引汉济渭椒溪河隧洞施工通风数值模拟研究

引汉济渭工程是陕西省为缓解关中渭河沿线城市和工业缺水问题,而提出的由汉江调水到渭河流域的大型水利工程。椒溪河段工程为穿河段,地形地质相对复杂,隧洞施工期的通风问题也相对比较严重。采用CFD(Computational Fluid Dynamics)数值模拟方法对带有支洞隧洞的通风过程进行模拟,研究几种典型工况下隧洞内的流场和浓度场在施工期时随时间的变化规律,分析掌子面以及支洞内涡流对气流及有害气体分布的影响。在气流排散通道不顺畅时,掌子面附近的涡流区域内涡流的大小和位置呈现周期性的变化,并随通风时间的增加影响范围逐渐降低。隧道爆破产生的有害气体和烟尘会随着气流的流动发生移动和扩散过程,并逐渐排向洞外。通过对隧洞主洞与支洞内气流和有害气体排散过程的研究,得出隧洞爆破后在通风作用下隧洞的掌子面附近和支洞与主洞的交叉位置处形成涡流区,涡流的产生和变化不断的消耗通风的机械能,降低通风效率,对有害气体的排散造成一定的阻滞作用,隧洞内有害气体的排散过程包括移动和扩散两方面,移动过程将CO排向洞外,扩散过程不断的降低洞内CO峰值,总结出了不同工况下隧洞内达到安全浓度的时间,对隧洞施工进度给出一定的参考意见。

Numerical simulation of ventilation in the Jiaoxihe tunnel of the Hanjiang-to-Weihe River Water Transfer Project

Hanjiang-to-Weihe River Water Transfer Project is a large water conservancy project to ease the water shortage in Guanzhong Plain in Shaanxi province. The Jiaoxihe tunnel crosses a river and faces complicated geographical and geological conditions. We simulated the ventilation in the tunnel with a branch tunnel using CFD numerical simulation, studied the variation of the flow and concentration fields in the tunnel during the construction period under several typical conditions, and analyzed the influence of the vortex on airflow and harmful gas distribution near the working face and in the branch tunnel. When the exhaust passage was hindered, the size and position of vortexes would change periodically near the working face, and their influence range would gradually decline with the ventilation time. In addition, the harmful gas and smoke produced from tunnel blasting would move and diffuse gradually out of the tunnel. After studying the airflow and dissipation of harmful gas in the main tunnel and branch tunnel, we had the following findings: A vortex zone would form after tunnel blasting due to ventilation near the working face and the intersection of the main tunnel and branch tunnel. The production and variation of vortexes would continuously consume the mechanical energy of ventilation, reduce ventilation efficiency, and hinder the dissipation of harmful gas. The dissipation process of the harmful gas in the tunnel included movement and diffusion. The movement process drove the CO out of the tunnel. The diffusion process continuously reduced the peak CO value in the tunnel. We calculated the time needed to reach safety concentration in the tunnel under different conditions and gave relevant suggestions on the construction progress.