Grain-scale behaviour of crystalline rock under coupled hydro-mechanical process

This thesis studies the grain-scale behaviour of crystalline rock under coupled hydro-mechanical processes. It aims to provide insights into rock micro-cracking behaviours at the presence of rock grain-scale heterogeneity and uncover the micro mechanisms. The main objectives of this thesis are (a) To identify the influence of in-situ stresses on the fluid-driven micro-cracking behaviour of crystalline rock and (b) To investigate the effect of rock grain-scale mechanical properties on the macro and micro-behaviours in hydraulic fracturing. The findings suggest that majority of shear cracks are found on the grain boundary, while tensile cracks can be found in mineral grains and on the grain boundary. The orientation of a tensile crack tends to orientate perpendicular to the minimum principle stress, while a shear crack tends to orientate towards the direction of the minimum principle stress.