Netshivhazwaulu, Nyandano2023-04-112023-04-112022https://hdl.handle.net/10539/34968A research report submitted in partial fulfilment of the requirements for the degree of Master of Science in Engineering to the Faculty of Engineering and the Built Environment, School of Mining Engineering, University of the Witwatersrand, Johannesburg, 2022Geotechnical engineering occurs in natural geological material that cannot be modified and is often not fully understood or known. Variability within the geological rock mass introduces uncertainty in slope designs that can never be eliminated but must be understood. Various geotechnical investigations are conducted to define rock mass properties which assist geotechnical engineers in understanding the level of variability within the rock mass. Investigations allow for uncertainty to be minimised during the design of rock slopes. However, mining organisations are often unwilling to fund geotechnical investigation programs because it is considered wasting resources. However, rock engineering design principles require uncertainty to be minimised during the design definition before design execution. Middelburg Mine Services is a large open-cast coal operation that comprises multiple pits located within the Witbank coalfields. The mine had previously experienced various slope failures and related rock falls, which led to injury, damage to property and production losses. Investigations into slope failures revealed that, although detailed geotechnical models form the basis for slope design and slope stability analysis, design within Middelburg Mine Services was not based on such models. As a result, the design and stability analysis processes are often highly dependent on local experience and rules of thumb. A new pit, the KE project, was used as a case study to determine whether conducting geotechnical investigations improves slope design and stability analysis processes. After collecting geotechnical data, the study entailed implementing kinematic, limit equilibrium and numerical modelling stability analysis methods. The probability of failure from stability analysis forms a basis for the design risk assessment. A risk-based design demonstrated that the original KE design was very conservative and that the subsequent optimised design is within the acceptable safety and economic evaluation criteria. In addition, this case study demonstrated that value is created by conducting geotechnical investigations, allowing for a risk-based design for highwall and low wall slopes.This value created was translated to a significant cost-saving and improved productivity.enDissertation