Spatiotemporal Diffusion Law and Transport Calculation of Slag Dust in Tunnel by Drilling and Blasting Method

In order to clarify the spatio-temporal diffusion law of slag dust in the drilling-blasting tunnel,and to clarify the calculation method of dust particle migration under ventilation conditions,based on the field concentration monitoring data of dust and respiratory dust,the distribution characteristics and laws are analyzed,and the calculation method of the final velocity of particle free settlement is optimized.The calculation formula of dust particle settlement velocity and the calculation method of spatial distribution of particle size are proposed.The results show that:In terms of time scale,the variation law of dust concentration at different measuring points in the longitudinal direction of the tunnel during slag discharge is basically the same,and the lining trolley has a certain inhibitory effect on the longitudinal diffusion of dust.In terms of spatial scale,from the working face to the secondary lining trolley,the height distribution of dust concentration gradually changes from the type of ‘upper small and lower large’ to the type of ‘lower small and upper large’.At different times,the proportion of respirable dust was always greater than 0.6,and increased significantly away from the tunnel face.During slag discharge,the proportion of exhaled dust changed little and the effect of slag discharge was small.The dust particle size determines the particle dissipation pathway.The large particle dust is dominated by the settlement in the tunnel,and the small particle dust is dominated by the diffusion outside the tunnel.Compared with the dust control in the working area of the working face,the air quality problems in the commuting area and near the tunnel entrance are also worthy of attention.The comparison with the field monitoring and dust sample test results shows that the calculation formula of dust particle settling velocity and the calculation method of particle size spatial distribution based on the particle free settling final velocity optimization algorithm are highly reasonable.