Mine planning is one of the most crucial stages at the beginning of each mining project, laying the foundation for the successful, cost-effective, economical, and safe operation of the mine. It is an overly complex procedure, including many steps and the consideration of various aspects from different disciplines as the mineral resource, legal frameworks, environmental considera-tions, available and required infrastructure, processing of ore, geotechnical restrictions and much more. Consequently, the application of suitable modelling and design methods and tools and the careful consideration of the needed input parameters is required to perform mine-planning procedures effectively and efficiently.
This thesis, which took place as part of a technical study by DMT Consulting GmbH, investigates the mine planning process of the life of mine plan of an open pit gold project consisting of the Diga and Duba deposits in Ethiopia. Covering a large part of the long-term mine planning cycle, the planning and modelling procedures performed within this study comprises three main steps, mine optimization, design, and production scheduling.
Starting with the determination of economically optimized pit limits using GEOVIA Whittle™ pit optimization software, ultimate pits and pushbacks were derived and sequenced. The optimized pit shells and interim pushbacks were used to develop detailed pit designs. GEOVIA Surpac™ 3D mine modelling software was used to determine the best lay-out of the mine, including de-signing and dimensioning of access ways and developments. Different practical pit design scenarios were evaluated for the project considering variations options of ore access and ramp designs.
Long-term production schedules were produced using HxGN MinePlan Schedule Optimizer based on results derived from the designed pushbacks and the corresponding mining se-quence. The resources from both pits were allocated to activities for material extraction over time to achieve production targets. From the selected final pit designs, different production scheduling scenarios were evaluated based on the project's aim to maximize project value.
The long-term production schedule estimates, that 345.6 kt of ore with an average gold grade of 8.67 g/t Au is expected to be mined and processed over 33 months. The production schedule has been developed allowing for simultaneous operations from the Duba and Diga pits with the strategy to maximize the project value. Financial modelling of the Project NPV at a 5% dis-count rate is estimated to be MUSD$73.2, with a payback period of 12 months.
The short-term nature of the operations and the strategic importance of developing and exploiting Duba and Diga deposits can unlock further resource development options.