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Determination Of Optimal Stope Strike Length On Steep Orebodies Through Laser Scanning At Lubambe Copper Zambia
[Full Text]
AUTHOR(S)
Kalume H, Chileshe P R K
KEYWORDS
Geotechnical investigation; Optimal Stope length; Steep Orebody; rock mass; time dependant deformation
ABSTRACT
Lubambe Copper Mine is located in Chililabombwe, Zambia, and is a joint copper mining venture with three partners that include African Rainbow Minerals (40%), Vale (40%) and the Government of Zambia (20%). The current mining method utilises Longitudinal Room and Pillar Mining (LRP) on 70m long panels strike length. However, these long panels have resulted in unprecedented levels of dilution mainly from the collapse of hanging wall laminated ore shale (OS2) leading to reduced recoveries. Observations made underground show high variability in geological and geotechnical conditions of the rock mass with factors such as weathering on joints, lamina spaced joints and stress changes induced by mining all contributing to weakening and early collapse of the hanging wall. Therefore a study was undertaken to establish the optimal stope strike length of steep ore bodies at Lubambe. The exercise involved the use of Faro Laser Scanner every four stope rings blasted, with time when the scan was performed noted. The spatial coherence of lasers makes them ideal measuring tools in situations where measurements need to be taken in inaccessible areas. Recent advances in laser scanning coupled with the exponential increase in processing power have greatly improved the methods used to estimate stope tonnages extracted from massive inaccessible stopes. The collected data was then used to construct digital three dimensional models of the stope contents. Sections were cut every metre with deformations taken and analysed with respect to time. Deformation rates from the hanging wall was reducing from 0.14t/hr to 0.07t/hr between rings 1 to 8. This reduction was as a result of slot blasting that involved drilling and blasting a number of holes at the same time. Between rings 8 to 25 deformation was constant averaging 0.28t/hr and between rings 26 and 28, a sharp increase in deformation rate was experienced from as low as 0.16t/hr to 6.33t/hr. This sharp increase defines the optimal stope length as 50 m beyond which there is excessive levels of dilution mainly from the hanging wall.
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