The overall strength of a rockmass is determined by the intact rock strength and characteristics of the rockmass structure. In complex rockmasses this structure consists of both joints and other fractures (interblock structure) and intrablock structure such as veins. As excavations go deeper, intrablock structure has been found to have a significant impact on rockmass behaviour. Complex numerical modelling for modern geotechnical design requires input parameters for structure, including normal and shear stiffness, and strength, which have a critical influence on modelled rockmass behaviour. This study focusses on extending joint stiffness and strength concepts to veins by calibrating numerical finite element Unconfined Compressive Strength (UCS) tests with explicit vein geometries that were determined by petrographic analysis of veins in thin section. In some cases, different calibrated properties were found to have equivalent stress-strain profiles in UCS tests. The behaviour of the calibrated stiffness and strength vein properties are examined at an excavation scale using a numerical example of a 10 m-diameter tunnel.

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