Experimental study of different sealing ratios on the self-extinction of tunnel fires

摘要

Firefighting in a long tunnel with large fires is quite difficult as the hot smoke and radiation prevent firefighters from approaching the fire seat. Sealing the portals of the tunnel to prevent the access of fresh air provides an alternative approach and it can be implemented by blocking the two tunnel portals with sand bags to prevent fresh air supply from outside after all motorists are evacuated. However, it is difficult to completely seal both portals as high pressure arises from fires. Whether partial sealing could extinguish fires or not in tunnels is an interesting topic. A series of fire tests using propane with nominal heat release rates from 2.8 kW to 11.2 kW were carried out in a 1/20 reduced-scale model tunnel measuring 10 m long, 0.45 m wide and 0.23 m high to explore the impact of different sealing ratios, varying from 0%, 65%, 75%, 85% to 100%, on the self-extinction of fires. The experimental results showed that self-extinction occurred at a sealing ratio of 75% or above except for a heat release rate of 2.8 kW, where self-extinction occur only at a 100% sealing ratio. This finding demonstrates that the partial sealing strategy at a sealing ratio of 75% or above could extinguish medium or large fires in relatively short tunnels and provides a promising method for firefighting catastrophic fires in tunnels.