Research On Deep Hole Pre-Splitting Blasting Technology For Fracture And Permeability Enhancement In Low Permeability Coal Seam

Gas extraction is the main measure to prevent coal and gas outburst in China,but most of the outburst coal seams in China also belong to low permeability coal seams,which leads to the problems of low extraction efficiency,difficult extraction and high treatment cost.As a coal seam antireflection technology using blasting energy,deep hole pre-splitting blasting technology can effectively improve the permeability coefficient of coal seam,improve the gas extraction efficiency and ensure the safety production of coal mine.In this paper,the deep hole pre-splitting blasting technology in low permeability coal seam of Jiulishan mine is systematically studied and analyzed by using the research methods of theoretical analysis,numerical simulation and field industrial test.Firstly,the cracking process of through layer deep hole presplitting blasting is described,and the formation range of crushing circle and fracture circle is determined.Based on fracture mechanics,elasticity and blasting theory,the effects of stress wave,explosive gas,coal seam gas and control hole on fracture development are analyzed,and the transmission and reflection of stress wave at the interface of layered medium are discussed.Secondly,according to the field data of Jiulishan mine,the single blasting hole model and the single blasting hole double pre splitting hole model are established by using ANSYS pre-processing software;The simulation results of the blasting model under different blasting process parameters are compared,and the crack propagation and stress wave propagation laws under different blasting parameters are analyzed.It is determined that the optimal decoupling coefficient of deep hole presplitting blasting technology in Jiulishan mine is 1.25 and the optimal hole spacing is 3M.Finally,the field experiment is carried out in the bottom drainage roadway drilling yard of 16071 working face of Jiulishan mine.The experimental results show that the effective influence radius of through layer deep hole presplitting blasting technology in Jiulishan mine is 3 ～ 3.5m,and all gas drainage parameters are greatly improved after blasting,which proves that it is feasible to use through layer deep hole presplitting blasting technology to improve gas drainage efficiency in 16071 working face of Jiulishan mine.This paper has 42 figures,13 tables and 85 references...