![]() However, the explosive classification of rock mass corresponding to commonly used explosives such as emulsion explosives has formed a relatively complete system. At present, there is no relevant classification evaluation standard for rock mass cracking in the CO 2 of phase change fracturing and rock breaking at home and abroad. Rock mass fracture ability refers to the difficulty of rock mass cracking under high pressure in the process of CO 2 phase transformation. At present, in the research of CO 2 phase change fracturing and rock breaking, in order to ensure efficient fracturing of the target rock mass, it is necessary to carry out the fracture grading evaluation for various target rock masses existing in different geological environments, which can help in the parameter design and crack scheme optimization. investigated a new liquid CO 2 rock breaking technology through a series of field tests and successfully applied the technology to rock excavation at the construction site of a subway station. studied the phase change fracturing process of liquid CO 2 from theoretical analysis and numerical simulation, established a mathematical model of coal seam fracturing pressure, and analyzed the fracturing influence range. Nowadays, CO 2 phase change fracturing has once again attracted attention due to the advantages of rock-soil blasting and excavation in complex environments. Subsequently, it was widely used in coal mines in many countries. This technology originated at the beginning of the last century and was initially used to increase the permeability and mining of coal seams in British coal mines. Gas explosion excavation technology is the most widely used CO 2 phase change fracturing technology. In order to overcome the above shortcomings of blasting, it is necessary to actively develop gas blasting excavation technology with high safety as a supplementary means of blasting excavation. In addition, there are certain safety hazards when applied in coal seams with a high concentration of gas. In traditional blasting engineering, vibration, shock wave, flying stone, and other hazards are inevitably caused. IntroductionĪt present, blasting is still the most important means of rock crushing excavation in open pit mining and underground engineering construction. According to the characteristics of fracture ability, the rock masses in the area to be rebuilt on the Tibet Highway are divided into grade II, grade III, and grade IV, which provides scientific guidance for the construction of the project. ![]() Therefore, it has validity and feasibility. In addition, it is combined with the cloud model for the classification division, overcoming the traditional classification method fixed with appraisal pattern flaw. The results present that this new classification method of rock mass fracture ability uses AHP–EWM to carry out the weight distribution of the classification index. Through this evaluation method, the rock mass in a reconstruction project section of Nyingchi, Tibet, is classified and evaluated. In this method, rock density, rock tensile strength, rock wave impedance, and rock mass integrity coefficient are used as the factors to determine the level of rock mass fracturing, and the evaluation index system of rock mass fracturing is established. In order to study the fracture ability classification of rock mass under the cracking action of supercritical CO 2 phase transition, based on the classification theory of rock mass in blasting engineering, an analytic hierarchy process (AHP)-entropy weight method (EWM) and the cloud model classification method for rock mass cracking under CO 2 phase transformation are proposed.
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