Fire evacuation strategy analysis in long metro tunnels

Once emergency situations take place in metro tunnels, the most common respond is moving toward next station. However, with metro system expanding outward from city centers, the distance between stations is increasing to tens of kilometers. It would take several minutes for a train to drive through a long tunnel, which wastes the evacuation time in the early stage of a disaster such as fire and increases the possibility of casualty. Therefore, we introduce an internal wind evacuation strategy for metro tunnel evacuation and compare the strategy with traditional station evacuation strategy and tunnel evacuation strategy. Besides, the train travel stage is taken into account in evacuation strategy comparison with the clarification of steps before the train stops. To analyze the smoke diffusion characteristics and the effect of smoke on evacuation, an actual metro tunnel in Beijing is modelled with FDS and BuildingEXODUS to acquire the smoke diffusion characteristics and evacuation performance of different strategies. The results indicate that: (1) the internal wind evacuation strategy is the best one when available. The station evacuation strategy is recommended only after the train has missed the last internal wind. (2) during the train travel stage, the diffusion range of smoke inside the train gradually increases, which would increase the likelihood of casualty. After the train arrives at the destination, the smoke diffusion range inside the car would soon stabilize. (3) stairs are the bottlenecks in tunnel evacuation which directly determines the flow rate and evacuation performance in destination. The length of train travel stage would also affect the selection of evacuation strategies.