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.

To study the influence of fracture inclination angle on the dynamic mechanical properties of sandstone under dynamic and static combined loading conditions, impact compression tests were conducted on prefabricated fractured sandstone specimens with inclination angles of 0°, 15°, 30°, 45°, 60°, 75°, and 90° using dynamic and static combined SHPB test device. The results show that: Under dynamic and static combined loading conditions, the dynamic stress-strain curves of prefabricated fractured sandstone specimens with different inclination angles are located below the complete sandstone specimen curve. As the inclination angle of fracture increases, the dynamic compressive strength, dynamic strain, dynamic elastic modulus, and average particle size of fragments all show a variation of first decreasing and then increasing, and the inflection point is located at fracture inclination angle of 45°. When the fracture inclination angle is 0°, the failure mode of the specimen is tensile failure along the loading direction, while failure mode is tensile-shear composite failure for fracture inclination angle of 15° ~ 60° and shear failure for fracture inclination angle of 75° ~ 90°. Moreover, the fragmentation degree of the specimen is largest at fracture inclination angle of 45° and is smallest at 0°.