Study on oxygen concentration distribution of Sejila mount tunnel construction based on fluent

Sichuan-Tibet Railway is a major construction project to ensure national defense security and support social and economic development in the west. Due to the geographical environment at high altitudes in the Sichuan-Tibet region, for every 1000 m increase in the average altitude, the atmospheric pressure decreases by about 11.55 %, and the oxygen partial pressure decreases accordingly, forming a low-pressure and low-oxygen environment, which affects the construction safety. The oxygen consumption of mechanical equipment in the tunnel and the discharge of pollutants make the construction personnel’s hypoxia problem more serious. Based on the project of the Sejila Mountain Tunnel, this paper divides the tunnel into the working face and the construction section along the tunnel according to different construction procedures. Based on the numerical simulation by CFD software, the distribution law of oxygen concentration in the tunnel construction process before the implementation of the environmental control scheme under different factors is proposed, and the relationship between various influencing factors and oxygen concentration distribution is obtained. It is concluded that oxygen consumption and emission of internal combustion engines and tunnel excavation length are important factors affecting oxygen concentration in the tunnel construction environment