Study on the characteristics of CO2 fracturing rock damage based on fractal theory

CO2 fracturing is emerging as a carbon-neutral technology for underground excavation. Traditional studies on structural stability during excavation have largely focused on the vibration characteristics of rocks. However, the inherent damage in rock layers during CO2 fracturing poses significant challenges for understanding damage mechanisms under complex multi-field coupling. This study introduces a novel approach for calculating rock damage induced by CO2 fracturing . We developed a physical model of CO2 fracturing and applied a "two-stage effect" division method, creating a staged damage calculation model based on fractal damage mechanics theory. Experiments were conducted under combined dynamic and static loads to evaluate rock damage. A two-factor Analysis of Variance (ANOVA) was used to assess the significance of dynamic and static effects on the extent of rock damage. The findings revealed that static loads guide crack propagation direction, reducing the angle between the crack and vertical axis, while initial CO2 dynamic load pressure strongly influences crack patterns, with higher pressures resulting in more fractures. The extent of rock damage observed ranged from 0.680 to 0.845. Although dynamic loads showed no significant impact, static loads exhibited a notable effect, as indicated by a P-value approaching 0.01. This study's fractal-damage calculation model provides a valuable tool for addressing stability concerns in structures affected by CO2 fracturing.