Rocks are the most ubiquitous and most diverse materials on the earth's surface, and their mechanical and fluid transport properties play important roles in many different fields. The macroscopic behavior of rocks is conventionally represented by constitutive models that are formulated within the framework of continuum mechanics, and are phenomologically established from element tests. In many cases, model reliability can only be guaranteed over the range of conditions in which the model is calibrated. Phenomological models have difficulty in predicting the behavior of rocks under extreme environments involving large stresses, high temperatures, and extremely slow or fast loading. The main objectives of this Small Grant for Exploratory Research (SGER) research are: 1) to develop computational models for simulating the nanoscale behavior of rock minerals and their interfaces, 2) to develop homogenization schemes for nanoscale response of rock minerals and their interfaces, and 3) to implement nanoscale response in macroscopic models of rock masses. The approach to be used for modeling of rock masses involves subdividing rock into its multiscale components. The behavior of the minerals forming an individual grain and the contact properties between minerals will be analyzed at the nanoscale using Molecular Dynamics simulations based on the Atomistic-Scale Finite Element Method and Virtual Internal Bond (VIB) Model. The nano- and micro-scale behavior will be homogenized using the Smeared Crack Model validated against Distinct Element simulations. The primary intellectual merits of this work stem from the development, use and integration of advanced and cutting edge nano- to macro-scale characterization, modeling and computational capabilities, and applications to outstanding problems in rock mechanics. These capabilities are evolving and have not been fully exploited in the geoengineering and geoscience community. Development of these capabilities will significantly advance the state-of-the-art in geomechanical modeling. Broader impacts include improved prediction of rock mineral and interfacial behavior under extreme environments and under wide temporal and spatial scales. Such capability will have homeland security and environmental implications, for instance in projectile penetration problems and nuclear waste disposal. Improved understanding of rock mineral structures and mechanical behavior at the nanoscale and the interaction of nanoscale response with macroscopic behavior can also lead to new and innovative "geo-inspired nanomaterials." Training of today's and future engineers in the exciting area of nanomechanics and nanotechnology will ensure the competitiveness of the US workforce. The project will promote diversity in the research activities of the proposal by actively encouraging the participation of minorities and women. Active and timely dissemination of research results in journals, conferences and via the world-wide-web will ensure immediate impact of the research.
