ABSTRACT
In fractured rock masses, the mechanical behavior is strongly dependent on the discontinuities. In order to understand the structural stability of jointed rock mass, it is necessary to study of the behavior of rock discontinuities under different loading conditions. The mechanical behavior of rock discontinuities is commonly studied in the laboratory using a direct shear apparatus. Many studies have been performed on artificial joints with saw-tooth (Crawford & Curran 1981, Huang et al. 1993, Homand et al. 2001, Lee et al. 2001, Biran et al. 2009) or on mortar replicas (Bandis et al. 1981, Jing et al. 1993, Gentier et al. 2000). Some authors have performed shear tests on natural rock joints (Huang et al. 1993, Armand et al. 1998). Huang et al. (1993) found that the natural rock joints showed some different characteristics as compared the artificial joints under cyclic loading.
