Submarine Landslide Flows Simulation Through Centrifuge Modelling
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SUBMARINE LANDSLIDE FLOWS SIMULATION THROUGH CENTRIFUGE MODELLING by Chang Shin GUE A dissertation submitted for the degree of Doctor of Philosophy at the University of Cambridge Churchill College January 2012 “Do not go where the path may lead, go instead where there is no path and leave a trail” - Ralph Waldo Emerson “If I have seen further than others, it is by standing upon the shoulders of giants” - Isaac Newton “Continuous effort – not strength or intelligence – is the key to unlocking our potential” - Winston Churchill ABSTRACT SUBMARINE LANDSLIDE FLOWS SIMULATION THROUGH CENTRIFUGE MODELLING Chang Shin GUE Landslides occur both onshore and offshore. However, little attention has been given to offshore landslides (submarine landslides). Submarine landslides have significant impacts and consequences on offshore and coastal facilities. The unique characteristics of submarine landslides include large mass movements and long travel distances at very gentle slopes. This thesis is concerned with developing centrifuge scaling laws for submarine landslide flows through the study of modelling submarine landslide flows in a mini-drum centrifuge. A series of tests are conducted at different gravity fields in order to understand the scaling laws involved in the simulation of submarine landslide flows. The model slope is instrumented with miniature sensors for measurements of pore pressures at different locations beneath the landslide flow. A series of digital cameras are used to capture the landslide flow in flight. Numerical studies are also carried out in order to compare the results obtained with the data from the centrifuge tests. The Depth Averaged Material Point Method (DAMPM) is used in the numerical simulations to deal with large deformation (such as the long runout of submarine landslide flows). Parametric studies are performed to investigate the validity of the developed centrifuge scaling laws under the initial and boundary conditions given in the centrifuge tests. Both the results from the centrifuge tests and numerical simulations appear to follow the proposed centrifuge scaling laws, which differ from the conventional centrifuge scaling laws. The results provide a better understanding of the centrifuge scaling laws that need to be adopted for centrifuge experiments involving submarine landslide flows, as well as giving an insight into the flow mechanism involved in submarine landslide flows. ACKNOWLEDGEMENTS I am deeply grateful to my supervisor, Prof. Kenichi Soga, for his interest, help and encouragement throughout this study. His advice and constructive criticism during the preparation of this dissertation are very much appreciated. In addition, I am particularly indebted for his time spent and patience. Sincere thanks are extended to Prof. Malcolm Bolton for his encouragement, enthusiasm, many invaluable discussions, comments and guidance, which inspired me tremendously throughout this study. Thanks must also go to Dr. Stuart Haigh for his advice and expertise with the mini- drum centrifuge and the creative ideas for developing the centrifuge model. I am also grateful to Dr. N.I. Thusyanthan and Dr. Dongfang Liang for their practical advice on the research topic as well as carrying out the experiments. I am grateful to Keita Abe for his kind assistance and advice in using and implementing the DAMPM code for the numerical simulations involved in this study. I would like to thank all the technicians at Schofield Centre for helping me on countless occasions; my laboratory work would not have been able to progress without their expertise. Special thanks to Dr. Suzanne Lacasse of the Norwegian Geotechnical Institute (NGI) for her endless support; first by providing the financial support through NGI and, later, the fellowship at NGI. Similarly, special thanks to Dr. Farrokh Nadim of the International Centre for Geohazards (ICG). This study and the once-in-a-lifetime experience at Cambridge would not have been possible without the financial support from NGI, ICG and the Cambridge Commonwealth Trust. I would also like to thank my fellow students in the Geotechnical Research Group for their assistance, friendship and great memories in Cambridge: Alec, Andrew, Andy, Christopher, Chris, Fiona, Hisham, Kaushal, Khalid, Kok Hun, Leonard, Leo, Matthew, Mohammed, Panos, Piau, Senthil, Sidney, Shun, Te and Zheming. I would like to extend my gratitude to my colleagues at NGI during the final writing- up stage of the dissertation, in particular Tom Lunne and Karl Henrik Mokkelbost for their patience and encouragement. Thanks also to Dr. Jörgen Johansson, Dr. Vaughan Meyer and Tore Kvalstad of NGI for their kind assistance and discussions. I wish to express my heartiest appreciation to my parents in Malaysia, who have supported me from afar. Finally, but by no means least, I would like to thank my wife Tricia, for her unconditional support and encouragement throughout the preparation of this dissertation, and for taking care of our son, Isaac. This dissertation is dedicated to them. DECLARATION I hereby declare that, except where specific reference is made to the work of others, the contents of this dissertation are original and have not been submitted in whole or in part for consideration for any other degree or qualification at this, or any other University. This dissertation is the result of my own work and includes nothing which is the outcome of work done in collaboration except where specifically indicated in the text. This dissertation is presented within the limits of 65,000 words and 150 figures. Chang Shin GUE January 2012 TABLE OF CONTENTS ABSTRACT ................................................................................................................... i ACKNOWLEDGMENTS ........................................................................................... ii DECLARATION........................................................................................................ iii TABLE OF CONTENTS ........................................................................................... iv LIST OF FIGURES ................................................................................................. viii LIST OF TABLES .................................................................................................... xiv NOTATIONS ............................................................................................................ xvi CHAPTER I INTRODUCTION 1.1 Background ..................................................................................................... 1 1.2 State of the Art - Limitations ........................................................................... 2 1.3 Objectives and Purpose of .............................................................................. 4 1.4 Significance of Study ...................................................................................... 5 1.5 Report Structure .............................................................................................. 5 CHAPTER II LITERATURE REVIEW – SUBMARINE LANSLIDES 2.1 Introduction ..................................................................................................... 7 2.2 Submarine Landslides ..................................................................................... 7 2.3 Classification and Characteristics ................................................................... 8 2.4 Documentation and Recognition ................................................................... 12 2.5 Causes of Failure ........................................................................................... 18 2.5.1 Rapid sedimentation ............................................................................... 18 2.5.2 Retrogressive failure .............................................................................. 19 2.5.3 Earthquake and tectonic activity ............................................................ 22 2.5.4 Gas hydrate ............................................................................................ 23 2.5.5 Wave loading ......................................................................................... 24 2.5.6 Other possible causes ............................................................................. 25 2.6 Mechanics of Submarine Landslides ............................................................. 26 2.6.1 Limit equilibrium ................................................................................... 26 2.6.2 Possible boundary conditions ................................................................ 29 2.6.3 Flow behaviour ...................................................................................... 30 iv 2.6.4 Governing equations and analytical solutions through mass and momentum conservations ...................................................................... 39 2.6.5 A numerical model that incorporates various rheologies ...................... 47 2.6.6 Runout efficiency ................................................................................... 49 2.7 Major Research Efforts ................................................................................. 52 2.8 Experimental Works by Other Researchers .................................................. 54 2.8.1 Past experimental works in 1 g environment ......................................... 55 2.8.2 Overview of other submarine slope experimental works in 1 g ............ 72 2.8.3 Past experimental works in centrifuge ..................................................