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UBC Theses and Dissertations

Span design for entry-type excavations Lang, Brennan Davis Allan


Underground entry-type excavations require higher factors of safety than do non-entry excavations yet not as high as those required for permanent underground structures. A review is made of underground excavation span design techniques and the conditions under which they can be applied. Shortcomings of these existing methods, as they are applied to cut and fill stopes and other entry-type excavations, are highlighted. A design procedure specific to conditions found in entry-type mining is proposed. At the centre of the procedure is an empirical span design chart, called the “Stability Graph for Entry-Type Excavations”, which provides a practical tool for mining engineers to design stable entry-type excavations. The development of this chart and its use as a design tool is a result of the statistical analysis of 172 stoping case histories collected at a large underground gold mine in northern Ontario, The influence of artificial support in maintaining stability and increasing span is investigated. A report is given of a trial support program carried out at the same operation using a concentrated pattern of cable bolts to replace a post pillar in order to increase span.

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