Study on the Energy Evolution Mechanism and Fractal Characteristics of Coal Failure under Dynamic Loading

The damage to coal-rock masses induced by mining disturbance cannot be overlooked, and the damage deformation characteristics under dynamic loading urgently require investigation. Therefore, this study employs Split Hopkinson Pressure Bar (SHPB) impact tests to reveal the energy evolution mechanism and fractal characteristics of coal failure under dynamic loading. Research indicates that coal deformation exhibits significant strain rate dependence, with both dynamic strength and energy consumption parameters increasing linearly with strain rate. Energy evolution drives crack development through four stages: no damage, microcrack initiation, macroscopic nucleation, and collapse, where the energy consumption required for crack formation exceeds that for crack propagation throughout the entire development process. The fractal dimension of fragmented coal satisfies a positive correlation with both strain rate and fragmentation energy density. Coal possesses favorable self-similarity, and under this condition, increased strain rate enhances the coal's ability to resist impact through elevated elastic energy density, thereby further strengthening dynamic strength. This confirms intensified fragmentation degree and refined fragment particle size under high energy consumption conditions, providing theoretical support for the prevention and control of mine dynamic disasters.