Energy-accumulation blasting and water injecting under local water storage and pressure retention in heading face

WANG Zhenfeng; WANG Yu; ZHANG Tao

doi:10.13225/j.cnki.jccs.2022.1832

Abstract：Due to the poor effect of local energy-accumulation blasting and water injection in the Xuehu Coal Mine and the undetermined influence range of local energy-accumulation blasting and water injection pressure relief,the spacing of blasting holes cannot be reasonably arranged in heading face.Through theoretical analysis,ANSYS/LSDYNA numeric-alsimulation and industrial experiments,designing a local water storage and pressure retention device,this study investig-ated the application of energy-accumulation blasting and water injecting under local water storage and pressure retention in the Xuehu Coal Mine.The results showed:①the ANSYS/LSDYNA simulation reveals that the low compressibility of water can accumulate explosive energy,resulting a significant increase of coal damage range.Complete damage range of coal mass in the water medium coupling is 3.14 times of that in the air medium coupling,the range of damage crack length of coal mass in the water medium coupling is 2.71 times of that in the air medium coupling.Water medium makes the en-ergy of energy-accumulation explosive uniformly act on coal,then weakens the directional effect of the energy-accumula-tion pipe,and uniforms the development and extension of cracks around borehole.Effective energy accumulation and dir-ectional propagation of fractures can be achieved by installing energy-accumulation pipe between water medium and bore-hole walls.When the explosive is in the center of the borehole and the water body,the crack propagation and the blasting cavity area are better than that when the explosive is in the lower part of the borehole and the water body.②The water storage and pressure retention device makes the explosive always in the center of borehole and water body,restricts the ex-plosive circumferentially,reduces the radial energy loss of explosive explosion,and enhances the energy of explosive act-ing on coal body.The energy-gathered pipe set inside water storage and pressure retention device integrates water storage,pressure retention and energy accumulation,and plays an effective directional role.③The change of gas parameters in borehole before and after energy-accumulation blasting and water injecting is compared by industrial experiments,and the influence radius of blasting is 2.5 m.The local concentrated stress is transferred and released when the energy-accumula-tion blasting and water injecting holes are arranged with 5 m spacing in the Xuehu Coal Mine.By injecting water into the coal seam through the water storage and pressure retention device after blasting,the blasting and water injection holes are changed into the coal seam water injection holes,which can further moisten the coal body,change the nature of the coal body and improve the heading face environment.Due to the advantages of large blasting cavity area,directional energy-gathering expansion cracks and water injection to change the properties of surrounding rock,this technology can be used to cut the roof and forced roof caving.