高海拔高地温铁路隧道施工通风CO扩散特性分析

Analysis on CO Diffusion Characteristics of High Altitude and High Ground Temperature Railway Tunnel Construction Ventilation

在隧道钻爆法施工的通风阶段,受高海拔、高地温的影响,空气特性(如空气密度、气压、温度等)发生改变,使隧道内气流组织运移规律趋于复杂,因此有必要研究特殊环境影响下隧道施工通风CO扩散问题。基于CFD模拟方法,建立三维模型,采用k-ε湍流模型进行非稳态计算。首先考虑海拔、地温分别对CO扩散的影响,再分析海拔与地温耦合对CO扩散规律的影响。结果表明:不考虑地温的影响,对比各海拔的施工排烟安全距离,发现随着海拔逐渐升高,CO气团跨度增大,排烟安全距离相应增加,根据公式推导和数据分析得到修正后的排烟安全距离计算公式;考虑地温影响,隧道内环境温度与掌子面距离呈三次非线性增长,隧道内CO的扩散受地温影响明显。

In the ventilation stage of tunnel construction affected by drilling and blasting method,air density,air pressure,temperature and other air characteristics change,the air flow in the tunnel migration law tends to be complex.Therefore,it is necessary to study CO diffusion in tunnel construction ventilation.Based on the CFD numerical calculation method,a three-dimensional model is established,and the k-εturbulence model is used for unsteady calculation.The effects of altitude and ground temperature on CO diffusion were considered respectively,and the effects of altitude and ground temperature coupling on CO diffusion were analyzed.Results showed:without considering the effect of ground temperature,the safety distance of smoke extraction at different altitudes is compared.It is found that with the increase of altitude,the span of CO air mass increases,and the safe distance of smoke extraction increases correspondingly.Modified calculation formula of smoke exhaust safety distance based on formula derivation and data analysis.Considering the influence of ground temperature,the environment temperature has a cubic nonlinear growth with the tunnel surface,and the CO diffusion in the tunnel is obviously affected by ground temperature.