Emergency exits are one of the most critical elements during fire safety design in railway tunnels, allowing for a quick evacuation from the endangered area to the nearest safe location. At the present-state, there is lack of a comprehensive regulation framework for the design of the ventilation systems protecting the exits from smoke and other by-products during a tunnel fire and the design is normally case-tailored. With the ultimate goal of finding the most appropriate design requirements as the main parameters involved vary, this paper discusses the simulation of two scenarios identified as highly critical for a mixed traffic line: a 10 MW fire of a passenger couch and a 250 MW fire of a freight wagon. The method used is the Computational Fluid Dynamics (CFD) supported by the Fire Dynamics Simulator (FDS). The key requirement is the minimum airflow needed to keep the exits safe according to the variability of parameters, such as position of fire, wind, single or twin tunnel. The scenarios are a short cross-connection between single-track twin tunnels and a connection to a safe zone in a double-track single tunnel. In each case, temperature, pressure and smoke entering the compartment demonstrate to be relevant parameters affecting the results. The results of an extensive simulation campaign pave the ground for next developments aimed at setup a design handbook covering a large set of infrastructure and operation conditions represent a step ahead a recognized standards in railway tunnels design.

Fire simulation; Railway Tunnel; Fire Safety