Study On The Mechanism Of Increasing Permeability By CO₂ Blasting And The Arrangement Of Coal Seam Holes

CO₂ blasting is a new type of coal seam increasing permeability technology.Because of its simple operation,safety and high efficiency,it is often used in lowpermeability coal seams.To this end,this article systematically analyzes the mechanismof CO₂ blasting anti-reflection and the layout of the coal seam pore network by a combination of laboratory experiments,theoretical analysis,numerical simulation,and field applications:The pressure response characteristics of the liquid CO₂ blasting system were explored through the self-made blasting experiment device,and the pressure time relation curve of CO₂ in the blasting tube was obtained.The change law of the pressure time history curve was analyzed based on the theory of thermodynamics and gas dynamics,and then the aerodynamic impact model was established.Using(SHPB)experimental system,the impact experiments on coal samples of xinyuan mine were carried out at different rates.The dynamic damage constitutive model is established based on the obtained dynamic stress-strain curves at different rates.Based on dynamic damage constitutive model,with the help of ANSYS platform,APDL language was used to write the calculation program of damage and failure of coal body in CO₂ blasting,and the pressure time-history curve of CO₂ blasting was introduced to realize the numerical simulation of damage evolution under different blasting schemes.The simulation results show that the radius of fracture relief zone is larger than that of single hole blasting.The radius of the pressure relief zone in the cavitation hole blasting scheme is obviously larger than that in the single-hole and double-hole blasting scheme.The conclusion of the numerical simulation is verified by the observation of anti-permeability pumping effect of coal seam blasting in xinyuan mine.It shows that the mechanism of permeability improvement in blasting is to relieve the pressure of hydrostatic pressure in the fractured zone,and increasing the blasting hole and cavitation hole can obviously improve the permeability improvement in blasting.