Study On Spray Dust Control Technology In Tunnel Construction By Mining Method

The generation of dust during the tunnel construction by drilling and blasting is inevitable,and the long-term exposure of construction operators to high concentrations of dust will cause irreversible effects on their bodies,while the traditional ventilation for dust control has limited effects.Based on this,the article carries out the research of spray dust reduction technology of drilling and blasting tunnel through theoretical analysis,field test,model test and numerical simulation.The main conclusions are as follows:(1)Based on the analysis of typical spray dust removal theories,the influencing factors of spray dust removal efficiency,such as droplet size,droplet distribution,relative velocity between dust and droplet,were identified;(2)Based on on-site dust testing of the Qinling Tiantaishan highway Tunnel(Baoji-Pingkan)LJ-10 section at different construction stages and different working conditions(shotcreting,slagging,drilling),the dust generation characteristics under different surrounding rock conditions are studied.Field test results show that the surrounding rock conditions have a significant impact on the characteristics of dust generation.Under the conditions of III surrounding rock,the integrity of the surrounding rock is better,and it is easier to produce dust with a larger particle size during excavation.Under the conditions of excavation of V surrounding rock,the percentage of small-particle dust generated by excavation is greater;(3)Using the self-built spray dust reduction test platform,the spray atomization performance and spray dust reduction equipment parameters were tested and researched.The spray atomization performance test results showed that reducing the nozzle diameter and increasing the spray pressure can effectively improve the nozzle atomization effect,but the improvement of the atomization effect is not unlimited;the test results of spray dust reduction show that spray dust reduction has a higher settling efficiency for total dust and respirable dust.The parameter of the spray equipment with the best dust reduction efficiency in this spray dust reduction test is the nozzle diameter is 0.3 mm and the spray pressure is 4 MPa.Under these parameters,the characteristic particle size of the spray group is D10=22.208 μm,D50=41.261 μm,D90=67.012 μm,and the sedimentation efficiency for total dust and respirable dust is 74.1% and 73.8%;(4)FLUENT software is used to numerically simulate the process of spray dust reduction in the tunnel to study the influence of different ventilation flow rates on the spray dust reduction efficiency.The results show that increasing the ventilation speed within a certain range can make the spray spread more widely in the entire tunnel space,and the effect of dust capture by droplets is better,but if the ventilation speed is too high,it will further reduce the spray system’s control of the dust concentration near the head and reduce the efficiency of the spray system.The conclusions of this paper have certain reference significance for the selection of equipment parameters and environmental parameters of the dust suppression system when applying the spray dust suppression technology to the construction of tunnels by drilling and blasting.