Abstract: Fluent software is employed to simulate the wind velocity and dust concentration fields during shotcreting and mucking in a tunnel to clarify the influence of environmental parameters, such as air pressure, on dust transportation and explore the dust concentration distribution during crucial dust-producing processes in high-altitude tunnel spaces. The impact of altitude on the airflow and dust concentration fluctuations in the tunnel is then analyzed. A dust concentration prediction model is established by fitting the wind velocity and dust concentration distribution along the tunnel. A linear regression equation is constructed to relate altitude to wind velocity and dust concentration distributionnonuniformity parameters. The research results demonstrate the following: (1) In areas of high altitude, the dust transport speed during ventilation reaching wind speed is longer than that of plain areas. In low-altitude areas, the airflow is nearly linear and flows out of the tunnel along the entire cross-section. As the altitude increases, the coverage range of the airflow gradually decreases, and the airflow along the tunnel moves in an S shape. (2) During shotcreting, the wind speed is higher within 40 m from the tunnel face; it lowers rapidly when the distance from the tunnel face is more than 40 m, and it uniformly fluctuates when the distance from the tunnel face is between 60 and 180 m. The overall dust concentration within the tunnel fluctuates with increasing altitude, decreasing uniformly between 20 and 180 m from the tunnel face and approximately linearly. (3) During mucking, the average wind speed and dust concentration of the entire cross-section remain unchanged with increasing altitude, whereas the nonuniformity of the wind speed and dust concentration increases linearly. For every 1 000 m increase in altitude, the nonuniformity of wind speed and dust concentration increases by 0.156 m²/s² and 4.42×10^-6 kg/m³, respectively.

Key words: high-altitude tunnel, press-in ventilation; shotcreting; , mucking, wind velocity field, dust transport, numerical simulation