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Journal of the Southern African Institute of Mining and Metallurgy
versão On-line ISSN 2411-9717
versão impressa ISSN 2225-6253
Resumo
MATHEY, M. e VAN DER MERWE, J.N.. Critique of the South African squat coal pillar strength formula. J. S. Afr. Inst. Min. Metall. [online]. 2016, vol.116, n.3, pp.291-299. ISSN 2411-9717. http://dx.doi.org/10.17159/2411-9717/2016/v116n3a11.
The South African squat coal pillar strength formula, developed by researchers from the Chamber of Mines Research Organization in the 1980s, predicts an exponential increase in coal pillar strength once a critical width-to-height ratio of 5 is exceeded. The arguments that have been proposed in favour of this formula are discussed critically in this paper. Field experience with squat pillars in the USA and evidence from published physical, analytical, and numerical model pillar studies corroborate the fact that a squat effect is unlikely to occur in coal pillars at width-to-height ratios less than 10. Furthermore, an exponential increase in peak strength of coal pillars does not exist. An alternative design criterion for squat pillars in South Africa is therefore suggested.
Palavras-chave : squat pillars; coal pillar strength; bord-and-pillar mining.