MULTIPLE ENTRY PILLAR STABILITY ASSESSMENT USING THE LIMIT EQUILIBRIUM METHOD

The paper introduces the basic concepts of coal pillar behaviour in re lation to pillar geometry and covet load with an emphasis on pillars i n deep UK coal mining conditions. Results from three dimensional physi cal models m e presented to illustrate the three zones within a heavil y loaded pillar proposed by Barron. A limit equilibrium model, based u pon Barren's principles but including a number of important modificati ons, is described. A Windows-based computer package, based upon the mo del, is developed capable of dealing with multiple openings in square, rectangular and rib pillar combinations with a longwall abutment alon g one side. Load transfer from failing pillars to adjacent pillars is automatically taken into account. The degree of confinement within the pillar can also be adjusted to simulate the reinforcing effect of bol ting. The model classifies the pillar into solid elastic, yielded (pse udo-ductile) and fracture zones. Results from the model ar e compared and reviewed in the context of other recognized techniques and UK deep mining conditions.