Distinct element modeling of strength variation in jointed rock masses under uniaxial compression

Rock masses exhibit strong anisotropy due to the structure of fracture networks embedded within the mass. We use a particulate discrete element method to quantitatively investigate the effect of spacing and inclination angle of the joints on anisotropic strength under uniaxial compression. In all of the numerical models, the intact rock masses are represented by the bonded particle model, and the joint planes are simulated by the smooth-joint model. Observations are made of the evolving stress-strain curves relative to the distribution and orientation of micro fractures. Apparent from this is that: (1) for the same fracture spacing, the strength and deformation parameters of jointed rock masses change in a U shaped curve when plotted against an increase in the inclination angle of the joints. The maximum value occurs at the inclination angles of 0 degrees and 90 degrees, and the minimum value occurs at an inclination angle of 40 degrees or 50 degrees; (2) for the same joint spacing, the failure mode of the jointed rock mass with different joint inclinations can be classified into three categories: splitting tensile failure, shear sliding failure along the joint surface and mixed failure of the two modes above; (3) for the same joint inclination angle, the normalized compressive strength and normalized elastic modulus both increase with an increase of the normalized joint plane layer spacing.