Identifying mechanisms of environmentally driven long-term crack growth in brittle rocks

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Cracks forming in rock near the surface of an excavation or at the Earth's surface can result in critical damage to existing infrastructure, disruption of operations, and loss of life when unexpected failures occur. Even if critical damage is not caused, the cracks formed can result in problematic flow pathways for containment facilities. Typically, empirical and numerical designs focus on the extent of damage and mitigation measures, with little attention to long-term processes. In addition, the influence of environmental drivers on crack growth remains a frontier of research. To improve engineering practice to the point that environmentally driven long-term crack growth mechanisms, the associated hazards and proper mitigation strategies are included in design is the long-term goal of this program. The program includes developing field monitoring methodologies, designing laboratory testing scenarios that reflect the field conditions, and using these findings to develop and validate hazard assessment and predictive numerical tools. ***In the short-term, the research program will aim to determine the most suitable numerical software to model environmental influence of long-term crack growth, to understand the influence of thermal cycles on the magnitude of crack opening and growth at different scales, to determine if stress corrosion in stressed brittle rock is a dominate crack growth mechanism over other identified mechanisms, and to evaluate the transferability of different data sources from one field location to another. ***The methods to be used to address the objectives mentioned above will include a variety of field, laboratory, and numerical modelling approaches. For the field sites, geological mapping, strength estimation and sample collection, advanced photogrammetric and spatial analysis of the results will augment the monitoring data to address the transferability of this information to new locations. In the laboratory, standard strength and advanced long-term tests under variable climates will be used to characterize the rock and crack behaviour and develop inputs for numerical models. Models to back analyze both the field and laboratory behavior will be computed and compared with different approaches from common engineering to advanced multi-physics and fracture mechanics software. These findings will lead to new testing procedures, novel methods of monitoring and utilizing monitoring data, and most importantly will lead to the development of much needed numerical tools to capture long-term crack growth mechanisms. ***With the applicant's past experience in these areas, along with a team of HQP, the program will make major advances in the areas of rock and fracture mechanics, and near surface process research. Major impacts on the way the Civil Engineering community thinks about and deals with environmental influences on long-term crack growth are expected.