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Unlike metals, rocks show bi-modularity (different Young’s moduli and Poisson’s ratios in compression and tension). Displacements monitored during the Brazilian test are used in this study to obtain the Young’s modulus and Poisson’s ratio in tension. New equations for the displacements in a Brazilian test are derived considering the bi-modularity in the stress–strain relations. The digital image correlation technique was used to monitor the displacements of the Brazilian disk flat surface. To validate the Young’s modulus and Poisson’s ratio obtained from the Brazilian test, the results were compared with the values from the direct tension tests. The results obtained from the Brazilian test were repetitive and within 3.5% of the value obtained from the direct tension test for the rock tested. [ABSTRACT FROM AUTHOR]

Numerical modelling is playing an increasing role in the interpretation of geological observations. A similar phenomenon is occurring with respect to the interpretation of the stress–strain response of intact rock measured in laboratory tests. In this research, the three-dimensional (3D) bonded particle model (BPM) with flat-jointed (FJ) contact was used to investigate the impact of stress paths on rock failure. The modified FJ contact model used for these studies numerically captured most of the intact rock behavior of Lac du Bonnet granite observed in the laboratory. A numerical simulation was used to track the behavior of this rock for different stress paths, starting with uniaxial tension and compression loading conditions. The migration from uniaxial tension to triaxial compression is challenging to simulate in physical laboratory tests but commonly observed around underground excavations. The numerical modelling methodology developed for this research tracks this stress path and the impact of the intermediate stress on peak strength at low confinements, commonly found around underground excavations. [ABSTRACT FROM AUTHOR]