Experimental investigation on smoke propagation in a transversely ventilated tunnel

Abstract

In order to determine the key features of the fire safety design in transversely ventilated tunnels, the smoke propagation characteristics are examined as a function of fire size, fire location, and airflow rates of supply and exhaust. A 12-m long scale model of the Memorial tunnel, with a scale down ratio of cross section 1/20, is used. Fire sizes and ventilation rates in real tunnels are then deduced from the Froude similarity. In general, it is found that the smoke propagating distance increases with the fire size and decreases with the exhaust ventilation rate. When the fire location is off-centered, the propagating distance becomes substantially larger than that of the centered fire with the same size. A hazardous situation generated from an imbalance between the supply rate and the exhaust rate is also observed. The results suggest that the smoke propagating distance and/or the smoke filling may serve as good criteria for determining the transverse ventilation rate.