ABSTRACT: The empirical scaled span approach for assessing surface crown pillar stability has been in use for over a decade. In this time it has been widely applied for dimensioning new pillars and for assessing the stability of old, often abandoned crowns. Based on updated knowledge of the behaviour of some of the case records, this paper re-evaluates and updates the original database compiled in 1989/1990 and re-examines the basic mechanisms considered of relevance to the development of the Scaled Span concept. On the basis of observations for some of the case records on the time from original excavation to failure, some suggestions are given on application of the scaled span concept for assessing pillar longevity.

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