网络型地下隧洞群控排烟策略优化仿真研究

Simulation study on optimization of smoke control and exhaust strategies for networked underground tunnel groups

  • 摘要: 针对网络型地下隧洞群结构烟气控制难题,建立了“四穿六”网络型隧洞群全尺寸模型,对竖井自然散烟、机械通风排烟、挡烟垂壁防烟3种典型策略下的烟气蔓延及温度分布特性开展仿真研究。结果表明:① 竖井自然散烟策略下,烟气蔓延路径与构筑物断面尺寸直接相关,主要沿水工隧洞传播;非竖井区烟气与空气分层明显,高温烟气沿顶部稳定传播,中下部低温新鲜空气传输至火源位置补给,竖井区域烟气与空气分层破坏,烟气卷吸程度加大,温度降低;在竖井下游区域具有一定的排烟能力,但范围有限,隧洞群整体控烟能力弱。② 机械通风排烟策略下,火源上游区域烟气层高度升高,烟气抑制区沿水工隧洞蔓延能力减弱,大部分烟气向火源下风向蔓延,竖井内部温度升高,竖井下游出现烟气“低温区”;机械通风排烟与竖井散烟路径一致,竖井自然散烟能力增强,安全救援能力得到一定提升,但整体控烟能力较弱。③ 挡烟垂壁防烟策略下,烟气蔓延减缓,在单隧洞蔓延阶段,改变了烟气主要沿水工隧洞传播的特性,该阶段烟气整体可控性强;在烟气网络未贯通阶段,存在较强的烟气逆转现象,竖井及挡烟垂壁的耦合控烟作用明显削弱火源下游烟气抑制区域的蔓延强度,竖井散烟和机械通风排烟能力增强,整体可控性较高;在烟气网络已贯通阶段,烟气大范围蔓延,挡烟垂壁防烟效果不明显,但提升机械通风速度可直接削弱烟气经由施工支洞向上游水工隧洞蔓延的能力,烟气整体可控性一般。在安全救援路径设计上,火源下游烟气促进区域为竖井散烟和通风排烟的主要路径,考虑人烟路径分离,设计施工支洞主通道和旁侧通道分别为安全救援与烟气蔓延通路,水工隧洞中可经由横通道向远离火源通道逃生。本研究成果对同类工程防排烟策略及安全救援设计具有参考意义。

     

    Abstract: Smoke control in the complex structure of network-type giant underground tunnels is a difficult problem. Due to the multiple and random fire causes, high temperature of smoke gathering at the top of the enclosed space, multipath rapid propagation, and disorganization of the ventilation system due to the smoke flows, the fire condition is expanded accidentally. A full-scale model of the giant underground tunnel group was developed, and simulation studies were carried out to characterize the smoke propagation and temperature distribution under three typical strategies of natural smoke dissipation in a shaft, exhausted smoke by mechanical ventilation, and blocked smoke by smoke barriers. The smoke propagation is divided into promotion and suppression areas to analyze the effect of smoke control and extraction, and the conclusions of the smoke control and safe rescue design are as follows: ① under the strategy of natural smoke dissipation in shaft, the smoke spread is directly related to the cross-section of the tunnel, and the smoke mainly spreads along the hydraulic tunnels. The stratification of smoke and air in the non-shaft area is obvious, high-temperature smoke spreads steadily along the top, and the low-temperature fresh air in the middle and lower parts of the shaft is transmitted to the location of the fire source to replenish, and the stratification of smoke and air in the shaft area is destroyed, and the degree of smoke entrainment is increased, and the temperature is lowered. The area near the shaft has a certain smoke evacuation capacity, and the overall capacity of smoke control is very weak. ② under the strategy of the ventilation-based smoke exhaust, the smoke is mainly exhausted in shaft. The path of smoke exhaust from ventilation and shafts is the same, with the characteristic of coupling to enhance the smoke exhaust capacity. The height of the smoke layer in the upstream area of the fire increased, most of the smoke propagated downwind, the temperature inside the shaft increased, and a “low-temperature zone” appeared at rear of the shaft. The propagation ability of the smoke suppression zone along the hydraulic tunnels is weakened, and the overall capacity of smoke control is improved. ③ Under the strategy of smoke exhaust by ventilation and smoke barrier, the smoke propagation is delayed, and in the single-tunnel spreading stage, the characteristic of smoke propagation mainly along hydraulic tunnels is changed, and the overall controllability of the smoke at this stage is strong; in the stage of smoke network is not connected, there is a strong smoke reversal phenomenon, the coupling control effect of shaft and smoke barrier significantly weakened the smoke spread intensity in the region of smoke spread suppression area downwind of the fire source, the overall capacity of smoke control is relatively high; in the stage of the smoke network has been connected, the effect of the smoke barrier is not obvious, but the enhancement of the mechanical ventilation speed directly weakens the ability of the smoke to spread to the upstream hydraulic tunnel through the construction branches, and the overall capacity of smoke control is general. In the design of safety rescue path, area of smoke spread promotion area downwind of the fire source is the main path of shaft and ventilation smoke exhaust. The main and side passages of the construction branch are the pathways for people and smoke spreading respectively, and escape via a connecting tunnel to hydraulic tunnels far from the fire. The results of this study provide a reference for similar projects in smoke control and safety rescue.

     

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