TUNNELLING IN HORIZONTALLY LAMINATED GROUND: THE INFLUENCE OF LAMINATION THICKNESS ON ANISOTROPIC BEHAVIOUR AND PRACTICAL OBSERVATIONS FROM THE NIAGARA TUNNEL PROJECT by Matthew Adrien Perras A thesis submitted to the Department of Geological Sciences and Geological Engineering In conformity with the requirements for the degree of Masters of Science and Engineering Queen’s University Kingston, Ontario, Canada (September, 2009) Copyright © Matthew Adrien Perras, 2009 Library and Archives Bibliothèque et Canada Archives Canada Published Heritage Direction du Branch Patrimoine de l’édition 395 Wellington Street 395, rue Wellington Ottawa ON K1A 0N4 Ottawa ON K1A 0N4 Canada Canada Your file Votre référence ISBN: 978-0-494-65250-3 Our file Notre référence ISBN: 978-0-494-65250-3 NOTICE: AVIS: The author has granted a non- L’auteur a accordé une licence non exclusive exclusive license allowing Library and permettant à la Bibliothèque et Archives Archives Canada to reproduce, Canada de reproduire, publier, archiver, publish, archive, preserve, conserve, sauvegarder, conserver, transmettre au public communicate to the public by par télécommunication ou par l’Internet, prêter, telecommunication or on the Internet, distribuer et vendre des thèses partout dans le loan, distribute and sell theses monde, à des fins commerciales ou autres, sur worldwide, for commercial or non- support microforme, papier, électronique et/ou commercial purposes, in microform, autres formats. paper, electronic and/or any other formats. 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Abstract The Niagara Tunnel Project is a 10.4 km long water diversion tunnel being excavated under the city of Niagara Falls, Ontario by a 14.4 m diameter tunnel boring machine. This tunnel has descended through the entire stratigraphy of the Niagara Escarpment, including dolomites, limestones, sandstones, shales and interbedded zones of these rock types, passed under St. Davids Buried Gorge ascending to surface. Working at the tunnel provided an opportunity to assess and document the horizontally laminated ground behaviour for this large diameter circular tunnel and provided the backdrop for this study. A detailed understanding of the geological history was necessary. Modelling of laminations, ranging between 0.16 to 16 m in thickness, was conducted to determine critical behaviour and cut-offs for failure modes. A critical normalized lamination thickness (thickness/radius) of 0.9 was found to exist, above which the excavation response is similar to the equivalent isotropic model, and below which the laminated behaviour corresponds to a characteristic failure mode controlled by bed deflections and bed parallel shear. Initially, as the normalized lamination thickness is decreased below 0.9, the stresses are channeled through the crown beam which concentrates the yield and increases the crown deflections. This results in crown beam failure. As the lamination thickness decreases, further the stresses are shed to multiple laminations increasing the displacements significantly and changing the shape and extent of the yield zone. From multiple lamination coupling to self-limiting yield the development of chimney style failure is controlled by the degree of tensile yielding. Tensile yielding first begins in the haunch area and progressively extends above the crown, as the lamination thickness decreases, until a self-limiting plastic yield zone shape is reached at normalized lamination thicknesses below 0.026. Incorporation of discrete anisotropy is necessary to accurately model the excavation response in horizontally laminated ground. ii Co-Authorship The following thesis represents the original work of the author. Two conference papers, attached in Appendix B, were co-authored with Dr. Mark S. Diederichs. iii Acknowledgements This research project has been made possible by Ontario Power Generation and Hatch Acres, who allowed me the opportunity to work on the Niagara Tunnel Project. Those people on the project team encouraged, supported and offered invaluable guidance and motivation throughout my two year stay. A special thanks to Rick Everdell, Mike Hughes and David Besaw. They in particular have propelled me forward and supported this project from the beginning. David Besaw mentored me at the tunnel, shared his knowledge of tunnelling with me, and became a close friend. Data, photographs, and images have kindly been provided by OPG from the Niagara Tunnel Project. Interpretations based on this data, photographs, and images and personal observations, from the Niagara Tunnel Porject, are my opinions. This information was invaluable in this study and it use is greatly appreciated. Many other individuals have generously contributed to the success of this research; Dr. Mark Diederichs has provided invaluable guidance, support and motivation. He has shared with me a wealth of knowledge and experience and provided many opportunities, which would have otherwise not been possible. The Geomechanics group at Queen’s University has provided feedback, advice and friendship throughout this project. Many other close friends have also supported my pursuits and kindly listened to me talk about this project. I am grateful for their patience and moral support. My family has always been supportive of my pursuits in life and they have given me the motivation and inspiration to excel, kept me focused and when needed, got me back on track when times were difficult. Many thanks to my mother and father, Andre and Sharon Perras and my sister and brother in-law, Jenny and Mike Murdock for all your patience and kindness. iv Table of Contents Abstract ............................................................................................................................................ ii Co-Authorship ................................................................................................................................ iii Acknowledgements ......................................................................................................................... iv Table of Contents ............................................................................................................................. v List of Figures ............................................................................................................................... viii List of Tables ................................................................................................................................. xv List of Symbols …………………………………………………………..……………….……..xvi Chapter 1 : Introduction .................................................................................................................. 1 1.1 Large Tunnel Boring Machine Challenges ............................................................................ 1 1.2 The Niagara Tunnel Project ................................................................................................... 3 1.2.1 Power Generation from the Niagara River ..................................................................... 3 1.2.2 Alignment and Components ........................................................................................... 6 1.2.3 Geological Overview .................................................................................................... 10 1.2.4 Construction Challenges ............................................................................................... 12 1.2.5 Big Becky – The Tunnel Boring Machine for Niagara ................................................. 15 1.3 Large TBM Excavation and Engineering Geology .............................................................. 20 1.4 Numerical Methods .............................................................................................................. 21 1.5 Thesis Objectives ................................................................................................................. 22 1.6 Problem Statement ............................................................................................................... 23 1.7 Summary of Findings ........................................................................................................... 24 1.7.1 The Glacial Impact on the Niagara Region ................................................................... 24 1.7.2 Failure Modes of Anisotropic Ground around Circular Tunnels .................................. 25 1.8 Thesis Outline ...................................................................................................................... 27 Chapter 2 : Tunnel Construction and Geological History of the Niagara Region ........................ 29 2.1 Tunnel Construction ............................................................................................................