Structural analysis and modelling in an evolving mineral resources operation

Authors: Shahin, S; Jani, A; Arrys, N Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2535_26

Cite As:
Shahin, S, Jani, A & Arrys, N 2025, 'Structural analysis and modelling in an evolving mineral resources operation', in JJ Potter & J Wesseloo (eds), SSIM 2025: Fourth International Slope Stability in Mining Conference, Australian Centre for Geomechanics, Perth, https://doi.org/10.36487/ACG_repo/2535_26



Abstract:
Optimising pit slope stability and reducing the strip ratio of a mining operation are two key tasks in geotechnical engineering. With a growing demand for minerals and an increasing cost associated with extraction, companies are constantly re-evaluating the viability of mineral deposits and challenging their geological understanding. Within Rio Tinto Iron Ore, the structural geology (SG) team investigate and collect critical data, such as pointbased orientations, mapping and geological inferences from adjacent pits to re-model deposits where previous interpretations have failed to account for structurally controlled slope failures. Utilising innovative data collection methods and data-driven investigation, SG aims to address the root causes of slope instability and the opportunity for improved mineral mining. Resource drilling evaluation is often the majority source of data in bulk commodity extractions and will often bias data collection to a specific orientation with their vertical drilling orientation and regimented grid layout. This data bias can significantly reduce the capability to identify and qualify complexity, hence limiting confidence and reliability of the structural model which geotechnical design and decisions are built upon. Without the consideration of complexity and the capability of capturing the appropriate nature of geotechnical design domains, mining operations run the risk of inadequately designed slopes that may fail and potentially harm personnel. Regional structural trends have been considered in conjunction with surface and in-pit mapping data to model multi-batter fold structures that were absent from previous iterations of the structural model. The structural model update is a 3D compilation of the upper Marra Mamba stratigraphy partitioned into six sub members and the detrital/bedrock contact spanning a model volume of ~6.25 × 2.50 × 3.80 km (length, width, breadth). Modelled stratigraphy in the Marra Mamba subunits are often defined by shale bands or packages amongst banded iron formation (BIF) units that are the target mineralised ore. A rheological contrast between the BIF and shale in the stratigraphy denotes potential anisotropic surfaces that are of concern in geotechnical design. The latest iteration of the structural model aims to address the issues of historical slope instability along planes of anisotropy and linking observed structures in the pit with the Pilbara regions deformational history. Critical risks and opportunities have been identified in newly identified dip-slope and rock mass controlled sectors of the geotechnical design rather than a ubiquitous dip-slope sector across the previously adopted pit design. Such improvements forecast a reduced cost to operation and improved extraction of ore at depth.

Keywords: structural geology, geotechnical design, optimisation, slope stability, risk mitigation

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