From micro- to macro-scale characterization of geomaterials: the role of heterogeneities and scale in geomechanics

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Mechanical and geometrical properties of rock at grain (micro-) scale govern the behaviour of rock-masses at all scales. ***In recent years, my research group, among others, has developed and successfully used micro-mechanical hybrid finite/discrete element modeling techniques (FDEM) to simulate tunneling and other underground engineering activities. These results support the hypothesis that physically-based calibrated micro-mechanical models can inherently capture the heterogeneity and the scale effect observed in all geomaterials, and reproduce, as emergent behaviours, those underlying physical processes associated with complex failure mechanisms in rock (i.e., spalling, fracking, progressive slope instabilities). However, to date, no accepted procedure exists on how to relate micro-scale input parameters to specific lab measured values; thus, researchers have difficulties when it comes to soundly calibrating and verifying their models.***Long-term goal of my research program:***to understand the role that heterogeneities have, at all scales, on the behaviour of engineering and geological structures (i.e., tunnels, mines, reservoirs) subjected to varying multi-physics (Thermo-Hydro-Mechanical-Chemical) conditions, and to translate it into numerical solutions. ***Short-term objectives***Obj.1 Understanding how spatial, volumetric, and scale distributions of heterogeneities influence localization and progression of deformational and failure processes.***Obj.2 Development of a general methodology for the quantitative validation and calibration of micromechanical numerical codes. ***Obj.3 Development of a reproducible and reliable strategy for upscaling the use of micromechanical numerical codes to study rock behaviour at various spatial resolutions, from laboratory to tunnel/mine/reservoir scale. The validation process will evaluate the micro-scale physics implemented in the numerical codes and their ability to reproduce, as an emergent property of the model, macro-scale behaviours observed both in the laboratory and in the field.***The novelty of this research program is the unique combination of advanced micromechanical laboratory investigations, empirical and machine learning analysis, and micromechanical FDEM modeling, to address a very old, but still unsolved problem in geomechanics: the scale effect.***The anticipated outcome of this research will greatly contribute to reduce the scale-related uncertainties inherent to most geomechanical engineering projects (e.g., excavation of deep geological nuclear waste repositories, tunnels, mines, energy exploitation activities for shale oil and gas reservoirs), as well as increase confidence in rock engineering design. The research program offers a unique opportunity for HQP training in experimental and numerical geomechanics, a subject of great interest to the whole Canadian natural resource industry.