2425 The necessity of 3D analysis in open pit, rock slope, stability analysis: in theory and practice
DOI:
https://doi.org/10.17159/Abstract
Geotechnical models developed during the open pit mine planning stage are generally three-dimensional in component to capture the spatial variation in geological, structural, hydrogeological and geomechanical conditions. Yet when geotechnical analysis is completed, often the three-dimensional geological, hydrogeological and structural models are simplified to two-dimensions. This paper demonstrates this simplification can lead to the wrong failure mechanism being analysed and/or a conservative Factor of Safety being calculated, leading to a false sense of stability.
There exists a paradigm that the Factor of Safety calculated using two-dimensional modelling methods (limit equilibrium or finite element) is generally conservative, i.e. lower than the true Factor of Safety. However, this assumption that the three-dimensional Factor of Safety is always higher than two-dimensional Factor of Safety, is not always correct.
This paper demonstrates the variation in Factor of Safety calculated between two-dimension and three-dimension slope stability analysis methods. Through case studies this paper also shows how three-dimensional analyses methods are more suited to rock slopes, particularly with anisotropic material strength and non-linear slope geometry. When analysing the same slopes in two-dimensions, the failure mechanism calculated can be fundamentally incorrect. The case studies presented further importantly highlight that the Factor of Safety calculated in three-dimensions is not always higher than the two-dimensional Factor of Safety, which is commonly assumed in the mining industry.
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Copyright (c) 2024 Alison McQuillan
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