Mining Of Orebodies under Shear Loading Part 2 -Failure Modes and Mechanisms

Abstract

Part 1 of the paper defined shear loaded orebodies and showed through case histories that bothpillars and excavations are at elevated risks of failure when mining these orebodies. Part 2 of thepaper presents new knowledge on the behaviour of pillars and excavations when mining suchorebodies. Numerical modelling is used to understand the behaviours of these structures in theorebodies. It is established that pillars in shear suffer confinement loss compared to theirequivalents under pure compression. The confinement loss increases with increasing shearloading in pillars with width : height (W : H)§1. For pillars with W : H §1, the Lunder andPakalnis (1997) empirical pillar design chart should be used with caution. For excavations ineccentrically loaded orebodies, passive and active high stress envelopes are created in theexcavation process. The combined effect of the active high stress and tension zones often resultsin excavation surface sloughing.