Abstract:
Anglo American Platinum’s Khomanani 2 shaft changed over from
down-dip mining to breast mining in 2004. The changeover was
made to ensure that production targets were met, as it was said that
predevelopment for down-dip mining was not fast enough to
sustain the required ore reserves; nevertheless, production
performance did not increase as expected. In this study a trade-off
was performed between down-dip mining and breast mining on the
Merensky Reef at Khomanani 2 in order to find the most suitable
method for mining the Merensky Reef. Data was gathered by means
of a literature survey, underground observations, and interviews
with personnel as well as data from various departments on the
mine. The two mining methods were studied and then evaluated in
terms of the following criteria: safety, mining rate, cost and other
factors which were identified as the main drivers of the mine. A
scaling system was used to rate the performance of the two mining
methods. Analysis of the results shows that down-dip mining and
breast mining have the same safety performance ratings. Breast
mining has a better mining rate performance than down-dip mining.
Breast mining was found to be costly in comparison with down-dip
mining, which has a good cost performance rating. The overall
ratings of the two mining methods are very similar, with down-dip
mining achieving a rating of 76 and breast mining 75.5 out of an
optimum 102. Khomanani 2 currently practices breast mining, and
with such a slight difference in performance rating between the two
methods, it will not be worth changing over to down-dip mining as
production is likely to be adversely affected during the changeover.
Down-dip mining does, however, have potential for improvement in
its performance rating. Further studies focusing on the improvement
of the mining rate performance for down-dip mining are needed to
see if this potential can be realized. If significant improvement can
be made in the performance rating for down-dip mining, a
changeover to down-dip mining can be reconsidered.
