2002ITAOpenSession:FireandLifeSafetyThefireintheChannelTunnel૾
C.JKirkland*
HalcrowConsultingEngineers,7IrwinRoad,Guildford,SurreyGU27PW,UK
Abstract
TheChannelTunnel,whichconnectstheUnitedKingdomwithFrance,wasdesignedandbuiltbetween1986and1993withconsiderationoffireandlifesafetyatthetopoftheagenda.Itsdesignwasconstantlymonitoredbyabi-NationalSafetyAuthorityappointedbyanInterGovernmentalCommissionoftheGovernmentsofFranceandtheUK.InNovember1996ashuttletraincarryingheavygoodsvehiclessufferedaseriousfire,whichseverelydamagedthetunnel,thoughnobodywasseriouslyhurtintheincident.Thispaperdiscussesthedesignforfiremanagement,thefireitself,andlessonslearnedfromtheincident.ᮊ2002ElsevierScienceLtd.Allrightsreserved.
1.Tunneldesignandfiredefences1.1.Overallconfiguration
Althoughcalled‘thechanneltunnel’,thereareinfactthreetunnelsrunningparallelbeneaththeEnglishChan-nel.Tworailwaytunnelsof7.6mdiameter,set30mapart,andbetweenthemaservicetunnelof4.8mdiameter.Thesethreetunnelsareconnectedtogetheratintervalsof375mbycrosspassages,andtherailwaytunnelsarealsoconnectedat250mintervalsbypistonreliefductsof2mdiameter.Freshairissuppliedtothesystemthroughtheservicetunnel,viacontrolledlouvresinthecrosspassages,thusmaintainingapositiveairpressureintheservicetunnel.Therearetwocrossovercavernsatroughlythe‘thirdpoints’alongthetunnel’slength,dividingtherailtunnelsintosix‘intervals’.1.2.Tunnellining
Thegreaterproportionofthetunnelsarelinedwithprecastreinforcedconcreteliningrings,1.5mwide.Thethicknessoftheringsvarieswithloadingconditionsbetween400and800mm.
૾ThisarticlewaspresentedattheITAOpenSession:FireandLifeSafety,atthe28thITAGeneralAssemblyandWorldTunnelCongress,2–8May2002,Sydney,Australia.
*Correspondingauthor.Tel.:q44-1483-831-268;fax:q44-1483-831-268.
E-mailaddress:colin.kirkland@which.net(C.JKirkland).
Whereconcretewasconsideredinappropriate,theliningringsareofcastiron.
Thecrossovercavernsarelinedwithin-situmassconcrete.Atthelocationofthefirethetunnelliningwasprecastreinforcedconcretesegments.1.3.Permanentinstallations
Therearetwoventilationsystemsinstalledinthetunnel.TheNormalVentilationSystemsuppliesfreshairtotheservicetunnelatbothendsofthetunnelatarateof88m3ys,sufficienttoprovidefortheneedsof20000peopleinthetunnel.
Asecondsystem,calledtheSupplementaryVentila-tionSystem,supplieslargevolumesoffreshairdirectlyintotherailwaytunnelstocontroltheflowofsmoke,ortoprovideadditionalcoolingcapacityintheeventoftractionpowerfailure,260m3ys.ontheEnglishside,and300m3ysontheFrenchside.Thefanssupplyingthisairarereversiblesothataircanbefedinononesideanddrawnoutattheother.
Firehoseconnectionsareavailableadjacenttoeachcrosspassage,fedwithwaterfromafiremaininstalledintheservicetunnel.
Powersupplyandothercablinginthetunnel,aswellasanyequipmentwhichusesinherentlyflammablematerialswererigorouslytestedforflamepropagation,smokedensityandtoxicity,andallareclassifiedas‘lowsmokeandfume’.
0886-7798/02/$-seefrontmatterᮊ2002ElsevierScienceLtd.Allrightsreserved.PII:S0886-7798Ž02.00014-7
130C.JKirkland/TunnellingandUndergroundSpaceTechnology17(2002)129–132
1.4.Rollingstock,touristandHGV
Thetouristwagons,whichformtheshuttletrains,arethelargestrailwayvehiclesintheworld,aremadeofstainlesssteel,andareinsulatedagainstnoiseusingfireresistantrockwool.Thedoorsystemswhichcloseoffthewagonendsduringtransitofthetunnelaredesignedtoresistafireinsidethewagonforupto30min,i.e.foraperiodlongerthanthetransittimeof27min.Airconditioningunitscarriedbeneaththefloorofthewagonsalsoperformthefunctionofpurgingthewagonoffuelvapoursbeforethetraincommencesitsjourneythroughthetunnel.
Eachwagonisequippedwithcomprehensivefiredetectionandextinguishingsystem.Aswellaspassen-ger-operatedalarmsthereareaseriesofdetectorsthatareautomaticallytriggeredbysmoke,fumesandinflam-mablevapours.Thesedetectorsaresensitivetoions,orultra-violetradiations,smokeandgases.Ifsmokeden-sitycontinuestoincreasetoapresetdangerlevel,halongasisautomaticallydischargedintotheareaconcerned.HGVshuttlewagonsarebasicallyflatwagonsuponwhichismountedanopenframeworkofstainlesssteelwhichsupportsathinsheetroof.Thisdesignenables44tonnetruckstobecarriedwithoutbreachingthe22tonneaxleloadrestriction,andalsoprovidesprotectionagainstthepossibilityofflappingtarpaulinsontheHGV’sdamaginglinesideequipmentortheoverheadpowersupplycable.
BecauseoftheopennatureoftheHGVshuttlewagonsitwasnotpossibletoinstallfiredetectionsystemsonthewagonsthemselves.Instead,fireandsmokedetectorswereinstalledontheloadingwagonsandatintervalsalongtherailwaytunnels.
2.Firefighting,firstline,watersupply,smokecontrolThefirstreactionwhenfirebreaksoutmustbetoalerttheNationalFireService,however,Eurotunnelhasitsownresidentemergencyreactionforce,trainedandequippedtoquicklymoveintoactioninanypartofthesystem,andthisforcecanbemobilisedimmediately.Accesstothetunnelsystemisnormallyviatheservicetunnelusingspeciallydesignedvehicleswhicharewire-guidedinthetunneltopreventcollisions.Eachvehiclecarriesa‘pod’containingequipmentappropriatetotheemergency,andthesepodsareinterchangeablebetweenvehiclestogivemaximumflexibilityofresponse.
Firefightingwaterissuppliedtothetunnelsystemthroughawatermainlocatedintheservicetunnelinordertoobviatetheriskofdamageintheeventofatrainderailment.Waterissuppliedtotwooutletsintherailwaytunnelsadjacenttoeachcrosspassage,at125mintervalsalongthetunnel.
Asnotedearlier,freshairissuppliedtothesystemthroughtheservicetunnel,andthedirectionofsmoke
movementintherailtunnelsiscontrolledbyactivationofthesupplementaryventilationsystem.2.1.Specialarrivalsidings
Intheeventofafirebreakingoutonatrainthenormalreactionistotransferpassengersfromtheaffect-edwagonintoadjacentwagons,andthentoisolatethewagoncontainingthefirebyclosingthefireresistantdoorsateitherendofthewagon.Thetrainshouldnotbestopped.Onarrivalatthedestinationterminaltheburningtrainwouldberunintoaspeciallydesignedreceptionsidingwherepassengerevacuationandfirefightingcanbecarriedoutexpeditiouslywithoutaffect-ingtheoperationoftherestofthesystem.2.2.Dangerousgoodsrestriction
InordertominimisetheriskoffireonshuttleandthroughfreighttrainsEurotunnelhasbannedawiderangeofhazardouscommoditiesfrompassagethroughthetunnel.Generallytheseareproductswhicheitherburnfiercelyifignited,orwouldrendertheatmosphereinthetunneltoxicifreleased.Fueltankersandnuclearwasteflasksarethemoreobviousexamples.3.Thefire
3.1.Sequenceofevents
ThefireoccurredinInterval3ofthetunnelonthe18thNovember1996.Theexactcauseofthefireremainsunknown,butitappearsthatthefiremayhavebeentheresultofthedeliberatesettingfiretoaheavygoodsvehicleonboardoneoftheshuttlewagonsbeforeitenteredthetunnel.ItwascertainlynotcausedbyanymechanicalorsystemsfailureinEurotunnel’sequipmentorrollingstock.
Thetrain,whichcarriedthefireintothetunnel,wasanHGVfreightshuttletrainwhichlefttheloadingplatformat21.42h,enteringthetunnelat21.48h.At21.49hTheFireEquipmentManagementCentreintheUKreceivednoticeofasmokealarmtriggeredinthetunnel.Twofurthersmokealarmswereregisteredby21.50h.
By21.54h,followingfurthersmokealarmsandaconfirmedflamealarm,theRailControlCentrehadorderedalltrainstoreducespeedandthedampersinthepistonreliefductswereorderedtobeclosedtopreventthespreadofsmoketotheotherrailtunnel.At21.57hanalarmsignalonboardthetrainindicatesthatoneoftheloadingjacksmayhavedropped,andthedriver’sstoplampilluminates.Thetrainmustnotcontinuewithajackdroppedforfearofcausingaderailment,sothetrainisbroughttoacontrolledstopwiththeAmenityCaradjacenttoacrosspassage.
C.JKirkland/TunnellingandUndergroundSpaceTechnology17(2002)129–132131
At21.59hthetraindriverinformstheRailControlCentreofalossoftractionpower.
By22.04hboththeUKandFrenchFirstLineofResponseteamshadenteredthetunnel.
At22.12htheRailControlCentrebegantheactiva-tionoftheSupplementaryVentilationSystem.
At22.21hTheRailControlCentreopenedthecrosspassagedoorsadjacenttotheincidentinordertodispersesmokelocallytopermittrainevacuation.
By22.25hallpassengersfromthetrainhadbeenevacuatedintotheservicetunnel,andby22.42hhadbeenremovedtosurfaceonboardaTouristShuttletrain,whichhadbeenstoppedintheotherrailtunnelforthispurpose.
FrenchSecondLineofResponseteamwasonlocationby22.56h,andwerejoinedbytheUKteamat23.55h.
NationalFirefightingteamswereatthefirelocationbymidnightandbeganfightingthefire.
05.00hthefirewasdeclaredextinguished.3.2.Severityanddamage
Whatnodoubtbeganasasmallfireonboardoneofthevehiclesonthetrainmayhaveincreasedinsizeasthetrainprogresseddownthetunnelthoughtheindica-tionsarethatonlyonevehiclewasonfirewhenthetrainstopped.Thetrainwasstoppedinthetunnelduetoasecondaryfailureindicatornotconnectedtothefire.Theoriginalsourceofthefirespreadtoseveralwagonsduetothemovementofothertrainsinthetunnel,andtotheactivationofthesupplementaryventilationsystem.Itisestimatedthattemperaturesupto10008Cwerereachedattheheartofthefire.
Thetunnelwasseverelydamagedoveralengthof46m,sufferedseriousdamageoverapproximately280m,andwasaffectedtosomeextentoveratotalof500m.4.Recoveryandrepair
4.1.Makingsafeandremovalofdebris
Afterthefirehadbeenextinguishedthefirsttaskwastoremovethedamagedtrainfromthetunnel.TherewassomedelayincommencingthisoperationtopermittheFrenchAuthoritiestocarryouttheirinvestigationinthetunnel,butthistimewasusedtoprepareplansforrecoveryofthetunnelitself.
TheInitialappraisalofthedamagetothetunnelindicatedthataconsiderableproportionofthethicknessofthereinforcedconcretelininghadbeendestroyed,andadecisionwastakentoquicklytoinstallsometemporarysupporttothedamagedlining.Steelcollieryarcheswereerectedat1.5mcentres,supportingalightsteelmeshtopreventfurtherfallofdebrisasthetunnelwasbeingcleared.
4.2.Schedulingofrepairs
BeforeanyactualrepairworkcouldbeginthemethodofrecoveryandrepairhadtobeagreedindetailwiththeSafetyAuthority,setupbytheintergovernmentalCommissionbeforeconstructionoftheTunnelitselfbegan.
Apreliminaryproposal,supportedbycalculationswassubmittedtotheAuthorityonNovember27,andagreementwasreachedby24January1997.
Repairofthetunnelwasdividedintotwocategoriesofwork,civilengineeringandelectromechanicalengineering.
Civilengineeringconsistedmainlyofthepreparationofthedamagedconcreteoftheliningbygritblasting,forwhich250tonnesofgritwererequired,andthereplacementofdamagedreinforcingsteel.Thereplace-mentofliningconcreteby680tonnesofplainshotcreteand630tonnesoffibrereinforcedshotcrete,followedfinallybyfinishingtoprofile.FrenchcontractorFreys-sinetcompletedallofthisworkin60days.
Electro-mechanicalworkbeganwiththereplacementof500mofrailwaytrackandsupportingtrackblocksfollowedbythereplacementof2600moftractionpowercatenarycable,4000mofsignalcabling,over4400moflightingandotherpowercables,4200moffibreopticcommunicationscables,and1000mof400mmdiametercoolingwaterpipes.AllofthisworkwascompletedinlessthanonemonthbyEurotunnel’sownteams.4.3.Logistics
Theguidingprincipleinthelogisticalplanningwastocauseminimumdisruptiontothecommercialopera-tionoftheunaffectedpartofthetunnel.
ThefireoccurredinthemiddlethirdoftheSouthrunningtunnel,anditwaspossibletoclosethissectionbyutilisingthetwocrossovertunnelsateitherendofthissectiontoroutetrainsaroundtheworkarea.
Theworkareaitselfhadtobeisolatedfromtheoperationaltunnelbyclosingofftherailwaytunnelateachendwithairtighttemporarybulkheads.
Allnecessaryplant,equipmentandmaterialsforthewholeoftherecoveryoperationwasloadedontoasingleworkstrain,whichenteredthetunnelonthe29thJanuary1997,anddidnotleavethetunneluntilallworkwascompleteonthe26thMarch1997.
Theworkforcegainedaccesstotheworkviatheservicetunnelwhichrunsparalleltoandbetweenthetworailtunnelsforthewholeoftheirlength.
OncompletionofthecivilengineeringworkEurotun-nel’steamsmobilisedasecondworkstrain,loadedwithallthenecessaryrails,blocks,cabledrumsandpipesfortherenewalofthefixedequipmentinthetunnel.
132C.JKirkland/TunnellingandUndergroundSpaceTechnology17(2002)129–132
Theinitialtargetdateofthe15thMay1997,setforre-openingoffullcommercialoperationwasmet,withintheoriginalbudgetaryprovision.5.Lessonslearned5.1.Forconstruction
1.Thevariousdetectorsinstalledinthetunnelsystemtogivewarningofsmokeorflamesinthetunnelwereeffective.
2.Numerouson-trainsensors,insisteduponbythesafetyregulators,haveprovedunreliable,frequentlygivingwarningsignalslaterfoundtobeincorrect.3.Theprecastconcreteliningofthetunnel,thoughnotspecificallydesignedforfireresistance,generallystoodupwelltoallexceptthemostsevereheatconditions.
4.Thefailureoftractionpowerisbelievedtohavebeenduetoacombinationofheatandsmoke,causingashort-circuitwhichtrippedoutthepower.
5.Somedifficultywasencounteredduringevacuationofpassengers,firstlybecausetheRailControlCentrecouldnotascertainwithsufficientprecisionwherethetrainwaswithrespecttothenearestcrosspassage,andescapingpassengershaddifficultyfindingtheescapepassageduetosmoke.Thesetwoissueshavebeenaddressedandrectified.
6.ThefiredetectormonitoringpanelsshouldbelocatedintheRailControlCentreratherthantheFireEquipmentMonitoringCentre.
7.Afiresuppressionsystem,basedonhigh-pressurewatermist,shouldbedevelopedandinstalledontheshuttles.Thissystemisnowdevelopedandacontractforinstallationhasbeenawarded.5.2.ForOperation
Itshouldberecordedthatallpassengersandcrewoftheaffectedtrainwereabletowalkawayfromapotentiallydevastatingfire.
However,certainaspectsofprocedurewereseentobecapableofimprovement:
1.ThereshouldbesystematicchecksofeachloadedtrainbeforedeparturebystaffindirectcontactwiththeRailControlCentre.
2.Onreceiptofthefirstin-tunnelfirealarmthetunnelshouldimmediatelybeputintoemergencyconfigu-ration,ratherthanwaitingforconfirmatoryindicators.Onreceiptofasecondalarm,thetrain,whichtriggersthealarm,shouldbestoppedandevacuatedunlessitisclosetothetunnelexit.
3.BecauseoftheopennatureoftheHGVwagons,thenormal‘driveout’policyshouldonlyapplyifthetrainisclosetoexitingthetunnel.Inallothercasesthedrivershouldcarryoutacontrolledstopandevacuatethetrain.
4.ThepolicyofdecouplingthefrontlocoandamenitycaronHGVshuttleshasbeendroppedinfavourofpriorityevacuationofpassengers.
5.TheChefdeTrainshouldbeinchargeoftrainevacuation,ratherthanthedriver.
6.Theprocessofclosingpistonreliefductsandacti-vatingtheSupplementaryVentilationSystemshouldbeginimmediatelythereisasinglefirealarmofanytype.6.Conclusion
Thiswasanextremelyintenseanddisastrousfire,whichcausedamajordisruptionofEurotunnel’scom-mercialoperation.
Thatfullcommercialoperationwasabletorecornm-enceafteronlysixmonthsisnotonlyatributetotheorganisationanddeterminationoftherepairteams,butprovesagainthevalueoftwintunnelsandtheprovisionofacontinuousservicetunnel,bothforevacuationandrepair.
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