Effect of ventilation parameters on dust pollution characteristic of drilling operation in a metro tunnel

Dust pollution generated from metro construction can cause serious pneumoconiosis in workers. To efficiently relieve dust pollution in personnel breathing zones during drilling operations, this study applied a numerical simulation of a metro tunnel to analyze the effects of ventilation parameters (supply airflow volume and distance of forced air duct outlet from driving face) on the distribution behaviors of airflow velocity and dust concentrations. Sixteen ventilation conditions were designed to determine dust pollution characteristics in four personnel breathing zones, and optimal dimensionless ventilation parameters corresponding to efficient dust suppression performance were determined. The numerical simulation results indicated that each supply airflow volume corresponded to an optimal installation position of the forced air duct outlet. Without considering advancement of the driving face, the optimal dimensionless distance of the forced air duct outlet from the driving face (ratio of the distance of the forced air duct outlet from the driving face to the equivalent diameter of the excavated section) was 3.125 and 3.906 when the dimensionless supply airflow volume (ratio of supply airflow volume to the minimum supply airflow volume corresponding to the average section airflow velocity of 0.15 m/s) were 1.002-1.336 and 1.671-2.005, respectively. However, the recommended dimensionless distance of a forced air duct outlet from a driving face should not be 5.469 when the dimensionless supply airflow volume is 1.002-2.005. Considering a 5-10 m advancement of the driving face, the optimal dimensionless distance of the forced air duct outlet from the driving face was 3.125 when the dimensionless supply airflow volume was 1.002-2.005. The accuracy of the numerical simulation results was validated in field measurements.