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Geotechnical Characterization of the Bearpaw Shale

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Geotechnical Characterization of the Bearpaw Shale GEOTECHNICAL CHARACTERIZATION OF THE BEARPAW SHALE by Jacqueline Suzanne Powell A thesis submitted to the Department of Geological Sciences & Geological Engineering In conformity with the requirements for the degree of Doctor of Philosophy Queen’s University Kingston, Ontario, Canada January, 2010 Copyright © J. Suzanne Powell, 2010 Abstract This research takes a multidisciplinary approach to comprehensively investigate the material and mechanical properties as well as pore water chemistry of the Bearpaw shale. This made it possible to characterize how these properties relate to the mechanical strength of this material. The results of this research challenge our ideas of the hydrogeology and of the geological history of the region. Core samples of the Bearpaw Formation and the overlying glacial till were collected from a field site in southern Saskatchewan, Canada. A combination of laboratory tests including multi-staged oedometer tests, constant rate of strain oedometer tests, specialized triaxial swell tests, along with pore water chemistry and finite element modelling were used to meet the following objectives: (1) To investigate the material properties and compression behaviour of the Bearpaw in addition to assessing disturbance due to specimen size; (2) Examine the time dependent behaviour of the Bearpaw and the transferability of time rate models developed for soft soils to stiff soils; (3) Examine the swelling potential and behaviour of the Bearpaw Formation and the influence of boundary conditions on this behaviour, while assessing the applicability of the swell concepts developed for compacted materials to a naturally swelling clay material; and (4) Constrain the depositional age of the till overlying the Bearpaw Shale. Contrary to what is seen in soft soils, smaller sized specimens were found to reduce disturbance, and produce more accurate and consistent results. Creep was found to follow the same laws as it does in soft soils, calling into question whether the use of preconsolidation pressure to predict geological history in stiff clays is appropriate. There was significant variation in the observed swell pressures of samples of the same size and depth. Finally, the glacial till at site was found to belong uniquely to the Battleford Formation and ranges in age from 22,500 to 27,500 years which is much younger (over 100,000 years younger) than previously believed. ii Acknowledgements The efforts of many people made this research possible and their contributions over the course of this work have been greatly appreciated. Firstly, I’d like to thank my three co- supervisors: Vicki Remenda, Greg Siemens and Andy Take. Thank you for your encouragement, patience and understanding. Special thanks to Andy and Greg for your exceptional efforts and for taking me under your wing. Your guidance was instrumental in setting and achieving milestones that marked the steps toward compiling this thesis. Your belief in me helped to keep me focused at times when progress became difficult. This research could not have been completed without the involvement and support of technicians in the various labs at Queen’s and RMC. Thank you to Joe Dipietrantonio, Dexter Gaskin and Lou Zegarra for all the technical advice and support, for sharing your experience and knowledge so freely and so openly. Thank you, most importantly, for your friendship. Thank you to Mark Diederichs and Jean Hutchinson for your guidance and advice over these years. The commitment you’ve made to research, teaching and your family is something that truly inspires me. I very much enjoyed being a pseudo member of the Geomechanics Group. Thank you to Dianne Hyde and Jo-Anne Doucette for always keeping your doors open and for the support and encouragement you provided. Throughout my time in Kingston I developed a wonderful network of friends and colleagues whose relationships were such an important part of this experience. While I couldn’t possibly thank every person, I would like to acknowledge the following people: Wanda Beyer, Drew Brenders, Kathy Kalenchuk, Neil Kjelland, Marc Laflamme, Alicia Larson, Maureen Matthew (White), Amelia Rainbow, Stephanie Villeneuve and Marlène Villeneuve. Thank you for the intellectual debates, lunch time chats, coffee breaks and stress relief (in whatever form it iii took). Your friendship and the continuous support you have provided me both in the completion of this thesis and to me as a person means more than I can express. Thank you to my entire family who has been there every step of the way providing support and encouragement and never once giving up on me, I could not have done it without you behind me. You mean the world to me and I love you. A special thank you to my grandpa, Bob Downie, whose constant support and wise words of ‘make us proud’ I carry with me every day. Finally, thank you to Scott Viger for your support and encouragement, for pushing me when I needed an extra push and for being there when I needed you (or simply when I needed a break). Your patience and understanding, especially during the final days of this thesis, were remarkable and truly appreciated. Thank you for everything. iv Statement of Originality I hereby certify that all of the work described within this thesis is the original work of the author. Any published (or unpublished) ideas and/or techniques from the work of others are fully acknowledged in accordance with the standard referencing practices. J. Suzanne Powell January, 2010 v Table of Contents Abstract............................................................................................................................................ii Acknowledgements.........................................................................................................................iii Statement of Originality...................................................................................................................v Table of Contents............................................................................................................................vi List of Figures.................................................................................................................................xi List of Tables ...............................................................................................................................xvii List of Symbols and Abbreviations.............................................................................................xviii Chapter 1 Introduction .....................................................................................................................1 1.1 Background............................................................................................................................1 1.2 Objectives ..............................................................................................................................4 1.3 Methods .................................................................................................................................4 1.4 Organization of Thesis...........................................................................................................5 1.5 References..............................................................................................................................7 Chapter 2 Characterization of the Bearpaw Shale in oedometric compression. ..............................9 2.1 Introduction............................................................................................................................9 2.2 Background..........................................................................................................................12 2.2.1 Consolidation Testing ...................................................................................................12 2.2.1.1 Coefficient of Compressibility...............................................................................12 2.2.1.2 Coefficient of Consolidation..................................................................................13 2.2.1.3 Compression Indexes .............................................................................................13 2.2.1.4 Preconsolidation Pressure ......................................................................................14 2.2.2 Soil Compressibility......................................................................................................15 2.2.2.1 Structure and Intrinsic Compression Line (ICL) ...................................................15 2.2.2.2 Disturbance and Specimen Quality........................................................................16 2.3 Materials and Methods.........................................................................................................17 2.3.1 Physical Properties........................................................................................................17 2.3.2 Sample Disturbance ......................................................................................................18 2.3.3 Consolidation Testing ...................................................................................................18 2.3.4 Apparatus Compliance..................................................................................................20 2.4 Test results ...........................................................................................................................20 2.4.1 Index Properties ............................................................................................................20
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