Abstract: Existing standards for gas hazards in traffic tunnels have several limitations, including overly stringent safety measures and high construction costs that are not feasible in high-altitude regions. To address these issues, numerical simulation and theoretical analysis methods are employed in this study. A numerical model is developed to analyze the dynamic spatial variations of average wind speed and gas concentration, leading to the proposal of safety factors for both wind speed and gas concentration and the determination of the stable return airflow section. The study simulates high-altitude environmental conditions to reveal the mechanisms by which altitude influences gas explosion characteristics, explosion limits, and gas concentration. Altitude-based coefficients for gas explosion limits and concentration are introduced to establish a correlation model to link gas tunnels in flat regions with those in high-altitude regions. The main findings of the study are as follows: (1) A revised calculation formula for the classification standards of gas work areas in traffic tunnels is proposed, incorporating adjustments for the cross-sectional area of return airflow sections. (2) The disequilibrium coefficient for gas emission is optimized and integrated into the calculation formula for measured absolute gas emissions during the construction phase, along with safety factors for wind speed and gas concentration, to yield a modified formula. (3) For high-altitude gas tunnels, a classification standard suitable for varying altitudes is proposed, including a formula for calculating classification values and standards.

Key words: gas tunnel, classification standards for gas work areas, high altitude, gas explosion