不同分岔角的卜型隧道施工通风三维数值模拟研究

A 3D Numerical Simulation Study on the Ventilation of T-Shaped Tunnels with Different Bifurcation Angles during Construction

为研究卜型隧道分岔角对钻爆法施工隧道爆生气体扩散的影响,以成兰铁路跃龙门隧道左线正洞与38#横洞形成的卜型分岔结构为研究对象,分别建立分岔角为45°、60°、75°、90°的三维网格模型,利用Fluent对隧道通风情况开展数值模拟研究,并结合局部损失理论,探究分岔处的风能损耗规律。结果表明:卜型分岔隧道施工通风过程中,横洞钝角侧及主线隧道下游无分岔侧附近出现大范围的通风死区,且死区范围随分岔角增大而增大;对比各工况爆生气体排出时间,可知隧道分岔角越大,通风效果越差,所需通风时间越长;通过推导局部损失系数与分岔角之间的关系式,发现主线隧道局部损失系数几乎不受分岔角影响,而横洞局部损失系数则与隧道分岔角呈正相关关系。

To investigate the influence of the bifurcation angle on the diffusion of blasting gas in T-shaped tunnels built by the drilling and blasting method, this study, on the basis of the bifurcation structure formed by the left main tunnel and 38# cross tunnel in the Yuelongmen Tunnel on the Chengdu-Lanzhou Railway, establishes the 3D mesh models with bifurcation angles of 45°, 60°, 75° and 90° respectively, carries out numerical simulations of the tunnel ventilation by using Fluent and, taking into account the local loss theory, investigates the pattern of wind energy loss at the bifurcation. The results show that in the process of ventilating for the construction of T-shaped bifurcated tunnels, a large ventilation blind zone appears near the side of the obtuse angle of the cross tunnel and the downstream side of the main tunnel without bifurcation, and the range of the blind zone expands with the increase of the bifurcation angle. Comparing the time required to discharge the blasting gas under each construction condition, it is found that the larger the bifurcation angle of the tunnel is, the worse the ventilation effect will be, and the longer the required time will be for ventilation. Through the deduction of the relationship equation between the local loss coefficient and the bifurcation angle, it is also found that the local loss coefficient of the main tunnel is almost independent of the bifurcation angle, while the local loss coefficient of the cross tunnel is positively correlated to the bifurcation angle of the tunnel.