The second stage, from 291 to 295 ms, was rapid crack propagation with maximum opening rate increment and propagation rates of 0.1865 and 5.35 m/s, respectively. The first stage, from 0 to 290 ms, included energy storage at the crack tip and a maximum opening rate increment of 0.0043 m/s. The results showed that there were three stages in the propagation of a prefabricated crack under the action of a CO 2 gas explosion. We conducted the gas explosion experiments on prefabricated cracked samples with a crack length of 10 mm and width of 0.2 mm to analyze the dynamic response of the crack tip. We used a test platform for the independent development of CO 2 gas explosions under experimental conditions of 1 MPa axial pressure and 2 MPa CO 2 gas pressure and a VIC-3D measurement system. To explore the effects of CO 2 gas explosions on crack tips, we constructed an analytical model of gas pressure attenuation at different positions based on fluid motion equations, proposed equations for crack opening and growth rates, and inverted the energy field of the whole process of CO 2 blasting.
In the process of a CO 2 gas explosion, the initial burst crack generated by the shock wave expands the crack tip under the splitting action of high-pressure CO 2 gas. CO 2 deep-hole presplit explosions are an important technology for enhancing gas drainage in low-permeability coal seams.
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