Study on the Concentration Distribution of Gas in the Heading Face and Optimization of Duct Arrangement

Coal mine gas is one of the primary hazards encountered in mining operations. The continuous emission of gas in the heading face during tunneling poses potential dangers, with a significant likelihood and magnitude of gas-related accidents. Tunnel ventilation not only dilutes the concentration of pollutants but also ensures underground air quality, safeguarding the physical and mental health of workers. Therefore, underground tunnel ventilation is particularly crucial. Analyzing the airflow field in single-heading tunnels and optimizing ventilation layout are of paramount practical significance for ensuring mining safety. Initially, based on engineering realities, on-site experimental measurements were conducted in the simulated area of the single-heading tunnel. The essential parameters for ventilation simulation were obtained, and a numerical three-dimensional model of the ventilation in the single-heading tunnel was established using Fluent software. Subsequently, through numerical simulations, the airflow field and gas concentration distribution patterns in the single-heading tunnel were obtained. It was verified that the tunnel airflow field exhibits distinct layering and uneven distribution. Gas concentration on the return air side is higher than that on the intake air side, with elevated gas concentrations in the upper corner and the lower right corner on the return air side. Further, four main factors influencing gas concentration were identified: duct diameter, duct exit velocity, distance from the duct exit to the heading face, and the suspension position of the duct. Finally, an orthogonal design approach was employed, and numerical simulations were conducted to study the sensitivity of these factors to gas concentration. The optimal ventilation layout was determined and validated: a duct diameter of 0.7 m, an airspeed of 13 m/s (without considering a fixed air volume), a distance of 7 m from the duct exit to the heading face, and the duct suspended in the lower part of the tunnel. The stabilized gas concentration under these conditions was determined to be 0.1378%.