| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 809534 | International Journal of Rock Mechanics and Mining Sciences | 2012 | 12 Pages |
This study presents the results of laboratory diametrical compression tests performed on Brisbane tuff disc specimens to investigate their mode-I fracture toughness response to static and cyclic loading, as a function of the applied load. Both the static and cyclic loading tests were carried out on Cracked Chevron Notched Brazilian Disc (CCNBD) rock specimens. Two different types of cyclic loading were applied: (a) cyclic loading with constant mean level and constant amplitude, termed sinusoidal cyclic loading and (b) cyclic loading with increasing mean level and constant amplitude, termed increasing cyclic loading. The fracture toughness response to cyclic loading was found to be different from that under static loading in terms of the ultimate load and the damage mechanisms in front of the chevron crack. A maximum reduction of the static fracture toughness (KIC) of 46% was obtained for the highest amplitude increasing cyclic loading test. Conversely, for sinusoidal cyclic loading, a maximum reduction of the static KIC of 29% was obtained. Detailed scanning electron microscope (SEM) examinations revealed that both loading methods cause fatigue in the CCNBD specimens. When compared with static rupture, the main difference with the cyclically loaded specimens was that intergranular cracks were formed due to particle breakage under cyclic loading, SEM images showed that fatigue damage in Brisbane tuff is strongly influenced by the failure of the matrix because of both intergranular fracturing and transgranular fracturing.
► An impressive reduction of fracture toughness of rocks due to rock fatigue was found. ► A reduction of static KIC of 46% was obtained for increasing cyclic loading test. ► For sinusoidal cyclic loading, a reduction of the static KIC of 29% was obtained. ► Damage mechanism of notch crack tested under cyclic loading was investigated. ► Rock fatigue damage was found result of grain decohesion and intergranular cracks.
