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Paper Awarded Silver Medal by SAIMM

A recent paper entitled "A risk-based methodology to improve the definition of geotechnical sectors in slope design", published by the Southern African Institute of Mining and Metallurgy, has been awarded a Silver Medal.

These are awarded to articles that contribute significantly to the professions of mining and metallurgy and to the prestige of the SAIMM.

The contribution was lead-authored by Marnus Bester, Principal Geotechnical Engineer at Anglo American. Co-authors are Thomas Stacey at the University of the Witwatersrand, Ian Basson, Corné Koegelenberg and Pieter Creus of Tect Geological Consulting, and Loren Lorig and Alex Cabrera (formerly) of Itasca Consulting Group, Inc.

Abstract

In the planning of open pit mines, it is often difficult to determine the shapes and sizes of slope design sectors prior to their analysis, particularly in structurally complex geological environments. This problem is exacerbated in sectors encompassing significant strike changes of lithological units or contacts. This variability in strike is often poorly addressed/represented by applying median values or averages for key parameters, thereby increasing uncertainty and risk. The design process may be improved by the early identification of specific lithological units – of any shape or size – that show unfavourable interaction of geological features with slope geometries on future pushbacks or on final designs, utilizing inputs from apparent dip analysis and synthetic rock mass modelling. Focused data acquisition and more rigorous stability analysis in areas of concern will result in more robust and practical sector-specific design parameters, typically applied in block model format as inputs for mine design. A case study at Sishen mine, in the Northern Cape Province of South Africa, demonstrates that an ongoing, risk-based approach leads to a higher-confidence dynamic geotechnical model, thereby allowing for an integrated mine design process with the ultimate goal of achieving early risk mitigation and delivering optimized designs that unlock significant value without compromising the geotechnical risk profile of the mine.

Keywords

slope design, anisotropy, optimization, synthetic rock mass model