Effect of dip on pillar strength

typically left between the openings (stopes) to maintain the stability of the openings. They are usually rib pillars (vertical or near vertical) or crown/sill pillars (horizontal and near horizontal). Pillars need to be adequately designed to avoid sudden failure and maintain stability, and not be over-designed, such that rock-related safety is maintained and extraction and profit are maximized. Depending on the nature of the orebody and the mining method, the pillars can vary in complexity. Flat-lying tabular orebodies generally use room-and-pillar or drift-and-fill mining operations, where the pillars are left for the macro-roof support and larger barrier pillars for regional support. When the orebody has a significant dip, rib pillars are frequently used for local support, with sill pillars to divide the orebody into multiple mining horizons. Crown pillars can be used to prevent collapse to surface, for example. This paper will deal mainly with the pillars that are used for local stope roof support. Pillar stability is essential for the efficient working of underground mining activities. Unless designed as yield pillars, underdesigning can result in failure of a pillar, and furthermore the failure of a pillar may trigger a domino effect, leading to instability of the whole excavation. Conversely, overdesigned pillars can result in sterilization of ore and may be uneconomical to mine.