Performance-based design is anchored in predicting the serviceability deformations of a structure. This requires adequate knowledge of the deformation characteristics of the foundation material. With argillaceous shales constituting as much as 50% of the global sedimentary rock mass and outcrop in about one third of the emerged earth surface, shale formations often comprise the foundations of major civil developments. Sampling, testing, and consequently predicting deformations of these clay-rich shales based on laboratory testing is challenging as they rapidly deteriorate and experience irrecoverable damage when exposed. Moreover, their response to loading/unloading is complex and can vary considerably as a function of local stress history, dominant mineral variation, and scale. As part of a testing program at the Site C Dam project to assess foundation response, pressuremeter testing was conducted in the Shaftesbury Shales below the RCC buttress which supports the spillways and generating station on the Right Bank. This presentation will center around the pressuremeter testing procedures, data, key inferences, and instrument limitations. Interpreted variability in stiffness and deformation behavior will be discussed, including an assessment of sources of uncertainty.
Expected Outcomes for participants:
Colin DregerMr. Dreger is a professional Geotechnical Engineer with over nine years of consulting experience in the geotechnical field in Alberta, British Columbia, Saskatchewan, Yukon, Northwest Territories, and Nunavut. He is currently engaged in a geotechnical doctorate program with the Civil and Environmental Department at the University of Alberta.
Colin enrolled in the Ph.D. program in 2020 and was subsequently seconded to the Site C Hydroelectric Development Resident Engineering Team during the Fall 2020 term to oversee production-scale lateral load testing of the Shaftesbury Shale. He has been exploring the constitutive behavior of argillaceous shales in collaboration with leaders in the energy sector and in-situ testing practitioners. His research will improve deformation models and design and construction methodologies by providing a framework to better understand observed deformation behavior, thereby informing risk. A practicable approach will be developed which uses high quality, relatively lower cost insitu and laboratory testing coupled to address complex rock mass behavior in evolving stress conditions.
