Study on the evolution mechanism of three-dimensional fracture networks in rock induced by CO2 fracturing tube blasting

Carbon dioxide (CO₂) fracturing tubes have been applied as a novel blasting technique in rock blasting. However, the three-dimensional evolution of fracture networks induced by CO₂ blasting remains poorly investigated. Therefore, this study conducted on-site blasting tests on 1 m³ rock specimens. Field data were used to validate numerical simulations, and phase-transition blasting processes were further simulated under varying expansion ratios and loading durations. The results indicated a fractal dimension of 1.578 for the fracture network, with rock fragments exhibiting greater uniformity than those generated by traditional explosive blasting. The internal fracture network comprised interconnected radial and circumferential fracture planes. A linear positive correlation was observed among the particle expansion ratio, the total fracture count, and the input energy. Moreover, the density of radial fracture planes and the fracture network increased with the expansion ratio. In contrast, the total number of fractures and blasting energy demonstrated a quadratic inverse relationship with loading duration. Shorter loading durations led to a dense distribution of fracture networks around the blasting hole and increased heterogeneity of rock fragments. As the loading duration increases, the fracture number curve exhibited a significant lag compared to the particle expansion curve. These findings advance the mechanistic understanding of CO₂ fracturing tubes and optimize blasting efficiency.