Research On Deep Hole Pre-split Blasting And Anti-reflection Technology In Wenjiaba No. 1 Mine

The gas in Wenjiaba No.1 Coal Mine is high,so it is necessary to drain gas from coal seam to prevent gas accumulation from endangering mine production safety.But the coal seam gas permeability coefficient is low,the original gas extraction efficiency is low,it cannot meet the needs of continuous recovery of the working face.The deep seam pre splitting blasting technology is used to enhance the permeability of the coal seam.Through the study of the effect of energy action,stress wave,detonation gas and gas pressure on the formation and expansion of cracks in the process of deep hole pre splitting blasting,the parameters of borehole layout and explosive related parameters of deep hole pre splitting blasting are optimized,and the monitoring and evaluation of gas extraction effect after the actual deep hole pre splitting blasting are evaluated.The following conclusions are obtained:(1)In the process of blasting,blasting stress wave,blasting gas and gas in coal seam play a certain role in the development of coal seam cracks.The high pressure wave produced by blasting crushed the coal to form a crushing zone around the hole.With the attenuation of the stress wave,the fracture zone was formed around the crushing zone,and the crack was expanded by the gas and gas.The formation of gas flow channel in coal body is formed in the process of deep hole pre splitting blasting in coal seam,which aggravate the analysis of coal seam gas,reduce the stress of coal seam and reduce the possibility of coal and gas outburst.(2)The deep hole pre splitting blasting can produce more cracks and effectively reduce the initial stress in the coal seam by using the uncoupled charge method in the radial charge structure.The coefficient of axial charge is 1,which can improve the utilization ratio of unit explosives and increase the pressure relief and permeability enhanced effect.(3)In the initiation mode,multi-point initiation is adopted,and the charge detonates at both ends and extends to the middle until the detonation of the whole explosive.When the explosive in multiple boreholes is detonated,the stress wave produced by each hole is superimposed on the middle of the borehole and produces tensile damage to the coal body,and its pressure time history curve presents two peaks,which can effectively increase the range of blasting fracturing and increase the permeability and increase the penetration effect.(4)In the A110605 working face of the mine,the deep hole pre splitting blasting is adopted to increase the permeability of the coal seam.The design hole of the hole pre splitting blasting hole is carried out,and the 6 groups are put into practice,with a total of 18-hole spacing of 10 m,each hole charge is 66.5kg/ hole,and each drill will need 14 detonators for cracking and blasting.After pre-splitting blasting,the coal seam gas extraction purity and extraction concentration increased more than twice,effectively solving the gas problem in Wenjiaba No.1 Coal Mine.