Impact Dynamic Characterization and Energy Dissipation Analysis of Porous Sandstone Specimens

In order to investigate the dynamic characteristics and energy dissipation behavior of porous sandstone under impact loading, sandstone from a coal mine roadway was used as the research subject. Impact compression tests with varying impact velocities were conducted on axially porous sandstone specimens using the Split Hopkinson Pressure Bar (SHPB) test apparatus. The results indicate that: With increasing impact velocity, the dynamic compressive strength of porous sandstone specimens increases exponentially, while the dynamic strain increases quadratically. The dynamic compressive strength exhibits an exponential increase with strain rate, showing a pronounced strain rate effect. Under the same loading conditions, the dynamic compressive strength of porous sandstone specimens decreases, while the dynamic strain increases, compared to intact specimens. As impact velocity increases, the fracture mode of the porous specimens transitions from axial splitting to pulverization, with the degree of fracture becoming more severe and the damage being greater than that of intact specimens. From an energy perspective, the higher the energy dissipation density during fracture, the more severe the fracture of the porous sandstone specimens. The average fragment size is negatively correlated with energy dissipation density in a quadratic relationship, which can be quantitatively describes the degree of rock fragmentation.