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(Title of the Thesis)* LARGE LANDSLIDES IN SENSITIVE CLAY IN EASTERN CANADA AND THE ASSOCIATED HAZARD AND RISK TO LINEAR INFRASTRUCTURE by Peter Eugene Quinn A thesis submitted to the Department of Geological Sciences and Geological Engineering In conformity with the requirements for the degree of Doctor of Philosophy Queen’s University Kingston, Ontario, Canada April, 2009 Copyright © Peter E. Quinn, 2009 Abstract The Saint Lawrence Lowlands in eastern Canada contain extensive deposits of marine soils deposited in post-glacial seas during and following the retreat of the most recent continental glacier. These marine soils include silt and clay deposits known collectively as Champlain clay. When the pore fluid in these marine deposits has changed over time to a lower salinity, the clay can become very sensitive, or demonstrate substantial strength loss after reaching the peak strength with sufficient strain under undrained load conditions. Sensitive clay soils are subject to a peculiar type of very large landslide that typically involves great extents of nearly horizontal ground, usually occurring suddenly and without warning. These landslides tend to be described as “retrogressive” in the literature and practice, implying that they develop as a series of successive small failures that advance rearward until a final stable position is reached. The work of this thesis is organized into four different themes, with an overall objective of understanding the hazard and risk associated with large landslides in sensitive clay to linear infrastructure such as railways. The first theme, documented in Chapter 2, develops a number of spatial relationships between specific physiographic and geologic features and landslide occurrence or absence, as determined through air photo analysis and a review of the literature. The second theme, documented in Chapter 3, presents the construction of a digital database of large landslides in sensitive clay in eastern Canada, for the purposes of studying landslide susceptibility, hazard and risk. The third theme, documented in Chapters 4 and 5, presents and defends a novel mechanical model for development of these large landslides. This model suggests the landslides ii develop progressively, rather than retrogressively, and the science of fracture mechanics is employed to substantiate the model. The fourth theme, documented in Chapters 6 and 7, synthesizes the findings of the earlier themes and presents a methodology for estimating landslide susceptibility in Champlain clay. That approach is then extended to develop an understanding of the hazard. The concluding chapter extends that work to present an initial appreciation of landslide risk to railways. iii Co-Authorship This thesis represents primarily original work by the author, however, significant contributions were made by co-authors who collaborated in preparing conference papers and draft journal papers, some of which have been used in modified forms as Chapters in this thesis. Chapters 1 and 8 are entirely the original work of the author. Chapter 2 is primarily the original work of the author; however, a small portion of this Chapter was published in a slightly different form in the following conference paper: Quinn, P.E., Hutchinson, D.J., and Rowe, R.K. 2007c. Toward a risk management framework: sensitive clay landslide hazards affecting linear infrastructure in eastern Canada. Proceedings of the 1st North American Landslide Conference, Vail, Colorado, 102-114. Chapter 3 was prepared from work submitted in two different conference papers: Quinn, P.E., Hutchinson, D.J. Diederichs, M.S., Rowe, R.K., Harrap, R., Alvarez, J. 2007b. A Digital Inventory of Landslides In Champlain Clay, Proceedings of the 60th Canadian Geotechnical Conference, Ottawa, 713-720. Quinn, P., Hutchinson, D.J., Diederichs, M.S, Rowe, R.K. and Alvarez, J. 2008. Susceptibility mapping of landslides in Champlain clay from a digital landslide inventory. Proceedings of the 4th Canadian Conference on Geohazards, Quebec City, 469-476. Chapter 4 has been submitted for consideration by the Canadian Geotechnical Journal as follows: iv Quinn, P.E., Diederichs, M.D., Rowe, R.K. and Hutchinson, D.J. 2009a. A new model for large landslides in sensitive clay using a fracture mechanics approach. Submitted to Canadian Geotechnical Journal, November 2008. Chapter 5 has been adapted from a draft paper that has been prepared for consideration by the Canadian Geotechnical Journal as follows: Quinn, P.E., Diederichs, M.D., Rowe, R.K. and Hutchinson, D.J. Development of progressive failure in sensitive clay slopes. To be submitted to the Canadian Geotechnical Journal. Chapter 6 has been submitted for consideration by the Canadian Geotechnical Journal as follows: Quinn, P., Hutchinson, D.J., Diederichs, M.S, and Rowe, R.K. 2009b. Regional scale landslide susceptibility mapping using the weights of evidence method: an example applied to linear infrastructure. Submitted to Canadian Geotechnical Journal, Submitted November 2008. Chapter 7 has been adapted from a draft paper that has been prepared for consideration by the Canadian Geotechnical Journal as follows: Quinn, P., Hutchinson, D.J., Diederichs, M.S, and Rowe, R.K. Characteristics of large landslides in sensitive clay in relation to hazard and risk. To be submitted to Canadian Geotechnical Journal. v Acknowledgements I have always enjoyed the intellectual stimulation of university studies. When I finished my undergraduate work, I was anxious to start a graduate program, but work and life interfered for several years. In due course, I was able to complete a masters degree in Civil Engineering, starting first in Structures, then switching to Geotechnical after taking two soil mechanics courses and falling in love with its complexity and balance of art and science. Upon completing my masters degree, I remained motivated to continue graduate work, but once again life and work interfered, delaying my return to formal studies until I was well into my peak earning years. The first and most important person I need to recognize is my patient and understanding wife Darlene, who agreed with my plan to abandon paying employment in pursuit of new intellectual challenges. She has shouldered the financial load the past 3 ½ years, and done it in remarkably good spirits. Our son John has also been patient, if perhaps a little perplexed, with his father’s need to be back in university at a time when he was beginning post-secondary studies himself. My parents Gene and Elayne gave me the genetic predisposition for inquisition. I have enjoyed the rare privilege of working with three accomplished, enthusiastic and knowledgeable supervisors: Professors Jean Hutchinson, Mark Diederichs and Kerry Rowe. Dr. Hutchinson was my primary supervisor, helping guide the overall research program and taking a particularly strong interest in the GIS-based components of the work focused on landslide susceptibility, hazard and risk. She was extremely generous with her time and money, and I was never without the necessary resources to complete my work or advice when I needed it. She was a steady guiding influence, and her vi thorough critiques of my work strengthened the result considerably. Dr. Diederichs was a constant source of creative energy, and often seemed to have more enthusiasm for my work than even I had. He was also generous with his time, money and equipment, and provided continuing excellent advice in the analytical and numerical modelling components. Dr. Rowe challenged a key part of my initial path, which I stubbornly pursued for some time until my own inquiries led me to agree, eventually, with his initial advice. I think this temporary philosophical conflict resulted in a more aggressive search for answers, and thus yielded a better outcome to the research following an entirely unanticipated path. Dr. Rowe was also particularly interested in the analytical and numerical modelling components of this work, and was a source of key strategic advice in crafting the work for publication. I consider myself very lucky to have worked with these talented and caring individuals. This work has benefited substantially from contributions by a large number of people, who have not all necessarily agreed with the positions proposed herein. The following contributed to development of ideas through discussion, which often involved lively debate: Jan Aylsworth and Didier Perret (Geological Survey of Canada), Serge Leroueil (Laval University), Marten Geertsema (BC Ministry of Forests), David Cruden (University of Alberta), Denis Demers (Quebec Ministry of Transport), Stig Bernander (private consultant, Gotebörg, Sweden), Vikas Thakur and Staynor Nordal (Norwegian Technical University, Trondheim, Norway), Tore Kvalberg, Odd Gregerson, Hans Petter Jostad, Kjell Karlsrud, Lars Andresen, Kalle Kronholm, and Peter Gauer (Norwegian Geotechnical Institute, Oslo, Norway), and, Dave McClung (University of British Columbia). vii The idea to use fracture mechanics as a means to explaining progressive failure in large landslides bubbled beneath the surface for several months after a random discussion with Louis Delmas, a French graduate student at NTNU in Trondheim, Norway. We were having a casual chat about our respective research, and his explanation of the behaviour of snow in dry slab avalanches struck me as remarkably similar to that of sensitive clay under certain loading conditions. This thought remained buried for several months as I continued to pursue a numerical modelling solution to my problem. When
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