ABSTRACT
479Engineering structures in rocks are always subjected to triaxial or polyaxial stress fields. Analysis and design of these structures involves assessment of rock strength subject to the prevailing stress state. Mohr-Coulomb criterion is the most widely used strength criterion in rock engineering problems. However, in its conventional form, the criterion treats the strength behavior as linear function of confining pressure. Also, the effect of intermediate principal stress σ2, which is quite substantial in rock engineering problems, is ignored. The present article suggests modified forms of the Mohr-Coulomb criterion to incorporate non-linearity in triaxial strength behavior of intact isotropic, jointed anisotropic and intact anisotropic (transversely isotropic) rocks. Barton’s critical state concept for rocks has been employed to correctly define the shape of the strength criterion. The triaxial strength criterion is further extended to polyaxial stress conditions for intact isotropic and jointed anisotropic rocks. The applicability of the proposed MMC criteria has also been verified by applying them to database of experimental test results compiled from worldwide literature.
