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Abstract An important question which arises during numerical analysis of mining is the residual strength of the rock mass since it significantly affects the stress-carrying capability of yielded ground and the potential for stress-shedding to more competent ground. There are few guidelines for estimation of the residual strength of rock masses. In many ways a rock mass that has yielded and subsequently bulked a significant amount acts similar to rockfill. Although rockfill shear strength is controlled more by fragment shape, fragment strength and porosity of the assembly than by the shear strength of discontinuities, it is possible to draw analogies between these two behaviors. For example, a bulked assembly of rock fragments and an individual rock joint have several common characteristics when subject to shear, including a transition from dilative behavior (with minimal fragment or asperity damage) at low normal stress to extensive crushing of contact points at high normal stress. These results in high instantaneous friction angles at low levels of confinement and a curved peak shear strength envelope for both rock masses and rockfills. In this paper the Barton and Kj?rnsli [1] model for predicting rockfill shear strength is explored as a criterion for estimating the residual strength of rock masses at both low and high strains (i.e. immediately post-peak and after a significant amount of shearing). The proposed model is tested through analysis of simple slope and pillar models.
- North America > United States (0.94)
- North America > Canada > Ontario > Toronto (0.28)
Abstract Stability of large room-and-pillar panels, which is a function of mechanical response of typically large number of pillars and deformation of the overburden on the scale of the entire panel, could be a challenging problem to analyze because it requires consideration of deformation and damage of rock mass occurring at different length scales. Panel stability is a function of response of both pillars and the overburden, and when the room-and-pillar panels collapse very often it is not clear if it is a consequence of pillar or overburden failure. Two-scale analysis approach is presented here. Pillars are analyzed first in a pillar-scale model with necessary discretization to represent stress-strain concentrations and high-strain gradients. The derived pillar stress-strain curves then are used in the panel-scale analysis of deformation and stress redistribution over the panel, in which the pillars are represented in an average sense (on the level of tributary area). The methodology for approximation of pillar response and calculation of pillar average properties is presented in the paper. Further, the "ground-reaction curve" approach is proposed for stability assessment of room-and-pillar panels.
- Geology > Geological Subdiscipline > Geomechanics (0.96)
- Geology > Rock Type (0.70)