Abstract: In order to obtain a more accurate critical wind speed algorithm for tunnel fire, the fire source blocking ratio φ1 is considered in this study, blockage ratio upstream of fire source φ2 are set of 0, 0.23, 0.41 and 0.64, and the heat release rates of 1.6, 3.2 and 9.3 kW fire sources are selected. The critical wind speed values under 48 blocking conditions are calculated through orthogonal numerical experiments. The dimensionless correction algorithm of critical wind speed under simple fire source blocking, simple fire source upstream blocking and simultaneous blocking of fire source and upstream is deduced. The results show that whether the blockage ratio at the fire source is increased or the blockage ratio upstream of the fire source is increased, the critical wind speed will gradually decrease, and the blockage at the fire source has a greater impact on the critical wind speed. As the heat release rate of fire source increases, the critical wind speed will also increase. When only the fire source is blocked, the critical wind speed is proportionate?to (1-φ1)2/3. When only the upstream of the fire source is blocked, the critical wind speed is proportionate?to (1-φ2)1/3. When the fire source and upstream are blocked at the same time, the critical wind speed is proportionate?to (1-φ1)2/3(1-φ2) 1/3.

Key words: tunnel fire, critical wind speed, blocking effect, numerical calculation