Multi-scale modeling of coupled multiphysics processes in geomaterials: Theoretical and experimental study

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Multiphysics processes and different levels of mutual coupling have been observed in various aspects of geotechnical and environmental engineering and of energy production, such as waste disposal (including nuclear waste) and soil pollution problems where heat effects add to the complexity of multi-phase couplings, hydro-mechanical interactions during hydraulic fracture of shale or other tight rocks in oil and gas industry and slope failure induced by infiltration of water into the ground surface. It is not sufficient to solely carry out analysis on each physical process separately for these complicated engineering problems. Instead, it is crucial to consider their mutual coupling in the analysis. These processes cover different scales, from particle size to much larger engineering scales. Therefore, it is required to study the performance of relevant infrastructures by considering various coupled multiphysics processes on multi-scales.*** The main objectives of the research are to understand the coupled effects of different physics processes (particularly fluid flow and stress-induced deformation) on underlying mechanisms of instability and degradation in geomaterials. Thereafter, a mathematical framework will be developed across scales to describe material behavior, with micromechanical aspects of soil behaviour being properly taken into account.*** The research consists of theoretical analysis, laboratory tests and numerical modelling of soil behaviour involving mechanical, hydraulic and environmental processes. The experimental study includes the characterization of internal structure on particle level using X-ray micro-CT digital image analysis and laboratory tests on engineering soil properties to understand the effect of different processes, such as stress-induced deformation, internal structure change and water flow. The mathematical work will develop a new multi-scale, multi-phase formulation that penetrates down to details of grain activity at the particle-scale, and back to the macro-scale through a micromechanical analysis and homogenization. The mathematical framework, after being implemented into a computer modelling code and validated against benchmark problems, will be used to analyze a variety of practical problems such hydraulic fracture of rock. *** The proposed research is unique in that it accounts for the effect of coupled hydro-mechanical-environmental processes on the behaviour of geomaterials. The developed multi-scale modeling methods employ information at the grain level for larger scale simulations for difficult problems, such as seasonal deterioration of highway pavements, hydraulic fracture of rock, as well as for the impact of climate change on geotechnical infrastructures. Six graduate students will be trained in the proposed research. Clearly, each would become a highly trained researcher at the end of the project.********