Southern Ridge is a cutback excavated into the slope of the original Mt Tom Price at Tom Price Iron Ore Mine. The mine is located on the outskirts of Tom Price town. The ore is contained within the Dales Gorge Member of the Hamersley Group, a unit widely regarded as a premium source of iron ore. Extension of the cutback proposed a final wall 400 m high, the highest for the Pilbara. The water table is about 70 m above the proposed pit floor.
PSM was engaged to prepare a slope design for the cutback, train staff in data collection methods and make depressurisation recommendations.
Due to the existing cutback configuration only one berm was accessible, albeit a wide one, for positioning the drill-rig for the investigation. This constrained the orientation that holes could be drilled.
Engineering and technical opportunities included:
Following a rigorous assessment and modelling, PSM’s tailored approach included:
Design of a cutback of this scale required detailed understanding of the relationships between strata, structure and rock mass and how these interact as potential failure mechanisms. PSM’s familiarity with the site assisted in developing a geotechnical model that accurately reflected the variability in rock mass conditions due to alteration resulting from large scale faulting. PSM’s extensive experience with Pilbara geology and large scale structurally controlled slopes contributed to recommendation of a robust slope design based on a combination of kinematic, limit equilibrium and finite element analysis.
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