Management of the Nkomati Mine crusher slope failure
R Armstrong, K Moletsane
Due to limited available level ground, Nkomati Nickel Mine cut a weathered
rock slope at the base of a mountain spur in order to create a platform for
construction of the primary crusher plant and run-of-mine stockpiles. As
space is limited around the mining area, ore processing at Nkomati is based
on a high reliability of flow of material through the crusher plant, with
minimal usage of other and larger designed stockpiles. Evidently, any
crusher plant shutdown will render the mine as a whole unproductive and
put excessive strain on the medium- to long-term large ore stockpiles, the
deposition rates for which are restricted by founding material consolidation
requirements.
At the onset of the 2012 rainy season, movement was identified on the
slope monitoring system and cracks developed on the slope. After a minor
failure on the crusher slope an assessment of the slope stability was
conducted and a slope management plan recommended, which included
deployment of real-time monitoring. An evaluation of the conditions
leading to instability was conducted and the likely causes for the failure
identified. A full evaluation of the slope monitoring, rainfall, and mining
conditions was undertaken and movement triggers were determined. This
paper describes the events leading to the development of the failure and
the evaluation of the monitoring data to determine a management plan for
the failure that allowed for minimal shutdowns of the primary crusher.
Keywords: slope stability, slope management, slope monitoring.