEdition,Perga-SimpleState-of-the-ArtDesignApproach,’’mon,April1997.)DownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.AnyuseissubjecttotheTermsofUseasgivenatthewebsite.
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