In this study, proper design of coal pillar has ever remained a difficult and challenging task because of two conflicting objectives, namely the conservation of coal on one hand that requires coal pillars to be of minimum size and stability of pillars, and on the other hand that ensures safety of working. The complex loading conditions, the occurrence of seams in close succession and geological abnormalities present in seams make the design problems of coal even more complex and complicated. An attempt has been made in this paper to enlist and describe briefly factors affecting pillar strength and empirical strength equations/formulae developed by different researchers in different parts around the globe. Further, a comparative study has been made for a given set of geo-mining conditions to know the suitability of these equations in terms of their being either over-estimators or under-estimators.
Key words: Pillar strength, coal pillar design, pillar strength.
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