Failure in rocks is attributed to crack initiation and coalescence processes upon loading. Crack behavior study, which has been extensively conducted in various rock types containing artificially created flaws under a quasi-static loading condition over the past decades, is extended to dynamic loading conditions by using the Split Hopkinson Pressure Bar (SHPB) technique.
The loading tests are conducted on specimens containing a single pre-existing open flaw (60mm × 30mm × 20mm) in Carrara marble. Similar to those loaded quasi-statically, white patches are observed to develop in the specimens loaded dynamically at the early stage of the loading prior to the development of observable cracks. The respective failure modes are however significantly different. For quasi-static compression, normally two macro-cracks linking the two opposite corners of the specimen and the flaw tips cause the failure of the marble specimens, producing two main fragments. In contrast, under high strain rate, four fragments associated with "X" shape deformation bands are produced irrespective of the inclination angle of the flaws. The failure is attributed to the more or less simultaneous propagation of the horsetail and anti-wing cracks. In this paper, the detailed cracking processes will be compared and discussed.