Experimental Study on the Damage Evolution Behavior of Coal Under Dynamic Brazilian Splitting Tests Based on the Split Hopkinson Pressure Bar and the Digital Image Correlation

Fully understanding the dynamic tensile behavior of coal is of great significance to the prevention and control of rock burst in underground coal resource mining. In this study, the split Hopkinson pressure bar and the digital image correlation were used to conduct dynamic Brazilian splitting experiments on coal to explore its dynamic tensile behavior. The evolution behaviors of vertical displacement, displacement velocity, and displacement acceleration fields in the process of dynamic tensile fracture of coal were investigated; the damage process of coal was characterized quantitatively; and the relationship between damage and energy was analyzed. The results showed that absolute values of displacement, displacement velocity, and displacement acceleration gradually expand along the central axis to the upper and lower ends of coal. The displacement changed in the form of variable velocity and acceleration, proving that the damage of coal evolves in the form of variable velocity and acceleration. The damage acceleration reached the maximum soonest, followed by the damage velocity, and the degree of damage was last. Before the peak stress, the absorbed energy can only cause slight damage to the coal but it led to high damage velocity and acceleration. After the peak stress, a little added absorbed energy can lead to more severe damage to the coal, with high damage velocity and low damage acceleration. Although the strength, energy, displacement, displacement velocity, and displacement acceleration of coal at different impact velocities were different, their forms of evolution and damage modes were similar.