| The dust pollution generated during the mining method construction process seriously affects the construction environment and causes irreversible damage to the occupational health of workers.In view of this,research and dust concentration testing were conducted based on the Fangyushan Tunnel,and the results showed that the dust distribution in the palm face area is high and it is difficult to eliminate the continuous dust production.The workers’ work area and the high concentration dust distribution area are highly overlapping in time and space.In response to this issue,high-pressure micro mist dust removal equipment has been designed and customized,and a large-scale experimental platform has been built to conduct experimental testing and research on centralized dust removal in the palm area.The research results are expected to provide operational guidelines for the promotion and application of related products in the future,and optimize the working environment in the tunnel’s palm face area.The main research conclusions are as follows:1.From the on-site dust concentration test,it can be seen that the dust concentration near the blasting face is the highest,followed by slag discharge,shotcrete,and rock drilling.The dust source highly coincides with the working time and space of workers.2.The difference in environmental humidity within tunnels of the same surrounding rock level and lithology has a significant impact on the distribution of dust concentration during drilling,blasting,and slag removal stages,but has a relatively small impact on the spraying concrete stage.The test results show that the dust concentration in condition 2(humidity 65%)during drilling,blasting,slag discharge,and shotcrete construction is about 30%,15%,35%,and 5% lower than that in condition 1(humidity 40%).3.The dedusting efficiency of the high-pressure spray dedusting equipment for the whole dust is slightly higher than that for the exhaled dust.When the pressure at the nozzle is constant,the dedusting efficiency generally decreases with the increase of the nozzle diameter.But when the diameter of the nozzle is less than 0.3mm,the diffusion area of water mist is not enough to cover the tunnel cross-section,resulting in a decrease in dust removal efficiency.When the nozzle diameter is fixed,as the nozzle pressure increases,the dust removal efficiency of total dust and exhaled dust shows an increase,and the growth rate changes from a sharp increase to a slow increase,and finally gradually converges.4.Considering the influence of many factors such as dust removal effect,economy and energy saving,the selection result of relevant parameters in the spray test is: the corresponding pressure of the nozzle with a diameter of 0.3 mm is the fifth gear(6.9 MPa),at this time,the dust removal efficiency of the whole dust is 73.22%,and the dust removal efficiency of the exhaled dust is 69.66%;The pressure corresponding to the nozzle with a diameter of 0.4mm is in the fifth gear(6.6MPa),at which time the dust removal efficiency of the entire dust is 75.78%,and the dust removal efficiency of the exhaled dust is 72.28%.5.The dust removal efficiency is influenced by environmental factors.As the distance from the nozzle to the dust concentration tester continues to increase,the dust removal efficiency begins to appear stable and then sharply decreases.Therefore,the active dust capture area of the product can be defined.When the ratio of the diffusion area of the nozzle at 1m to the cross-sectional area of the tunnel is about 0.6-1,the dust removal efficiency is relatively ideal.A small number of nozzles can lead to insufficient water mist area,while a large number of nozzles can lead to a larger thickness of the water curtain and affect construction operations.As the wind speed increases,the dust removal efficiency gradually increases.The airflow at the palm can increase the kinetic energy of dust,and during the irregular movement of dust,the distribution of dust is more uniform;On the other hand,wind and mist acquire greater kinetic energy,thus increasing the chances of collision with dust during subsequent movements. |
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