EFFECT OF TIME ON SOIL-GEOMEMBRANE INTERFACE SHEAR STRENGTH Thesis Submitted to The School of Engineering of the UNIVERSITY OF DAYTON In Partial Fulfillment of the Requirements for The Degree of Master of Science in Civil Engineering By Saeed Alzahrani, B.E. Dayton, Ohio May, 2017 EFFECT OF TIME ON SOIL-GEOMEMBRANE INTERFACE SHEAR STRENGTH Name: Alzahrani, Saeed Kloofah APPROVED BY: ______________________________ ______________________________ Ӧmer Bilgin, Ph.D., P.E. Steven L. Donaldson, Ph.D. Advisory Committee Chairman Committee Member Associate Professor, Department of Associate Professor, Department of Civil and Environmental Engineering Civil and Environmental Engineering & Engineering Mechanics & Engineering Mechanics ______________________________ Elias Toubia, Ph.D. Committee Member Assistant Professor, Department of Civil and Environmental Engineering & Engineering Mechanics ___________________________ ____________________________ Robert J. Wilkens, Ph.D., P.E. Eddy M. Rojas, Ph.D., M.A., P.E. Associate Dean for Research and Innovation Dean, School of Engineering Professor School of Engineering ii © Copyright by Saeed Kloofah Alzahrani All rights reserved 2017 iii ABSTRACT EFFECT OF TIME ON SOIL-GEOMEMBRANE INTERFACE SHEAR STRENGTH Name: Alzahrani, Saeed Kloofah University of Dayton Advisor: Dr. Ӧmer Bilgin, P.E. In the past thirty years, geosynthetic materials have been used widely in various civil engineering applications due to their numerous advantages. Geomembranes are one of the most common geosynthetics that are used primarily as an impervious boundary for liquids or gases. High density polyethylene (HDPE), the material used for geomembranes, shows a viscoelastic behavior to the applied loads over a period of time in the form of creep or stress relaxation. Effect of time on soil-geomembrane shear strength is critical factor that should be studied carefully, because soil-geomembrane interfaces usually form weak planes and may cause failures. A series of large direct shear tests were carried out in the laboratory to investigate the effect of time on soil- geomembrane interface shear strength. The geomembrane samples were placed under a sustained load for two weeks then the shear tests were performed. The test results showed that the interface friction angle increases with time due to further penetration of soil particles into the geomembrane, resulting in the increase of soil-geomembrane contact areas. This thesis presents the tests performed, results obtained, discussion of the results, findings, and recommendations for future studies. iv This thesis is dedicated with love to my mother who is suffering from a breast cancer since 2013. She deserves all the kind words in the world due to her great sacrifices which I will not ever forget. Also, I would like to dedicate this work to my father who supports my journey in education. Finally, I dedicate my thesis to my wife “Maha”. v ACKNOWLEDGMENTS I would never have been able to complete my thesis without the guidance of my advisor, support from my family, and help from my colleagues. I would like to express my sincere gratitude to Dr. Ӧmer Bilgin, my advisor, who provided me with the opportunity to work under his supervision in the geotechnical engineering discipline. I thank him for his excellent guidance, encouragement, supervision, and advices not only about my thesis but also about my academic life. I am very grateful to Kevin Arens who trained me on some equipment in the geotechnical engineering laboratory. I would like to thank Bernard Glascoe who helped me with preparing the samples. I would like to thank Geosynthetic Lining System, GSE, for providing geomembranes samples. Finally, special thanks go to my family and my wife for prayers, love, caring, and sacrifices. I could not achieve this work without their encouragements and supports, for which I will always be grateful. vi TABLE OF CONTENTS ABSTRACT ...................................................................................................................... iv DEDICATION ...................................................................................................................... v ACKNOWLEDGMENTS ............................................................................................... vi LIST OF FIGURES .......................................................................................................... x LIST OF TABLES .......................................................................................................... xv CHAPTER I: INTRODUCTION .................................................................................... 1 1.1 Introduction and Motivation for the Thesis .............................................................. 1 1.2 Scope of Thesis ......................................................................................................... 8 CHAPTER II: LITERATURE REVIEW .................................................................... 10 2.1 Overview of Geosynthetics ..................................................................................... 10 2.2 Geosynthetics Definition, Types, and Functions .................................................... 12 2.3 Geosynthetics Manufacture .................................................................................... 17 2.4 Geomembranes ....................................................................................................... 19 2.4.1 Side Slopes of Landfills ................................................................................... 20 2.4.2 Landfill Cover Systems.................................................................................... 21 2.5 History of Research in Soil-Geomembrane Interface ............................................. 22 2.6 Determination of Interface Shear Strength Properties in the Laboratory ............... 22 2.7 Past Studies on the Interface Shear Behavior between Geomembranes and Soils . 25 2.8 Time-Dependent Behavior of Polyethylene............................................................ 31 2.9 Friction and Contact between Surfaces ................................................................... 32 2.10 Effect of Time on Soil-Geomembrane Contact Surfaces ..................................... 35 2.11 Contact of Single Particles and Particle Assemblages .......................................... 39 vii 2.12 Friction of Particle Assemblages and Single Particles ......................................... 40 2.13 Reevaluation of Shear Process .............................................................................. 41 2.14 Temperature Effects on Interface Shear Resistance and Surface Hardness of Geosynthetics ......................................................................................................... 42 2.15 Other Factors Influencing the Interface Shear Characteristics ............................. 45 2.15.1 Shear Displacement Rate ............................................................................... 45 2.15.2 Type and Roughness of Geomembrane ......................................................... 46 2.15.3 Normal Stress ................................................................................................. 46 2.15.4 Shear Box Size ............................................................................................... 47 CHAPTER III: TESTING PROGRAM AND MATERIALS .................................... 48 3.1 Introduction ............................................................................................................. 48 3.2 Materials ................................................................................................................. 49 3.2.1 Ottawa Sand ..................................................................................................... 49 3.2.2 Geomembranes ................................................................................................ 50 3.3 Large Direct Shear Machine ................................................................................... 51 3.4 Selection of Loads................................................................................................... 52 3.5 Equipment ............................................................................................................... 53 3.6 Testing Procedure ................................................................................................... 54 3.7 Calculations............................................................................................................. 61 CHAPTER IV: RESULTS AND DISCUSSION .......................................................... 62 4.1 Introduction ............................................................................................................. 62 4.2 Results ..................................................................................................................... 63 4.2.1 Results of Interface Friction Angles for Instantaneous Loadings .................... 63 4.2.2 Effect of Two Weeks Loading on Geomembranes .......................................... 67 4.3 Discussion ............................................................................................................... 75 4.3.1 Setup the Large Direct Shear Machine ............................................................ 75 4.3.2 Major Problems in the Large Direct Shear Machine ....................................... 75 4.3.3 Discussion of the results of the Interface Friction Angles – Instantaneous Tests 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