Dust diffusion laws during partition excavation by boom-type roadheader in a metro tunnel

When the drill bit of the boom-type roadheader cuts the dolomite at the tunnel face, it generates a lot of dust, which will have an adverse impact on human health and the surrounding environment. In order to clarify the laws of dust diffusion during partition excavation by a boom-type roadheader in a metro tunnel, the respirable dust and particle size distribution characteristics of tunnelling dust are studied through field experiments. Combined with FLUENT numerical simulation, the axial and radial diffusion laws of dust in the air field and the upper and lower parts of the tunnel face are further explored. The results show that at a position 5 m away from the tunnel face, the excavation dust concentration in the lower partition is 65.88% higher than that in the upper partition, and the concentration of respirable dust reaches 313.46 mg/m³, which has a greater impact on a boom-type roadheader operator. In the simulated excavations in the upper and lower partitions, the optimal distance between the air duct outlet and tunnel face is 12 m and 15 m, respectively, and 550 m³/min is the optimal pressure airflow.