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RESEARCH PAYS OFF

Memorial Tunnel Fire Test ProgramSERGIU F. LUCHIAN

xposure to smoke generated by fireswithin highway tunnels is a criticalsafety issue in the United States, where

no standards have been established for smoke-control ventilation in such structures. The Mas-sachusetts Highway Department conducted theMemorial Tunnel Fire Test Program to developa data base that gives tunnel designers and op-erators a proven means to determine the venti-lation rate and system configuration that willprovide the most effective smoke control dur-ing a tunnel fire. The test results are applicableto the design of new tunnels and the optimalconfiguration management of ventilation inexisting tunnels.

PROBLEM

Smoke-control ventilation has two purposes:to protect life by allowing evacuation of tun-nels and, if possible, to give fire-fighting per-sonnel a clear path to the site of the fire. De-signs for smoke-control ventilation have beencreated on the basis of theoretical computa-tions or empirical rules of thumb instead of onfull-scale instrumented tests. Consequently,the design approach to detection, control, andsuppression of fire and smoke within highwaytunnels has become a controversial issueamong tunnel engineers, tunnel operators, andfire fighters. To resolve this issue, investiga-tions of ventilation strategies and their effec-tiveness in full-scale fire tests have been un-dertaken as part of the largest undergroundhighway project ever initiated in the UnitedStates: the $8 billion Boston Central Ar-tery/Tunnel (CA/T) project, funded by theFederal Highway Administration and theMassachusetts Highway Department.

SOLUTION

A test facility was constructed at MemorialTunnel, a two-lane, 854-meter (2,802-foot),decommissioned highway structure that for-merly was part of the West Virginia Turnpike.The existing ventilation equipment was re-moved to allow installation of new variable-speed, reversible, axial-flow, central-ventilation fans. The equipment rooms weremodified to accommodate the ventilation com-ponents needed for supply or exhaust operationfrom both ends of the tunnel. Six fans with asupply or exhaust capacity of 94.4 cubic metersper minute (3,334 cubic feet per minute) wereinstalled: three each in the modified north andsouth portal fan rooms. The existing overheadair duct was split into longitudinal sections toserve as supply and exhaust ducts, and a mid-tunnel duct bulkhead was placed in a positionto allow a two-zone ventilation operation.High-temperature insulation was applied tostructural elements and support systems.

Fires with heat-release rates ranging from 10to 100 megawatts were produced. The fireswere generated in four floor-level steel pans inwhich a metered flow of fuel oil was floated ontop of a layer of water.

The ventilation systems were configured andevaluated in the context of varying flow andheat-release rates, with one or two zones ofventilation, in accordance with a test plan de-veloped in cooperation with the American So-ciety of Heating, Refrigerating, and Air-Conditioning Engineers. Six configurationswere tested: transverse ventilation, partialtransverse ventilation, ventilation with single-point extraction, transverse ventilation withoversized exhaust ports, natural ventilation,and longitudinal ventilation with jet fans. InTR

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full transverse ventilation, a configurationcommon in the United States, air is supplied atthe roadway level and extracted through ceilingports. In longitudinal ventilation with jet fans,a configuration used worldwide, air is pushedfrom portal to portal along the tunnel.

Instruments monitored air temperature, airvelocity, and gas concentrations during tests.Two towers outside the portals were equippedwith instruments to monitor meteorologicalvariables. In total, there were approximately1,450 instrumentation sensing points. Ap-proximately 4 million observations were re-corded during a typical fire test, which lastedas long as 45 minutes.

By September 1993, 100 tests had beencompleted. The results were made available onCD-ROM for use in the development of tunnel-ventilation design and emergency procedures.

APPLICATION

The cost of different types of ventilation sys-tems varies significantly. Safety is paramount;however, when more than one ventilation con-figuration offers an acceptable level of firesafety, the life-cycle cost of a project should beaddressed to identify the best option.

Results of the Memorial Tunnel fire testshave been used to increase the cost-effectivenessof fire-safety measures. The Boston Fire De-partment agreed to change required ceiling-panel fire ratings throughout the 60 lane-kilometers (38 lane-miles) of tunnels along theCentral Artery/Tunnel. In addition, the FederalHighway Administration lifted its moratoriumon the use of jet fans for longitudinal ventilationin tunnels similar to the Memorial Tunnel.

BENEFITS

The Memorial Tunnel Fire Test Program hasbenefited the Central Artery/Tunnel project intwo ways. First, the program led to ceiling-material design changes, saving $20 million inconstruction costs without compromisingsafety. Second, it led to the modification of theCA/T design to provide for jet-fan use, saving$25 million through the reduction of cross-sectional envelopes and the elimination of airducts and ventilation fans.

The biggest payoff, in construction and oper-ating cost savings and possibly in lives saved, islikely to be realized as tunnel designers aroundthe world begin to take advantage of the dataproduced by the Memorial Tunnel fire tests. Theuse of longitudinal ventilation, made possible by

the lifting of the moratorium on the use of jetfans, has already resulted in significant costsavings for three dual-bore tunnel projects inthe United States. The estimated savings rangefrom $3,000 to $5,000 per meter of structure.Operating and maintenance costs for these tun-nels have also been reduced.

For further information contact Sergiu F.Luchian, Massachusetts Highway Depart-ment, One South Station, Boston, Massachu-setts 02110 (telephone 617-342-1174) orvisit the fire test Internet site atwww.firetest.com.

EDITOR'S NOTE: Special appreciation is ex-pressed to Joseph R. Morris and G. P. Jayapra-kash, Transportation Research Board, for theirefforts in developing this article.

Suggestions for "Research Pays Off" topiesare welcome. Contact G. P. Jayaprakash,Transportation Research Board, 2101 Con-stitution Avenue, N.W., Washington, D.C.20418 (telephone 202-334-2952; e-mailgjayapra@nas.edu).

View of south portal offire-test facilityconstructed atMemorial Tunnel,formerly part of theWest Virginia Turnpike.

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