Volume Change Consideration in Determining Appropriate Unsaturated Soil Properties for ...

456 Pages·2013·8.04 MB·English

by  Sam Abbaszadeh

Volume Change Consideration in Determining Appropriate
Unsaturated Soil Properties for Geotechnical Applications
by
Elham Bani Hashem

A Dissertation Presented in Partial Fulfillment
of the Requirements for the Degree
Doctor of Philosophy

Approved April 2013 by the
Graduate Supervisory Committee:

Sandra Houston, Chair
Edward Kavazanjian
Claudia Zapata

ARIZONA STATE UNIVERSITY
May 2013
ABSTRACT
Unsaturated soil mechanics is becoming a part of geotechnical engineering
practice, particularly in applications to moisture sensitive soils such as expansive and
collapsible soils and in geoenvironmental applications. The soil water characteristic
curve, which describes the amount of water in a soil versus soil suction, is perhaps the
most important soil property function for application of unsaturated soil mechanics. The
soil water characteristic curve has been used extensively for estimating unsaturated soil
properties, and a number of fitting equations for development of soil water characteristic
curves from laboratory data have been proposed by researchers. Although not always
mentioned, the underlying assumption of soil water characteristic curve fitting equations
is that the soil is sufficiently stiff so that there is no change in total volume of the soil
while measuring the soil water characteristic curve in the laboratory, and researchers
rarely take volume change of soils into account when generating or using the soil water
characteristic curve. Further, there has been little attention to the applied net normal
stress during laboratory soil water characteristic curve measurement, and often zero to
only token net normal stress is applied. The applied net normal stress also affects the
volume change of the specimen during soil suction change. When a soil changes volume
in response to suction change, failure to consider the volume change of the soil leads to
errors in the estimated air-entry value and the slope of the soil water characteristic curve
between the air-entry value and the residual moisture state. Inaccuracies in the soil water
characteristic curve may lead to inaccuracies in estimated soil property functions such as
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unsaturated hydraulic conductivity. A number of researchers have recently recognized the
importance of considering soil volume change in soil water characteristic curves.
The study of correct methods of soil water characteristic curve measurement and
determination considering soil volume change, and impacts on the unsaturated hydraulic
conductivity function was of the primary focus of this study. Emphasis was placed upon
study of the effect of volume change consideration on soil water characteristic curves,
for expansive clays and other high volume change soils. The research involved extensive
literature review and laboratory soil water characteristic curve testing on expansive soils.
The effect of the initial state of the specimen (i.e. slurry versus compacted) on soil water
characteristic curves, with regard to volume change effects, and effect of net normal
stress on volume change for determination of these curves, was studied for expansive
clays. Hysteresis effects were included in laboratory measurements of soil water
characteristic curves as both wetting and drying paths were used.
Impacts of soil water characteristic curve volume change considerations on fluid
flow computations and associated suction-change induced soil deformations were studied
through numerical simulations.
The study includes both coupled and uncoupled flow and stress-deformation
analyses, demonstrating that the impact of volume change consideration on the soil water
characteristic curve and the estimated unsaturated hydraulic conductivity function can be
quite substantial for high volume change soils.
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DEDICATION
To my wonderful husband
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ACKNOWLEDGMENTS
First and foremost I offer my sincerest gratitude to my committee chair, Dr.
Sandra L. Houston on her supervision and guidance during my study and research. Her
perpetual energy and enthusiasm in research had motivated me greatly. In addition, she
was always accessible and willing to help me with my research. As a result, research life
became smooth and rewarding for me. She is an excellent teacher and mentor and I shall
always be indebted to her.
I gratefully acknowledge Dr. Claudia Zapata for her advice and crucial
contribution, which made her a backbone of this dissertation. Many thanks to Dr. William
N. Houston, Dr. Delwyn G. Fredlund, and Dr. Edward Kavazanjian for their guidance
and for making the valuable inputs, I am much indebted to them for their advice and
comments.
I am grateful to Dr. Sam Abbaszadeh for his wonderful support, help, and
guidance through this research, particularly with regard to the numerical modeling and
laboratory testing procedures.
I would also like to thank the laboratory manager, Mr. Peter Goguen for his help
throughout my laboratory testing program. Many thanks to Dr. Marcelo Sanchez and
Ajay Shastri of Texas A&M University for their help with numerical modeling using
CODE-BRIGHT.
This dissertation was partially funded by National Science Foundation (NSF)
under grant number 1031238.The opinions, conclusions, and interpretations expressed in
this dissertation are those of the authors, and not necessarily of NSF.
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TABLE OF CONTENTS
Page
LIST OF TABLES .................................................................................................................... x
LIST OF FIGURES ................................................................................................................ xv
CHAPTER
1. INTRODUCTION ................................................................................................................ 1
1.1. Background ........................................................................................................................ 1
1.2. Problem Statement ............................................................................................................. 4
1.3. Research Objectives and Scope of Work .......................................................................... 5
1.4. Report Organization ........................................................................................................... 8
2. LITERATURE REVIEW ................................................................................................... 10
2.1. Introduction ...................................................................................................................... 10
2.2. Soil Water Characteristic Curve Determination ............................................................. 11
2.3. Air-Entry Value (AEV) of Clays ..................................................................................... 15
2.4. Hysteresis in Soil Water Characteristic Curves .............................................................. 17
2.5. Impacts of Stress State on Soil Water Characteristic Curves ......................................... 26
2.6. Correcting Soil Water Characteristic Curves for Soil Volume Change ......................... 33
2.7. Equations to Best-Fit Soil Water Characteristic Curves Data ........................................ 45
2.8. Use of Soil Water Characteristic Curves in Constitutive Relations for Unsaturated
Soils ......................................................................................................................................... 50
2.9. Models of Unsaturated Hydraulic Conductivity ............................................................. 51
2.9.1. Model Proposed by Green and Corey (1971) .................................................. 61
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CHAPTER Page
2.9.2. Model Proposed by Fredlund et al. (2004) ...................................................... 64
2.9.3. Model Proposed by van Genuchten (1980) ..................................................... 68
2.10. Current State of Knowledge .......................................................................................... 74
3. LABORATORY TESTING ............................................................................................... 82
3.1. Introduction ...................................................................................................................... 82
3.2. Laboratory Tests Performed ............................................................................................ 88
3.3. Soils Used in the Laboratory Testing Program ............................................................... 90
3.4. Soil Water Characteristic Tests ....................................................................................... 93
3.4.1 SWCC Determination Using 1-D Oedometer Pressure Plate Cells ................ 93
3.4.2 SWCC Determination Using Filter Paper Test .............................................. 101
3.5. Results of SWCC Tests ................................................................................................. 104
3.5.1. SWCC of Compacted Specimens .................................................................. 106
3.5.2. SWCC of Slurry Specimens ........................................................................... 123
3.5.3. Drying and Wetting SWCC of Compacted Specimens with Various Net
Normal Stresses ........................................................................................................ 132
3.6. Summary and Conclusions ............................................................................................ 155
4. NUMERICAL MODELING OF Expansive Clays ......................................................... 162
4.1. Introduction .................................................................................................................... 162
4.2. Model Geometry ............................................................................................................ 174
4.3. Soil Properties ................................................................................................................ 175
4.3.1. Anthem Soil .................................................................................................... 179
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CHAPTER Page
4.3.2. Colorado Soil .................................................................................................. 181
4.3.3. San Antonio Soil ............................................................................................ 184
4.4. Boundary Conditions ..................................................................................................... 186
4.5. VADOSE/W .................................................................................................................. 188
4.6. SVFLUX ........................................................................................................................ 196
4.7. CODE-BRIGHT ............................................................................................................ 204
4.8. Uncoupled Analysis ....................................................................................................... 210
4.9. Coupled Flow-Deformation Analysis ........................................................................... 213
4.10. Results of Numerical Modeling .................................................................................. 221
4.10.1. Results of Uncoupled Analyses ................................................................... 222
4.10.1.1. Anthem Soil ...................................................................................222
4.10.1.2. Colorado Soil .................................................................................226
4.10.1.3. San Antonio Soil ...........................................................................235
4.10.1.4. Comparing Results Produced by VADOSE/W, SVFLUX, and
CODE-BRIGHT ...........................................................................................239
4.10.1.5. Deformations (Heave) from Uncoupled Analyses ........................242
4.10.2. Results of Coupled Analyses ....................................................................... 249
4.11. Summary and Conclusions .......................................................................................... 264
5. NUMERICAL MODELING OF OIL SANDS TAILINGS ........................................... 277
5.1. Introduction .................................................................................................................... 277
5.2. Properties of Oil Sands Tailings .................................................................................... 283
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CHAPTER Page
5.3. Boundary Conditions ..................................................................................................... 285
5.4. Uncoupled Analyses of Oil Sands Tailings .................................................................. 286
5.5. Results of Uncoupled Analyses of Oil Sands Tailings ................................................. 288
5.5.1. Deformations from Uncoupled Analyses ...................................................... 300
5.5.2. Comparing Results Produced by VADOSE/W, SVFLUX, and CODE-
BRIGHT ................................................................................................................... 305
5.6. Summary and Conclusions ............................................................................................ 307
6. SUMMARY, CONCLUSIONS AND RECOMMENDATIONS FOR FUTURE
RESEARCH .......................................................................................................................... 315
6.1. Summary ........................................................................................................................ 315
6.2. Conclusions .................................................................................................................... 322
6.3. Recommendations for Future Research ........................................................................ 350
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APPENDIX Page
A IMAGES OF SOIL SPECIMENS TESTED BY SWC-150 DEVICE ....................... 369
B RESULTS OF NUMERICAL MODELING: PROFILES OF SOILS SUCTION FOR
CORRECTED AND UNCORRECTED SWCC'S .............................................................. 385

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