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Volume Change and Swelling Pressure of Expansive Clay in the Crystalline Swelling Regime

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Volume Change and Swelling Pressure of Expansive Clay in the Crystalline Swelling Regime VOLUME CHANGE AND SWELLING PRESSURE OF EXPANSIVE CLAY IN THE CRYSTALLINE SWELLING REGIME A Thesis presented to the Faculty of the Graduate School University of Missouri In Partial Fulfillment of the Requirements for the Degree Ph.D. Civil & Environmental Engineering by ALEXANDRA WAYLLACE Dr. William Likos, Thesis Supervisor MAY 2008 The undersigned, appointed by the Dean of the Graduate School, have examined the thesis entitled VOLUME CHANGE AND SWELLING PRESSURE OF EXPANSIVE CLAY IN THE CRYSTALLINE SWELLING REGIME Presented by Alexandra Wayllace A candidate for the degree of Doctor of Philosophy of Civil & Environmental Engineering And hereby certify that in their opinion it is worthy of acceptance. ____________________________ Professor William Likos ____________________________ Professor John Bowders ____________________________ Professor Erik Loehr ____________________________ Professor Stephen Anderson ____________________________ Professor Michael Underwood To my family… ACKNOWLEDGEMENTS I would like to thank first and foremost my advisor, Dr. William Likos. His advice, guidance and support were invaluable throughout my graduate studies and in the completion of this research. Thanks are also due to the other members of my graduate committee, Dr. John Bowders, Dr. Erik Loehr, Dr. Stephen Anderson, and Dr. Michael Underwood. They helped me analyze my research from different perspectives. I would also like to thank the Civil & Environmental Division of Engineering of the University of Missouri-Columbia for supporting my studies during the major part of my graduate studies. Financial support was also provided by the American Chemical Society (Petroleum Research Fund) and the Portland Cement Association Education Foundation. Special thanks are due to Mr. Robert Maytag for first giving me the opportunity to study in this country. Finally, I want to thank my family and friends for their continuous support and encouragement. ii TABLE OF CONTENTS ACKNOWLEDGEMENTS.......................................................................................ii LIST OF FIGURES ..................................................................................................vi LIST OF TABLES ....................................................................................................xi ABSTRACT...............................................................................................................xii CHAPTER I. INTRODUCTION...............................................................................1 1.1 Background...................................................................................................1 1.2 Objectives .....................................................................................................3 1.3 Scope and organization of the thesis.............................................................5 CHAPTER II. LITERATURE REVIEW .................................................................7 2.1 Smectite mineralogy .....................................................................................7 2.2 Water adsorption mechanisms ......................................................................9 2.2.1. Mineral surface hydration................................................................10 2.2.2. Capillarity ........................................................................................11 2.2.3. Osmosis............................................................................................11 2.3 Crystalline swelling .....................................................................................13 2.4 Role of particle and pore properties on swelling behavior ..........................15 2.4.1. Particle and pore fabric ....................................................................15 2.4.2. Effect of interlayer cation ................................................................17 2.4.3. Effect of compaction........................................................................19 2.5 Suction control methods ..............................................................................21 2.5.1. Saturated salt solutions ....................................................................22 2.5.2. Automated humidity control system................................................23 2.6 Typical water vapor sorption behavior for smectite ....................................24 2.7 Pore-scale porosity evolution model............................................................26 2.8 Barcelona Basic Model................................................................................27 CHAPTER III. METHODS AND MATERIALS .....................................................34 3.1 Introduction..................................................................................................34 3.2 Materials ......................................................................................................34 3.3 Specimen preparation...................................................................................37 iii 3.4 Experimental set up......................................................................................39 3.4.1. Salt solutions for control of relative humidity ................................39 3.4.2. Automated humidity control system...............................................44 3.4.2.1. Humidity chamber: free swelling conditions.....................46 3.4.2.2. Humidity chamber: constant strain/constant stress conditions.................................................................48 3.5 Experimental program .................................................................................51 CHAPTER IV. RESULTS.........................................................................................53 4.1 Scanning electron imaging results ...............................................................53 4.2 Void ratio and compaction pressure ............................................................57 4.3 Free swelling behavior.................................................................................60 4.3.1. Sorption isotherms ..........................................................................61 4.3.2. Bulk volume change .......................................................................64 4.4 Swelling pressure under constant strain conditions.....................................68 4.5 Summary of experimental observations.......................................................71 CHAPTER V. ANALYSIS OF RESULTS ...............................................................74 5.1 Interpretation of general observations .........................................................75 5.1.1. Sorption isotherms ..........................................................................75 5.1.2. Bulk volume change and swelling pressure behavior.....................76 5.1.2.1 Sodium smectite...................................................................76 5.1.2.2 Calcium smectite..................................................................81 5.1.2.3 Calcium-exchanged smectite ...............................................82 5.1.3. Effect of compaction density ..........................................................83 5.1.3.1 Effect on bulk volume change .............................................84 5.1.3.2 Effect on bulk swelling pressure..........................................87 5.2 Fabric model for upscaling interlayer volume change.................................89 5.2.1. Idealized fabric geometry ...............................................................90 5.2.2. General model behavior..................................................................92 5.3 Porosity evolution ........................................................................................100 5.4 Barcelona Basic Model................................................................................108 5.4.1. Macrostructural behavior................................................................109 iv 5.4.2. Microstructural behavior.................................................................110 5.4.3. Coupling of micro and macrostructure ...........................................111 5.4.4. Bulk volume change .......................................................................112 5.4.5. Bulk swelling pressure....................................................................119 CHAPTER VI. SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS ...122 6.1 Major observations and conclusions............................................................122 6.2 Recommendations for additional research...................................................128 REFERENCES .........................................................................................................131 v LIST OF FIGURES Figure 1.1 Translation of crystalline swelling to macroscopic volume change and swell pressure ..........................................................................................4 Figure 2.1 Schematic diagram for smectite structure (after Mitchell, 1993) ............9 Figure 2.2 Typical water retention curve (SWCC) for clay showing water adsorption regimes...................................................................................10 Figure 2.3 Distribution of ions adjacent to a clay surface (after Mitchell, 1993)......12 Figure 2.4 Conceptual illustration of the sequential crystalline swelling process for smectite (Likos, 2004) ........................................................................14 Figure 2.5 Pore size distribution by Mercury
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