Modeling of shallow rock slope failures has been undertaken to explore the validity of two commonly used failure criteria for discontinuities. The Mohr-Coulomb (MC) and the Barton-Bandis (BB) joint shear strength models have been examined. The 2-D Universal Distinct Element Code (UDEC) version 4.0 has been used to model a rock slope failure in a slate quarry which involves sliding and toppling types of failure. The results have shown that the BB joint model gave larger slope deformations than those indicated by the MC model. The modeled non-linear behavior of BB allowed for creating more space so that the blocks can rotate, promoting instability. The comparison of frictional strength parameters for the critical discontinuity shows that there is an inherent degree of conservatism associated with extracting values of friction from either shear testing or the technical literature which is likely to be related to the scale effects on the discontinuity and additional strength being mobilized from rock bridges. Further research is still ongoing to confirm the applicability of the observations made.


Traditional models of discontinuity shear strength have often provided different estimates of shear strength based on variations in input parameters. Two of the most commonly used failure criteria are the Mohr-Coulomb (MC) and Barton-Bandis (BB) models. In an attempt to obtain a clearer understanding of when different criteria may be used most effectively, the shear resistance mobilized at the onset of deformation in a rock slope has been compared with the estimates of strength using MC and BB failure criteria. This was done using a Discrete Element Method for the rock slope in question. Modeling in rock slope engineering has changed dramatically in recent years. The focus has moved from simple 2D plane strain limit-equilibrium models and kinematic assessments, to numerical and computational models.

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