Experimental investigation on pre-cracking by aerodynamic pulse hydraulic coupling impact
To address the challenges posed by high geo-stress in deep coal mines below one kilometer in China and achieve safe and efficient coal seam unloading as well as pre cracking for enhanced permeability,a deep-hole pneumatic pre-cracking and rock breaking system was independently developed using large-sized concrete as the fracturing object.Tests were conducted to investigate the attenuation law of pneumatic pulse pressure during propagation and its rock-breaking effect under the condition of pre-existing cracks.The experimental results showed that the higher the initial air pressure,the lower the attenuation coefficient of pressure after propagating a certain distance.When the pressure exceeded 35 MPa,the attenuation coefficient was less than 0.1,and the attenuation coefficient under 100 MPa pressure was only 0.064 8.Low-pressure gas pulses had no significant fracturing effect on rocks,while under the action of high-pressure gas pulses above 40 MPa,the number and width of cracks in concrete specimens increased significantly,with the maximum crack width reaching 1 cm,accompanied by a large amount of high-pressure water vapor ejected from the cracks.The research findings may serve as a preliminary basis for further exploration of rock fragmentation and related engineering fields in deep mines where high stress conditions prevail.
rock-breaking equipmenthigh-pressure pulseadvanced pre-crackinghigh pressure and low permeability
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