Fracturing behavior of inclined cracks under Static and Cyclic Loading

This study presents the results of laboratory diametrical compression tests performed on Brisbane tuff disc specimens to investigate their mixed mode fracturing response to static and cyclic loading. Both the static and cyclic loading tests were carried out on Cracked Chevron Notched Brazilian Disc (CCNBD) rock specimens. Static diametrical compression resulted in the opening of the notch cracks at the centre of the specimens (Mode I), up to a 30° crack inclination angle (β), whereas crack closure (Mode II) was observed for β > 33°, with closure becoming more pronounced at the higher crack inclination angles of 45° and 60°. A second series of diametral compression testing with increasing cyclic loading amplitude showed that the failure load decreased between 30% and 45% compared with that under static loading. Comparison of the load–CMOD (crack mouth opening displacement) plots of monotonically and cyclically loaded CCNBD specimens showed that the 45° and 60° chevron notch cracks started to open from the beginning of the cyclic loading test, while under static loading they closed. This outcome is a very important finding for examining rock fatigue damage mechanisms