Mixed-Mode Fracturing of Rocks Under Static and Cyclic Loading

Static diametrical compression tests conducted on inclined cracked chevron notched Brazilian disc (CCNBD) Brisbane tuff specimens showed that the notched cracks at the centre of the specimens opened (Mode I) up to 30A degrees crack inclination angle (beta), whereas crack closure (Mode II) started for beta > 33A degrees, and closure became more pronounced at even higher beta of 45A degrees and 70A degrees. Both the experimental and numerical results showed that the crack initiation angle (theta) was a function of the beta. Scanning electron microscope (SEM) images showed that fatigue damage on cyclic loading of Brisbane tuff is strongly influenced by the failure of the matrix due to both intergranular and transgranular fracturing.