The mechanism of crack propagation under dynamic loading stress at different rates

The generation and propagation of cracks are influenced by dynamic loading stresses induced by different fracturing methods. In order to investigate the influence of dynamic loading stress rate on the crack propagation and crack distribution characteristics, theoretical analysis and numerical simulation were used to study the crack propagation mechanism and distribution state of the rock, and zoning standards for different loading stresses were proposed. The form of fracture around the borehole is determined by the peak value of dynamic loading stress and the dynamic strength of the rock, while the number of rock fractures is influenced by the propagation rate of dynamic loading stress and the dynamic path of unloading wave propagation. Under high-stress and rapid dynamic loading, the rock around the borehole undergoes dynamic compression failure. For moderate dynamic loading, the rock mass experiences initial fracture due to tensile stress, leading to the generation of multiple radial cracks through the combined action of shock and unloading waves. Under quasi-static loading, the rock mass undergoes tensile failure under tensile stress and is effectively unloaded. Based on the peak value of dynamic loading and loading time, different fracture modes are divided into crushing fracture zone, multiple fracture zone, and single fracture zone. The relationship between the characteristics of rock fragments and loading stress was determined, and the fractal method was used to describe the distribution characteristics of cracks. The effects of loading rate and rock fragmentation were finally discussed, providing guidance for the selection and utilization of different fracturing methods.