Transport laws of aerosol pollutants in high-flow wet shotcreting operations in tunnels

Wet shotcreting operations in tunnels produce large amounts of dust that threaten workers' health. In this study, a coupled airflow - dust model was developed based on gas - solid two-phase flow theory to simulate dust migration under different ventilation airflow and shotcreting positions. Using CFD simulations in ANSYS FLUENT and field data validation, the spatiotemporal evolution of dust concentration was analyzed. The results indicate that dust diffusion can be divided into three zones - jet - recirculation, transition, and stable - and that the average dust concentration decreases along the airflow direction, following the order: working face region > shotcreting operation region > transition region > stable region. Increasing ventilation speed effectively reduces peak dust levels and shortens the time to reach permissible concentration. An air duct outlet velocity of 12 m/s (corresponding to a ventilation volume of 1374.1 m³/min and an average tunnel cross-sectional wind speed of approximately 0.64 m/s) is identified as the optimal velocity. Different spraying positions significantly alter dust distribution characteristics, with crown spraying showing the widest and most uneven diffusion. The findings provide a quantitative reference for ventilation optimization and occupational dust control during tunnel shotcreting operations.