Strength and dilation of jointed granite specimens in servo-controlled triaxial tests

Abstract

We investigated the complete stress–strain response of artificially jointed granitic rock specimens with two joint sets. A series of confined compressive tests on these jointed rock specimens were performed in a fully servo-controlled press. Elastic, strength and post-failure parameters were calculated and analysed, with special attention paid to the dilation angle. The results were compared to those for corresponding intact specimens investigated in a previous study. Although the peak strength of the jointed cores was much lower than that for the intact cores, the residual strength envelopes were practically equal. The apparent elastic and drop moduli tended to be lower for jointed specimens than that for intact specimens. At low confining stress levels, the jointed rock tended to dilate less than the intact rock, but at higher confinement dilation behaviour converged. Another finding with respect to post-yield behaviour was that the dilation angle of the jointed specimens could adequately be represented by an existing plastic-shear–strain and confinement-dependent model developed for intact specimens.