盾构隧道顶侧壁排烟模式的排烟效果研究

On the smoke-fire discharge effect of the top and lateral combined exhaust mode in the shield tunnel

为了研究顶侧壁排烟模式对盾构隧道排烟效果的影响,基于CFD数值模拟分析方法,通过烟气蔓延范围、隧道拱顶温度、烟气层厚度、排烟口的排烟速率和排烟效率等参数的变化规律分析对比顶侧壁、侧壁及顶部3种排烟模式对盾构隧道内火灾烟气的控制效果。结果表明,顶侧壁排烟模式和侧壁排烟模式的烟气蔓延距离较远,3种排烟模式下烟气层厚度和拱顶温度在火源两侧均呈现近似对称分布,顶部排烟模式的排烟效率明显高于顶侧壁排烟模式和侧壁排烟模式。综合考虑,顶侧壁排烟模式的烟气控制效果欠佳,因此从烟气防治的角度考虑盾构隧道排烟设计应避免顶侧壁排烟模式。

This paper intends to pursue whether the top and lateral combined exhaust mode can have a nice smoke exhaust effect in the shield-type tunnel.As is well known,in the current studies,little attention has been paid to the top and lateral combined exhaust mode.It is just for this reason that we have carefully examined and observed the smoke exhaust features of such mode,the lateral exhaust and the top as well as the lateral combined exhaust mode by using the method of the CFD numerical simulation.And,then,based on the numerical simulation,we began to make a careful investigation and comparative analysis of the parameters of the smoke spreading distance,the dome temperature of the tunnel,the smoke layer depth,the smoke exhaust rate of the smoke ventilation and its exhaust efficiency.And,later,we have done further evaluation of the effects of the top and lateral combined exhaust modes on the fire smoke discharge in the shield tunnel based on the simulated confirmations.The re-sults of the above mentioned investigation and evaluation show that it wouldn’t be possible for the smoke spread distance or scale to be effectively controlled under the such tunnels,rather,they could be well controlled under the top exhaust mode within a comparatively short distance.This may account for the symmetrical feature of the smoke layer depth and the dome temperature of the tunnel on the both sides of the fire source under all the 3 exhaust modes.The smoke layer depth in the lateral exhaust mode is significantly thicker than that in the other two modes.Besides,the dome temperature of the tunnel is usually over 800℃under the top and lateral combined exhaust mode,whereas the total smoke exhaust efficiencies of the above mentioned top exhaust mode,the lateral exhaust mode and the top and lateral combined exhaust modes have been found respectively equal to 60%,37.8%and 46.74%,respectively.Besides,the total smoke exhaust efficiency of the top and the lateral combined exhaust mode stands at about 8.94%higher than that of the lateral exhaust mode,though 13.26%lower than that of the top exhaust mode.Thus,it can be concluded that the smoke under the above mentioned items fail to be effectively controlled under the top and lateral combined exhaust mode in the shield tunnel,which remains needed for further careful and cautious investigation and to be improved for better smoke prevention and control.