| In China’s energy industry,coal resources have long occupied the main position,but coal mine accidents seriously restrict the development of the coal industry.In recent years,China pays more and more attention to the safe production of enterprises,the coal accident rate is decreasing year by year,but with the increasing depth of coal mining,the proportion of high gas low permeable coal seams has increased significantly,which has aggravated the difficulty of gas extraction in coal mines and is not conducive to the safe production of coal mines.In order to solve this problem,scholars at home and abroad have done a lot of research.Among them,the pre-cracking permeation technology has been widely used because of its wide applicability and good effect.On the basis of explosive force,rock force and fracture force,this paper consults the research results of domestic and foreign scholars on the explosion permeation of coal seams,analyzes the shortcomings existing in the current research institute,and puts forward the research topic of pre-cracking blasting of low-breathing coal seam cutting drug packs.Through similar simulation matching experiments,the material ratio of each layer of the test model is determined,wherein the coal seam ratio is:sand:cement:gypsum:mica powder:coal powder:water:3.3:0.3:0.8:0.05:1.2:0.8.A comparative experiment of different width cut blasting and ordinary blasting was carried out.In the test,the ultra-dynamic strain gauge was used to measure the strain dynamics of the strain brick under normal blasting and 3 different seam widths,and the test data analysis showed that when the seam width was 6 mm,the strain peak in the seam direction was the largest and the strain peak in the non-cut direction was the smallest.Comparing the cutting drug package control blasting with the ordinary medicine package controlling blasting,the cutting drug package has a larger strain at the near end of the coal body and the far end of the coal body in the direction of the cut,while the strain in the non-cut drug package is smaller,which reflects the good directional effect of the seam package control blasting.After observing the change of macro crack after blasting,it is found that the main crack of the slit medicine package with a width of 6 mm develops optimally,and no extra secondary cracks are produced,and the crushing area is relatively small,which is the best cut width.Through the numerical simulation software ANSYS/LS-DYNA to simulate the stress changes of ordinary blasting and the best cut width under seam blasting,the simulation results show that after the explosion of ordinary medicine package,energy consumption is in the coal body crushing area,hindering the development of distant fissures.In summary,the blasting of the cutting medicine package is more conducive to the development of the cut in the direction of the cut,while in the direction of the non-cut will reduce the damage to coal and rock bodies.The macro crack results,the strain results of the blasting process and the numerical simulation results show each other,indicating that the cutting drug package with a cut width of 6 mm can better promote crack development and increase the breathability of the coal seam in the direction of the cut,and the results can provide some reference for engineering practice.Figure[41]table[10]reference[82]... |
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