Quantifying the Effect of Hanging Wall Undercutting on Stope Dilution

CIM Vancouver 2002
Doug Milne, Mike Yao, Gary Allen,
Abstract Unplanned open stope dilution is a major cost factor for many mining operations, even though significant advances in empirical and analytical approaches for estimating stope dilution have been made. Many factors that influence hanging wall dilution are still either ignored or assessed in purely subjective terms.

Undercutting the stope hanging wall on both the overcut and undercut development are well recognized factors which contribute to hanging wall instability and dilution. In many mines, undercutting the hanging wall breaks the integrity of the rock mass that may form along continuous foliation or bedding planes parallel to the stope hanging wall contact, reducing stability. This undercutting also increases the zone of destressed or relaxed rock that may potentially fall into the open stope as dilution. An approach is introduced for quantifying the effect of undercutting on potential stope dilution. Example case histories showing the influence of undercutting on resulting dilution are presented from an extensive database of stoping and dilution information from Hudson Bay Mining and Smelting operations (HBMS) in Flin Flon. Computer modelling results are also presented which show the influence of undercutting on the zone of rock in a relaxed or destressed state.
Keywords: Stope Dilution, Numerical modelling, Hanging Wall Undercutting, Database Analysis
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