Dynamic behavior and failure characteristics of granite with different shapes of holes

During mining, dynamic loads significantly affect the instability of goafs. Therefore, investigating the mechanical behavior of granite specimens with holes under dynamic loading is essential. This study conducted SHPB tests on granite specimens with different shaped holes: circular (C), rectangular (R), short-axis elliptical (SE), and long-axis elliptical (LE). After reaching peak stress, the strain rebound of C and LE specimens is about 0.8%, and the strain rebound of R and SE specimens is 0.2%. The peak stress ranks as follows: LE, R, C, and SE. As the strain rate increases, the debris in the sample shifts from block debris to long strip debris. When the gas pressure rises from 0.14 MPa to 0.23 MPa, both the peak stress and energy input of each specimen increase with every 1% increase in strain rate. The crack propagation and force chain evolution also were explored using PFC2D. The crack initiation stress to damage stress ratio is 1:2. Upon failure, specimens primarily develop penetrating cracks aligned with the impact direction and symmetrical cracks at the upper and lower edges of the holes. Compression force chains concentrate at the upper and lower edges of the specimen, while tension chains relate to macroscopic cracks. Finally, dimensionless equation is derived to analysis the influence factors of dynamic strength.