Study on Impact Dynamic Behavior and Failure Characteristics of Coal based on True Triaxial Split–Hopkinson Pressure Bar Experiments

Full understanding of dynamic mechanical characteristics of coal samples under true triaxial condition is of great significance for preventing and controlling deep coal and rock dynamic disasters. The results of this study showed that the transmission amplitude decreases with the increase in σ 1 and increases with the increase in the impact velocity. The peak stress and absorbed energy of coal decreased with the increase in σ 1 under true triaxial conditions. Under uniaxial and true triaxial conditions, the peak stress and absorbed energy of coal increased with the increase in impact velocity, and the stress change under true triaxial conditions was more sensitive to the action of dynamic load. Compared with uniaxial impact, the damage degree of coal sample under true triaxial condition was lower. The fractal dimension of broken blocks increased linearly with the increase in σ 1 and dynamic load, indicating that the degree of broken coal was intensified. This study effectively reveals the failure mechanism of coal under unequal static load and dynamic load.