This Faculty Early Career Development (CAREER) Program grant will enhance engineers' understanding of the formation and healing of rock fractures as it pertains to underground energy and waste storage systems, while providing undergraduate students from a diverse background with both research and international collaboration experiences. The safe storage of energy or waste products in underground rock formations relies on an understanding of the fractures that exist within the rock mass, and the fluid flow through the fracture system. Currently, engineers have an incomplete understanding of how microscopic theories of fracture formation and the healing of fractures can be used to develop models of rock mass behavior. Therefore, the objectives of this CAREER award are to: understand and predict changes in rock fractures; develop numerical models of fracture networks; formulate and assess innovative models of fracture damage and healing; and interpret rock deformation and fluid flow instabilities resulting from fracture damage and healing. In addition to preventing subsidence, borehole instabilities and contaminant leakage, the proposed models will be applicable for optimizing containment and shielding properties of geomaterials and assessing the environmental impact of energy geotechnologies. Research and education activities will be integrated to train undergraduate students in design and research, engage graduate students in mentoring and public deliberation, and foster long-term international collaborations. The PI will collaborate with a number of educational and outreach programs at Georgia Tech in order to assess the effectiveness of the activities and improve the participation of students, especially those from under-represented groups.
The specific research goal of this CAREER plan is to understand and predict the evolution of rock microstructural and poromechanical behavior upon chemo-mechanical damage and healing. Geological storage in salt and carbonates is used as an illustrative problem for investigating the following fundamental scientific questions: why do pores and cracks heal? how long do mechanical and hydraulic recovery take? how much energy does healing require? A major expected outcome of this project is a new continuum damage and healing theoretical framework for rock mechanics, which uses a minimal set of explanatory dissipation variables defined as moments of probability of microstructure descriptors. Original contributions include: a theory to predict pore geometry evolution upon multi-physics damage and healing processes; creative mathematical models to describe pore network topology with geometric variables that control damage and healing; fundamental relationships between pore-scale healing time and macroscopic mechanical recovery time - a step forward to bridge poromechanics and damage mechanics; innovative computational methods to predict mechanical instabilities and percolation thresholds upon damage and healing, verified in collaboration with leading experimentalists; and realistic multi-physics simulations of geological storage, in collaboration with industry partners. The rigorous integration of topology, thermodynamics, poromechanics and continuum mechanics will transform the theory of damage and healing mechanics and provide a framework to interpret rock stress path history from topology descriptors. Research findings will be useful to recommend the conditions of moisture and temperature necessary to minimize damage and/or enhance healing in rocks and to design safe and sustainable geological storage systems. The education goal of this CAREER plan is to engage an international and cross-disciplinary community of undergraduate and graduate students in energy geotechnology research and engineering. Research, education and outreach activities will be integrated by: collaborating with geoscientists to train geosystems students on how to design and conduct rock mechanics experiments; making students' thinking visible in undergraduate classes to implement solution design strategies; engaging graduate students in public deliberations on energy geotechnology; supervising a Vertically Integrated Laboratory that will build a trans-generational, cross-disciplinary and international scholar network, improve undergraduate students' learning outcomes and inspire students in geomechanics; and creating a sustainable student exchange program between Georgia Tech and top European institutions including Ecole des Ponts Paris Tech (France).
