Effect of blockage ratio on the maximum temperature under the ceiling in tunnel fires

Tunnel blockage ratio is defined as the ratio of the cross-sectional area of the fire source to that of the tunnel. These fire sources in reality correspond to those that have considerable cross-sectional area such as trains or heavy goods vehicles, which are very common. The effect of tunnel blockage ratio on the maximum temperature under the ceiling in tunnel fires is analyzed using experimental data from three past studies. Results indicate that the maximum temperature decreases with the increase in the blockage ratio for small fires, while it does not vary with the blockage ratio for large fires. Previous models are modified based on above analysis by introducing a factor that accounts for the blockage effect. The modified models are more generally applicable.