Dynamic progressive fracture behavior of axially confined sandstone specimens containing a single flaw

Abstract

Rock masses are frequently subjected to dynamic disturbance in addition to pre-stress, which plays a key role in the stability and safety of underground projects. In this paper, the effects of flaw inclination angle and pre-stress on the mechanical properties and fracture behavior of sandstone specimens under repetitive impact loadings were investigated through a series of laboratory tests using a modified split Hopkinson pressure bar (SHPB) system. The results show that the dynamic strength decreases gradually with the increasing repetitive impact number. A larger flaw inclination angle produces fewer repetitive impacts for a given axial pre-stress. The repetitive impact counts and the cumulative absorbed energy peak at an axial pre-stress of 20–40 MPa. By the digital image correlation (DIC) technique, high strain localizations around the flaw periphery can be observed after the application of pre-stress. During the repetitive impact loadings, wing and anti-wing cracks occupy the dominant position. Compressive cracks also contribute to the ultimate failure if the specimen is subjected to solely repetitive impacts. Except for 90° specimens, shear cracks make a difference as well in the cracking process as the pre-stress increases.