Fracture response and damage evolution features of coal considering the effect of creep damage under dynamic loading

When coal under creep deterioration is disturbed by impact load, it is easy to induce catastrophic instability disasters, rock burst. To analysis the fracture and failure evolution of coal considering the effect of creep damage under dynamic loading, the SHPB simulation experiment under different creep and impact stress was carried out, and the mesoscopic mechanism, damage de- gree, force chain fabric and energy evolution were analyzed. The results show that coal meso- scopic particles move inward along the axial direction and outward along the minimum principal stress, and there are most tensile shear cracks near the incident end face, the most shear cracks along axial direction, the main tension cracks along radial direction. Crack damage shows an S- shaped trend with time, increasing significantly during the pre-peak stress stage and growing linearly with dynamic stress at the peak stage. Fragment damage shows a J-shaped trend with time, rising significantly after the peak and increasing linearly with the creep stress at the peak stress. The strong fabric mainly transmits stress waves, and changes from axial compression to radial expansion at the peak stress. The aggregation distribution and strength enhancement of strong chains destroy the coal mesoscopic bond and cause macroscopic cracks expanding and penetrating. During the creep and pre-peak stage, there is most external energy changed into strain energy. At peak stress, sliding and dashpot energy grows significantly under high creep stress, and the strain energy ratio decreases with dynamic stress. The study can theoretically describe mesoscopic coal failure evolution and reveal deep mining disasters process.