Study on dust suppression performance of a new spray device during drilling and blasting construction in the metro tunnel

Abstract

In order to solve the problems of excessive blasting dust concentration and portal pollution in a metro tunnel of a central urban area, a new spray device is discussed and its related parameters are studied in this paper. Through field sampling and an experimental spray dust settling platform, the particle size distribution characteristics of the tunnel blasting dust and the applicability of the nozzle are analysed. The tunnel and spray device are simulated by CFD software, and the variation laws of the droplet field concentration, velocity and particle diameter under different different incident angles, pressures and wind velocity are studied. The dust suppression performance of the new partition spray device is tested through field application. The results show that the droplet field generated by the spray device can effectively cover the whole section of the tunnel. At the same angle of incidence, the high concentration area first increases and then decreases in the direction away from the device, and the maximum concentration section gradually shifts away from the spray device. With the increase of the incident angle, the growth and attenuation trend of the high concentration region gradually flattens. The best incident angle for partitioning and dust reduction is 30°. When the nozzle pressure is set to 8 MPa, the parameters such as concentration, velocity and particle size distribution are the most appropriate. The effect of the air velocity at the air outlet on the characteristics of the droplet group generated by the device is not obvious. The field application shows that when the spray device is used, the dust reduction efficiency of respiratory dust and total dust at each measuring point is higher than 70 %. Compared with the original dust control measures, the average dust reduction efficiency is increased by 30 %, which can effectively improve the working environment of constructors in the tunnel and prevent the outward diffusion of dust.