Study on the effect of sprinkler layout parameters on dust removal in tunnel construction

Dust pollution caused by tunnel construction has a serious impact on workers' health and how removing it quickly and effectively has become a key issue. To investigate the dust‑suppression mechanism and optimal design of spraying systems in tunnels, this study integrated numerical simulation and experimental validation to analyze the dynamic development characteristics of water mist, the spatial evolution of dust, and systematically examined the effects of spray angle and location. The results indicate that the development of water mist can be divided into three stages: pre, mid, and post. Under the combined influence of jet entrainment and return airflow, the highest spray concentration occurs in the region 15-25 m from the tunnel face. While spraying effectively reduces dust concentration, it also intensifies spatial inhomogeneity, leading to a distinct dust accumulation zone along the wall on the return‑air side. Increasing the spray angle enlarges the cross‑sectional coverage but shortens the projection distance. Different factors dominate during different ventilation stages: in the initial stage, the contact time between mist and dust is primary, with a 0° angle achieving the highest dust reduction rate within 10 m; in the middle stage, both contact time and coverage area play a role; after spraying stops, the 45° angle produces broader residual mist coverage in the tunnel, resulting in a dust removal efficiency of up to 86.7%. The influence of spray location shows a phased pattern: during the early stage of dust dispersion, closer proximity to the tunnel face yields higher interception efficiency; after spraying ceases, residual mist becomes dominant, and efficiency continues to improve when the device is placed 15-25 m from the face. Experimental verification demonstrates that after system activation, PM2.5 concentration drops rapidly, with residual mist continuing to capture dust. The concentration in the monitoring section eventually stabilizes, showing a reduction of 73.84% compared to the non‑spraying condition, confirming the system's effectiveness and sustained purification capability.