| Deep hole bench blasting is the important means of open-pit mining.A large amount of blasting dust produced in the blasting process has a negative impact on the environment and personnel health of the mining area.In order to improve the prevention and control efficiency of blasting dust in open-pit mines,this thesis proposes a combined dust sup-pression technology based on the study of the generation mechanism and diffusion law of blasting dust.Taking an open-pit limestone mine in Tongling as the research background,the source and diffusion law of blasting dust were studied,and the dust suppression measures and technical schemes for each dust production site were proposed.Through theoretical analysis,field research and numerical simulation,the following main conclusions are drawn:1)According to the different states of the formed dust cloud,the process of blasting dust diffusion is divided into three stages according to the time sequence and shape:take-off stage,mushroom cloud stage and diffusion stage.In the take-off stage,the force of the shock wave generated by the explosive explo-sion on the dust is much larger than the gravity of the dust itself,the friction force and the adsorption force of the dust and its attachments,so that the dust can take off quickly.The mushroom cloud stage is that after the dust is separated from the surface,it continues to rise under inertia,and a large number of dust trajectories are superimposed to form a mushroom-shaped powdery cloud layer.In the diffusion stage,the dust completely dif-fuses and merges with the airflow.Under the action of the airflow,the spacing between the dust gradually increases.The dust with large weight will settle in a short time,while the dust with small weight will diffuse with the airflow for a long time.2)The field measurement and analysis of the dust distribution in the blasting area were carried out by arranging the dust collection box.The results showed that the dust amount at 50 m from the blasting area was 3.52 times that at 100 m.The blasting dust continued to settle during the diffusion process,and the concentration gradually decreased.3)The results show that the average concentration of dust in the environment after blasting increases rapidly,and the highest concentration can reach more than 2000 mg?m-3.It reached 1256 mg?m-3 in 10 s after blasting,and the farthest diffusion distance was 35m.Then it diffuses under the action of airflow,and the concentration gradually decreases.It decreases to 153 mg?m-3 in 40 s after blasting,and the farthest diffusion distance is 99m.4)Based on the analysis of the mechanism of explosive rock breaking,the influence of the minimum resistance line,hole spacing and row spacing on the dust production in the hole network parameters was analyzed by orthogonal experiment.Based on the pur-pose of minimizing the blasting dust production,the blasting hole network parameters were optimized,and the hole spacing was 8.5m,the row spacing was 5.5m,and the min-imum resistance line was 6.5m.While using the optimized hole network parameters to reduce the amount of blasting dust,the combined use of water-sealed blasting and water pre-wetting technology inhibits the generation and diffusion of dust.The field compara-tive experimental results show that the dust concentration in the area without dust sup-pression measures is 1209 mg?m-3,and the dust concentration in the area with dust sup-pression measures is 363 mg?m-3,and the dust reduction efficiency reaches more than70%.The results of this thesis can provide reference for dust suppression in blasting min-ing of limestone mines with similar geological conditions.Figure[43]Table[16]Reference[90]... |
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