Geomechanical characterisation of massive rock for deep TBM tunnelling

A combined geological and rock mechanics approach to tunnel face behaviour prediction, based on improved understanding of brittle fracture processes during TBM excavation, was developed to complement empirical design and performance prediction for TBM tunnelling applications in novel geological conditions. A major challenge of this research is combining geological and engineering languages, methods, and objectives to construct a unified geomechanics characterisation system. The goal of this system is to describe the spalling sensitivity of hard, massive, highly stressed crystalline rock, often deformed by tectonic processes. Geological, lab strength testing and TBM machine data were used to quantify the impact of interrelated geological factors, such as mineralogy, grain size, fabric and the heterogeneity of all these factors at micro and macro scale, on spalling sensitivity and to combine these factors within a TBM advance framework. This was achieved by incorporating aspects of geology, tectonics, mineralogy, materials strength theory, fracture process theory and induced stresses.