Abstract: Abstract: Aiming at the existing critical velocity research, less consideration is given to the obstacles in the tunnel or only the small obstructions in the tunnel are discussed. Taking a railway tunnel as the research object, the numerical calculation model of the train fire of the railway tunnel is constructed, the influence of train blockage on the critical velocity is analyzed. The results show that the numerical simulation results are in good agreement with the Li model under block-free conditions. The increase in the tunnel blockage ratio tends to bring about a decrease in the critical velocities. Based on the simulation data analysis, the correspondence between the critical velocity reduction rate ε and the tunnel blocking ratio φ is corrected, a theoretical model of the critical velocities of railway tunnel train fire is obtained, and the reliability is verified by the existing tunnel fire experimental data and CFD accident simulation results.

Key words: Key words: railway tunnel, fire accident, train blockage, critical velocity