Initiation and propagation of tensile wing cracks and anti-wing cracks from a pre-existing open flaw under compression

Abstract

Various crack types have been reported to initiate from a pre-existing flaw in rocks under compression. In addition to the most commonly observed tensile wing cracks, anti-wing cracks propagating in an opposite direction to that of the tensile wing cracks are also observed in the field and in the laboratory testing. Although a substantial portion of the anti-wing crack path was observed to be associated with tensile cracking, signs of shearing such as the production of shearing dust were identified adjacent to the flaw tip in experimental studies. The objective of this paper is to numerically study the cracking processes involved in the anti-wing crack formation and compare it with those in the tensile wing crack formation. The numerical analysis was performed by a dynamic analysis software by incorporating the static damping technique to achieve a quasi-static loading condition. The numerical study revealed that for the anti-wing crack, the initiated crack segment adjacent to the flaw tip is "shear" in nature, while the remaining segment is "tensile" in nature. © 2012 Taylor & Francis Group, London.