风机布置方式对高瓦斯隧道施工通风效果的影响

Impact of the fan arrangement mode on the construction ventilation effect along the highly intensive gas tunnel

为了优化瓦斯隧道施工通风方案,提高瓦斯在隧道内的排出效率,以新建鸪山隧道高瓦斯段施工通风为背景,采用数值模拟和现场监测对隧道横通道处射流风机的布置、轴流风管与掌子面距离、风管放置高度、射流风机放置高度对隧道内通风效果的影响进行了研究。结果表明,射流风机最好布置在与横通道距离为5 m的气流上风向,该处瓦斯的排出效果最佳。风管与掌子面的距离不宜太近或太远,距离太近,会造成掌子面两侧风速差异过大;距离太远,射流未能到达掌子面,并在掌子面附近形成涡流区,使得掌子面处瓦斯未能与新鲜空气混合。但是,风管与掌子面的距离不同,隧道内最后稳定的轴向风速几乎相同。轴流风机风管布置在较高的位置,掌子面总体风速分布更为均匀,并且由于瓦斯密度相比空气小,易聚积于隧道顶部,将风管布置在高处,有利于隧道顶部的瓦斯排出,减少瓦斯聚积。射流风机的布置位置较低时,瓦斯易聚积在隧道下方,反之,瓦斯易聚积在隧道上方,因此,射流风机布置在较高处,瓦斯沿着隧道上部空间排出,有利于隧道内作业人员的安全。

The paper is intended to optimize the construction ven- tilation scheme of the gas tunnel and improve the gas discharge efficiency in the tunnel by taking the construction ventilation of the newly built Zhegushan project of high gas as a case study sample. For the said purpose, we have examined the jet fan arrangement in the cross passage, the distance between the axial flow duct and the headirig face, the＇layout height of the air duct and the jet fan effects on the tunnel ventilation through a numerical simulation and the corresponding field monitoring. The results of our investigation and examination reveal that the gas discharge efficiency can be said optimistic when the jet fan is arranged in the upward 5 ms＇ flowing direction in a distance of the cross passage. Such a distance between the air duct and the heading-forward face should be neither too close nor too far, so that the difference of the air velocity on the both sides of heading face is so big as to be blocked by the close distance. For, if so, the jet is unable to reach the heading face so as for an eddy to be formed that the gas at the face fails to mix up with the fresh air. However, the stable axial velocity in the tunnel may remain almost the same in a dif- ferent distance from the heading face. On the other hand, the overall wind velocity distribution would be otherwise made more uniform with the axial flow fan duct being arranged at a higher position. And, since the gas is easy to be dlusttered at the top of the tunnel due to its smaller density, the air duct at the higher positions would be made beneficial to the discharge of the gas and its accumulation. Nevertheless, if the gas is easy to be accumulated at the lower part of the tunnel when the jet fan placed at a lower position, the gas would also be easy to be piled up at the upper part of the tunnel. Therefore, the gas should be discharged along the upper space of the tunnel when the jet fan is arranged at a higher place, for it would be beneficial to the safety for the workers to do their repair activities in the tunnel.