Abstract
Slopes in open pits exhibit fracturing around excavations, often initiated by extension strain which results from a combination of principal stresses adjacent to the slope boundaries. This extension strain is commonly described using minimum principal strain or minimum principal stress equations. These equations show that the extension strain can expand and fracturing occurs if the extension strain exceeds a critical value. Anisotropic rock masses with multiple and complex structures increase the potential of the development and coalesce of cracks with pre-existing discontinuities for further potential failure.
This paper presents finite element analysis to model the extensions strain implementing the criterion of Stacey (1981). The distributions of extension strain are predicted around slope of Handlebar Hill open pit mine at Mt Isa, Queensland, Australia. Around the pit wall, fracturing near the excavation boundary is often the result of extension strain of the rock. Through the mining activities, fractures in the slope face can manifest into slabbing and spalling. Extension strain may develop circumferential fractures close to the slope surface, the closer to the excavation perimeter, the more open the cracks. The result of the extension strain distribution simulated in this paper is in accord with failure events observed on site. The numerical modelling and the discussion of this study focused on the prediction of potential fracturing zones within the critical values of the extension strain around the slope.
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Acknowledgements
Authors wish to thank Prof. T. Stacey for kindly providing his hypothetical observations on the rock failure mechanisms occurring at the pit slopes, and being available for helpful comments.
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Al Mandalawi, M., Sabry, M., Sabry, M. (2020). Initiation Mechanism of Extension Strain of Rock Mine Slopes. In: Bezvijen, A., Wittke, W., Poulos, H., Shehata, H. (eds) Latest Advancements in Underground Structures and Geological Engineering. GeoMEast 2019. Sustainable Civil Infrastructures. Springer, Cham. https://doi.org/10.1007/978-3-030-34178-7_5
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