Dynamic Fracture Mechanism and Fragment Characteristics of Sandstone Specimens with Asymmetrical Conjugate Fissures under Static Pre-compression

Abstract This paper systemically investigates the dynamic mechanical response and fragment characteristics of sandstone with asymmetrical conjugate fissures subjected to preexisting static stress based on the split Hopkinson pressure bar apparatus. The cross-fissured sandstone with a higher dynamic strain rate is characterized by a greater coupled strength under the same static pre-stress; for a given dynamic load, the highest coupled strength occurs under the static pre-stress of 60% UCS. The failure mode of the cross-fissured sandstone is mainly influenced by the dynamic strain rate, ignoring the static pre-stress in this investigation. Under low dynamic strain rates, mixed tensile-shear failure can be generally observed, and large fragments dominate the broken specimen. However, cross-fissured sandstone features typical shear failure mode under the high dynamic impact, and the specimens are broken into small fragments with homogenous size distribution in this case. Higher dynamic strain rate and static pre-stress can induce smaller mean fragment size, smaller location parameter µ in GEV fitting, and higher fractal dimension of the cross-fissured sandstones corresponding to smaller fragment size and more homogeneous distribution.