2/15/2023 0 Comments E book mekanika batuanIn many countries mines are now required to file closure plans and post bonds for decommissioning. Updated aids to application of the guidelines are presented for applying the mining Scaled Span concept for determining both mine opening and civil tunnel cover thicknesses of variable quality. This paper presents an updated methodology and a new chart developed through use of logistic regression techniques aimed at improving the ease of application of the Scaled Span method of Surface Crown Pillar dimensioning for assessing collapse risk. The fact that problems from collapses of near-surface workings have plagued mining operations for years led to the development nearly 20 years ago of the Scaled Span empirical design guidelines for crown pillar rock thickness dimensioning. The difficulties of predicting behaviour and of correctly dimensioning crowns is borne out by the fact that in recent years there have been a number of highly publicized near-surface mine working cave-ins and urban tunnel collapses, with breakthroughs to surface that have in several cases seriously damaged surface infrastructure. Assessing collapse risk for any near surface mine opening or for a civil tunnel is challenging, while defining an appropriate minimum rock cover thickness that should be left above the crown is a particularly difficult design task.
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