This study proposes a rational process that can be used by the mining engineer to control rockfall by the design of catch bench geometry in surface mines. The problem of rockfall in surface mines is defined and factors causing rockfall are identified. Four civil engineering models that predict rockfall motion are presented and compared to rockfall field tests from eight different test sites. Based on these results, a computer program was written that combines aspects of the two best models. The Ritchie empirical model provides the most conservative result of catch bench width and berm height necessary to contain rockfall on mine slopes. The Colorado Rockfall Simulation Program is used to check the reliability of the design and to permit selection of the minimum catch bench geometry to insure both mine safety and the most economic slope angles.

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.