Structural complexity and slope design at the ArcelorMittal Mont-Wright mine

Authors: Chemali, L; Castro, L Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2535_28

Cite As:
Chemali, L & Castro, L 2025, 'Structural complexity and slope design at the ArcelorMittal Mont-Wright mine', 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_28



Abstract:
Large-scale geological structures and rock mass fabric exert significant kinematic controls for slopes excavated in hard rock masses. At the ArcelorMittal Mining Canada (AMMC) Mont-Wright mine, slopes are developed in a stratified, highly foliated orebody that has undergone tight folding due to at least two major orogenic events. The resulting shearing and faulting has led to significant variations in foliation orientation, both vertically and laterally, and often over short distances. Additionally, complexly folded lithological contacts, locally altered and overprinted by shears, result in variable rock mass conditions at these contacts. This structural complexity poses challenges in collecting representative structural data necessary to achieve an industry-standard geotechnical confidence level (GCL) for slope design. As some design sectors of this mine are currently approaching final pit wall phases, AMMC has implemented a long-term geotechnical investigation program to increase the GCL. This includes regional geological interpretation, wall mapping, drone surveys, drilling with core orientation and televiewer surveys to refine geological and development of structural models. These models define structural domains, assess data reliability and delineate the extent of data extrapolation. Additionally, the mine has developed a laboratory testing program to characterise materials at contact zones, allowing for classification based on shear strength. This information will be used to enhance the slope design of the final walls and implement robust risk assessment tools, such as stability analyses using discrete fracture network models to complement kinematic assessments. This paper discusses the challenges of defining structural domains along kilometre-scale pit walls. A case study is presented of a multi-bench instability event, where an unexpected fold altered the dip of a weak contact zone despite a high confidence level, highlighting the complexities of structural interpretation in slope design.

Keywords: kinematic, slope stability, structural domain, geotechnical confidence level, structural data investigation and interpretation, hard rock mining, foliated orebody

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