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UBC Theses and Dissertations

Empirical stope design at the Ruttan Mine, Sherritt Gordon Mines Ltd. Pakalnis, Rimas Thomas


This thesis evaluates the factors that influence the stability of large, open stopes for an existing mining operation. The Ruttan mine, a 6000 tpd base metal operation has mined by open stoping methods since 1979. This has resulted in a large data base of information which includes forty-three (43) stopes at various stages of extraction, thereby yielding 133 observations of: Rock Mass Rating (footwall, hanging wall, ore) Stope Dimensions (height, width, length) Observed Dilution Excavation Rates Stope Configuration (isolated, rib, echelon) Mining Sequence/Method In addition, the observations were supplemented with in-situ measurements, structural mapping, stress and deformation monitoring and historical observation. It was concluded through numerical modelling, observation and measurement that the hanging wall and footwall of the individual stopes are in a state of relaxation, thereby enabling structural blocks to be released. This would generally be the case for most stope geometries whose major in-situ stress direction lies perpendicular to the long dimension of the opening. Consequently the critical parameters were quantified in terms of their effect on dilution by employing multivariate analysis. The relationships derived were entirely confined to the Ruttan operation as they were empirically delineated and quantified. The Ruttan operation is a multi-lensed ocebody with individual stopes dipping at 70°. The following empirically derived relationships were found to correlate strongly with the observed dilution: [See Thesis for Diagrams] where: DIL(%) - refers to predicted stope dilution (tons waste/tons reserves) RMR(%) - Rock Mass Rating of the critical wall contact, generally the hanging wall Exp. Rate('1000m²/mth) - refers to the rate at which the hanging wall is exposed (excavation rate/stope width) Area(m²) - refers to the exposed surface area of the hanging wall r , s – Refers to the correlation coefficient and the unbiased standard error of estimate respectively. The empirical relationships were related to stopes mined subsequent to the study and yielded errors of estimate (ŝ) of predicted dilution to within 2 - 4% of the observed dilution. The blast induced dilution was subsequently added to the predicted dilution. This value is difficult to estimate and is presently recorded as the dilution that is observed as the slot (initial cut) is being excavated. The design equations were based on a relatively large data base, considering, that the works of Bieniawski (1973) and Barton (1974) were based on 49 and 200 case histories respectively. It is suggested that the empirical methods of design outlined in this thesis be attempted at other operations where structural failure is the main factor contributing to stope dilution. This would augment the data base and extend its applicability. Parameters unique to Ruttan that were employed in establishing the data base are as follows: hanging wall and footwall of all stopes are In relaxation groundwater is not a factor mean stope inclination = 68° ± 9° mean stope dilution = 10% ± 6% mean RMR = 56% ± 20% mean exposure rate = 0 . 18m² ± .09m² (x 1000)/mth mean excavation rate = 2700m³ ± 1300m³/mth mean span = 31m ± 13m mean stope width = 15m ± 8m mean stope height = 68m ± 20m mean exposed surface area = 2250m² ± 1120m² mean stope depth = 360m ± 48m below surface mean blast correction factor = 3% ± 6%

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