Equivalent Properties Approach to Jointed Viscoplastic Rock Slopes

ABSTRACT: An equivalent properties approach to time-dependent behavior of jointed rock masses is applied to the important problem of mine slope stability. A non-representative volume element (NRVE) approximation accounts for joints without explicit representation and makes the analyses possible. Small elements that contain only a few joints or none at all are allowed in the NRVE approach, so mesh gradation can be made adequate in regions of high stress concentration. Two-dimensional simulations of open pit mining sequences result in rounded, stair-step curves that are qualitatively similar to those observed in many open pit mines. When an excavation step results in a diminishing rate of displacement, numerical stability is achieved that is also indicative of physical stability. Comparisons with elastic-plastic analysis are made and the question of whether viscoplasticity is simply delayed plasticity is addressed relative to the extent of yielding, stress distribution and displacements.