Study On Numerical Simulation Of Deep Penetration Pre-splitting Blasting For Low Permeability Coal Seam

Coal is one of the most important energy sources in China,the low permeability coal seam gas is seriously restricted by the low gas extraction efficiency and long construction period,through deep hole pre-splitting blasting anti-reflection technology can improve the gas extraction efficiency,improve production efficiency,to ensure the safety of production.This paper is based on the mechanism of blasting rock breaking,by using theoretical analysis,ANSYS finite element software simulation analysis and the field industrial experiment,in addition the low permeability coal seam control deep hole pre-splitting blasting plan and parameters,and it's got different coupling coefficients,the presence of empty hole,hole sealing length and hole spacing around the parameters such as hole crack propagation,and through field test to verify.The main conclusions are as follows:1)In the same diameter of the hole,the length of the rift is increasing,and the coefficient of non-coupling has decreased by 2.1 to 1.2,and the trend is slowing down.Hole diameter of 75 mm,63 mm cartridge diameter,fracture around the hole development degree are the best.2)The existence of empty hole(control hole)between gun holes can induce the explosion crack to expand to the position of empty hole,and then increase the crack expansion range.The more obvious the effect is with the increase of blasting dosage,for blasting with hole diameter of 75 mm and cartridge diameter of 63 mm,the optimal spacing between blasting hole and empty hole is 3.5m,too small hole spacing will cause hole collapse.Too large hole spacing is not conducive to the formation of the main crack through the control hole,and is not conducive to the interconnection of the cracks in the whole coal seam.3)Double hole blasting starts simultaneously compared with single-hole blasting,the fracture density in the fractured zone increases by 70%,which is conducive to improving the permeability of the coal seam and ensuring the extraction effect.4)The results of the field application show that,in the 14 days after the blast of the deep hole,the amount of hundred-meter of drilling gas flow in the first 14 daysof the explosion has increased by more than 6 times,the same hundred-meter suction cap has increased the maximum value of the gas and the limit of the gas and the limit of the gas in the time of the experiment,which is 5.65 times better than the limit before the test,and it has a good effect.