Abstract
The purpose of this numerical research is to assess the evacuation process in a tunnel under the contraflow condition. Numerical simulations utilizing FDS+Evac codes associated with a fire dynamic simulator (FDS) model simulating a fire scenario are used to simulate evacuation and to predict the impact of a 100 MW fire scenario on the occupants inside the tunnel. Traffic and passenger conditions are based on real data from a tunnel in the UK. Two fire loads, 100 MW and 5 MW, are studied to represent an HGV and a passenger car fire. The 100 MW fire source, caused by an unexpected heavy good vehicle (HGV) catching fire, is located in the middle of the tunnel and at 20% of tunnel length to study the effect of fire source location on the usage of emergency exits and tenability thresholds. The dimensions and the inclination angle of the existing roadway tunnel are 1836 m (L) × 7.3 m (W) × 5 m (H) and 4%, respectively. It should be noted that the 4% inclination of the tunnel causes asymmetry propagation of smokes thus the visibility of the downstream and upstream from the fire behave differently. The maximum needed time to evacuate using all egress, the amount of fractional effective dose and visibility at the human’s height are analyzed. Simulation results indicate that when a realistic worst-case fire scenario is modeled, all evacuees can survive before the combustion gases and heat influence their survivability.
Highlights
The role that road tunnels play in the urban transit system has been more significant especially with the development of society
According to the prof of the capability of fire dynamic simulator (FDS)+Evac as mentioned above, this model is used in this study to simulate the evacuation process in a sample tunnel
The first scenario, which is the worse fire scenario in road tunnels, is a 100 MW fire positioned in the middle of the tunnel
Summary
The role that road tunnels play in the urban transit system has been more significant especially with the development of society. It is obvious that determining parameters related to occupants’ behaviour is not straightforward due to their natural variability presented in the research as their behavioural uncertainty [1,2] The effects of these factors on the process of egress models analyzed by [3,4]. Fridolf’s study [10] showed that the occupants’ safety is affected by consequences of the fire event such as the spread of toxic gases and reduced visibility due to smoke. Another factor that affects the evacuation process is the tunnel structure strength in case of tunnel fire which is influenced by maximum temperature beneath the tunnel ceiling
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