Abstract:

Quantitative fire risk assessment (QRA) is a method to design the accident scenarios, estimate the accident probability and thus quantify the degree of risk. QRA is affected significantly by tunnel specifications, fire characteristics, ventilation method, normal ventilation and smoke control methods and the other factors. In this paper, ventilation velocity and relationship between the ventilation and evacuation directions were selected to study their effects on the fire risk assessment in the tunnels of 18-26 km long and 5-25% grade. The results show that in a double track tunnel with the cross sectional area of 97m2, it is most effective to evacuate in the opposite direction of the ventilation regardless of the fire location. In addition, when the mechanical ventilation is applied for the fire control, the risk index decreases by up to 10% compared to the case only with the natural ventilation.