Mechanism Analysis of Liquid Carbon Dioxide Phase Transition for Fracturing Rock Masses

The technique of breaking rocks using carbon dioxide phase transition technology is being widely applied in current research. This article combines theoretical and practical methods to analyze the mechanism by which high-pressure gas breaks rock at different stages. Using the observation that liquid carbon dioxide forms a high-pressure jet from release holes at the moment of release, a formula for calculating the initial pressure on the wall in the direction of release was obtained, and the pattern of initial crack formation on the borehole wall under different initial stress conditions was examined. An experiment using carbon dioxide phase transition technology to fracture rock without an initial stress field was conducted. The mechanism of generation and expansion of subsequent cracks under stress waves and high-pressure gas was analyzed, and the formula for calculating crack propagation radius under stress waves was obtained. The results suggested that under the quasi-static action of high-pressure gas, cracks begin to develop when the stress intensity factor K-I at the crack tip is equal to or greater than the fracture toughness K-IC of the rock.