ABSTRACT
Although the frequency of fire accidents in tunnels or metro stations is low, in worst cases they may lead to severe fatalities and damages. During a fire incident an underground space, smoke is the main source of danger for the occupants. In order to have a more accurate prediction of fire impacts, most safety standards enforced worldwide suggest the development of special risk analyses. However, there is no specific guidance regarding the selection of fire size, fire duration or burning materials. These parameters affect the thermal and smoke propagation within the underground space and therefore the available safe egress time. In this paper several rail-fire cases are selected, based mainly on information gained through real-scale experiments and a fire dynamic analysis is conducted for different geometries of metro tunnels. The available safe egress time for every case is determined through the fractional effective dose (FED) that occupants might receive in a period of time, which is a measure of incapacitation because of toxicity. Based on the above, detailed data on the environment created for each fire case in a given tunnel geometry are presented. These data can provide an indication for the risk that each case may produce for the occupants and they could be used as a first guidance for an engineer, before the conduction of the risk analysis. Furthermore, conclusions about the influence of the key parameter’s evolution on the tenability conditions inside the tunnel can be drawn.
