Abstract:For rock specimen with smooth ends and with initially random material imperfections, the effects of dilation angle (DA) on the failure process and stress—strain curve were numerically modeled using FLAC in uniaxial plane strain compression. Using a written FISH function, the initial imperfections within the specimen were prescribed. For intact rock exhibiting linear strain-softening behavior beyond the occurrence of failure and then ideal plastic behavior, the failure criterion is a composite Mohr-Coulomb criterion with tension cut-off. Initial imperfection undergoes ideal plastic behavior beyond the occurrence of failure. Rock specimen with higher DA is subjected to severe failure in the final deformation stage. Wider and steeper shear bands are observed at higher DA. The effects of DA on the stress—axial strain curve can be neglected. Less steep stress—lateral strain curve at post-peak is expected at higher DA since the contribution of the increase in shear band width to lateral strain exceeds the contribution of the increase in shear band inclination according to an analytical expression proposed by Wang and coworkers. Higher DA leads to higher value of maximum shear strain increment within the specimen. Therefore, more apparent precursor to failure can be observed at higher DA. Shear band inclination is closer to Arthur theory and is lower than Coulomb theory. Higher DA results in higher values of shear strain and volumetric strain in shear band.

Key words: heterogeneity; material imperfections; dilation angle; shear band; axial strain; lateral strain; precursor