大纵坡双向行车公路隧道火灾控制风速研究

城万二级公路白芷山隧道和八台山隧道为双向行车的大纵坡公路隧道,火灾后烟流控制难。采用火灾动力学计算软件FDS对其进行了火灾三维数值模拟,分析了仅火风压作用及0.5 m/s、1 m/s和-0.5 m/s控制风速作用下的烟流扩散和能见度的分布规律。结果表明:在大纵坡隧道中,火灾后仅靠火灾效应能引起火灾烟流的流动,其流动的规律是烟流从火源点流向高洞口方向,火灾烟流能完全从高洞口排出,而烟流向火源点下坡方向的蔓延距离仅在100 m左右;当风速为0.5 m/s时,烟流在火源两侧基本呈对称状蔓延;下坡方向的隧道中的烟流也因风速较小,产生的扰动比较小,这种烟流控制是最为合理,有利于灾害情况下逃生。因此,建议将白芷山隧道和八台山隧道的火灾控制风速取为0.5 m/s左右,且该速度应为自然风速、火风压引起的风速和风机提供风速的合速度。

Study on Wind Flow Velocity under Fire Control in Two-direction Road Tunnel with Large Longitudinal Slope

Both Baizhishan tunnel and Bataishan tunnel located in Chengwan second-class highway are super-long and two-direction road tunnels with large longitudinal slope, so it is hard to control the smoke flow after a fire in the tunnel. This paper conducts a 3D numerical simulation in a fire and analyses the smoke flow diffusion and the distribution of visibility only under wind pressure with control velocity of 0.5m/s,1m/s and -0.5 m/s by FDS. The results show that the fire effect can lead fire smoke to flow in large longitudinal slope road tunnel. The flow regulation is that the smoke flows from the burning point to the high openings where all the smoke can exhaust and the flow spreads down only 100m from the burning point. The smoke flow spreads symmetrically on both sides of the fire source when the velocity is 0.5m/s. Because of the low flow velocity in the downhill direction, it only produces a small disturbance, so it is the most reasonable situation to escape after disaster. So the fire control velocity in the two tunnels is better to be controlled around 0.5m/s and this velocity is a resultant speed consists of natural wind speed, wind speed under fire pressure and wind speed provided by fans.