LAUSR

Abstract In order to investigate the diffuse pollution mechanisms of high-concentration dusts in the working regions of fully-mechanized excavation faces under forced-exhaust ventilation, a CFD-DEM airflow–dust coupled simulation approach was developed based on k – e two-equation turbulent model and the Hertz-Mindlin model. The diffuse pollution characteristics of the dust particles with different sizes were analyzed by combining on-site measurements with simulation. Results show that, in the region 0–15 m away from the heading face, a large horizontal-vortex field was formed due to the effect of forced jet field. Under the airflows' drag force, the dust flows were stratified in a dense strip pattern, among which the larger dust particles flew zonally at lower heights. The airflow drag force dominated the movements of the dusts with a diameter range of 2.5–20 μm, while gravity significantly affected the diffusion of the dusts with a diameter range of 40–80 μm. The final dust emission ratio approximately decreased linearly with the increase of dust particle size. Large dust particles were more easily settled. Specifically, the dust particles with a diameter range of 7–20 μm showed long sedimentation regions, while the other dusts were intensively settled at around the head-on region. In addition, the dust particles with a diameter range of 2.5–7 μm showed stable passing ratios during the diffusion process, and the average z value presented non-significant decrease. Finally, the dust emission ratio of 2.5 μm reached as high as 63.4% due to the absorption of the negative pressure. Therefore, comprehensive dustproof measures should be taken by considering the diffuse pollution characteristics of dusts.