Study of fractal characteristics and energy release in rocks under impact loading

In order to investigate the fragmentation characteristics and energy release mechanism of rocks under impact loading, Split Hopkinson Pressure Bar rock dynamics tests were conducted on red sandstone and limestone. The study obtained stress-strain curves, strength parameters, and fragmentation characteristics of the rocks at various strain rates through impact tests. The impact crushed rock fragments were sieved with a standard sieve and the fractal dimension was calculated on the basis of the fragment size distribution model. This analysis explored the relationship between the fractal dimension and dynamic loading parameters. Furthermore, the energy release characteristics of rocks at different strain rates were investigated by applying energy theory to calculate the dissipated energy and elastic strain energy of rocks under different impact loading. The findings revealed that dynamic compressive strength increases with higher strain rates, showing a multiplicative power function relationship. Rock fragmentation increases during loading at higher strain rates, leading to a rise in the fractal dimension. The stress-strain curve of rocks was segmented into five stages based on the energy evolution process, with elastic energy dissipation occurring after peak stress. With increasing strain rate, both the elastic energy storage limit and dissipated energy followed a multiplicative power function relationship. This research provides a theoretical foundation for enhancing rock fracturing efficiency and effectively preventing geological disasters.