Prevention and control technology of coal-rock and gas dynamic disaster based on water jet slotting pressure relief

With the gradual extension of coal mining to the deep,high-intensity mining gas surge volume is large,and the high stress of coal and rock and gas disasters are coupled with each other. Aiming at the coal rock and gas dynamic disaster control problem faced by high-intensity mining in deep mine,based on the principle of high-pressure water jet slotting pressure relief,the coal rock and gas dynamic disaster hydraulic control technology of stress and gas double pressure relief is proposed. Through theoretical analysis and numerical simulation,the mechanism of ultra-high pressure water jet slotting is analyzed,and the double effects of ultra-high pressure water jet slotting on regional coal stress and gas drainage are studied. The results show that the ultra-high pressure water jet slotting inside the coal seam can effectively destroy the integrity of the coal seam,weaken the supporting capacity of the coal seam to the overlying strata,and effectively alleviate the stress concentration state in the slotting area; The seam groove formed by slotting inside the borehole changes the gas drainage mode of the borehole from radial flow to radial and axial compound flow,which makes the gas content and gas pressure in the coal seam decrease rapidly. The ultra-high pressure hydraulic slotting technology reduces the risk of coal rock and gas dynamic disaster through stress relief and gas drainage. The field test in Hujiahe coal mine shows that the average Micro-seismic energy in the area of ultra-high pressure water jet slotting is reduced by 18%,the Micro-seismic energy per unit footage is reduced by 37%,the times of strong mine pressure behavior assessed by the method of geostrophic trend is reduced by 17%,and the gas extraction rate is increased by 4.1 times. The research shows that the ultra-high pressure hydraulic slotting technology can effectively realize the double pressure relief of ground stress and gas pressure,effectively reduce the risk of coal rock and gas dynamic disaster and provide technical support for high-intensity and safe mining in deep coal mines.