Mechanical characteristics of sandstone under cyclic impact loading at different strain rates

Studying the mechanical characteristics and damage mechanism of rock under cyclic impact loading of different intensities is of great significance for research on the stability of surrounding rock mass. In this study, laboratory experiments were conducted to investigate the mechanical characteristics and damage mechanism of sandstone under cyclic impact loading at different strain rates. The main results are as follows, the cumulative irreversible strain shows a good increasing trend with the number of impacts, and the entire increase process can be roughly divided into two stages: a slow rise stage and a rapid rise stage. While the dissipated energy decreases, the elastic energy of the rock increases, and its ability to resist irreversible strain temporarily increases. At lower strain rates, the dissipated energy used for the development and propagation of rock cracks increases accordingly. Under lower strain rates, the impact loading causes the rate of crack compaction inside the rock to be greater than the rate of crack propagation; therefore, after a certain number of cyclic impacts, the peak stress may increase once or multiple times. As the impact loading continues, the peak stress tends to stabilize after reaching its maximum value, fluctuating around a certain value. If impact loading continues at this point, the crack propagation rate will exceed the crack compaction rate, causing a rapid decrease in peak stress and eventual failure. Our findings can provide a basis for studies on the stability of surrounding rock mass under cyclic disturbances of different intensities.