Effect of structural discontinuities on coal pillar strength as a basis for improving safety in the design of coal pillar systems.

Abstract

The stability of underground coal mines depends on the integrity of the pillars which are required to support the overlying strata. Should the pillars collapse, the safety of the persons in the workings will be threatened. The strength of a coal pillar is affected by the strength of the coal material which forms the pillar. Coal contains many natural discontinuities which adversely affect its strength. Discontinuities are explicitly taken into account in the empirical methods of pillar design currently used in South Africa. As a result, pillars which are formed in coal with a high intensity of discontinuities may be under designed, while pillars in undisturbed coal may be over designed. This study sets out to investigate the effect of discontinuity on the strength of coal pillars.