Fire and smoke management in a uni-directional road tunnel for a congested traffic condition

Emergency smoke ventilation for a uni-directional traffic road tunnel is studied using a CFD modelling approach. Fire scenarios in an uphill ramp for congested traffic conditions have been considered. Based on a longitudinal smoke ventilation system with a damper smoke-extraction device on the ceiling soffit, the impact of longitudinal ventilation (LV) control, operation of fire suppression intervention and emergency response delay have been quantitatively investigated. An assessment conducted with CFD modelling quantitatively shows to what extent the visibility is influenced. It has been revealed that airflow velocities can influence the performance of damper smoke-extraction. Different longitudinal airflow velocity should be maintained for fires in different tunnel locations under congested traffic conditions. This is important for tunnels with a fire suppression system, as smoke flows to the lower location when hot layer stratification is disturbed by the application of water. Fire suppression can cool down the smoke temperature significantly, but the visibility in the downstream portion of the tunnel can be impacted if longitudinal ventilation is not properly controlled. For the modelled conditions with a heavy goods vehicle (HGV) fire in a 5% uphill ramp section of a tunnel, an LV flow velocity of 2m/s can maintain tenable conditions downstream for congested traffic conditions.