Abstract
M.Ing. (Engineering Management)
The design of the optimum open pit slope angle is one of the major challenges
during open pit mine planning, as it implies attaining the ideal balance between
utilizing the maximum slope angle whilst achieving acceptable stability and safety
standards as indicated by the mine. The aim of open pit mines should thus be to
seek the steepest possible slope angle without compromising the safety of the
personnel, equipment or ore reserves, utilizing both stability analyses as well as risk
assessments. The typical open pit mine plan aims to achieve an acceptable balance
between operational risks and geotechnical design considerations by analysing
factors such as the slope stability design, the rock mass properties and existing
structural geological conditions. These factors are used as inputs towards an
optimum slope angle design which will be used in the final pit design and aims to
provide maximum economic viability to the mine.
The risk analysis methodology aims to improve traditional slope design methods and
is used to evaluate risks and failure consequences in terms of economic impacts.
The economic impact analysis is a useful method in comparing the performance of
various mine plans and slope designs. The risk analysis methodology thus provides
a valuable indication of optimum slope design configurations and as such can be a
great asset to the mine design process.
This research paper aims to identify the key risks used as input to an open-pit mine
plan in a feasibility stage and to define an approach to minimize these risks in order
to achieve maximum economic benefit. The effectiveness of this approach will be
evaluated by means of a case study which will attempt to achieve an optimum
balance between value and risk, and to compare the magnitude of the economic
impact of an individual risk with the probability of occurrence of said risk. The case
study will utilise a risk map in order to define years with higher economic impacts as
well as defining critical pit areas causing these risks, so as to identify areas requiring
further investigation which will assist the mine in evaluating mitigation strategies in
order to reduce overall risk.