THE PROJECT
The Murrawombie Open Pit Mine, historically known as Girilambone Mine, is in the central west of NSW and 2 km west of the town of Girilambone. Mining of oxide and transitional copper ore in the 1990s produced an open-cut pit approximately 150 m deep. The resource is a massive sulphide deposit with existing pit walls comprising meta-sediments which are highly foliated and structurally complex.
PSM was engaged to complete a feasibility stage geotechnical study to provide pit slope design parameters for the proposed cut-back of existing pit walls.
ENGINEERING AND TECHNICAL OPPORTUNITIES
The resource is a massive sulphide deposit with existing pit walls comprising meta-sediments which are highly foliated and structurally complex. Low-grade metamorphic sequences comprised highly foliated silicified meta-sediments. There was also restricted access to pit walls for collection of relevant geotechnical data.
APPROACH AND INNOVATION
PSM’s tailored approach included:
- Completion of feasibility studies for a cut-back affecting three of the existing pit walls and deepening the pit by about 70 m, using performance of existing pit walls and results of stability analyses
- Provision of reliable pit wall structural orientation data using photogrammetry
- Assessment of rock characteristics using in-pit geotechnical mapping
- Development of the geotechnical model, using existing data, photogrammetry and in-pit mapping results
- Assessment of slope stability of the proposed cut-back walls using kinematic and statistical methods, and numerical modelling using limit equilibrium methods.
OUTCOMES
PSM successfully completed feasibility studies, identified design risks and provided mitigation strategies.
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