INFLUENCE OF STRENGTH PARAMETERS ON OVERALL DEFORMATIONS OF ROCK SPECIMENS WITH INITIALLY RANDOM MATERIAL IMPERFECTIONS

For heterogeneous rock specimen with smooth ends and initially random material imperfections in uniaxial plane strain compression, the effects of initial cohesion and internal friction angle on the overall deformational characteristics (such as the axial, lateral and volumetric strains as well as the calculated Poisson's ratios) are modeled using FLAC. A few written FISH functions are used to set the random imperfections and to calculate the overall deformational characteristics. For intact rock, the failure criterion is a combined Mohr-Coulomb criterion with tension cut-off, exhibiting linear strain-softening and then ideal plastic behavior beyond the occurrence of failure. Imperfection undergoes ideal plastic behavior beyond the occurrence of failure. As strength parameters (such as initial cohesion and internal friction angle) increase, the peak stress and related lateral strain increase, and the peak volumetric strain increases also, and the calculated Poisson's ratio corresponding to the peak stress increases slightly. At post-deformational stage, the volume of the specimen can dilate although the dilation angle is zero, as is in agreement with the analytical solution proposed by Wang (2006). This is attributable to the relative sliding between adjacent rock blocks separated by shear zones. With lower strength parameters, the nonlinear pre-peak portions of lateral strain-axial strain curve, volumetric strain-axial strain curve and calculated Poisson's ratio-axial strain curve become shorter. The numerically predicted upper bound of shear band inclination is lower than that predicted by Coulomb theory, and the lower bound approaches that predicted by Roscoe theory. The predicted results by Arthur theory are closer to the present numerical shear band inclination.