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

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 (figure 1) and in the laboratory testing (Wong and Einstein, 2006, 2009) (figure 2). 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. 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. In the present study, numerical analysis was performed by a dynamic analysis software by incorporating the static damping technique to achieve a quasi-static loading condition. The numerical tool was then used to model the crack initiation and