This study aims at identifying the failure tendencies of rocks in relation with crack growth. Therefore, several disc shaped specimens with (H/D) ratio of 0.5 were prepared from various rocks. First, notches of four different lengths were sawn on the specimens. Then, a single notch was formed in each specimen, which was tested as the load was applied up to failure level. The results yielded a linear relation-ship between the failure load and corresponding crack lengths. It was concluded that the slope values (m) of the lines be related to the failure tendencies and crack propagation velocities of rocks. Finally, statistical relationships were established between the slope values of the relationship lines and certain rock properties.
For a comprehensive understanding of mechanical rock breakage in mechanical excavation an effective understanding of crack propagation is essential. Many researchers have investigated the behaviour of crack propagation in various materials such as rocks [Labuz et al. (1985), Kranz (1983), Nara et al. (2006), Nara and Kaneko (2006), In-Bog Park (2004), Dyskin (1993), Li and Moelle (1992 and 1993), Cook et al. (1984), Suzuki et al. (1998), Szczepanik et al. (2003)], concrete [Pardikaris and Calomino (1987), Sain and Chandra (2008), Xu and Zhang (2008), Unger (2007), Yang and Chen (2005)], glass [Denoyer and Pollack (1963), Chai (2006), Cannillov et al. (2006)], ceramics [Evans and Fuller (1974), Evans (1980), Olagnon et al. (2006)] and metals [Dlouhy and Strnadel (2008), Liang et al. (2008), Baglin (2007), Ishihara and McEvily (2002)]. Alan Griffith (1921) theorized the fail-ure of brittle materials. They have investigated the crack growth in granite. When the stresses in this region exceed the strain, crack development begins. In the investigation of crack de-velopment, crack-crack and crack-pore interactions and the relations were studied for different rocks [Kranz (1979)].