Mechanism and application of carbon dioxide phase change blasting fracturing

The structural transformation of coal and rock mass is a common core scientific problem to solve many technical problems in coal mines. Carbon dioxide phase change blasting has become one of the effective methods for coal and rock mass cracking due to its advantages of safety, controllability, and easy energy regulation. In order to determine the mechanism of carbon dioxide phase change blasting and expand the application of phase change blasting in engineering, the principle of carbon dioxide phase change blasting and the equipment for cracking were analyzed. Statistical comparisons were made between different methods for calculating the energy of phase change blasting. Compared to traditional explosive blasting, phase change blasting belongs to a low energy fracturing method. By analyzing the propagation characteristics of carbon dioxide phase change jet, the synergistic effect of medium stress initiation and high-pressure gas in phase change blasting is determined. Under medium impact, the coal and rock mass are subjected to tensile stress damage, resulting in radial initial fracture. Under the combined action of shock wave and unloading wave, multiple initiation characteristics are formed, and high-pressure gas further expands in multiple fractures, driving them to expand outward, Clarified the synergistic cracking process of phase change blasting stress gas. Further research was conducted on the effects of factors such as energy release direction, coal rock mass properties, blasting parameters, initial geostress, drilling layout parameters, and drilling groove characteristics on the cracking effect of phase change blasting. The energy release direction plays a direct role in the failure of coal rock mass, leading to asymmetric damage and failure. The compressive strength and cracking spacing of coal rock mass are key factors affecting the cracking effect. The initial geostress, drilling layout parameters, and drilling groove characteristics affect the development and propagation characteristics of cracks. In terms of the engineering application of phase change blasting fracturing, the multiple crack seepage characteristics of phase change blasting were revealed, the crack and permeability enhancement effect of high gas coal seams were determined, the coal cutting characteristics before and after presplitting were compared, the feasibility of presplitting to increase lump coal rate was verified, and the collapse characteristics of presplitting roof in phase change blasting were explored. Further expansion should be made towards the direction of multi rate fractturing caused by phase change blasting, multi-scale analysis of damage and failure, coupling of multiple physical fields during the cracking process and carbon dioxide phase delayed change blasting, which will expand the application scenarios of carbon dioxide phase change blasting.