Ultrasonic and Acoustic Emission Imaging of Brittle Fracturing Processes to Investigate the Progressive Failure of Rock

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***Canada is facing a new generation of engineering challenges involving deep underground excavations and resource extraction. Several mines are approaching 3000 m depth resulting in excavations experiencing significant stress-induced brittle failure and rock bursting hazards. This has significant implications for mine designs, including safe and effective support. Canada's nuclear waste management program is now searching for a site for a deep repository with the geological conditions necessary to satisfy safety requirements. Assessing the potential for stress-induced brittle fracturing is essential for this as the resulting excavation damage zone may increase the permeability of the rock acting as a geological barrier by 2 or 3 orders of magnitude. Hydraulic fracturing operations to enable production from Canada's unconventional gas reservoirs have been subject to public, industry, and regulator concerns regarding induced seismicity. Growing concerns are heightened due to knowledge gaps in our understanding of fault slip mechanisms and the factors controlling the likelihood and magnitude distribution of events. The experimental equipment being requested in this proposal will help us to accelerate our research programs addressing these challenges, by allowing us to image and therefore improve our understanding of brittle fracture processes and ability to measure and quantify their effects on rock strength, deformation and permeability change. ******The equipment requested will leverage an existing state-of-the-art rock testing facility capable of simulating the high stresses, pore pressures and temperatures experienced deep within the Earth, while measuring rock stress, strain, and permeability change. To this, the requested equipment will add unique capabilities to detect and image the initiation of brittle fracture damage and its evolution through progressive rock failure. Specifically, this includes simultaneously conducting time-lapse ultrasonic velocity imaging of brittle fracture damage anisotropy and failure localization, as well as detecting the source locations and source mechanisms of the brittle fractures generated using acoustic emissions (AE). We have a proven track record in experimental rock mechanics that is amplified by our ability to integrate experimental results with field-based observations, state-of-the-art numerical modelling, and new 4-D holographic visualization. This synergy leads to both improved experimental design and more robust interpretation of results. We have published extensively on these topics, and the requested equipment will allow us to continue to build upon our previous research successes. Separately, the equipment will also create numerous opportunities for interdisciplinary collaboration involving colleagues studying the role and evolution of brittle fracture processes related to CO2 sequestration, geothermal energy, and earthquake, landslide and volcano hazards.**