《隧道衬砌的防火保护》中英文Word格式文档下载.docx

《隧道衬砌的防火保护》中英文Word格式文档下载.docx

《《隧道衬砌的防火保护》中英文Word格式文档下载.docx》由会员分享，可在线阅读，更多相关《《隧道衬砌的防火保护》中英文Word格式文档下载.docx（21页珍藏版）》请在冰豆网上搜索。

Abstract:

RecentfiredisastersinEuropeanroadtunnelshaveshownthatfiresinatunnelrepresenthighrisks.Theusersandtherescueservicesareendangeredbyheat,smokeandalsoexplosiveconcretespallingofthetunnellining.Thetunnelitselfisoftendamagedconsiderably.Thenecessarylongrefurbishmentworkshavenegativeeffectsonthetunnelserviceavailabilityandalsocausehighcostsforthetunnelowner.Thushighsafetydemandsmustbeplacedoncomplexinfrastructuralfacilitiessuchasroadtunnels.Preventivemeasuresdesignedtoavoidhazardscausedbyfireareconstantlybecomingmoreandmoreimportant.Inaddition,structuralfireprotectionisaswellapointofincreasinginterest.Intheeventoffirethetemperatureinatunnelrisesextremelyrapidlywithinashortamountoftime.Largescalefiretestshaveshownthatmaximumtemperaturesof1200°

Corevenabovecouldoccur.Theresultisanincreasedriskofexplosiveconcretespallingofthetunnellining.Dependingondepthandquantityofthesespallings,thestructurecouldbedamagedseriouslyandintheworstcasethetunnelstabilitycouldbeinfluencednegatively.

Differentpossiblestructuralmeasurestoprotecttheconcretetunnellininginordertoreduceoravoiddamagesincasesoffireareexplainedanddiscussed.Afire-proofconcreteisonerelativelynewandpromisingmeasuretoavoidexplosiveconcretespallingofthetunnelliningduringafire.Thefireresistanceofconcretecanbeimprovedbyaddingpolypropylenefibresaswellasthroughtheapplicationofselectedconcretemixturesandaggregates.WithinthescopeofaresearchprojectoftheFederalHighwayResearchInstituteofGermany（BASt）,fireprotectingsystemsandespeciallyfireproofconcrete,aswellastheirfirebehaviourandapplicationpossibilitiesinroadtunnelsareexamined.

Keywords:

Tunnelfire,tunnelsafety,tunnelconstruction,concretespalling,structuralfireprotection,fire-proofconcrete

1Introduction

Besidebridgestunnelsarethemostexpensiveinvestmentpartsofhighways,namelynotonlyconcerninginitialinvestmentcostsfortheconstructionofthetunnelsbutalsowithregardtolatercostsofoperation,maintenanceandpreservation.Duetothefactthatthenumberofconstructionsofroadtunnelshasconsiderablyincreasedinrecentyears（Fig.1）theFederalMinistryofTransport,BuildingandUrbanAffairs（BMVBS）andtheFederalHighwayResearchInstituteofGermany（BASt）havelistedtheessentialdemandsforstructuraldesign,suitabilityofuse,durability,economyanddemandsforlateroperationandmaintenanceofthesetunnelsinasetoftechnicalregulations.Structuralfireprotectionplaysanimportantrolebecauseofthesubstantialdamageswhichcanarisefromfireinatunnel.

InthelasttwodecadesthenumberofroadtunnelsinGermanyhasincreaseddisproportionatelycomparedwiththeincreaseofthetotalroadnet.Thus,theamountofhighwaytunnelshasmorethandoubledfrom90in1992to213in2005.Inthesameperiodthetotallengthoftubesincreasedfrom50toalmost212km,thatcorrespondstoanaveragetubelengthof665mstatistically（Fig.1）.Attheendof2005,25tunnelswereunderconstruction,45tunnelswereintheprocessofplanningorinthepreparationphasejustbeforebuildingand60tunnelswereinthepreplanningphase.

2Fireaccidentsandtheireffectsonthetunnelstructure

Firesinroadtunnelsarecharacterisedbytheaffectedpersonsbeingendangeredandinmanycasesbytheconsiderableamountofdamagecausedtofacilities.Anumberofseriousaccidentsthattookplacenationallyandinternationallyintherecentyears（Tab.1）leadtoanincreasingpublicinterestintunnelsafetyandtoeffortsbythehighwayauthoritiesinordertomaketunnelssafer.

Tab.1:

Chronologyofrecentfireevents[12]

Majorfirescanresultintunneluserscomingtoharmandvehiclesbeingseriouslydamagedquiteapartfromeffectsonthetunnelsthemselves（Fig.2）.Thedamageiscausedparticularlybythespontaneousdevelopmentofgreatamountsofheatandaggressivefiregases.Followingthefire,thedamagecausedtothetunnelitselfcanbadlyaffecttheserviceavailabilitybecausethetunnelisclosedtotrafficduetothenecessaryrefurbishmentworks.Dependingonthedurationofthefireandthechronologicaltemperaturedevelopment,thestabilityofthetunnelcanbenegativelyinfluenced.Redevelopmentandtheassociateddiscontinuationofservicescanlastforweeksorevenmonths.

Themaindamagepatternstoatunnelobtainedfrominvestigationsonfireaccidents[2]canbesummarisedasfollows:

-Some5–10min.mustbeestimatedforthe“flashover”–thetimerequiredforasmoulderingfiretobecomea“fullfire”resultinginasteepriseintemperatureintheaffectedareainthecaseofheavyvehicles.

-Thedurationofthefirevariesconsiderably–between30minutesandanumberofhours.

-Theinsomecasesconsiderabledamagetothetunnelstructureresultingfrommajorfiresiscausedbythehighfireloadofheavyvehicles.

-Damagetotheconcretetunnelliningismainlycausedbyspallingsaswellasthecondensationofsmokegasonthetunnelwall,theceilingandtheoperationalinstallations.

DuringafireintheTauernTunnelonMay29,1999,atotalof34vehiclesweredestroyed（Fig.3）.12personslosttheirlivesandconsiderabledamagewascausedtovehiclesandtothetunnelstructure.Concretespallingswithadepthof10to15cmweremeasuredatthetunnellining.

3Temperaturesduringatunnelfire

Inordertodeterminethetemperaturedevelopmentandthedamagepatternduringatunnelfiremoredetailedalotoffiretestswereexecutedduringthelast15years.Themostcomprehensivetestsserialwithrealisticfireloadswasundertakenwithinthescopeoftheso-called“EUREKAprogram”（EU499Firetun）between1990and1992.Ina2.3kmlong,abandonedminetunnel（Repparfjord-Tunnel）inthenorthofNorwaywitha35m2cross-sectionatotalof20firetestswithroadandrailvehicleswereexecuted.ThetestresultswerelatercompletedbyadditionalfiretestsofsinglestructureelementsinlaboratoriesalsoinGermany.

Themostessentialmeasurementresultsforhotgastemperaturesthatoccurredintheminetunnelduringafiretestwithaheavytruckisprovidedinfigures5and6.Theheavytruckwasloadedwith2tofofficefurnitureandburnedoutwithin75minutes（Fig.4）.Thefireloadamountedtosome100MW.Thefastrisingofthetemperatureaftertheflashoverafterabout5to10minutesuptotemperaturesof800to1000°

Cissignificant（Fig.6）.Themaximumtemperaturesforroadvehiclesofnearly1000°

Cweremeasuredatthetopofthetunnelaswellasatthesides（Fig.5）.

ThetestresultsoftheEUREKA-programwerethebasisforthedefinitionofthecurrentlyvaliddimensioningvaluesforthedifferenttemperaturetimecurvesinthecaseoftunnelfires（Fig.7）.Thesetemperaturetime-curvesareusedforfiretestsofalltunnelpartsforwhichthefireresistancehavetobeexamined（e.g.fixingelementsfortunnelinstallations）aswellasforstaticcalculationsofthetunnelstructureitself.ThetemperaturetimecurveforroadtunnelsinGermany,laiddowninthe“Additionaltechnicalcontracttermsandguidelinesforcivilengineeringworks（ZTV-ING）”[1],relatestoafiredurationof30minutesat1200°

C,followedbya110minutelongcoolingdownphase（Fig.7,curve[1]）.AlthoughtheprogressofthiscurveisshorterwhencompareddirectlywiththeETK/ISOcurve（Fig.7,curve[5]）,itissubstantiallymoreaggressivewhenrisinghigherintermsofthetemperaturereachedandmorecriticalduetotheveryfastrisingofthetemperatureupto1200°

Cwithin5minutes.ThelongerfiredurationoftheEBA-curve（Fig.7,curve[6]）forrailwaytunnelscanbeexplainedbythelongerrequiredtimeforrescueservicestoreachthefirecomparedwithroadtunnels.

CurrentlynewmajorfireinvestigationswereperformedwithinthescopeofanewresearchprojectcalledUPTUN（UPgradingmethodsforfiresafetyinexistingTUNnels）[8].Thisimportantresearchprojectstartedin2003andis,similartotheformerEUREKA-project,fundedbytheEuropeanUnion,butalsosupportedbyindustrypartners.FirstpublishedresultsstartedanewdiscussioninEuropeabouttemperature-timecurvesforthedimensioningoftunnelliningsagainstfireloads.Duringafirstlargescalefiretestwithasinglesimulatedtruckloadedwithroughly10twoodenandplasticpallets,carriedoutagaininanabandonedrocktunnelinNorway（Runehamartunnel）,temperaturesupto1350°

Cwithin35minutesinkeepingwiththeRWS-curve（Fig.7）andatotalfireloadof203MWweremeasured.Duetothesmallercross-sectionoftheRunehamartunnelcomparedwithanormalroadtunnelcross-section,thesetestresultscouldnotbetransferreddirectlytoGermanroadtunnels,buthavetobeconsideredforthepossibleadaptationofthevalidguidelinesfortunnelsinthefuture.

Asaconsequenceofallmajorfiretestandespeciallybecauseofthecriticalfeaturesoftunnelfires,specialfireprotectionmeasureshavetobeconsideredasessentiallyimportant.

4Damagemechanismsinthecaseoffire

Theeffectoftemperatureontheconcretetunnelliningcanleadtodamageinmanydifferentways:

-Thespallingprocessislargelyinfluencedbythespeedatwhichthetemperaturerises,themoistureoftheconcreteandthroughtheporestructure（compactness）.Theformationofwatervapourleadstostressesintheconcretematrixasfrom100°

C,whichcaninsomecasesleadtolarge-scalespalling.Dependingontheresidual