V. Levkovitch, F. Reusch, Beck Engineering, Germany
D. Beck, Beck Engineering, Sydney, Australia
The Mohr failure envelope for rock materials is a convex curve strongly dependent on the level of confinement and truncated at low normal stresses. The most commonly applied failure criterion – the Mohr-Coulomb criterion – matches the observed failure envelope poorly. Using this criterion it is not possible to accurately describe rock failure over the whole range of expected confinement conditions for many prob-lems and instead the engineer must choose parameters that will be applicable over only a limited range of confining stress. Accordingly, to achieve satisfactory results in a numerical simulation where operating condi-tions are ranging from open pit to deep underground a more realistic non linear failure criterion and plastic strain potential are required. In this paper we will focus on the application of a modified Menétrey and Willam constitutive model, utilising a smooth approximation of the Hoek-Brown failure criterion, to better account for the effects of varying confinement on the yield potential and the relationship between stress and strain.
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