| With the continuous development of science and technology,the mining intensity of coal mining continues to increase,and the existing coal resources that can easily be mined cannot meet the demand for energy.Coal companies have gradually increased their attention to the mining of coal seams at close quarters.The coal resources in the west of China are abundant.However,due to the mining of small coal mines in the early stage,the air leakage in the coal seam is relatively serious,and it is easy to form a large area of spontaneous combustion.The upper fire zone is affected by the mining of the lower coal seams,and the number of air leakage passages increases,which in turn tends to aggravate the development of the fire zone.At the same time,the coal face of the lower coal seam also faces the danger of the intrusion of toxic and harmful gases in the upper fire zone,which seriously threatens the safety of the mine.produce.In view of the difficulty in the treatment of the upper coal fire zone in close quarters and the threat of coal seams under fire being threatened,this paper takes the numerical simulation of discrete elements as the research basis.Firstly,a large number of uniaxial compression tests and splitting simulation experiments were carried out to determine coal.The inversion formula of the macroscopic and microscopic parameters of the rock mass solves the inaccuracy of the numerical simulation caused by the mismatch of the macroscopic and microscopic parameters in the long-term numerical simulation.The deduced formula was used to substitute the specific macroscopic parameters of the overlying strata,and the PFC2D software was used to establish the coal seam mining model under the fire zone.Based on the working procedure of 30110 working face,the phased mining simulation corresponding to the site was carried out,and the specific fracture evolution law of the overlying rock strata during the propulsion process was recorded,which proved that the harmful gas intrusion disaster occurred.In order to determine the occurrence time of harmful gas intrusion disasters,appropriate preventive measures are taken to dynamically record the changes in the porosity during the entire process,select porosity data at different time periods for processing,and use contour maps to form fire areas.The change of porosity in the process of coal seam mining under close distance is shown by the image,confirming that the harmful gas intrusion disaster will occur before the basic coal of the lower layer collapses.The numerical simulation results show that the expansion of cracks will lead to the generation of air leakage passages.Under the effect of pressure,harmful gases in the mined area of 2#coal may be pushed into the working face and cause injury to personnel safety.However,if the wind pressure on the 3#coal face is too high and oxygen is pressed into the fire zone,CO and O2 can easily cause the explosion.In order to solve this problem,harmful gas intrusion disasters have been treated using the prevention and control technologies of inerting technology in the fire zone and pressure equalization and ventilation technology.Firstly,nitrogen inerting technology was applied to the 2#coal gob area.The monitoring results showed that although the concentration of harmful gas was greatly reduced,it still threatened the mining of the coal face.After the ventilation parameters were measured on the 30110 working face,a pressure equalization ventilation system was established.Through calculation,it was determined that the safety pressure difference during the trial operation was 296Pa,and the pressure differential safety adjustment interval during normal operation was(118Pa,166Pa).The monitoring results show that the combination of the inerting technology in the fire zone and the pressure equalization ventilation technology can effectively prevent and control harmful gas intrusion disasters and ensure the normal production of the working face. |
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