ABSTRACT: Observations of brittle failure at the laboratory scale indicate that the brittle failure process involves the initiation, growth and accumulation of micro-cracks. Around underground openings observations have revealed that brittle failure is mainly a process of progressive slabbing resulting in a new stable geometry that in most cases is a V-shaped notch. Continuum models with traditional failure criteria, (Hoek-Brown or Mohr-Coulomb) based on the simultaneous mobilization of cohesion and friction, have not been successful in predicting the extent and depth of brittle failure. This has lead to a variety of continuum and discontinuum modeling approaches, with varying degrees of success. A brittle cohesion-friction model is introduced that demonstrates that continuum models can be used to simulate brittle failure provided a constitutive model is utilized that captures an essential component of brittle failure: cohesion weakening and frictional hardening as a function of plastic strain.

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