Mitigating coal dust from open-top trains in railway tunnels: Speed and headway control

Confined aerodynamic conditions in railway tunnels intensify coal surface scouring, challenging open-air chemical dust suppressant standards. This study developed a computational fluid dynamics and discrete phase (CFD-DPM) model to quantify coal-bed aerodynamic loading and dust recovery for an open-top train traversing a 6.9 km tunnel at 60–80 km/h. At 80 km/h, peak and time-averaged coal-bed wind speeds reached 38.95 m/s and 32.70 m/s, surpassing the 30 m/s (Type I) and 23 m/s (Type II) suppressant thresholds. Based on the near-linear relation between train speed and aerodynamic load, a conservative operating speed of 45 km/h was derived for the investigated tunnel to reduce the risk of crust failure. Tracking 10 μm residual floor dust revealed that particle concentration decay takes 300 s, lagging behind the 200 s airflow stabilization. Combining the 552 s tunnel transit time at 45 km/h with this 300 s particle-recovery period gives an operational minimum headway of 15 min for the investigated tunnel. These findings provide an engineering framework that links suppressant wind-resistance thresholds, train-speed control, and recovery-based headway control to mitigate fugitive coal dust in railway tunnels.