Authors: Bahrani, N; Kaiser, PK; Corkum, A

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Bahrani, N, Kaiser, PK & Corkum, A 2018, 'Suggested methods for estimation of confined strength of heterogeneous (defected) rocks', in Y Potvin & J Jakubec (eds), Caving 2018: Proceedings of the Fourth International Symposium on Block and Sublevel Caving, Australian Centre for Geomechanics, Perth, pp. 207-222,

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A grain-based model based on the distinct element method previously calibrated to the laboratory properties of intact and heat-treated (granulated) marble is used to simulate grain-scale heterogeneities, such as grain boundary cracks and laboratory specimen-scale heterogeneities (often referred to as defects), such as veins. The semi-empirical Strength Degradation Approach (SDA), originally developed for the estimation of the confined strength of crack-damaged rocks, is first applied and tested for the estimation of confined strength of laboratory specimen-scale rocks and rock blocks containing defects. In the second approach, called the explicit numerical modelling approach, the grain-based model is integrated with discrete fracture network (DFN) models, to construct defected rock models and to investigate the influence of defect orientation on the confined strength of defected rocks. It is concluded that the SDA can be used at the early stages of geotechnical projects, when limited information on the properties and geometrical characteristics of defects is available. The explicit numerical modelling approach provides more representative results than the SDA, as it requires a detailed knowledge of the properties of intact rock as well as the properties and geometrical characteristics of defects obtained from field mapping and laboratory testing. A step-by-step procedure is provided for the application of these two methods to estimate the confined strength of defected rocks.

Keywords: heterogeneity, defects, rock block strength, Strength Degradation Approach (SDA)

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