Study on the coupling pollution law of dust and gas and determination of the optimal purification position of air duct during tunnel excavation

In order to ensure that the gas concentration remains within a safe range and minimize the pollution of dust during the excavation of high gas mine, a new airflow-dust-gas multi-field coupling simulation method was proposed. Combined with this method, the distribution characteristics and evolution law of dust and gas were numerically simulated, and the purification position was optimized. It was found that the vortex field near the cutting face was the main reason for the generation of the high-pollution dust and gas masses at concentrations higher than 500 mg/m3 and 0.6%, respectively. On this basis, the concentration and pollution range of dust and gas were taken as the evaluation index, it was determined that the optimal purification position of the air duct was 2.5 m above the floor, on the left side of the tunnel. At this position, the concentration decreasing rates of dust and gas were 63.47% and 27.63%, respectively. [Display omitted] •The coupling migration law of the airflow–dust–gas field in a tunnel was investigated.•L2.5 was determined as the optimal air duct position for purification purposes.•The pollution laws of dust in the respiratory zone and of gas near the roof were obtained.•The causes of high-pollution masses and its influence on purification location were analyzed.