Mechanical Mechanism Analysis Of The Integrated Blasting And Injection In Coal-Rock

Since coal has always occupied a dominant position in our country’s energy resources,preventing gas outburst,reducing coal mine accidents,and achieving safe coal mining have always been our common goals.In this paper,the mechanical mechanism of a new type of mining process—the integrated blasting and injection technology was studied.The characteristic of the integrated blasting and injection technology is the combination of the traditional water injection technology and the loose blasting technology,at the mean while,water injection and blasting are performed in the same hole.Compared with the traditional blasting technology,this type of technology can buffer the initial pressure of blasting,improve energy utilization,and promote the development of cracks in the coal seam,which will greatly increase The fissure channels in the coal seam improve the permeability of the coal seam and increase gas drainage.Water injection helps to wet the coal body,effectively isolate explosive gases and fire sources,prevent the occurrence of explosion accidents,reduce the danger of coal and gas outburst,and play a good dust-reducing effect.In this paper,based on the observation of the microstructure of coal and rock mass and the experiment of permeability,the changes of pores and fissures of coal rock injected by the water injection zone are studied,and the reasons for the increased gas extraction after water injection blasting are analyzed;Combined with theoretical analysis and numerical simulation,the mechanical mechanism of single-hole blasting under different process conditions in the integrated blasting and injection technology was studied in depth,and then the solution ideas and methods were proposed for the selection of the hole spacing of porous blasting in engineering according to the best process conditions,main tasks as follows:Through nuclear magnetic resonance experiment and permeability experiment,the changes of pores and fissures of coal rock injected by water injection zone were studied.The results showed that:the increase of water content will increase the pore volume and total pore area of coal and rock bodies,and the effect on macropores and fissures is more obvious.When studying the effect of water injection on gas adsorption and diffusion,the following conclusions were drawn:The adsorption ofcoal on water is stronger than that of gas.After water injection,the gas in the pores will be displaced by the water to the fissures,and the gas in the fissures will be discharged outside the coal with the water.The above results show that water injection can create favorable conditions for gas drainage.ANSYS/LS-DYNA explicit kinetic analysis software is used to numerically simulate the blasting process under different water injection process conditions,and the mechanical mechanism of the blasting effect under different process conditions is analyzed.Specifically,the effective stress changes and plastic strain changes after blasting with 200 mm water-coupling charge,100 mm water-coupling charge and150 mm water-uncoupling charge at the same charge were compared.The result shows that compared with water-coupled blasting,water-uncoupled charge blasting has a larger radial and axial influence range,and the stress wave distribution is more uniform.It is not easy to form a crushing zone in the coal body,which effectively improves the energy in the coal body.The utilization rate is conducive to the development of fissures.Compared with several existing empirical formulas of stress wave attenuation,the simulation results in this paper are in good agreement with some empirical formulas.Based on the study of single-hole charging process conditions and considering the engineering porous charging process conditions,this paper establishes a double-hole blasting model with different hole spacings.The results show that when the shock wave propagates in the coal,the velocity of the same particle moving in a structure with a hole spacing of 1m is less than that in a hole spacing of 2m,but the effective stress is generally higher than the latter,the energy acts in the coal body for a longer time,and it is conducive to maintaining the stability of the roadway surrounding rock.