Authors: Figueiredo, L; Barros, M; Hammah, R; Santos, Y; Souza, T; Nogueira, C

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Figueiredo, L, Barros, M, Hammah, R, Santos, Y, Souza, T & Nogueira, C 2021, 'Case study: open pit three-dimensional slope stability back-analysis for an anisotropic iron ore rock mass', in PM Dight (ed.), SSIM 2021: Second International Slope Stability in Mining, Australian Centre for Geomechanics, Perth, pp. 107-120,

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The challenges of representing geotechnical failure mechanisms in software is being gradually addressed as search algorithms and computing power advance, especially to deal with complex anisotropic rock masses in which failure mechanisms are commonly three-dimensional (3D). This paper presents a case study of an iron ore mine with highly anisotropic rock mass strength that has been back-analysed using 3D limit equilibrium analysis methods. In order to provide as realistic model inputs as possible, field characterisation data and the reconstruction of the failed surface were used, as well as the material properties available from laboratory tests or bibliographic references. A probabilistic approach was applied to the initial parameters, resulting in a series of stochastic simulations that provided scenarios for the failure moment, when the Factor of Safety achieved close to 1.0. Then, based on the knowledge of the local geological-geotechnical context and failure mechanisms, a range of values for the geomechanical parameters were achieved to enhance the constitutive model of the rock mass.

Keywords: three-dimensional limit equilibrium, open pit slope stability, anisotropic iron rock masses, backanalysis

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