Abstract: The evacuation safety under reverse ventilation mode of fire in urban tunnel entrance ramp was studied by numerical simulation method. Select a typical fire scenario with a ramp length of 500 m, a slope of 6% and a fire scale of 22.5 MW, the temperature and visibility at 2 m height were used as the criteria, the evacuation safety under fire at different location was analyzed by FDS and Pathfinder. The results showed that reverse ventilation can be adopted directly when the distance between the fire source and the ramp entrance was small. The distance between the fire source and the ramp entrance would affect the margin for safety evacuation. When the fire source was far away from the ramp entrance, reverse ventilation mode would affect the process of safety evacuation.

Key words: tunnel ventilation, entrance ramp, reverse ventilation, smoke control scheme, evacuation