Influence of fissure distribution characteristics on the dynamic response of fissured Rock: Quantity and spacing

The impact test of red sandstone with different fissure distribution was carried out by Split Hopkinson Pressure Bar (SHPB). The failure process of the specimen in the time dimension was captured by high-speed camera and digital image correlation (DIC). The crushing characteristics of the specimen were discussed from the fractal dimension. Furthermore, the influence of fissure distribution characteristics (quantity and spacing of fissures) on the mechanical properties and fracture behavior of fissured red sandstone was analyzed. The experimental results show that the fissure spacing is negatively correlated with the dynamic compressive strength and peak strain of specimen, while the fissure quantity is negatively correlated with the dynamic compressive strength and positively correlated with the peak strain. Cracks are categorized into five types based on the manner of their initiation and expansion. The crack initiation and propagation are jointly affected by tensile stress and shear stress, but the tensile stress is dominant. With the increase of the fissure quantity, the failure mode changes from tensile failure to tensile-shear mixed failure. The increase of fissure spacing does not change its failure mode, but the formation mode of the main crack changes. The fractal dimension increases with the increase of the fissure quantity, and decreases with the increase of the fissure spacing, i.e., the larger the fissure quantity is, the higher the degree of fragmentation is, and the larger the fissure spacing is, the lower the degree of fragmentation is. The research results can provide a theoretical reference for the study of dynamic failure mechanism of rock mass with non-persistent discontinuities.