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Investigation of Geotechnical and Hydraulic Aspects of Landfill Design and Operation

Permanent Link: http://ufdc.ufl.edu/UFE0042104/00001

Material Information

Title: Investigation of Geotechnical and Hydraulic Aspects of Landfill Design and Operation
Physical Description: 1 online resource (196 p.)
Language: english
Creator: Cho, Young
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: angle, direct, foundation, friction, internal, landfill, municipal, overburden, piezometer, pore, pressure, profiler, settlement, shear, slope, solid, test, waste
Environmental Engineering Sciences -- Dissertations, Academic -- UF
Genre: Environmental Engineering Sciences thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Title: INVESTIGATION OF GEOTECHNICAL AND HYDRAULIC ASPECTS OF LANDFILL DESIGN AND OPERATION This study includes various topics related to landfill design and operation. The topics include evaluating the impact of pressurized liquid addition on the landfill pore pressure development, estimating the settlement of municipal solid waste and the landfill foundation due to waste placement, and evaluating the impact of food waste content on the internal friction angle of municipal solid waste. Pressure transducers were installed around horizontal liquid addition lines with trenches filled with crushed glass, shredded tires, and excavated waste as bedding material. It was found that the added liquids were successfully transferred to the end of the shredded tire and crushed glass trenches without considerable head loss, but were not in the excavated waste trench. As the added liquids migrated outward from the trenches, pressure head dropped sharply near the trenches. This suggests that in the design of landfills with similar horizontal liquids addition systems, a slope stability analysis may need to consider pore pressure variation in waste as a function of horizontal distance. Using analytical models and in-situ pore pressure measurements, horizontal and vertical hydraulic conductivities were estimated to be in the ranges of 7.0times10^(-4) - 3.0times10^(-4) cm/sec and 1.0times10^(-5) - 1.9times10^(-5) cm/sec, respectively. Anisotropy values of horizontal to vertical hydraulic conductivities were estimated to be from 37 to 277. Settlements of a bioreactor landfill subjected to surcharge were investigated using an in-situ settlement profiling technique. During the settlement profiling period, an average settlement rate was estimated to be 3.76 % per year which is 1.4 times greater than an average settlement rate prior to the waste placement (2.66% per year). Overall, relatively wide ranges of the values of compression properties (Cc?, mv, and cv) were estimated: Cc? (0.1 ? 1.7), mv (3.0times10^(-4) ? 7.3times10^(-3) m^2/kN), and cv (0.89times10^(-2) to 1.44times10^(-2) cm^2/sec). Vertical hydraulic conductivities of the bioreacted waste were estimated to be in a range of 4.6times10^(-7) to 9.8times10^(-6) cm/sec. To investigate the settlement behavior of the foundation of a landfill, total pressure cells and settlement sensors were installed under the bottom liner of a municipal solid waste landfill and monitored for 39 months. The readings of the total pressure cells near the toe of the landfill side slope averaged 1.3 times greater than the overburden pressure predictions calculated using the Boussinesq influence factor charts, the waste lift thickness, and the bulk unit weight while overburden pressures beneath the central area were found to be over predicted (average 0.8 of measured to estimated overburden pressure ratio). Settlement predictions made using conventional one-dimensional settlement models (elastic theory and Terzaghi?s consolidation model) did not provide reasonable settlement estimates of the foundation area beneath the landfill side slope toe. Settlement predictions of the area of the landfill central body were over predicted up to 2.6 cm, which might be overly conservative. The impact of food waste content on the municipal solid waste friction angle was studied. Using reconstituted fresh MSW specimens with different food waste content (0, 40, 58, and 80%), 48 small-scale (100-mm-diameter) direct shear tests and 12 large-scale (430 mmtimes430 mm) direct shear tests were performed. A stress-controlled large-scale direct shear test device allowing approximately 170-mm sample horizontal displacement was designed and used. At both testing scales, the mobilized internal friction angle of MSW decreased considerably as food waste content increased. As food waste content increased from 0 to 40% and from 40 to 80%, the mobilized internal friction angles (estimated using the mobilized peak (ultimate) shear strengths of the small-scale direct shear tests) decreased from 39 to 31 degrees and from 31 to 7 degrees, respectively, while those of large-scale tests decreased from 36 to 26 degrees and from 26 to 15 degrees, respectively. Most friction angle measurements produced in this study fell within the range of those previously reported for MSW.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Young Cho.
Thesis: Thesis (Ph.D.)--University of Florida, 2010.
Local: Adviser: Townsend, Timothy G.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2012-08-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0042104:00001

Permanent Link: http://ufdc.ufl.edu/UFE0042104/00001

Material Information

Title: Investigation of Geotechnical and Hydraulic Aspects of Landfill Design and Operation
Physical Description: 1 online resource (196 p.)
Language: english
Creator: Cho, Young
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: angle, direct, foundation, friction, internal, landfill, municipal, overburden, piezometer, pore, pressure, profiler, settlement, shear, slope, solid, test, waste
Environmental Engineering Sciences -- Dissertations, Academic -- UF
Genre: Environmental Engineering Sciences thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Title: INVESTIGATION OF GEOTECHNICAL AND HYDRAULIC ASPECTS OF LANDFILL DESIGN AND OPERATION This study includes various topics related to landfill design and operation. The topics include evaluating the impact of pressurized liquid addition on the landfill pore pressure development, estimating the settlement of municipal solid waste and the landfill foundation due to waste placement, and evaluating the impact of food waste content on the internal friction angle of municipal solid waste. Pressure transducers were installed around horizontal liquid addition lines with trenches filled with crushed glass, shredded tires, and excavated waste as bedding material. It was found that the added liquids were successfully transferred to the end of the shredded tire and crushed glass trenches without considerable head loss, but were not in the excavated waste trench. As the added liquids migrated outward from the trenches, pressure head dropped sharply near the trenches. This suggests that in the design of landfills with similar horizontal liquids addition systems, a slope stability analysis may need to consider pore pressure variation in waste as a function of horizontal distance. Using analytical models and in-situ pore pressure measurements, horizontal and vertical hydraulic conductivities were estimated to be in the ranges of 7.0times10^(-4) - 3.0times10^(-4) cm/sec and 1.0times10^(-5) - 1.9times10^(-5) cm/sec, respectively. Anisotropy values of horizontal to vertical hydraulic conductivities were estimated to be from 37 to 277. Settlements of a bioreactor landfill subjected to surcharge were investigated using an in-situ settlement profiling technique. During the settlement profiling period, an average settlement rate was estimated to be 3.76 % per year which is 1.4 times greater than an average settlement rate prior to the waste placement (2.66% per year). Overall, relatively wide ranges of the values of compression properties (Cc?, mv, and cv) were estimated: Cc? (0.1 ? 1.7), mv (3.0times10^(-4) ? 7.3times10^(-3) m^2/kN), and cv (0.89times10^(-2) to 1.44times10^(-2) cm^2/sec). Vertical hydraulic conductivities of the bioreacted waste were estimated to be in a range of 4.6times10^(-7) to 9.8times10^(-6) cm/sec. To investigate the settlement behavior of the foundation of a landfill, total pressure cells and settlement sensors were installed under the bottom liner of a municipal solid waste landfill and monitored for 39 months. The readings of the total pressure cells near the toe of the landfill side slope averaged 1.3 times greater than the overburden pressure predictions calculated using the Boussinesq influence factor charts, the waste lift thickness, and the bulk unit weight while overburden pressures beneath the central area were found to be over predicted (average 0.8 of measured to estimated overburden pressure ratio). Settlement predictions made using conventional one-dimensional settlement models (elastic theory and Terzaghi?s consolidation model) did not provide reasonable settlement estimates of the foundation area beneath the landfill side slope toe. Settlement predictions of the area of the landfill central body were over predicted up to 2.6 cm, which might be overly conservative. The impact of food waste content on the municipal solid waste friction angle was studied. Using reconstituted fresh MSW specimens with different food waste content (0, 40, 58, and 80%), 48 small-scale (100-mm-diameter) direct shear tests and 12 large-scale (430 mmtimes430 mm) direct shear tests were performed. A stress-controlled large-scale direct shear test device allowing approximately 170-mm sample horizontal displacement was designed and used. At both testing scales, the mobilized internal friction angle of MSW decreased considerably as food waste content increased. As food waste content increased from 0 to 40% and from 40 to 80%, the mobilized internal friction angles (estimated using the mobilized peak (ultimate) shear strengths of the small-scale direct shear tests) decreased from 39 to 31 degrees and from 31 to 7 degrees, respectively, while those of large-scale tests decreased from 36 to 26 degrees and from 26 to 15 degrees, respectively. Most friction angle measurements produced in this study fell within the range of those previously reported for MSW.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Young Cho.
Thesis: Thesis (Ph.D.)--University of Florida, 2010.
Local: Adviser: Townsend, Timothy G.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2012-08-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0042104:00001


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INVESTIGATION OF GEOTECHNICAL AN D HYDRAULIC ASPECTS OF LANDFILL DESIGN AND OPERATION By YOUNG MIN CHO A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORID A IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2010 1

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2010 Young Min Cho 2

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To my mother, father and brother 3

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ACKNOWLEDGMENTS I would like to thank my academic adv isor and committee chairman, Professor Timothy Townsend, for sharing his preci ous knowledge and experience. I was very lucky to work with him. He gave me a wonderful experience to work on these valuable projects, and his tireless endeavors toward academic accomplishment inspired me. I remember his all efforts to train me as a researcher, engineer, and presenter. I would like to thank my other committee members, Professor Frank Townsend, Professor Michael Annable, and Professor David Bloomquist for their guidance in completing my graduate studies. Also, I am ve ry thankful for all supports from people at the Polk County Waste Resource Management, Brooks Stayer, Allan Choate, Sharon Hymiller, Kimberly Byer, Matthew Dial, and David Huff It was always delightful working with them. I thank John Schert of Fl orida Center of Solid and Hazardous Waste Management. Many of my works could not be done without his supports. I would like to thank my friends, Dr. J aehyun, Dr. Yongchul Jang, Dr. Hwidong Kim, Dr. Jaehac Ko, Dr. Brajesh Dubey, Dr. Dinesh Kumar, Dr. Pradeep Jain, Dr. Qiyong Xu, Sejin Yoon, Myunghee Woo, and Hwanchul Cho, for providing me with wonderful advice and support. I acknowledge the support from my friends, Dr. Ravi Kadambala, Edmund Azah, Shrawan Singh, Wang Yu, Sendhil Ku mar, Stephanie Conner, Wesley Oehmig, Jose Antonio Yaquian Luna, and Karamjit Singh. At last, I would like to t hank my mom, dad, and brother for their love, support, and encouragement. I love you. 4

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TABLE OF CONTENTS page ACKNOWLEDG MENTS .................................................................................................. 4LIST OF TABLES ............................................................................................................ 8LIST OF FI GURES ........................................................................................................ 10LIST OF ABBR EVIATION S ........................................................................................... 15ABSTRACT ................................................................................................................... 16 CHAPTER 1 INTRODUC TION .................................................................................................... 19Background ............................................................................................................. 19Problem Stat ement ................................................................................................. 19Research Obje ctives ............................................................................................... 21Research A pproach ................................................................................................ 222 IMPACT OF PRESSURIZED LIQUID A DDITION ON THE PORE PRESSURE IN A BIOREACTOR LANDFIL L .............................................................................. 25Introducti on ............................................................................................................. 25Material and Methods ............................................................................................. 26Backgroun d ...................................................................................................... 26Site Description and Exper imental Prepar ation ................................................ 27Pressure Transducers (Piezomete r) ................................................................. 28Bioreactor O perati on ........................................................................................ 29Hydraulic Conduc tivity ...................................................................................... 30Results and Discussion ........................................................................................... 32Pore Pressure Change in Liqu id Addition Be dding Medi a ................................ 32Pore Pressure Changes within Landfilled Waste .............................................. 34Hydraulic Conductivity and Anisot ropy ............................................................. 36Summary and Conclusions ..................................................................................... 383 IN-SITU SETTLEMENT MEASUREMENTS OF A LANDFILL PREVIOUSLY OPERATED AS A BIOREACTOR SUBJECTED TO SURCHARG E ...................... 48Introducti on ............................................................................................................. 48Material and Methods ............................................................................................. 49Bioreactor Landfill Operation and Characte ristics ............................................ 49Post Bioreactor Settlement Pr ofiling ................................................................. 50Compression Properties and Hydraulic Conductivity Estimation ...................... 52Results and Discussion ........................................................................................... 54 5

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Settlement and Biorea ctor operat ion ................................................................ 54Settlement due to Surcharge ............................................................................ 55Compression Properties and Hydraulic Conductivity of Landfilled MSW .......... 57Summary and Conclusions ..................................................................................... 594 IN-SITU MEASUREMENTS OF LANDFILL FOUNDATION SETTLEMENT AND OVERBURDEN PR ESSURE .................................................................................. 71Introducti on ............................................................................................................. 71Material and Methods ............................................................................................. 72Site Descrip tion ................................................................................................ 72Instrumentation and Da ta Collection ................................................................ 73Unit Conversion of In strument Re adings .......................................................... 75Bulk Unit Weight and Overbur den Pressure Es timation ................................... 76Settlement Pr ediction ....................................................................................... 77Results and Discussion ........................................................................................... 78Overburden Pressure Change with Waste Pl acement ..................................... 78Landfill Foundation Settlement ......................................................................... 81Comparison of Settlement between Predi ction and In-situ Measurements ...... 83Summary and Conclusions ..................................................................................... 845 IMPACT OF FOOD WASTE CONTENT ON THE INTERNAL FRICTION ANGLE OF MUNICIPAL SOLID WASTE ................................................................ 96Introducti on ............................................................................................................. 96Methods and Ma terial ............................................................................................. 98MSW Specimen Pr eparati on ............................................................................ 98Direct Shear Test ........................................................................................... 100Data Analys is ................................................................................................. 101Results and Discussion ......................................................................................... 102Stress-Displacement Response with Different Food Waste Contents ............ 102Change in Mobilized Internal Friction Angle with Food Wast e Content .......... 104Comparison of Internal Friction A ngles with Previ ous studies ........................ 106Summary and Conc lusions ................................................................................... 1076 SUMMARY AND CO NCLUSION S ........................................................................ 117 APPENDIX A SUPPLEMENTAL TABLES .................................................................................. 120B SUPPLEMENTARY FIGURES ............................................................................. 136C LANDFILL BULK DENSITY EST IMATE METHOD OLOGY .................................. 170D UNIT CONVERSION OF PORE PRE SSURE TRANSDUCER RAW DATA AND THERMAL IMPACT CO RRECTION ..................................................................... 171 6

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E DERIVATION OF EQ UATION 2-3 ........................................................................ 172F EXAMPLE CALCULATION OF THE HYDRAULIC CONDUCTIVITY AND ANISOTROPY OF LANDFILLED WASTE USING IN-SITU PORE PRESSURE MEASUREMENT S ............................................................................................... 176G ELEVATION MEASUREMENT US ING A THEODO LITE ..................................... 178H UNIT CONVERSION OF SETTLEMENT PROFILER RAW DATA AND SETTLEMENT ESTIM ATION ............................................................................... 179I EXAMPLE CALCUATIONS OF CO MPRESSION PROPERTIES AND HYDRAULIC CONDUCTIVITY OF LANDFILLED WASTE ................................... 180J UNIT CONVERSION OF SETTLEMENT SENSOR RAW DATA AND BAROMETRIC PRESSURE AND THER MAL IMPACT CORRE CTION ............... 183K UNIT CONVERSION OF TOTAL PRESSURE CELL RAW DATA AND BAROMETRIC PRESSURE AND THER MAL IMPACT CORRE CTION ............... 185L EXAMPLE ESTIMATION OF LANDFI LL FOUNDATION SETTLEMENT ............. 187LIST OF REFE RENCES ............................................................................................. 190BIOGRAPHICAL SK ETCH .......................................................................................... 196 7

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LIST OF TABLES Table page 2-1 Bioreactor operation summary ............................................................................ 402-2 Summary of estimated hydraulic conductivity and anisotropy values of landfilled waste ................................................................................................... 403-1 Summary of the compression properties and hydraulic conductivities (K) of waste in the st udy landf ill .................................................................................... 624-1 Bulk unit weight change of the study landfill unit with wa ste placement ............. 865-1 Composition of MS W specimens for LSDSTs and LSDS Ts ............................. 1095-2 Size and moisture content (MC) of each waste component for SSDST and LSDST .............................................................................................................. 1095-3 Average moisture contents and dry densities (kg/m3) of the spec imens .......... 1105-4 Mobilized internal friction ang le and cohesion values ....................................... 111A-1 Hydraulic conductivities and compressi on properties of waste in previous studies .............................................................................................................. 120A-2 Summary of literature review and st udies on landfill settlement behavior ........ 121A-3 Settlement (%) measurements of the profilin g pipe 1 ....................................... 122A-4 Settlement (%) measurements of the profilin g pipe 2 ....................................... 123A-5 Settlement (%) measurements of the profilin g pipe 3 ....................................... 124A-6 Settlement (%) measurements of the profilin g pipe 4 ....................................... 125A-7 Settlement (%) measurements of the profilin g pipe 5 ....................................... 126A-8 Compressibility properties and hydrau lic conductivities estimated using the data obtained from Pipe 1 ................................................................................ 127A-9 Compressibility properties and hydrau lic conductivities estimated using the data obtained from Pipe 2 ................................................................................ 128A-10 Compressibility properties and hydrau lic conductivities estimated using the data obtained from Pipe 3 ................................................................................ 129A-11 Compressibility properties and hydrau lic conductivities estimated using the data obtained from Pipe 4 ................................................................................ 130 8

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A-12 Compressibility properties and hydrau lic conductivities estimated using the data obtained from Pipe 5 ................................................................................ 131A-13 Profiles of the subsurface soils of the st udy site ............................................... 132A-14 Summary of constrained modu li M of locations A and B .................................. 133A-15 Summary of constrained moduli M of locations C, D, E, and F......................... 134A-16 Summary of constrained moduli M of locations G and H .................................. 135L-1 Example settlement esti mates at loca tion A ..................................................... 189 9

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LIST OF FIGURES Figure page 2-1 Schematic drawings of the cross-sect ional and plan views of the study liquids addition system and piezom eter distri bution ....................................................... 412-2 Pore pressure change in the crus hed glass media trench due to liquids addition ............................................................................................................... 422-3 Pore pressure change in the sh redded tire media trench due to liquids addition .............................................................................................................. 432-4 Temperature variation in the cr ushed glass media trench due to liquids addition ............................................................................................................... 442-5 Pore pressure change as a function of cumulative liquids addition time ............. 452-6 Example plots of pore pressure changes with distance away from the trenches with A) crushed glass and B) shredded tire beddi ng material .............. 462-7 Comparison of pore pressure change as a function of a horizontal distance from the line source bet ween the field data and theor etical esti mates ............... 473-1 Installation of settl ement profili ng pipes .............................................................. 633-2 Cross-sectional views of exis ting and additional waste lifts ................................ 643-3 Schematic drawing of settlement profilin g .......................................................... 653-4 Change in the settlement rate (Rs, %/year) of the study landfill due to bioreactor operation and s ubjected to surcharge ................................................ 663-5 Example plot of false settlement readings recorded during the first settlement profiling (data fr om Pipe 3) ................................................................................. 673-6 Example plots of settlement over time at each settlement measurement location in settlement profiling pipes ................................................................... 683-7 Monthly leachate generation of th e study landfill and pr ecipitation ..................... 693-8 Histograms of the properties of landfilled wa ste ................................................. 704-1 Distribution of instrum ents .................................................................................. 874-2 Schematic cross-sectional view of t he instruments setting in the center berm of the study landfill .............................................................................................. 88 10

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4-3 Seasonal overburden pressure and tem perature variation prior to placing waste .................................................................................................................. 884-4 Examples of best-fit regressions of overburden pressure (P) versus temperature variation (T0-Ti) to estimate thermal correction fa ctors ................... 894-5 Impact of a thermal correction fact or on estimating over burden pressure .......... 904-6 Example of overburden pressure change with wast e placem ent. ....................... 914-7 Comparisons of overburden pressu res between measured and predicted at each monitoring location using topographi c survey data and bulk unit weight estimation on Sept ember 29, 2009 ..................................................................... 924-8 Changes in the ratio of measured to estimated overburden pressure as a function of wast e thick ness ................................................................................. 924-9 Settlement of the l andfill foundation and overburden pressure changes at Point C and C ov er time ..................................................................................... 934-10 Overburden pressure and settlement measurements at each monitoring location ............................................................................................................... 944-11 Comparisons of measured settlement with predicted settlement. ....................... 955-1 Large-scale direct s hear test de vice ................................................................. 1125-2 Stress-displacement response curves of SSDSTs with 0, 40, 58, and 80% food waste specimens under 145 kPa of effective norma l stress ..................... 1135-3 Stress-displacement response curves of LSDSTs with 0, 40, 58, and 80% of food waste specimens under 191 kPa of effective norma l stress ..................... 1135-4 Mohr-Coulomb failure envelopes of A) SSDSTs and B) LSDSTs ..................... 1145-5 Impact of food waste contents in syn thetic fresh MSW on friction angles at different displacement levels ............................................................................ 1155-6 Comparison of values of internal friction angle and cohesion values in this study to those of in previous studies ................................................................. 116B-1 Plan view of the study area of Chapt er 2 .......................................................... 136B-2 Cross-sectional view of t he study area of Chapter 2 ........................................ 137B-3 Data-logger and pore pressu re data downloading ............................................ 138B-4 Hydraulic conductivity versus effective stress ................................................... 139 11

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B-5 Comparisons of pore pressure change as a function of a horizontal distance from the line source bet ween the field data and theoretical estimates for Experiment 1. ................................................................................................... 140B-6 Comparisons of pore pressure change as a function of a horizontal distance from the line source bet ween the field data and theoretical estimates for Experiment 2. ................................................................................................... 141B-7 Plan view of the study landfill of Chapter 3 ....................................................... 142B-8 Changes in waste pr operties with depth ........................................................... 143B-9 Historic settlement records of the st udy landfill site of Chapter 3 ..................... 144B-10 Elevation change over time at each settlement measurement location in settlement profili ng pipe 2 ................................................................................. 145B-11 Elevation change over time at each settlement measurement location in settlement profili ng pipe 3 ................................................................................. 146B-12 Elevation change over time at each settlement measurement location in settlement profili ng pipe 4 ................................................................................. 147B-13 Elevation change over time at each settlement measurement location in settlement profili ng pipe 5 ................................................................................. 148B-14 Logarithm of time fitti ng model to estimate t50 (Pipe 1) .................................... 149B-15 Logarithm of time fitti ng model to estimate t50 (Pipes 1 and 2). ......................... 150B-16 Logarithm of time fitti ng model to estimate t50 (Pipes 2 and 5) ......................... 151B-17 Plan view of the identification of SPTs and CPTs locations at the study landfill of Chapter 4 ........................................................................................... 152B-18 Cross-sectional view of the identification of SPTs and CPTs locations at the study landfill of Chapter 4 ................................................................................. 153B-19 The topographic surveying of the study landfill of Chapter 4 (October 09, 2007) ................................................................................................................ 154B-20 The topographic surveying of the study l andfill of Chapter 4 (April 11, 2008) ... 155B-21 The topographic surveying of the study landfill of Chapter 4 (September 25, 2008) ................................................................................................................ 156B-22 The topographic surveying of the study landfill of Chapter 4 (September 29, 2009) ................................................................................................................ 157 12

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B-23 Variation of overburden pressure and settlement over time due to waste placement at lo cation A .................................................................................... 158B-24 Variation of overburden pressure and settlement over time due to waste placement at lo cation B .................................................................................... 159B-25 Variation of overburden pressure and settlement over time due to waste placement at lo cation D. ................................................................................... 160B-26 Variation of overburden pressure and settlement over time due to waste placement at lo cation E. ................................................................................... 161B-27 Variation of overburden pressure and settlement over time due to waste placement at lo cation F. ................................................................................... 162B-28 Variation of overburden pressure and settlement over time due to waste placement at lo cation G .................................................................................... 163B-29 Variation of overburden pressure and settlement over time due to waste placement at lo cation H .................................................................................... 164B-30 Large-scale direct s hear test de vice ................................................................. 165B-31 Large-scale shear tests results under 96 kPa of norma l stress ........................ 166B-32 Large-scale shear tests results under 192 kPa of nor mal stre ss ...................... 166B-33 Large-scale shear tests results under 287 kPa of nor mal stre ss ...................... 167B-34 Small-scale shear tests results under 48 kPa of no rmal stress ........................ 167B-35 Small-scale shear tests results under 97 kPa of no rmal stress ........................ 168B-36 Small-scale shear tests results under 145 kPa of nor mal stre ss ...................... 168B-37 Small-scale shear tests results under 194 kPa of nor mal stre ss ...................... 169B-38 Small-scale shear tests results under 290 kPa of nor mal stre ss ...................... 169E-1 Saturated flow zone surrounding a hor izontal line source under steady state condition s ......................................................................................................... 175F-1 Example S(R)-R curve to determine Kx .............................................................. 177G-1 Elevation determination us ing a leveling machine ............................................ 178I-1 Example time-consolidation curve: log of time fi tting met hod ........................... 180 13

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K-1 Example best-fit regre ssion to derive a thermal impa ct correction equation for TPC .................................................................................................................. 186 14

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LIST OF ABBREVIATIONS ASTM American society for testing and materials BMP Bio-chemical methane potential CPT Cone penetration test EPA Environmental protection agency FS Full scale HDPE High-Density Polyethylene LSDST Large-scale direct shear test MSW Municipal solid waste NGVD represents U.S. Nation al Geodetic Vertical Datum NOAA National Oceanic and Atmospheric Administration SCADA Supervisory control and data acquisition SPT Standard penetration test SS Settlement sensor SSDST Small-scale direct shear test TPC Total pressure cell US United States VS Volatile solid 15

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Abstract of Dissertation Pr esented to the Graduate School of the University of Florida in Partial Fulf illment of the Requirements for t he Degree of Doctor of Philosophy INVESTIGATION OF GEOTECHNICAL AN D HYDRAULIC ASPECTS OF LANDFILL DESIGN AND OPERATION By Young Min Cho August 2010 Chair: Timothy G. Townsend Major: Environmental Engineering Sciences This study includes various topics rela ted to landfill design and operation. The topics include evaluating the impact of pr essurized liquid addition on the landfill pore pressure development, estimating the settl ement of municipal solid waste and the landfill foundation due to wa ste placement, and evaluating the impact of food waste content on the internal friction angl e of municipal solid waste. Pressure transducers were installed ar ound horizontal liquid addition lines with trenches filled with crushed glass, shr edded tires, and excavated waste as bedding material. It was found that the added liquids we re successfully transferred to the end of the shredded tire and crushed glass trenches without considerable head loss, but were not in the excavated waste trench. As t he added liquids migrat ed outward from the trenches, pressure head dropped sharply near the trenches. This suggests that in the design of landfills with similar horizontal liquids addition systems, a slope stability analysis may need to consider pore pressure variation in waste as a function of horizontal distance. Using ana lytical models and in-situ por e pressure measurements, horizontal and vertical hydraulic conductivities were estimated to be in the ranges of 16

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7.0-4 3.0-4 cm/sec and 1.0-5 1.9-5 cm/sec, respectively. Anisotropy values of horizontal to vertical hydraulic co nductivities were esti mated to be from 37 to 277. Settlements of a bioreactor landfill subjected to surchar ge were investigated using an in-situ settlement profiling technique. Du ring the settlement profiling period, an average settlement rate was estimated to be 3.76 % per year which is 1.4 times greater than an average settlement rate pr ior to the waste placement (2 .66% per year). Overall, relatively wide ranges of the va lues of compression properties (Cc, mv, and cv) were estimated: Cc (0.1 1.7), mv (3.0-4 7.3-3 m2/kN), and cv (0.89-2 to 1.44-2 cm2/sec). Vertical hydraulic conductivities of the bioreacted waste were estimated to be in a range of 4.6-7 to 9.8-6 cm/sec. To investigate the settlement behavior of the foundation of a landfill, total pressure cells and settlement sensors were installed under the bottom liner of a municipal solid waste landfill and monitored for 39 months. The readings of the total pressure cells near the toe of the landfill si de slope averaged 1.3 times greater than the overburden pressure predictions calculated using the Bo ussinesq influence factor charts, the waste lift thickness, and the bulk unit weight, wh ile overburden pressures beneath the central area were found to be over predicted (a verage 0.8 of measured to estimated overburden pressure ratio). Settlement predictions made using conventional onedimensional settlement models (elastic t heory and Terzaghis consolidation model) did not provide reasonable settlement estimates of the foundation area beneath the landfill side slope toe. Settlement predi ctions of the area of the landfill cent ral body were over predicted up to 2.6 cm, which might be overly conservative. 17

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18 The impact of food waste cont ent on the municipal solid waste friction angle was studied. Using reconstituted fresh MSW spec imens with different food waste content (0, 40, 58, and 80%), 48 small-scale (100-mm-diame ter) direct shear tests and 12 largescale (430 mm mm) direct shear tests we re performed. A stress-controlled largescale direct shear test device allowing approximately 170-mm sample horizontal displacement was designed and used. At both testing scales, the mobilized internal friction angle of MSW decreased considerably as food waste content increased. As food waste content increased from 0 to 40% and from 40 to 80%, the mobilized internal friction angles (estimated using the mobilized peak (ultimate) shea r strengths of the small-scale direct shear te sts) decreased from 39 to 31 and from 31 to 7 respectively, while those of large-scale tests decreased from 36 to 26 and from 26 to 15 respectively. Most friction angle measurem ents produced in this study fell within the range of those previously reported for MSW.

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CHAPTER 1 INTRODUCTION Background While new municipal solid waste (M SW) disposal technologies have been developed over the last several decades, landf illing is still the pr eferred method in the United States. In 2005, approx imately 245 million tons of MSW were generated from residents, businesses, and institutions and 54 percent of this was landfilled (US EPA 2007). Difficulties in siting new landfills have led designers and operators to develop new landfill operation technologies, stimulat ing decomposition of landfilled waste and thus enhanced airspace (waste disposal capa city) recovery. Subsurface pressurized liquid addition technologies (referred to as bioreactor landfill operation) were developed as part of such efforts. The benefits of bioreactor landfill operat ion are well documented by multiple researchers (Pohland 1975; Townsend 1995; Townsend et al., 1996; Reinhart 1996; Townsend and Miller 1998; Reinhart et al., 2002). Introducing liquid into a landfill enhances waste decom position, and consequently, airspace can be recovered. In addition, stimulated waste stabilization reduces the required period for post-closure care of a landfill. Finally, the landfill leachate tr eatment cost can also be mitigated. Problem Statement The slope stability of a landfill is a majo r concern of designers and operators. Since liquids are added under pressure, under standing pore pressure variation in bioreactor landfills becomes especially import ant. That is, increased pore pressure due to pressurized liquids addition may decr ease an effective normal stress and therefore the slope stability of those l andfills. In spite of the im portance of monitoring pore pressure inside a landfill, few in-situ measur ement studies of the impact of pressurized 19

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liquid addition on the pore pressure change have been conducted. In addition, the internal friction angle of waste is one of the most important param eters to decide the side slope angle of a landfill. In previous studies, a wide range of friction angles have been reported, most typi cally between 15 and 35 which may lead to practical difficulties in applying friction angles reported in literature for landfill design (Kavazanjian et al. 1995; Kavazanjian et al. 1999; Sadek et al. 2001; Machado et al. 2002; Mahler and Netto 2003; Harris et al. 2006; Gabr et al. 2007; Zhan et al. 2007; Zekkos et al. 2007; Kavazanjian 2008; Zekkos et al. 2008; Reddy et al. 2009). Another geotechnical engineer ing factor of importanc e in landfill design and operation is landfill settlement. Researcher s and landfill owners are usually interested in landfilled waste and landfi ll foundation settlement. Unex pected instances of both may result in damage to landfill infrastructure su ch as landfill gas or leachate collection systems. Because the failure of those systems may result in deleterious consequences (e.g., the contamination of soil and groundwater), it is one of the major concerns of landfill design and operation. The aforementioned settlements were commonly predicted using various equations of conventi onal soil mechanics such as elastic theory and Terzaghis one-dimensional consolidation model (Sower s 1973; Powrie and Beaven 1999; Landva et al., 2000; Machado et al., 2002; Anderson et al., 2004; Durmusoglu et al., 2006). However, to the authors k nowledge, no landfill foundation settlement measurement using an in-situ hydrostatic settlement sensor has been conducted to verify these models. Therefore, the reli ability of such landfill foundation settlement predictions is in question. In addition, no study has been performed which investigates 20

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the settlement of a landfill previously operated as a bioreactor due to additional waste placement (surcharge). Research Objectives This doctoral research explores a number of important aspec ts of landfill design and operation. By conducting field-scale ex periments, mechanical and hydraulic properties of landfilled MSW were investigat ed. In addition, the variation of load and settlement of landfill foundation due to waste placement were monitored using in-situ instrumentation (total pressure cells and settlement sensors). Shear strength parameters (e.g., internal friction angle and apparent cohesion) of compacted MSW were estimated by conducting smalland large-scale direct shear tests. The first objective was to provide in-sit u measurements of pore pressure variation in waste due to liquids addition into horiz ontal trenches. Pore pressure was monitored by pressure transducers within the waste and the trenches surrounding the horizontal lines. As part of the in-situ data analysis fo r head loss in waste, hydraulic properties of landfilled waste (e.g., hydraulic conducti vity and anisotropy) were estimated by comparing field data with analytical models (Townsend 1995). The second objective was to present the settlement monitoring results of an MSW landfill due to additional waste placement. The settlement was measured using a settlement profiler. Assuming the settlement of the study landfill could be modeled as the consolidation settlement of soil, compression properties (e.g., coefficients of volume change, coefficients of consolidation, and modified primary compression indices) and hydraulic conductivities of waste were determi ned. The results are expected to provide better understanding of the settlement behavior of landfilled waste and basic inputs for landfill settlement pr ediction models. 21

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The third objective was to present the monitoring results of load variation and settlement of the foundation of an operating municipal solid waste landfill using field instrumentation consisting of settlement s ensors and total pressure cells. The in-situ settlement data (spanning 39 months) were compared with theoretical settlement estimates made using convent ional one-dimensional settl ement models (elastic settlement and Terzaghis consolidation). The fourth objective was to investigate the relationship between the internal friction angle of waste and food waste content. The food waste content in municipal solid waste varies geologically and seasonally, (2 70% by wet weight). This study is expected to provide guidelines for landfill designers to decide an internal friction angle of waste and thus a landfill side slope angle. Research Approach Objective 1. Evaluating the impact of pressu rized leachate addition on the pore pressure in a bioreactor landfill Approach. Two 110-m horizontal leachate addition lines were installed in excavated waste, crushed glass and shredded tire bedding media trenches (0.9 m 0.9 m 110 m). A total of eight y one vibrating wire pressure transducers (piezometers) were installed around the horizontal lines. The data was collected every 30 minutes during the operation of the leachate addition system. Liquids were added at a constant flow rate of 0.076 m3/min. Liquids addition was continued until pressure reached a halting pressure designated by the bioreac tor operation permit. The pore pressure variation in and near media trenches due to pressu rized liquids addition were monitored. Objective 2. Evaluating the impact of additi onal waste placement on the settlement of a landfill previously operated as a bioreactor landfill 22

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Approach. The settlement was measured by employing five 46 m settlement profiling pipes with 10-cm diameter, which were installed on the top surface of a landfill previously operated as a bioreacto r landfill. The initial locations and elevations of each pipe were surveyed in September 2008. Another waste lift was placed on top of the bioreacted waste layer from November to De cember 2008. Using a settlement profiler, settlement was monitored from December 2008 to March 2010. The relationship between landfill settlement and overburden pre ssure increase was investigated based on in-situ settlement measur ements. In addition, comp ression parameters (e.g., modified primary compressibility index, coefficient of consol idation and coefficient of volume change) and hydraulic conductivity of the landfilled waste were estimated based on the field settlement data. Objective 3. In-situ measurements of landfill foundation settlement and overburden pressure variati on due to waste placement Approach. Prior to waste placement, vibrati ng wire settlement sensors and total pressure cells were installed under the bottom liner of the study landfill in February 2006. The data from the instruments were collected periodically (every 2 to 4 weeks) before and during active waste placement. In-situ overburden pressure measurements during waste placement were compared with theoretical estimates. Based on standard penetration and cone penetration tests conducted before the landfill foundation construction, the theoretical settlements of the foundation as a function of vertical stress were calculated and compared with actual settlements. Objective 4. Evaluating the impact of food waste content on the internal friction angle of MSW 23

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24 Approach. Small-scale direct shear tests (SSD STs) and large-scale direct shear tests (LSDSTs) were conducted on fresh sy nthetic MSW samples containing various amounts of food waste (0, 40, 58, and 80% by wet weight). To pr epare a reproducible specimen, eight representative waste co mponents were selected: food waste, paper, plastic, metal, wood, textile, glass, and ash. For SSDSTs, a typical soil direct shear test machine with a 10-cm-diameter and 5-cm-height shear box was used. For LSDSTs, a stress-controlled direct shear box test ing device (430mm length 430mm width) was constructed and used. The effective norma l stresses used for SSDSTs were 48, 97, 145, 194, and 290 kPa, and those for the LSDSTs were 96, 192, and 287 kPa. Outline of Dissertation This dissertation is presented in six c hapters. Chapter 1 presents introductory material, problem statement, objectives, and research approach. Chapters 2 through 5 provide the methodologies, results and discussi on of each individual research topic. The results of evaluating the impact of pressurized leachate addition on the pore pressure in a bioreactor landfill are present ed in Chapter 2. Chapter 3 presents the results of evaluating the impact of additional waste placement on the settlement of a landfill previously operated as a bioreactor landfill. Chapter 4 presents the results of investigating the impact of waste placement on the landfill foundation settlement. The impact of food waste content on the internal friction angle of MSW is presented in Chapter 5. Chapter 6 provides the comprehensive summary and conclusion of the entire research of this dissertation. Supplementary tables, figures, and example calculations to determine various paramet ers are provided in the appendices. Cited references are incl uded at the end.

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CHAPTER 2 IMPACT OF PRESSURIZED LIQUID ADDIT ION ON THE PORE PRESSURE IN A BIOREACTOR LANDFILL Introduction In recent decades, numerous efforts have been made to develop and improve techniques for liquids addition into waste as part of bioreactor landfill operations (Pohland 1975; Townsend 1995; Townsend et al., 1996; Reinhart 1996; Townsend and Miller 1998; Reinhart et al., 2002). Buried horizont al liquids addition lines consisting of perforated pipes bedded in a trench with porous media are one of the more common methods because of good moisture distribution and less odor and vector issues compared to surface systems. Hydraulic pr operties (e.g., hydraulic conductivity and anisotropy) of landfilled material are key param eters for the design of liquid distribution systems; in this chapter anisotropy is defined as the ratio of horizontal to vertical hydraulic conductivities. The design of hor izontal liquids addition systems includes specification of spacing between trenches, b edding material, and operating constraints such as flow rate and pressure. The engineer s goal is to provide the landfill operator with a system that both provides needed moisture distribution in the target time period and prevents deleterious outcomes such as seeps and slope failure. While mathematical models to predict the movem ent of liquids added into a landfill have been developed and serve as helpful design tools (Townsend 1995; Reinhart and Townsend 1997; Al-Yousfi and Pohland 1998), a better understanding of actual field performance (e.g., moisture distribution and requir ed pressure) is needed. Only limited field experiments, however, have been conducted (Townsend 1995; Jain 2005; Townsend et al. 2008). 25

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This chapter reports the results of study at an operational la ndfill where liquids were added through horizontal lines, and the im pact of the pressurized liquids addition on pore pressures in the waste surrounding th e lines were examined. To monitor pore pressure variation, eighty one pressure tran sducers were installed within the waste and the trenches surrounding the horizontal lines. As part of the in-situ data analysis for head loss in waste, hydraulic conductivity and anisotropy of landfilled waste were roughly estimated by comparing field data with analytical models (Townsend 1995). Material and Methods Background The study landfill site and liquids addi tion system described here has been the subject of other research. Larson (2007) c onducted air addition tests using thirteen pressure transducers to determine the in-pla ce vertical air permeability of landfilled waste overlain by 3 6 m of waste plus cover soil layer (January March 2006). By comparing the field pore pressure measurements to a hydrogeologic analytical solution derived by Shan (1995) and revised by Shan and Javendel (1999), air permeability in the range of 2-13 to 8-13 m2 was estimated. Larson (2007) report ed that the corresponding vertical hydraulic conductivities were estimated to be 1.9-4 to 7.8-4 cm/sec. Kumar (2009) studied the spatial variation of pore water pressure in waste as a result of pressurized liquid addit ion from July to October 2007. At a constant flow rate of 0.057 m3/min, liquids were intermittently added through horizontal lines in bedding media trenches filled with shr edded tires, crushed glass, or excavated waste. The current study is the follow-up study of Kuma r (2009). This chapter includes the results and discussion of Kumars 2009 study which is designated as Experiment 1. The 26

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experiment conducted by the author is designated as Experiment 2. The main difference between Experiment 1 and Experiment 2 was liquids addition flow rate; a flow rate of 0.076 m3/min was used for Experiment 2. In addition, during Experiment 2, liquids were added into the tire and glass tr enches, not into the excavated waste trench. Site Description and Experimental Preparation Three horizontal liquids addition lines in trenches surrounded by bedding media were constructed on a 5,000 m2 area of a municipal solid wa ste landfill in Florida. Figure 2-1 shows the plan and cross-sectional views of the study area; detailed plan and cross-sectional views are provided in Figures B-1 and B-2, respectively. The three trenches were excavated to dimensions of 0.9 m 0.9 m 110 m; the distance between the trenches was approx imately 15 m. The trenches were back-filled to a height of 0.6 m with excavated waste, shr edded tires, or crushed glass. A 110-m length of perforated 10-cm-diameter HDPE pipe was placed in each trench. Two 1-cm perforations were added at 0.6-m intervals al ong with the pipe; the pipe was placed with the perforations facing downward at an angle of 90 to each other. The remaining top 0.3 m of each trench was backfille d with the same bedding media. Upon completion of waste filling (November 2007), the thickness of waste plus cover soil layers on top of the trenches was approximately 19 m. Experiment 1 was conducted from July to October in 2007, before the entire landf ill capacity had been reached, but after the completion of wast e placement over the horizontal lines. Experiment 2 was performed in April and May of 2010, approximately 30 months after the completion of the landf illing. Because no additional lift had been placed since Experiment 1, the thickness of the waste plus cover soil layers on top of the horizontal 27

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trenches during Experiment 2 was assumed to be same as that during Experiment 1. The details of the experiments are explained in a later section. A total of eighty one vibrating wire pr essure transducers were installed surrounding the liquids addition lines for the in-situ measurement of pore pressure change due to pressurized liquids addition (Figure 2-1). To prevent damage, as recommended by Geokon, Inc. (vendor), each pr essure transducer was inserted into a sand bag saturated with water. Also, the sand was chosen to quickly transmit the pressure developed in waste to the pressure transducer. The transducer wires were encased in PVC pipes filled with polyuret hane expanding foam to prevent damage and preferential liquid flow. As shown in Figure 21, two layers of transducers were installed in a V formation around each pipe. This fo rmation was selected to prevent disturbing the migration path of added liquids from the trenches to each transducer. Pressure Transducers (Piezometer) The pressure transducers (Model 4500S, Geok on, Inc.) were factory calibrated to a gauge pressure range of 0 to 345 kPa with a reported accuracy and resolution of 0.34 kPa and 8.6-2 kPa, respectively. The transducers were designed with thermistors to correct for the effects of temperature. T he thermistors have a measurement range of -20 C to 80 C. The transducer wires were connected to a data-logger (CR10X, Geokon, Inc.) placed on the side slope of the study landfill. The responses from all pressure transducers were recorded by the data-logger every 10 minutes for Experiment 1 and every 30 minutes for Experiment 2; the liquids addition data for the line in the excavated waste media trench were collected hourly. A laptop computer was used to download the raw frequency and temperature data fr om the data-logger (Figure B-3). 28

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The raw data (Hz) of each pressure trans ducer was converted to pressure (kPa) using the calibration reports that were s pecific to each pressure transducer. The calibration equation for the pressure transduc ers was provided by the manufacturer as follow: 21000 Hz R (2-1) P = G(R0-Ri) + K(Ti-T0) (2-2) where R = reading (digits); (Hz) = raw data of a pressure transducer; P = pressure (kPa); G = calibration factor (kPa/digits); R0 = initial reading (digits); Ri = reading at time i (digits); K = temperatur e correction factor (kPa/ C); Ti = temperature at time i ( C); T0 = initial temperature ( C). An example calculation is provided in Appendix D. Bioreactor Operation The bioreactor operation syst em at the study landfill was designed and built with a supervisory control and data acquisition (S CADA) system. Operation data such as liquids addition pressure, flow rate, added volume, and operation time were automatically recorded by the SCADA system The bioreactor system was operated 3 to 7 hours a day depending on the fiel d situation; due to various reasons (e.g., periodic SCADA system maintenance, breakage of a liquid distribution pipe, and cleaning leachate storage tanks), the bioreactor syst em was often stopped. In addition, the bioreactor operation permit limited the liquids addition pressure under a halting pressure in each horizontal line: 237 kPa for the excavated waste trench, 238 kPa for the shredded tire trench and 219 kPa for the crus hed glass trench. These halting pressures were estimated by summing hydrostatic pressure (the average elevation of each 29

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horizontal line which was in itially placed unit weight of water, 9.8 kN/m3) and 34 kPa of liquids addition pressure (the limit set in t he permit of the study bi oreactor landfill). This study consisted of two sets of liquids addition experiments; the details of the experiments are summarized in Table 2-1. In Experiment 1, liquids were added into all three lines at a constant flow rate of 0.057 m3/min until liquids addition pressures reached the halting pressures. During this peri od, the results from fifty out of eighty one pressure transducers were found to be useful to monitor the pore pressure variation. The rest of the transducer s produced unrealistic data (K umar 2009). One possible explanation for this high failure rate coul d be harsh landfill conditions (e.g., sharp material and compaction efforts) which result ed in damage to the instruments. During Experiment 2 (conducted in 2010), the lines in the shredded tires and crushed glass trenches were operated at a constant flow rate of 0.076 m3/min; no liquid was added through the line in the excavated waste trench. In the course of this experiment, twenty one out of eighty one pressure transducers were determined to be working properly. Hydraulic Conductivity Using the in-situ spatial pore pressu re change data, vertical and horizontal hydraulic conductivities of the landfilled waste could be r oughly estimated. Vertical hydraulic conductivities (Ky) were estimated using Equati on 2-3, which was developed to determine the horizontal extent of satura ted zone of a horizontal liquids addition line source (Townsend 1995); the derivation of E quation 2-3 is provided in Appendix E, and an example calculation of Ky using Equation 2-3 is pr esented in Appendix F. 4y wellq K x (2-3) 30

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where q = constant linear flow rate (flo w rate per unit length of line source, m2/sec); Xwell = horizontal maximum extent of saturated zone at the elevation of the horizontal liquids addition line source (m). Xwell values were determined based on in-situ pore pressure variation monitoring results. A Xwell value is a distance from the line source where practically no pressure is build-up; in this study, 5 kPa of pore pressure build-up was assumed to be practically negligible. Several assumptions need to be made to use Equation 2-3 (Townsend 1995) First, the medium is homogeneous and that axes of anisotropy of hydraulic conductivities are the principal axes of the system. Second, the primary driving forces for liquid transport are liquid addition pressure and gravity; capillary force within landfilled waste is negligible. Third, t he trench can be treated as a horizontal line source. Fourth, there is no el evation difference betw een the center of a horizontal line source and a pressure trans ducer (no gravity influence). Fifth, the distance between the line source and the landfill bottom is infinite and liquid flow downward is not deterred. With the same assumptions made for Equation 2-3, horizontal hydraulic conductivities could be roughly estimated us ing Equation 2-4 introduc ed by Bear (1979) and utilized by Townsend (1995). ()()()ln 2wRRr w xyq S r KK R (2-4) where S(R) = head drawdown (m); (R) = potential at a distance R (m); (rw) = potential in a horizontal trench (m); R = horizontal distance from a line source (m); rw = effective well radius (m); Kx = horizontal hydraulic conductivity (m/sec). A (KxKy)0.5 value was determined by finding a theoretical S(R)-R curve closest to an actual S(R)-R curve plotted based on the in-situ measurements; by varying (KxKy)0.5 values while keeping other 31

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parameters constan t, theoretical S(R)-R curves were developed and superimposed on an actual S(R)-R curve. Note that Equation 2-4 was developed to determine head loss (or build-up) as a function of horizontal dist ance from a vertical recharging well (Bear 1979). An effective well radius (rw) of 0.45 m (half of the trench width) was assumed; assuming rw = 0.3 and 0.6 m, Kx values were also determined. Since a steady-state condition with respect to li quids addition pressure was not achieved during the study period, the highest pressure values within the trenches were used for Equation 2-4. In Appendix F, an example calculation of Kx using Equation 2-4 is provided. Results and Discussion Pore Pressure Change in Liquid Addition Bedding Media Figures 2-2 and 2-3 present the responses of the pressure transducers in the crushed glass trench and the shredded tire tr ench for multiple days of intermittent liquids addition runs. G1/T1, G2/T2, and G3 /T3 are at distances of 0, 50, and 110 m away from the entry of each perforated pipe in each trench. When leachate addition began, the transducers in the trenches responded in a relatively short amount of time (approximately 30 minutes) to the pressure developed by the leachate addition. The injected leachate was delivered to the end of the trenches without considerable head loss. Based on the observation, crushed glass and shredded tires are good options as trench bedding material in bioreactor landfill design. During Experiment 1, liquids addition through the excavated waste trench was attempted. Liquid addition pressure increased up to its halting pressure (237 kPa) in just one day. This might be explained by the low permeability of waste surr ounding the line. In this study, 1.2-4 7.5-4 cm/sec and 8.2-6 2.1-5 cm/sec were estimated fo r horizontal and vertical hydraulic conductivities, respectively; the details of these hydraulic conductivity 32

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estimates are discussed in a later section. No liquid addition occurred following that day as the pressure required for addition would have been higher than allowed in the bioreactor operation permit. The times required for the trenches to be filled with added liquids were roughly estimated based on the data of temperature variation resulting from liquids addition. The hypothesis was that because the injected leachate had a much lower temperature (2025 C) than that of the waste in the study landfill (55-65 C), the temperature at each thermistor started to drop when the injected leachate re ached the thermistor; after leachate addition ceased, temperature gradually increased back to the surrounding temperature. Figure 2-4 shows the responses of the thermistors in the crushed glass trench during Experiment 2. Tem perature variations at G2 an d G3 were relatively small compared to G1 until day 6, corresponding to approximately 18 hours of cumulative liquids addition time; it was at this time that the tem perature began to drop sharply as more added liquids arrived. Similarly, it was found the tire trench was filled in approximately 16 hours of cumulative liqui ds addition during both Experiment 1 and Experiment 2. Theoretical estimations at flow rates of 0.057 and 0.076 m3/min suggested that approximately 3 8 additional hours liquids addition was needed for the saturation of the trench; assuming 0.5 of void ratio, void space volume = 0.5 ( 0.9 0.9 110) m3 = 44.6 m3. These delays in the trench saturation might be because some of the liquid add ed was distributed into surrounding waste while liquids were still being intermittently added. Du ring Experiment 1, approximately 35 hours (double the time needed in Experiment 2) was needed to fill the glass trench. The reason for this large difference is not clear ; the experimental conditions (e.g., liquids 33

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addition flow rates, the thickness of waste on top of t he lines and hydraulic conductivities of the waste) during Experi ment 1 and Experiment 2 were consistent. Once liquids addition stopped, pore pressu re built-up in the trenches began to dissipate as the added liquids migrated into the waste surrounding the trenches. In the case where liquids were added before the por e pressure built by previous additions dissipated, the pore pressure increased cu mulatively. Because pore pressure in landfilled waste at a constant liquids addition flow rate increases cumulatively, higher addition pressure is required to inject t he same amount liquid ac hieved from previous addition. Therefore, intermittent operati on with proper resting (shut-off) time is recommended to bioreactor landfill operators. Figure 2-5 shows the pore pressure change s in the trenches as a function of cumulative liquids addition time. During the study period, addition pressures (pore pressure in the trenches) seemed to approach steady-state at constant flow rates of 0.057 and 0.076 m3/min. In a later section, the peak pressures of the last addition events were considered pseudo steady-state addi tion pressures to estimate hydraulic conductivities and anisotropy of landfilled waste. Pore Pressure Changes within Landfilled Waste Figure 2-6 shows examples of the responses of the transducers in stalled at certain horizontal distances away from each additi on trench. The magnitude of pore pressure due to liquids addition decreased remarkably wit h distance away from the trench; the greatest pressure drop was observed near the trenches. For example, liquid added into the glass trench traveled through waste approx imately 1.1 m, 30 kPa of pressure loss was measured (Figure 2-6-A). The pressure drop between the trans ducers at 1.1 m and 2.6 m was 3 kPa (Figure 2-6-a). Figure 2-6-A clearly shows t he trend of the decrease in 34

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pore pressure with increasing distance away from the crushed glass trench. However, the pore pressure responses detected by the transducers surrounding the shredded tire trench showed no trend (Figure 2-6-B). During liquids addition through the pipe in the excavated waste bedding media, no considerable pressure build-up was detected by the transducers in the waste surrounding the trench. Overall, high pressure zones due to liquids addition were only observed in cl ose proximity to the crushed glass and the shredded tire trenches. Given that the spac ing between horizontal trenches is much greater than the radius of t he trenches, pressurized liquids addition should be much less of a slope stability concern compared to the case where pressures are assumed uniform throughout the waste. To estimate vertical hydraulic conductivity (Ky) using Equation 2-3, one must first determine the horizontal extent of the satura ted zone at the elevat ion of a horizontal trench (xwell). Values for xwell could be determined by examining pore pressure in the waste as it varied horizontally away from the trenches; these values are presented -in Table 2-2. For example, while pore pressure in the glass trench increased as high as 40 kPa during Experiment 1, only 5 kPa of pressure build-up wa s detected at a distance of 11.4 m. Based on this in-situ observation, xwell for the tire trench during Experiment 2 was determined as 11.4 m (Figure 2-7). In the same manner, xwell for the shredded tire trench was determined to be 21.3 m during Experiment 1. During Experiment 2, xwell was estimated at 23 m for the crushed glass trench; note that during Experiment 2 xwell for the shredded tire trench was not estima ted because liquids were added only for 24 cumulative operation hours in which liquid addition pressure was not considered to reach steady or ps eudo steady state. 35

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Hydraulic Conductivity and Anisotropy Using the xwell values determined in a previ ous section and Equation 2-3, Ky values of the landfilled waste surrounding the crushed glass and shredded tire trenches were estimated to be 1.0-5 and 1.9-5 cm/sec, respectively (Table 2-2). The Ky estimates of this study fell into a range of 3.0-6 to 1.5-2 cm/sec reported by other researchers (Townsend et al., 1995; Powrie and Beaven 1999; Durmusoglu et al., 2006). Note that the Ky values (1.9-4 7.8-4 cm/sec) estimated by Larson (2007) at the same landfill site are 10 to 78 times greater than those determined in this study. This difference might be attributed to the change in overburden stresses. The thicknesses of waste plus cover soils over the horizont al lines were 3 6 m when Larson (2007) conducted the study. Bleiker et al. (1995) and Powrie and Beaven (1999) indicated that hydraulic conductivity of landfilled wast e decreased with increas ing effective stress applied to the waste. Figure B-4 adapted from Bleiker et al. (1995) shows the variation of hydraulic conductivity with increasing effe ctive stress. Assuming a bulk unit weight of 12 kN/m3 and 19-m waste plus cover soil, an estimated load of 228 kPa was applied above the landfilled waste. At 228 kPa of effective stress, hydraulic conductivities fell into a range between 5.0 10-6 cm/sec and 1.5 10-5 cm/sec (Figure B-4); this range is close to that for Ky estimated in this study (1.0-5 1.9-5 cm/sec). Using the equation of K (m/sec) = 2.1( v)-2.71 introduced by Powrie and Beaven (1999), a Ky value was estimated at approximately 8.6-5 cm/sec. For each liquid addition exper iment, theoretical pore pressure variation as a function of horizontal distance (R ) from the center of the horizontal wells were estimated using Equation 2-4 and compar ed with in-situ measurements; an example plot is provided in Figure 2-7. Ov erall, a similar trend was observed from both the 36

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mathematical model and the in-situ data; pore pressure decreases with increasing horizontal distance. This trend in the field data became more obvious as liquids addition was continued (Figure 2-7). By varying (KxKy)0.5 values at a given flow rate and a given liquid addition pressure (pore pr essure in trench), mathematic al model plots close to insitu measurements could be developed. As (KxKy)0.5 value decreased, greater head drawdown was estimated at a given distance. In Experiment 1, t he theoretical pore pressure drawdown curves were cl ose to in-situ measurements where Kx values were 9.0-4 cm/sec and 2.5-3 cm/sec for the waste surrounding the crushed glass trench and the shredded tire trench, respectively. In Experiment 2, a Kx value of 2.53 cm/sec was estimated for the waste surro unding the crushed glass trench. Note that the Kx values were determined assuming rw = 0.45 m (half of the trench width). It was found that the variation of Kx values with respect to rw values (0.3 0.6 m) was not considerable (Table 2-2); the plots of the theoretical and actual head drawdown distance curves for rw = 0.3 m, 0.45 m, and 0.6 m are pr ovided in Figures B-5 and B-6, respectively. Using the estimated values of Kx and Ky, anisotropy (Kx/Ky) was estimated in the range of 37 to 277 (Table 2-2); this is much greater than anisotropy values (2 8) reported in literature (Landva et al., 1998; Hudson et al., 1999). This difference might be attributed to waste compaction efforts and wa ste composition. The anisotropy values estimated based on Experiment 2, conducted in 2010, were generally greater than the values estimated based on Experiment 1, conducted in 2007. There was no additional waste placement during the period between Experiment 1 and Experiment 2. Hence, 37

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the greater anisotropy during Experiment 2 might be due to settlement of waste with decomposition, resulting in a horiz ontal flattening of the waste. Summary and Conclusions Pore pressure variation in a bioreactor landfill was monitored while adding liquids under pressure. Pore pressure transducers we re installed in liqui ds-introducing bedding media trenches and in the surrounding waste. This study consisted of two sets of experiments; during Experiment 1 (2007) and Experiment 2 (2010), liquids were added intermittently up to 7 hours per day at constant flow rates of 0.057 m3/min and 0.076 m3/min, respectively. Transducers in the bedding medi a trenches responded relatively quickly (30 min) to liquid addition pressure. Added liquids were successfully transferr ed to the end of the crushed glass and the shredded tire trenches This was confirmed by monitoring temperature variation in the trenches; temp erature inside the tr enches dropped sharply once added liquids reached each monitoring point. Hence, the bedding media used here (crushed glass and shredded tires) represent good options for porous media for this type of liquids addition systems. Horizont al liquid distribution wit hin landfilled waste was also studied by monitoring pore pressure variation. Pressure build-up close to the limit set in the study bioreactor landfill op eration permit was only observed within the trenches. Pressure dropped sharply near t he trenches and then gr adually with distance away from the trenches. Thus, a slope stab ility analysis for bioreactor landfills equipped with this type of liquids addition systems should consider the rapid pressure loss in the waste with distance away from the injection source. Using analytical models presented by Townsend (1995 ) and in-situ measurements, hydraulic conductivities of the landfilled waste surrounding the horizontal trenches were 38

PAGE 39

39 estimated. Horizontal hydraulic conductivi ties were estimated in a range of 7.0-4 to 3.0-3 cm/sec, while estimated vertical hydraulic conductivities fell into a range of 1.0-5 to 1.9-5 cm/sec. Certain assumptions were made to estimate the hydraulic conductivities, but the estimated values fell with in a range reported in literature. Thus, it is concluded that the analytical models introduced in this chapter can be used as simple, useful tools to estimate hydraulic conductivities of landfilled waste. Anisotropy values of horizontal to vertical hydraulic conductivities were estimated to be in the range of 37 to 277; the magnitude of this data range, higher than reported in literat ure, may be due to compaction efforts during waste placement.

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Table 2-1. Bioreactor operation summary Trench bedding material Operation duration (days) Cumulative volume of leachate injected (m3) Addition flow rate (m3/min) Experiment 1 (2007) Shredded tire 14 309 0.057 Crushed glass 12 281 Excavated waste 1 24 Experiment 2 (2010) Shredded tire 6 106 0.076 Crushed glass 11 214 Excavated waste Table 2-2. Summary of estimated hydraulic conduc tivity and anisotropy values of landfilled waste Bedding material xwell (m) rw (m) Kx (cm/sec) Ky (cm/sec) Anisotropy (Kx/Ky) Experiment 1 (2007) Q = 0.057 m3/min Crushed glass 11.4 0.30 1.04-3 1.89-5 55 0.45 8.96-4 47 0.60 7.01-4 37 Shredded tires 21.3 0.30 2.80-3 1.01-5 277 0.45 2.47-3 245 0.60 2.08-3 206 Experiment 2 (2010) Q = 0.076 m3/min Crushed glass 23 0.30 3.04-3 1.25-5 243 0.45 2.45-3 195 0.60 2.17-3 174 Shredded tires 40

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A C B D Figure 2-1. Schematic drawings of the cr oss-sectional and plan views of the study liquids addition system and piezometer di stribution; the cross-sectional views of A) the horizontal liqu ids addition lines and trenc hes layout and B) the pressure transducers distribution surrounding each line and the plan views of C) the horizontal liquids addition lines and trenches layout and D) the pressure transducers distri bution surrounding each line 41

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Time (days) Pore pressure (kPa) 0 10 20 30 40 50 60 G1 G2 G3 G1 G2 G3 Injection Perforated pipe 1357 9 111315 17 50 m 110 m Experiment 1 (2007): flow rate = 0.057 m3/min A Time (days) Pore pressure (kPa) 0 10 20 30 40 50 60 G1 G2 G3 1357 9 11 13151719Experiment 2 (2010): flow rate = 0.076 m3/minB Figure 2-2. Pore pressure change in the crushed glass media trench due to liquids addition; G1, G2, and G3 are in t he trench: A) Ex periment 1 and B) Experiment 2. 42

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Time (days) Pore pressure (kPa) 0 10 20 30 40 50 T1 T2 T3 0 4 8 12 16 T1 T2 T3 Injection Perforated pipe 50 m 110 m Experiment 1 (2007): flow rate = 0.057 m3/min A Time (days) Pore pressure (kPa) 0 10 20 30 40 T2 T3 0 2 4 68Experiment 2 (2010): flow rate = 0.076 m3/min B Figure 2-3. Pore pressure change in t he shredded tire media trench due to liquids addition; T1, T2, and T3 are in the m edia trench: A) Experiment 1 and B) Experiment 2. 43

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Time (days) Temperature (oC) 30 40 50 60 70 G1 G2 G3 G1 G2 G3 Injection Perforated pipe 1357 9 11 13151719 50 m 110 m Figure 2-4. Temperature variation in the crushed glass media trench due to liquids addition; G1, G2, and G3 are in the trenc h. Data collected from Experiment 2 were used. 44

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Cumulative injection time (hours) 01 02 03 04 05 0 Pore pressure (kPa) 0 10 20 30 40 50 60 G1 G2 G3 G1 G2 G3 Injection Perforated pipe 50 m 110 m A Cumulative injection time (hours) 02 04 06 08 0 Pore pressure (kPa) 0 10 20 30 40 T1 T2 T3 T1 T2 T3 Injection Perforated pipe 50 m 110 m B Cumulative injection time (hours) 05101520253035 Pore pressure (kPa) 0 10 20 30 40 50 60 G1 G2 G3 C Cumulative injection time (hours) 0 5 10 15 20 25 Pore pressure (kPa) 0 10 20 30 40 T2 T3 D Figure 2-5. Pore pressure change as a func tion of cumulative liquids addition time: A) Experiment 1 (crushed glass trench), B) Experiment 1 (shredded tire trench), C) Experiment 2 (crushed glass trench), and D) Experiment 2 (shredded tire trench). 45

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Time (days) Pore pressure (kPa) 0 10 20 30 40 50 60 In trench 1.1 m away 4.1m away 10.2 m away 15 9 13 17 30 kPa 3 kPa A Time (days) Pore pressure (kPa) 0 10 20 30 40 In trench 1.1 m away 2.6 m away 4.1 m away 10.2 m away Trench 1.1 m 4.1 m 10.2 m y x 2.6 m1 3 5 7 B Figure 2-6. Example plots of pore pressure changes with distance away from the trenches with A) crushed glass and B) shredded tire bedding material; data collected during Experiment 2 (2010) were used. 46

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47 R (m) 024681012141618 Pore pressure (kPa) 0 10 20 30 40 50 Day 1 Day 3 Day 12 Model: (KxKy)0.5 =1.30x10-4 cm/sec 5 kPa 11.4 m Figure 2-7. Comparison of pore pressure c hange as a function of a horizontal distance from the line source bet ween the field data and theoretical estimates: the results of liquids addition into the crushed glass trench during Experiment 1.

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CHAPTER 3 IN-SITU SETTLEMENT MEASUREMENTS OF A LANDFILL PREVIOUSLY OPERATED AS A BIOREACTOR SUBJECTED TO SURCHARGE Introduction The settlement of waste over time at a landfill results from a combination of mechanical and biological processes. Wast e volume deforms in response to added stresses (e.g., new waste placement and other landfill infrastructure). Waste also settles as a result of mass loss accompanying biological decomposition. The settlement process is influenced by the presence of liq uids and gases in the landfill and by longterm physical changes in the structure of waste components. While many attempts to estimate landfill waste settlement rely on cl assic soil consolidation models (Sowers 1973; Powrie and Beaven 1999; Landva et al., 2000; Machado et al., 2002; Anderson et al., 2004; Durmusoglu et al., 2006), it has becom e more widely recognized that multiple processes need to be considered in such es timates (Ling et al., 1998; El-Fadel and Khoury 2000; Liu et al., 2006; Oweis 2006; Elagroudy et al., 2007). Detailed monitoring of full-scale landfill settlement resulting from distinct processes will result in a better understanding of the phenomenon and the development and refinement of predictive tools. This chapter reports the results of an experiment designed to measure waste settlement during one specific ph ase: mechanical settlement occurring in waste that is predominantly biologically degraded but still saturated or near saturated with moisture. In a previous study, waste settlement at a bi oreactor landfill was found to be affected by the physical presence of moisture (Kadambal a 2009). A follow-up study was conducted in which a load was placed on top of this ar ea and the settlement was monitored. It is 48

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hypothesized that this phase of settlement is si milar to classic soil consolidation: as excess pore pressure resulting from the appli ed load dissipates, the soil skeleton (in this case, degraded waste) is consolidated, resu lting in surface settlement. The main objective of this study is to present settle ment monitoring results of a municipal solid waste landfill subjected to surcharge. The settlement of the waste layer under the surcharge was measured using a settlement prof iling technique. In addition, coefficients of volume change, coefficients of consolidation, modified primary compression indices and hydraulic conductivities of waste were roughly estimated using the in-situ settlement measurements. The reported quantificat ion of these param eters is expected to provide further understanding of the se ttlement behavior of bioreacted waste and fundamental inputs for landfill settlement prediction models. Material and Methods Bioreactor Landfill Operat ion and Characteristics A4-hectare portion of the New River Regional Landfill (NRRL) in Florida, United States (Figure B-7) was chosen as the study site. MSW was accepted in this area from 1992 to 1998. Liquids addition was performed using vertical wells in an effort to promote waste stabilization (Jain 2005; Jain et al., 2005, 2006; Kadam bala 2009) from June 2003 April 2007. This liquids addition over 3.8 years delivered approximately 22.73 m3 of liquid (primarily leachate from the same landfill, with some groundwater). A liquids volume of 400 to 1000 m3 was added to each of 45 vertical well clusters. After this period, the liquids addition well field was decommissioned to allow for new waste placement. 49

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The well field area was subject to severa l research experiments before, during and immediately following the period of liquids a ddition. Jain (2005) and Jain et al. (2005, 2006) estimated waste permeability using two di fferent techniques: an air injection test and a borehole permeameter test. Kadambal a (2009) examined the settlement of different waste layers using individual ve rtical well settlement measurements and concluded that the layers in the middle of the waste, wher e most of the liquids were added, settled the least. Given that biochemic al methane potentia l measurements in these wetted areas indicated that biological decompositi on was largely completed; Kadambala (2009) hypothesized t hat waste settlement was limited by the pressure of moisture in the waste matrix. The resu lts of bio-chemical methane potential and moisture content analyses of t he study landfill befor e and after the bioreactor operations are provided in Figure B-8. In addition, t he settlement measuremen ts (meters and %) with time during Kadambalas 2009 st udy are provided in Figure B-9. Post Bioreactor Settlement Profiling Settlement of the decommissioned bior eactor area was monitored using a settlement profiler; this te chnique employs hydrostatic pressure measurement between a pressure transducer and a liquid reservoir re ference point. Prior to the placement of an additional layer of waste, five 46 m settlem ent profiling pipes (HD PE) with a diameter of 10 cm were placed on the top surface of the bioreactor area. Figure 3-1 shows a photograph of the settlement pr ofiling pipes over the top surface of the study landfill prior to waste placement and the plan view of the layout of the settlement profiling pipes. The baseline elevations of the settlement profiling pipes were surveyed on September 26, 2008 by a local professional surveying com pany (Patrick B. Welc h and Associates). 50

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Settlement profiling was conducted six times: December 2008 (10 days after waste placement), May 2009 (152 days), June 2009 (175 days), August 2009 (266 days), December 2009 (380 days), and Ma rch 2010 (450 days). Each settlement profiling included temporary plac ement of the liquid reservoir at a reference station located at a higher elevation than the settlement profiling pipe. Th e elevation of the reference station from a benchmark was me asured using a laser theodolite (Spectra Precision Gplus, Trimble); the method is explained in A ppendix G. The benchmark was installed on the ground surfac e approximately 40 m away from the study landfill. The elevation of the benchmark was surveyed in December 2008 and it was assumed no elevation change occurred during the study period. The pressu re transducer, liquid tube, and sensor cable tied to a series of 2.54-cm PVC pipes were slid into the settlement profiling pipe to a desired location. The vibr ating wire settlement profiler used in this study (Model 4651, Geokon, Inc.) is equi pped with a liquid t ube connecting the transducer and the liquid reservoir filled wit h de-aired 55:45 (distilled water:commercial grade ethylene glycol) solution, sp ecific gravity = 1.07. The pr ofiler is also equipped with a vent line so that the tr ansducer reading was not affect ed by barometric pressure variation. The settlement profiler had a gauge range of 7 meters with a reported accuracy and sensitivity of 7 mm and 1.75 mm, respectively. The readings from the settlement profiler were collected using a vi brating wire data recorder (Durham Geo Slope Indicator). The vibrating wire frequency detection range of the recorder was from 450 to 6000 Hz. The resolution and accuracy of the recorder were 0.01% full-scale and 0.02% of Hz reading, respectively. 51

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The elevation of a desired location in a settlement profiling pipe was estimated using the following equations prov ided by the manufacturer. 2() 1000 H z R (3-1) E = Eref G(Ro Rc) (3-2) where R = reading (digits); (Hz) = raw data of a pressure transducer; E = elevation of the sensor (m); Eref = elevation of the re ference station (m); Ro = reading at the reference station (digits); Rc = reading at a target loca tion (digits); G = calibration constant (meter per digits). An example se ttlement calculation using Equations 3-1 and 3-2 is provided in Appendix H. Compression Properties and Hydr aulic Conductivity Estimation With the hypothesis that the settlement behavior of high-moisture content landfilled waste is similar to consol idation settlement, the hydrau lic conductivity and compression properties of the landfilled waste were r oughly derived using the soil mechanics approach utilized by multiple researcher s (Sowers 1973; Morris and Woods 1990; Fassett et al., 1994; Landva et al., 2000; Durmusoglu et al., 2006). The modified compression indices (Cc) were calculated using the following equation. 1 logc f i iH C H (3-3) where H = change in elevation during the pr imary consolidation period (m); Hi= initial height of a bioreacted waste layer (m); i, f = initial and final stress applied to the midpoint of the bioreacted waste layer, 0.5 Hi, (kPa). It was assu med that the primary 52

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consolidation of the underlain (bioreacted) waste layer ended in June 2008 based on an inflection point of the thickness of waste time curve, and a difference in strain ( H/Hi) at each settlement monitoring location durin g the period was used to determine the modified primary compression indices (Cc). The increases in overburden pressures were estimated by multiplying a thickness of waste newly placed by a bulk unit weight; a bulk unit weight of the new waste layer was assumed to be 12 kN/m3 based on the bulk unit weight estimates in Chapter 4. An example calculation of Cc is provided in Appendix I. Coefficients of volume change (mv) were estimated with an assumption that the change in waste volume occurred vertic ally (no lateral volume change). 1 'v iH m H (3-4) where = pressure increment at 0.5Hi (kPa). Note that t he same assumptions made for the Cc estimation were used for mv determination. An exam ple calculation of mv is provided in Appendix I. To estimate the coefficient of consolidation (cv), the logarithm of time fitting method developed by Casagra nde (1940) was used. 2 2 50 50 500.197v vTd d c tt (3-5) where (Tv)50 = time factor corresponding to 50 % ultimate consolidation (-); 4ifHH d = average drainage path for the pr essure increment (m); Hi, Hf = initial and final thicknesses of the underla in waste layer (m); t50 = time to 50% ultimate consolidation 53

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(minute). An example calculat ion can be found in Appendix I. The plots of the logarithm of time-fitting model used to estimate cv are also provided in Figures B-14 to B-16. Vertical hydraulic conductivity (Ky) of media could then be estimated using mv and cv values. y v vwK c m (3-6) yvvKcmw (3-7) where w = unit weight of water (9.8 kN/m3). It was assumed that the horizontal movement of moisture was confined by cover soil, and thus the hydraulic conductivities estimated using Equation 3-7 are vertical hydraulic conductivities (Ky). An example of K calculation using Equation 37 can be found in Appendix I. Results and Discussion Settlement and Bioreactor operation At the study site, topographic surveying wa s conducted to evaluate the impact of liquids addition on the settlem ent of the bioreactor landfil l from June 2003 to October 2007, by Kadambala (2009). In addition, topographic surveying was performed by the author in September 2008 to meas ure initial elevations of settlement monitoring points prior to additional waste placement. Average settlement estimations (meter or %) in this time period are plotted as a function of time in Figure 3-4. Overall, three stages of settlement patterns were observed during this period: Stage 1 (August 2002 October 2004), Stage 2 (October 2004 April 2006), and Stage 3 (April 2007 September 2008). The stages were distinguished based on the inflection points of the settlement (%) time curve and a 54

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settlement rate (% per year) for each stage was estimated by linear regression (Figure 3-4). During Stage 1, a settlement rate of 1.15 % per year was estimated, which fell into a typical settlement rate range of conventiona l dry tomb landfills: 1.0 2.9 % per year (Edil et al., 1990; Sanchez-Aliciturri et al., 1995; El-Fadel et al., 1999; Yuen et al., 1999; Benson et al., 2007). As liquid was added, the study bioreactor landfill underwent accelerated waste decomposition and settlem ent; average settlement rate in Stage 2 was estimated to be approximately 5.1 % per year. In literature, settlement rates of bioreactor landfills including aerobic and an aerobic operation systems were reported in the range of 1.6% to 10.0% (Yuen et al., 1999; El-Fadel et al., 1999; Benson et al., 2007; US EPA 2007). In Stage 3, the landfill settlement rate decreased to approximately 1.7 % per year. This attenuation in settlem ent may be explained by the fact that a considerable amount of organic material in the waste was degr aded during Stage 2. Average BMP values decreas ed from 0.22 to 0.11 L CH4(g) per gram VS during the bioreactor operation period (Figure B-8). Settlement due to Surcharge Initial settlement profiling was conducted 10 days after additional waste placement in December 2008. Settlement data were co llected from eighty monitoring points and analyzed; settlement (%) data are compiled in Tables A-3 to A-7. The results showed extremely high settlement values; approximatel y 3.7 m of settlement were measured at a point where the thicknesses of waste la yers above and below the pipe were 5.2 and 17.4 m, respectively. This was found to be unreasonable based on the results of subsequent settlement profilings. Figure 3-5 shows an example plot of the settlement 55

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profiling results of Pipe 3; settlement measurements collected on Day 10 are much greater than those collected on Day 152. These false readings on Day 10 were attributed to air-bubbles in the liquid; airbubbles interfered with hydrostatic pressure transmission to a pressure transducer. Since the readings of the first profiling were found to be false after comparing with the next profiling conducted 3 months after the first profiling, no attempt to re-measur e the first readings could be made. During the first 152 days after waste placement, an average of 0.49 % of settlement was measured, whic h was greater than settlement occurred for the next 298 days (an average of 0.43%). Figure 3-6-A shows an example plot of settlement measurements over time at settlement monitori ng locations in Pipe 1. Near the entry of Pipe 1 above which only 0 0.3 m of wast e plus cover soils were placed, less settlement occurred than other monitoring locations above wh ich 0.3 8.5 m of waste plus cover soils were placed. However, no cl ear relationship between the thickness of waste plus cover soils (or overburden pressu re) and settlement was found from the data collected from Pipe 1. The data collect ed from Pipe 3 and Pipe 4 showed that settlement generally incr eased with increasing thickness of waste plus cover soils. The Pipe 4 data, for example, is presented in Figu re 3-6-B; the Pipe 3 data is provided in Figure B-11. After waste placement, the bioreact ed waste layers settled at an average settlement rate of 3.75 % per year (Figure 34), which is approximately 1.4 times greater than an average settlement rate (2.66 % per y ear) prior to the waste placement. It was hypothesized that the accelerated settlement of the profiling period could be attributed to the consolidation settlement of the bioreacted waste laye r subject to surcharge. As 56

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the trapped moisture was expelled due to surcharge, the waste layer might undergo consolidation settlement. Kadambala (2009) poi nted out that a considerable amount of moisture was trapped in the middle and bottom laye rs as a result of liquids addition; the average moisture contents of middle and bottom layers were 46% with standard deviations of 4.3% and 44 % with standard dev iations of 4.6%, respectively (Figure B-8). Figure 3-7 shows the monthly vari ation in leachate generation. Before the additional waste placement, average mont hly leachate generation volume was approximately 200 m3 (January 2007 June 2008). Note that after removing the top geomembrane cover of the bioreactor, the leachate generati on increased sharply due to rain water inflow into the leachate collection system of the landfill (July October 2008). Additional waste layer was placed on top of the bioreacted waste la yer in the period of November to December 2008. The leachate gener ation amount started to increase from February 2009 (approximately 2 months after the waste placement) and peaked at approximately 1100 m3 in May 2009. Since the top surfac e of the additional waste lifts was planted after the additional waste placement, rain wate r inflow into the leachate collection system was considered to be negligible in this period. The delay in leachate generation increase after the waste placem ent was likely attributed to the low permeability of landfilled waste. Compression Properties and Hydraulic Conductivity of Landfilled MSW Based on the in-situ settlem ent measurements, hydraulic conductivities (K) and compression properties (Cc, mv, and Cv) of MSW landfilled in the study landfill were roughly estimated and compared with the values reported in literature (Sowers 1973; Oweis et al., 1990; Shank 1993; Townsend et al., 1995; Landva et al., 1998; Powrie and 57

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Beaven 1999; Landva et al., 2000; Machado et al., 2002; Anderson et al., 2004; Durmusoglu et al., 2006; Jain 2005; Jain 2006). The values of the parameters were determined using Equations 3-3 through 3-8 and were compiled In Table 3-1. The details of the estimation method used in this chapter and an example calculation were provided in Appendix I. Figure 3-8 shows the histograms of Cc, mv, cv, and K of the bioreacted waste determined in this study; estimated comp ression properties and K values are compiled in Tables A-8 to A-12. A relatively wide range of Cc values (0.1 1.7) were estimated in this study while approxim ately 75% of the estimated Cc values fell into a range of 0.1 0.5, close to the values (0.1 0.41) repor ted in literature (Sower s 1973; Landva et al., 2000; Machado et al., 2002; Anderson et al ., 2004; Durmusoglu et al., 2006). The relatively large Cc values (0.5 1.7) estimated might be due to the compression of waste structure weakened by waste decomposition. The mv values estimated in this study are most frequently found in a range of 2.9-4 2.3-3 m2/kN which fell into the range of 2.5-4 5-3 m2/kN reported in literature (Powrie and Beaven 1999; Landva et al., 2000; Durmusoglu et al., 2006) ; the compression properties in the literature are provided in Table A-1. Overall, the mv values had a tendency to decrease with increasing load while the coefficient of consolidation showed no clear correlation to load change. Figure 3-8-C show s the histogram of the cv values estimated using Equation 3-6. The cv values were estimated to be in a range of 0.89-2 to 1.44-2 cm2/sec which are smaller than the range of cv values (5.62-2 5.12 cm2/sec) reported by Durmusoglu et al. (2006). Durmu soglu et al. (2006) pointed out that the lower values of cv are typically attributed to good compac tion. Note that not all data sets 58

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collected from each settlement monitoring lo cation could be used to estimate a cv because some of them were found to be inappr opriate to develop a semi-log plot of a time-consolidation curve including a primar y-secondary consolidation inflection point. The Ky values of 4.6-7 to 9.8-6 cm/sec could be estimated using the estimated values of mv and cv and found to be overall lower than those reported in literature, 36 1.5-2 cm/sec (Townsend et al., 1995; Landva et al., 1998; Powrie and Beaven 1999; Jain 2005; Durmusoglu et al., 2006; Larson 2007); the K values in the literature are provided in Table A-1 In addition, t he K values were low compared to those estimated at the same study landfill (5.4-6 6.1-5 cm/sec) by Jain (2005). The decrease in hydraulic conductivity of the l andfilled waste might be due to the increase in overburden pressure. Bleiker et al. (1995) and Powrie and Beav en (1999) pointed out that hydraulic conductivity of landfilled wa ste decreases as overburden pressure applied to the waste increases (Figure B-4). Summary and Conclusions Settlement patterns of a landfill site s ubjected to surcharge were investigated using an in-situ settlement prof iling technique. Prior to additional waste placement, five HDPE pipes with a 10-cm diameter were placed over the study landfill cells and equipped with 45 vertical liquids addition well clusters. This landfill had been previously operated as a bioreactor. The thicknesses of the waste layers above and below the pipes varied from 0 to 6 m and 13 to 20 m, respectively. Settlement profiling was conducted six times after the waste placemen t. However, the settlement profiler used in this study often generated false readings due to air-bubbles in the liquid employed by the profiler; this was corrected by exchanging the faulty liquid with de-aired solution. It is 59

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recommended that liquid in the profiler be ex amined to determine the presence of airbubbles prior to use. During the settlement profiling period, average settlement rate was estimated to be 3.76 % per year; this is 1.4 times greater than the average settlement rate prior to the waste placement (2.66% per year). It was hypothesized that the settlement mechanisms of the landfilled waste due to surcharge might be similar to the consolidation settlement of saturated clay, so the amount of leachat e generation would increase as the moisture trapped in waste matrix was expelled due to the surcharge. This hypothesis was verified by monitoring leachate generati on; average monthly leachate generation was found to increase from approximately 200 m3 to 1100 m3 approximately 5 months after the waste placement. In addition, Kadambala (2009) reported that the moisture content of the middle waste layer of the study landfill was incr eased to an average of 40% due to liquids addition. This increase in moistu re content and resulting pore pressure buildup hindered settlement. Using the settlement profiling data, compression properties (Cc, mv, and cv) were estimated. The estimated ranges of Cc (0.1 0.5) and mv (2.9-4 2.3-3 m2/kN) values most frequently found in this study were consistent with ranges reported in literature. Wide ov erall ranges of Cc and mv values were estimated; however, these wide ranges could be attributed to the heterogeneous nature of MSW. The estimated cv values fell into a relatively narrow range (0.89-2 to 1.44-2 cm2/sec); this range was lower than values reported in literature. These low cv values might be due to accelerated settlement during the bioreacto r operation period. Vertical hydraulic conductivities of the bioreacted waste were estimated to be in the range of 4.6-7 to 60

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61 9.8-6 cm/sec; this is lower than estimated ve rtical hydraulic conductivities at the same study landfill (5.4-6 6.1-5 cm/sec) by Jain (2005). The decrease in hydraulic conductivity of the landfilled wast e may be attributable to the increase in overburden pressure.

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Table 3-1. Summary of the compression pr operties and hydraulic conductivities (K) of waste in the study landfill Pipe ID-Distance from pipe entry Cc' cv (cm2/sec) mv (m2/kN) K (cm/sec) P1-10 m 0.97 0.012 4.63-3 5.62-6 P1-13 m 1.43 0.014 6.48-3 9.12-6 P1-16 m 1.64 0.014 7.10-3 9.84-6 P1-19 m 1.02 0.011 4.24-3 4.60-6 P1-22 m 0.72 0.011 2.91-3 3.08-6 P1-25 m 0.28 0.012 1.09-3 1.32-6 P1-31 m 0.16 0.012 5.46-4 6.29-7 P1-34 m 0.12 0.012 4.02-4 4.88-7 P1-37 m 0.11 0.014 3.40-4 4.59-7 P2-6 m 1.03 0.009 4.69-3 4.08-6 P2-9 m 1.00 0.010 4.38-3 4.18-6 P2-12 m 0.45 0.010 1.88-3 1.81-6 P2-15 m 0.47 0.012 1.88-3 2.24-6 P2-27 m 0.23 0.012 8.03-4 9.56-7 P5-14m 0.75 0.013 3.48-3 4.52-6 P5-23m 0.65 0.012 2.95-3 3.45-6 P5-35m 0.42 0.013 1.84-3 2.40-6 62

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Settlement profiling pipes (10 cm HDPE) A Pipe 1 Pipe 2 Pipe 3 Pipe 4 Pipe 5 100 m 60 m B B A A C C D D E E 46 m Approximate study area boundary B Figure 3-1. Installation of settlement profiling pipes: A) photograph of settlement profiling pipes on the study landfill cells (only three of five settlement profiling pipes installed were shown in this photograph) and B) plan view of locations of the profiling pipes and settlement monitoring. Each symbol represents a settlement measurement location. 63

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Elevation (NGVD, m) 58 60 62 64 66 68 70 Initial elevation of Pipe 5EE Elevation (NGVD, m) 58 60 62 64 66 68 70 Initial elevation of Pipe 4DD Elevation (NGVD, m) 58 60 62 64 66 68 70 Initial elevation of Pipe 3CC Elevation (NGVD, m) 58 60 62 64 66 68 70 Initial elevation of Pipe 2BB Elevation (NGVD, m) 58 60 62 64 66 68 70 Initial elevation of Pipe 1AA Additional waste lift Figure 3-2. Cross-sectional views of exis ting and additional waste lifts; A-A through EE correspond to those in Figure 3-1; NGVD represents U.S. National Geodetic Vertical Datum. 64

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Liquid reservoir Data reader Liquid tube and signal cable A Liquid tube and cable Pressure transducer Liquid reservoir Settlement profiling pipe MSW B Figure 3-3. Schematic dra wing of settlement profiling 65

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year 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Settlement (%) 0 5 10 15 20 25 Average Rs = 3.75 %/year Waste placement Bioreactor operation June, 2003 April, 2007 November 2008 December 2008 Stage 1: Rs = 1.15%/year Stage 2: Rs = 5.08%/year Stage 3: Rs = 1.69%/year Figure 3-4. Change in the settl ement rate (Rs, %/year) of the study landfill due to bioreactor operation and subjected to surcharge; the data points plotted are average settlement (%) values. 66

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Distance from pipe entrance (m) 01 02 03 04 0 5 0 Elevation (NGVD, m) 56 58 60 62 64 36 days before waste placement 10 days after waste placement 152 days after waste placement Figure 3-5. Example plot of false settlement reading s recorded during the first settlement profiling (data from Pipe 3); NGVD represents U.S. National Geodetic Vertical Datum. 67

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Distance from pipe entrance (m) 01 02 03 04 0 5 0 Elevation (NGVD, m) 56 58 60 62 64 36 days before waste placement 152 days after waste placement 175 days after waste placement 266 days after waste placement 380 days after waste placement 450 days after waste placement A Distance from pipe entrance (m) 01 02 03 04 05 0 Elevation (NGVD, m) 56 58 60 62 64 B Figure 3-6. Example plots of settlement over time at each settlement measurement location in settlement profiling pipes: A) data from Pipe 1 and B) data from Pipe 4. NGVD represents U.S. Nati onal Geodetic Vertical Datum. 68

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1/07 5/07 9/07 1/08 5/08 9/08 1/09 5/09 9/09 1/10 Leachate generated (m3) 0 200 400 600 800 1000 1200 Precipitation (mm) 0 100 200 300 400 500 600 Waste placement (Nov 08 Dec 08) Due to removing top geomembrane Figure 3-7. Monthly leachate generation of the study landfill and precipitation; the precipitation data co llected at the Raifor d State Prison Stati on, Florida, were used (National Oceanic and Atmospheric Administration, www.noaa.gov). 69

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Modified compression index (Cc') 0 1 0 0 0 2 9 9 0 3 0 0 0 4 9 9 0 5 0 0 0 6 9 9 0 7 0 0 0 8 9 9 0 9 0 0 1 0 9 9 1 1 0 0 1 2 9 9 1 3 0 0 1 4 9 9 1 5 0 0 1 6 9 9 Frequency 0 5 10 15 20 25 30 35 A Coefficient of volume change (mv, x10-3 m2/kN) 0 2 9 1 3 0 1 3 1 2 3 0 2 3 1 3 3 0 3 3 1 4 3 0 4 3 1 5 3 0 5 3 1 6 3 0 6 3 1 7 3 0 Frequency 0 10 20 30 40 B Coefficient of consolidation (cv, x10-2cm2/sec) 0 8 9 0 9 8 0 9 9 1 0 8 1 0 9 1 1 8 1 1 9 1 2 8 1 2 9 1 3 8 1 3 9 1 4 8 Frequency 0 1 2 3 4 5 6 7 C Vertical hydraulic conductivity (Ky, x10-5 cm/sec) 0 0 4 0 2 3 0 2 4 0 4 3 0 4 4 0 6 3 0 6 4 0 8 3 0 8 4 1 0 3 Frequency 0 2 4 6 8 D Figure 3-8. Histograms of t he properties of landfilled wast e: A) modified compression index, B) coefficient of volume change, C) coefficient of consolidation, and D) vertical hydraulic conductivity 70

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CHAPTER 4 IN-SITU MEASUREMENTS OF LANDFILL FOUNDATION SETTLEMENT AND OVERBURDEN PRESSURE Introduction Predicting the settlement of a landfill foundation is a critic al design consideration. Landfill bottom liners are graded to promote gravity drainage of leachate; unexpected excessive settlement could result in leachat e collection system failure by altering the grade. A fundamental input necessary for the prediction of landfill foundation settlement is the overburden pressure produced from the waste, cover soil, and other landfill infrastructure. Overburden pressure estimate s can be used with soil characterization data (e.g., stress-strain modulus ) to estimate foundation soil settlement at distinct points at the base of the landf ill. While overburden pressure estimates and subsequent settlement calculations are common in landf ill design, actual meas urements of these parameters is uncommon. The main objective of this study was to measure load and settlement patterns of the foundation of an operating MSW landfill in the early st ages of construction. The method of measurement was in-s itu settlement sensors and total pressure cells. Prior to bottom geomembrane installation, sixteen settlement sensors and sixteen total pressure cells were installed and monitored underneath the liner of the landfill for 39 months (before and during waste placement ). To the authors knowledge, this study was the first attempt to monitor landfill foundation settlement behavior using in-situ sensors. The insitu settlement data were compared with t heoretical settlement estimations normally calculated during the design phas e of landfill construction. This chapter was intended to 71

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provide insight into actual landfill f oundation settlement behavior, which is very important to ensure the int egrity of landfill structure. Material and Methods Site Description This study was performed on a lined l andfill unit (designat ed herein as the landfill) of the Polk County North Central Landfill located in Florida, US. The landfill began accepting waste in October 2007, accepting approximately 2000 tons of MSW per day during the course of this study. The planned landfill capacity upon completion of waste filling is 6.1million m3, with a 23-hectare area and a height of 55.6 m. Figure 41 shows the schematic of the plan and cross-sectional views of the study landfill consisting of two subcells bisected by a c enter berm. Detailed topographic drawing of the study site is provided in Figure B-20. The landfill is equipped with a double-liner system consisting of a geosynthetic clay liner and a 0.76-cm drainage net sandwiched by two 1.5-mm HDPE geomembrane (textured) overlain by 0.6-m sand drainage layer (K = 1.0-3 cm/sec). Standard penetration tests (SPTs) and cone penetration tests (CPTs) to 16.7 m below the ground surface were performed by design engineers prio r to bottom liner construction. Figures B-18 and B-19 shows t he locations of SPTs and CPTs. Table A13 presents a soil profile schem atic under the center berm bas ed on the results of the SPTs and CPTs performed near the center berm (overburden pressure and settlement monitoring area); a considerable amount of clayey soils, as well as silty and sandy soils, are present in this area. The groundwat er table is approximately between 3 and 4 m below the bottom liner. 72

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Instrumentation and Data Collection Prior to bottom liner installation, eight pai rs of settlement sensors (SS) and eight pairs of total pressure cells (TPC) were placed along the center berm (March 2006). At each monitoring location, a pair of TPCs were placed above a pair of SSs (Figure 4-1). To prevent damage, SSs were inserted in a 10-cm HDPE pipe. T he instrument wires were connected to a data st ation at the east end of the center berm (Figure 4-2). Designations A through H and in Figure 4-2 (A) indicate the instrument locations; duplicates (A through H) were insta lled approximately 0.6 m apart. The SSs used in this study (Model 4650, Geokon, Inc., New Hampshire) are designed to measure the relative settlement between two points: a reference point (the data-logger) and a target point. The settlement results reported in this chapter were measured assuming that the reference poi nt did not settle or upheave during the monitoring period. The SSs (pressure transdu cer) measure the hydrostatic pressure in the unit of hertz (frequency) caused by the height of liquid column difference between the sensor and the liquid reserv oir placed at a reference stat ion (data-logger). The liquid in the tube was a de-aired 55:45 (distilled water : commercial grade ethylene glycol) solution with a specific gravity of 1.07. Liquid tubes, vent lines, and signal cables were run from the data-logger to each settlement monitoring lo cation, approximately at distances of 30, 61, 122, 183, 244, 305, 366, 427 m from the datalogger. Two types of vibrating wire SSs were used in this study. Half of the SSs were equipped with air-vent tubes (labeled A through H), and the others were not (labeled A through H). The vent line was used to avoid the barometric pres sure impact on SS readings. Atmospheric pressure at the barometer moni toring point may be different from that at the point of the 73

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settlement sensor, which may lead to misi nterpreted data. From a maintenance standpoint, non-vented SSs are beneficial because blockages in the vent lines due to pinching, dirt, or moisture can cause false readings. However, the accuracy of a vented SS is better because they do not require barom etric pressure correct ion. The SSs were factory calibrated to a gauge r ange of 7 meters with a repor ted resolution and accuracy of 1.75 mm and 7 mm, respectively. Additionally, each SS was equipped with a thermistor for the thermal impact correct ion of SS readings. Temperature in a range between -20 and 80 C could be measured with C accuracy. The TPCs used (Model 4810, Geokon, Inc. New Hampshire) were designed to measure the total stresses in soil or the pressure of soil on structures. They are constructed from two stainless steel plates (diameter of 230 mm a nd thickness of 6 mm) welded together around the peri phery; the narrow space betw een them is filled with deaired oil which is connected by a liquid tube to a pressure transducer. The oil pressure is converted to an electrical signal (fr equency) which is transmitted through a signal cable to the data station. The TPCs were factory calibrated to a gauge range of 2 MPa with a reported resolution and accuracy of 0.5 kPa and 2 kPa, respectively. The TPC was equipped with a thermistor capable of detecting temperat ure in a range of -20 to 80 C. The outputs of the instrument s were collected every two to four weeks from March 2007 through June 2010. Over th e study period, no particular maintenance issues originated from the TPCs. In the early course of the study, se vere data fluctuations were observed from fourteen SSs due to air-bubble accumulation in the liquid; this problem was corrected by exchanging the solution with new de-aired liquid. The readings from 74

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the TPCs and SSs were collected using a vi brating wire data recorder (DURHAM GEO SLOPE INDICATOR, Washington). The dat a recorder can detec t vibrating wire frequency in the range of 450 to 6000 Hz and has a resolution of 0.01% FS (full-scale), and an accuracy of 0.02% of Hz. In addition, thermistor readings in resistance (ohm) were automatically converted into the unit of Celsius degree in a range between -20 and 120 C with C accuracy and recorded. Unit Conversion of Instrument Readings Readings from each TPC and SS have a unit of frequency and thus were converted to the proper units of kPa and cm, respectively. Unit conversion and calibration equations for the SSs are as follows: 2() 1000 H z R (4-1) E = G (Ro Ri) + Eres + K(Ti-T0) + {B0-Bi} (4-2) where R = reading (digits); (Hz) = raw data from settlement sensor; E = elevation of the sensor (cm); Eres = any change of the liquid level inside the reservoir sight glass (cm); Ro = initial sensor reading (digits); Ri = reading at time i (digits) ; G = calibration constant provided by the manufact urer (cm/digits); Ti = temperature at time i ( C); T0 = initial temperature ( C); K = temperature co rrection factor (cm/ C) provided by the manufacturer; {B0-Bi} = barometric pressure corre ction for non-vented SSs (cm H2O). An example calculation is provided in Appendix J. Unit conversion and calibration equations for the TPCs were as follows: 2() 1000 H z R (4-3) 75

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P = G(R0-Ri) + (B0-Bi) K(P) (4-4) where R = reading (digits); (Hz) = raw data from pressure transducer; P = pressure (kPa); G = calibration factor provi ded by the manufacturer (kPa/digits); R0 = initial reading (digits); Ri = reading at time i (digits); B0 = initial barometric pressure (kPa); Bi = barometric pressure at time i (kPa); K(P) = thermal im pact correction equation derived from a best-fit regression of P versus (T0-Ti) data; Ti = temperature at time i ( C); T0 = initial temperature ( C). An example calculation is provided in Appendix K. Bulk Unit Weight and Over burden Pressure Estimation To determine the bulk unit weight, landfill vo lume estimation is necessary; this was obtained from the sites survey record. Tabl e 4-1 provides the estimation of volume, mass placed, and bulk unit weight of the landfill site on each surveying day. The cumulative weight of waste plus cover so il deposited each surveying day was calculated assuming 18% of the apparent volume of the study landfill unit was comprised of cover soil with a unit weight of 25.5 kN/m3. The methodology to estimate a bulk unit weight was explained in Appendix C. Bulk unit weight of the site varied in a range of 11.3 12.2 kN/m3, and averaged 11.8 kN/m3. A theoretical overburden pressure at eac h monitoring location was estimated with two methods. First, overburden pressure was es timated by multiplying bulk unit weight by an apparent thickness of waste plus cover soil on top of a TPC (Equation 4-5). Second, using Boussinesq influence factor c harts, the stress distri bution beneath a side slope of the landfill was ev aluated (Equation 4-6). v = H B (4-5) v = IH B (4-6) 76

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where v = overburden pressure (kPa); H = appar ent thickness of waste plus cover soil (m); B = bulk unit weight (kN/m3); I = influence factor from Boussinesq charts. Settlement Prediction In this study, one-dimensional (verti cal) elastic and primary consolidation settlements of approximately 16.7 m of the subsurface soil layers were estimated using the following equations: teSSSc (4-7) 0 n vi ei i iSH M (4-8) ,0 0 ,0 1 0log 1n vivi i cc i vi i iH SC e (4-9) where = total settlement (m); = elastic settlement (m); = primary consolidation settlement (m); Hoi = thickness of soil layer i (m); tSeScS vi = overburden stress increase caused by the waste placement at midpoint of soil layer i; Mi = constrained modulus of soil layer i (MPa); Cci = primary compression index; eoi = initial void ratio of soil layer i; oi = initial overburden stress at the center of soil layer i. An average value of overburden pressure m easurements on each day was used as input of v Typical ranges of other engineering parameters were not measur ed and assumed as follow: Cc = 0.1 for clay (Budhu 2000), eo = 1.4 for clay (Das 1990), and Cc /(1+eo) = 0.002 for sand or silty sand (Coduto 2004). Various equations introduced in Bowles ( 1996) were used to estimate the stressstrain (Youngs) modulus E of each soil la yer with the CPT(N) and SPT(N) as follow. E(kPa) = 500(N + 15) for sand (normally consolidated) (4-10) 77

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E(kPa) = 40000 + 1050N for s and (over consolidated) (4-11) E(kPa) = 250(N + 15) for sand (saturated) (4-12) E(kPa) = 320(N + 15) for clayey sand (4-13) E(kPa) = 600(N + 6) + 2000 for gravelly sand, N>15 (4-14) Constrained moduli M were correlated with 1 112 E M (4-15) where = Poissons ratio; Poissions ra tio of 0.3 was assumed (Budhu 2000). Constrained moduli of each soil layer were compiled in Tables A-14 to A-16. An example settlement estimation is presented in Appendix L. Results and Discussion Overburden Pressure Change with Waste Placement All TPCs were determined to respond immediately to stress change during the study period. However, the thermal correction factors pr ovided by the manufacturer were too small to account for the actual TP C output fluctuation from daily or seasonal temperature change. Figure 4-3 shows an exampl e plot of the overburden pressure and temperature changes of TPC-H over time; eac h overburden pressure data point in the plot was estimated without including any thermal correction factor. The greatest magnitude of overburden pressu re output fluctuation observed was approximately 11 kPa which was beyond the accuracy of TPCs used in this study (2 kPa). The trend of overburden pressure variation over time was very similar with resp ect to temperature; this trend was consistently observed from other TPCs. Daigle and Zhao (2003) pointed out that thermal correction fa ctors of a TPC for increasing temperature was different for 78

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decreasing temperature and should be estimat ed as a function of overburden pressure. For example, new thermal correction equations for TPC-G were derived by best-fit regression of overburden pressure versus te mperature differences (Figure 4-4). The TPC-G readings corrected using thermal im pact correction equations were relatively steady compared to those not corrected (Figure 4-5). The TPCs used in this study were found to be reliable. Overall, the differences between field pressure measurements and t heoretical pressure predictions were relatively small. Figure 4-6-A shows example plots of theoretical overburden pressures estimated using Equation 4-6 and in-situ overburden pressure me asurements at the monitoring locations H and H. The step-wis e increment of the measured overburden pressure indicates three layers of waste we re placed during the monitoring period. TPCH initially generated slightly greater pressure outputs than did TPC-H, but this trend reversed, beginning in January 2009. This may be due to the change in stress distribution resulting from waste placement. Sowers (1973) pointed out that landfilled waste materials subjected to surcharge (or com paction efforts) would be distorted, bent, and reoriented. TPC duplicates at locations A and G generated markedly different pressure measurements. However, given the heterogeneity of landfilled materials, this is not surprising. Uneven stress distribution (arching effect) among the interstitial matrix of solid waste might increase or decreas e TPC readings. Spangler and Handy (1982) pointed out that in a soil matrix, positive and negative arching can effectively decrease and increase stress readings, respectively. For example, the outputs of TPC-G and -G approximately 38 kPa difference consistently since waste placement began (Figure 4-679

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B). Another explanation for this extreme variability could be malfunctioning of the TPCs. However, the TPCs were tested and installed carefully to ensure proper operation. In addition, the outputs of the TPCs were st eady. Thus, the discrepancy between TPC-G and G might not be due to malfunctioning. Overburden pressure measurements of TPC duplicates at each monitoring point (A to H) were presented in Figures B-16 to B22. In-situ overburden pressure measurem ents were compared with theoretical pressure predictions calculated using Equation 4-5; the pressure measurements were collected on dates closest to the topogr aphic surveying dates (September 25, 2009 and May 20, 2010); topographic drawings of t hose days are presented in Figures B-22 and B-23, respectively. Overall, the pressure pr edictions of the monitoring points under the toe of the side slope were underestimated while those under the central area of the landfill body were overestimated. Figure 4-7 shows example plots of estimated and measured overburden pressures at each monitoring location; data collected in September 2009, were used. The variation of predicted overburden pressure had a very similar trend to that of meas ured overburden pressures. Over all, as the thickness of waste plus cover soil increased, the in-sit u overburden pressure measurements also increased. The overburden pressure val ues measured near the edge of the side slope toe tended to be greater than theoretical pressu re values estimated using Equation 4-5, but smaller than the pressure values es timated using Equation 4-6. This may be because vertical stress from the central ar ea of the waste body was also applied to the bottom of the side slope. Beneath the centra l area of the landfill the measured pressure values tended to be smaller than predicted pr essure values, which might be due to the 80

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arching effect as explained earlier. Figur e 4-8 presents the change in the ratio of measured to estimated pressures as a function of waste thickness. Under the toe, the field measurements were 1.7 6.4 times gr eater than estimated pressures. Using the Boussinesq influence factor charts, ov erburden pressures under the toe was reestimated and the ratios of measured to esti mated pressures found to fall into a range of 0.4 3.5. Conversely, the ratios at the locations under the central area of the landfill body were in a range of 0.5 to 1.1 with an average value of 0.8; in short, overburden pressures under the central area were over pr edicted. A similar trend that near the side slope overburden pressures were under predi cted while over predicted under the central area was observed for another MSW landfill located in Florida, U.S. (Jason et al., unpublished internal report). Landfill Foundation Settlement To investigate the relationship bet ween overburden pressure and foundation settlement, settlement was measured by means of in-situ instrumentation consisting of eight pairs of SSs. As mentioned in the methods section, during the early course of the monitoring period, it was found that the readings of fourteen out of sixteen SSs fluctuated mainly due to air-bubbles in liquid; ten of them were corrected by replacing the liquid with de-aired solution, the re maining four could not be corrected and may have malfunctioned for different reasons such as pinching of the vent lines. At least one SS at each monitoring location was used for the analysis of this study; the duplicates at A, B, C, and G worked properly. Because of the delays in the liquid replacement process, some SSs (C, C, D, E, F, and G ) began to work properly several weeks after TPCs initially responded to waste placemen t. No considerable amount of overburden 81

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pressure increase was observed during the period. It was thus assumed that no considerable settlement occurred in the period; the vertical movements of the foundation after each SS began to work proper ly were reported in this study. Overall, the outputs of the SSs showed that the landfill foundation settled gradually with increasing overburden pressure (waste placement); immediate (elastic) settlement was not discernable based on the collected dat a. Figure 4-9 shows example plots of overburden pressure variation and settlement of t he foundation at the monitoring point C. With an average 6.5 kPa of overburden pressure increase during the early course of the waste placement, the foundation settled gradually up to 3.8 cm. As overburden pressure increased to approximately 45 kPa between October 2009 and March 2010, approximately 1.2 cm of addition al settlement was recorded. Similarly, from other SSs, more settlement was observed during the plac ement of the first waste lift than during the placement of subsequent lifts. Figure 4-10 shows average in-situ settlements and overburden pressures measured on September 25, 2009 and May 20, 2010. On September 25, 2009, the monitoring points A, B, C, and D were loca ted beneath the toe of the side slope of the waste lifts while E, F, G, and H were beneat h the bottom of the central area of the landfill (Figure B-22) Even though consistent overbur den pressure (approximately 10 kPa) was applied to the bottom of the si de slope toe (A through D), the settlement behaviors varied greatly by location (0.6 6.6 cm). No relationship between overburden pressure and settlement was found from the data collected at A through D. Under the central area of waste body (E through H) se ttlement generally increased as overburden pressure increased. On May 20, 2010, all SSs were located under the bottom of the 82

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central area of the landfill body (Figure B-23 ). The field data at this time showed a general trend that more settlement occurred with increasing overburden pressure. Note that at locations E, F, and H the aver age settlements measured on May 20, 2010 were smaller than those measured on September 25, 2009, indicating upward vertical movement of the foundat ion during the period. Similar upward vertical movement of the foundation (up to 4.2 cm) was consistently observed from other SSs while overburden pressure remained stable or increased. This magnitude of this vertical movement was beyond the accuracy of the SS (0.7 cm) and mi ght be due to the swelling or shrinkage of clay in the subsurface soils with c hanges in the groundwater table elevation or temperature (Aschieri and Uliana 1984; Abue l-Naga et al., 2006; Whelan et al., 2005; McCarthy 2007). Comparison of Settlement between Pr ediction and In-situ Measurements Settlement predictions of the landfill foundation were made using one-dimensional elastic and consolidation settlement m odels (Equation 4-5 and Equation 4-6). The settlement predictions were presented in Figure 4-11 along with actual average settlements measured at each monitoring lo cation on September 25, 2009 and May 20, 2010. Settlements were predicted in three scenarios. In Scenario 1, elastic settlement was estimated using various stress-strain m odulus equations which were considered to be most appropriate to the soil types and conditions present (Bowles 1996); example calculations for the soils bene ath location A is provided in Appendix L. Figure 4-11-A shows that the settlements beneath the side slope toe (A, B, and C) were under predicted while those beneath the central la ndfill body (F, G, and H) were over 83

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predicted. In Scenario 1, the one-dimensional settlement models provided reasonable settlement estimates for the locations under the central area; the difference between actual settlements and predictions were in a r ange of 1.0 to 2.1 cm. On the other hand, the settlement behavior beneath the side slo pe was found unpredictable with the onedimensional settlement models used in this study In Scenario 2, assuming that the soils were over-consolidated, the settlement predictions were calculated and found to be closest to actual settlements at locations D, F, G, and H; differences in the range of 0.01 to 7.0 mm between prediction and in-situ measurements we re estimated. For Scenario 3, the stress-strain modulus equation for saturated sand (Equation 4-12) was applied for all types of soils. It was found that this sc enario provided excessively over predicted settlement estimates at locations D through H. Using the same three scenarios, settlem ents were predicted in and compared with the in-situ measurements on May 20, 2010 when all SSs were located under the central area of the landfill bod y. Most of the in-situ settlem ents on May 20, 2010 fall in the middle of ranges of settlement estimates using various stress-strain equations and those estimated with the assumption that soils were overconsolidated. Settlement estimates using a stress-strain equation for saturated sand were found to be overly conservative; the predictions were up to 2.3 times greater than actual settlements. Summary and Conclusions To investigate the settlement behavior of a landfill foundation, total pressure cells and settlement sensors were installed under the bottom of a municipal solid waste landfill in Florida, United States, and monitored from March 2007 to June 2010. During the study period, all sixteen total pressure cells and twelve of t he sixteen settlement 84

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sensors were determined to work properly; the remaining four settlement sensors transmitted unreasonable readings (i.e., data collected fluctuated without showing any trend and reason). The readings of the total pressure cells near the toe of the landfill side slope averaged 3 times greater than t he overburden pressure values estimated by multiplying the thickness of waste and cover soils above each pressure cell by bulk unit weight (11.8 kN/m3); the readings averaged 1.3 times greater than those estimated using Boussinesq influence factor charts. Overbur den pressure estimates beneath the central area were found to be over predicted: the m easured to estimated overburden pressure ratio averaged 0.8. Settlement readings measured under the toe of the side slope showed no relationship between overburden pr essure and settlement while settlement under the central area was found to genera lly increase with increasing overburden pressure. Settlement predictions were made using conventional one-dim ensional settlement models: elastic theory and Terzaghis consolidation model. Constrained moduli for elastic settlement predictions were esti mated using SPT(N), CPT(N), and various stress-strain (Youngs) modulus equations fr om Bowles (1996). Overall, it was found that the one-dimensional settlement m odels may not provide reasonable settlement estimates of the area beneath the landfill side slope. In addition, settlement predictions of the area of the landfill central body were over predicted up to 2.6 cm which might be overly conservative; note that at one monito ring point settlement was under predicted by approximately 2.7 cm. 85

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86 Table 4-1. Bulk unit weight change of t he study landfill unit with waste placement Day Volume (m3) Mass ( 103 kg) Bulk unit weight (kN/m3) 4/11/2008 431,284 523,414 11.9 9/25/2008 853,341 980,094 11.3 9/29/2009 1,433,771 1,781,424 12.2 Average 11.8

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XX Height, mBwaste Current elevation As-built height YY Height, mCwaste Current elevation As-built height 10 0 20 30 40 50 60 Bottom liner Bottom liner G E F D C B A H Y XX A A A B B C C D D E E F F G G H H Data logger 10 0 20 30 40 50 60 Center berm Figure 4-1. Distribution of in struments: A) plan view and B) X-X and C) YY cross-sectional view s; A through H in (A) and (C) represent a location of each pairs of instruments (TPC and SS) and A through H represent locations of corresponding duplic ate instruments. 87

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Settlement sensors (SS) SSs wire bundles TPCs wire bundles Total pressure cells (TPC) Center berm Settlement profiling 10 cm HDPE pipe Figure 4-2. Schematic cross-sectional view of the instruments setting in the center berm of the study landfill Date 2/1/07 5/1/07 8/1/07 11/1/07 2/1/08 5/1/08 Overburden pressure, kPa -10 -5 0 5 10 15 20 Temperature, oC 0 5 10 15 20 25 30 Overburden pressure Temperature Figure 4-3. Seasonal overburden pressure and temperature variati on prior to placing waste; each overburden pressure data point was estimated using conversion factors provided by the manufacturer. 88

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T0-Ti (oC) 0123 P (kPa) 0 1 2 3 4 5 6 7 8 P = 2.280(T0-Ti)+0.250 R2=0.994 A T0-Ti (oC) 0123456 P(kPa) -6 -4 -2 0 2 4 6 8 P = 0426(T0-Ti)2-0.830(T0-Ti)-2.793 R2=0.985 B T0-Ti (oC) 2468 1 0 C T0-Ti (oC) 6.57.07.58.08.59.09.5 P(kPa) 10 12 14 16 18 P = 0.191(T0-Ti)2-0.057(T0-Ti)+1.515 R2=0.987 D 9 10 12 13 14 16 17 18 20 P(kPa)P = -0.113(T0-Ti)2+2.360(T0-Ti)+5.801 R2=0.998Figure 4-4. Examples of bes t-fit regressions of overburden pressure (P) versus temperature variation (T0-Ti) to estimate thermal correction factors: A) winter to summer and B) summer to winter at an average overburden pressure of 0 kPa: C) winter to summer and D) summer to winter at an overburden pressure of 15.5 kPa 89

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Date 1/1/07 7/1/07 1/1/08 7/1/08 1/1/09 7/1/09 1/1/10 Overburden pressure, kPa -20 0 20 40 60 80 100 120 Temperature, oC 10 15 20 25 30 35 40 Overburden pressure estimated with a thermal correction factor provided by the manufacturer Overburden pressure estimated with thermal correction factors determined using the field data Temperature Figure 4-5. Impact of a thermal correcti on factor on estimating overburden pressure: overburden pressure over time estima ted using thermal correction factors provided by the manufacturer and es timated based on the field data (from TPC-G) 90

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Date 1/1/08 5/1/08 9/1/08 1/1/09 5/1/09 9/1/09 1/1/10 5/1/10 Overburden pressure (kPa) 0 20 40 60 80 100 120 140 Measured overburden pressure (TPC-H) Measured overburden pressure (TPC-H') Estimated using Boussinesq chart A Date 1/1/08 5/1/08 9/1/08 1/1/09 5/1/09 9/1/09 1/1/10 5/1/10 Overburden pressure (kPa) 0 20 40 60 80 100 120 TPC-G TPC-G' Estimated B Figure 4-6. Example of overburden pressure change with waste placement: (predicted overburden pressure) = (bulk unit weight ) (thickness of waste plus cover soil) (Influence factor from Boussines q chart); the data used were collected from A) TPC-H and H and B) TPC-G and -G. 91

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Location A & A'B & B'C & C'D & D'E & E'F & F'G & G'H & H' Overburden pressure (kPa) 0 20 40 60 80 100 Thickness of waste plus cover soil (m) 0 2 4 6 8 Measured overburden pressure (kPa) A) predicted using Boussinesq influnce factor chart B) predicted overburden pressure (kPa) Measured thickness of waste plus cover soil (m) Figure 4-7. Comparisons of overburden pressures between measured and predicted at each monitoring location using topographic survey data and bulk unit weight estimation on September 29, 2009; A) overburden pressures were predicted using Boussinesq influence factor char ts; B) (predicted ov erburden pressure) = (bulk unit weight) (thickness of wa ste plus cover soil on top of each pressure cell). Waste thickness (m) 024681 0 1 2 Ratio (measured/estimated pressure) 0 1 2 3 4 5 6 7 (waste thickness) x (bulk unit weight) Using Boussinesq influence factor chart Under central area Under side slope toe Figure 4-8. Changes in the ratio of meas ured to estimated overburden pressure as a function of waste thickness; each rati o was estimated using each surveying date. 92

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Overburden pressure (kPa) 0 20 40 60 80 Measured overburden pressure (TPC-C) Measured overburden pressure (TPC-C') Date 1/1/08 5/1/08 9/1/08 1/1/09 5/1/09 9/1/09 1/1/10 5/1/10 Vertical movement (cm) -5 0 5 10 15 20 Measured settlement (SS-C) Measured settlement (SS-C') Figure 4-9. Settlement of the landfill f oundation and overburden pressure changes at location C over time: the positive vertic al movement indica tes settlement. 93

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Overburden pressure (kPa) 0 20 40 60 80 100 120 Location A & A'B & B'C & C'D & D'E & E'F & F'G & G'H & H' Settlement (cm) 2 4 6 8 10 Under side slope Under central area September 25, 2009 May 20, 2010 ; all under central area September 25, 2009 May 20, 2010 Figure 4-10. Overburden pressure and settl ement measurements at each monitoring location; each data point indicates an average value of dupl icate outputs or a value of one settlement sensor where a duplicate sensor was malfunctioning (D, E, F, and H). 94

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Location A & A'B & B'C & C'D & D'E & E'F & F'G & G'H & H' Settlement (cm) 0 2 4 6 8 10 12 14 Average measured Predicted (using various stress-strain modulus equations) Predicted (assuming overconsolidated sand) Predicted (assuming saturated sand) September 25, 2009 Under side slope toe Under central area A Location A & A'B & B'C & C'D & D'E & E'F & F'G & G'H & H' Settlement (cm) 0 2 4 6 8 10 12 14 Average measured Predicted (using various stress-strain modulus equations) Predicted (assuming overconsolidated sand) Predicted (assuming saturated sand) May 20, 2010 B Figure 4-11. Comparisons of measured settl ement with predicted settlement: data used were collected on A) September 25, 2009, and B) May 20, 2010. 95

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CHAPTER 5 IMPACT OF FOOD WASTE CONTENT ON THE INTERNAL FRICTION ANGLE OF MUNICIPAL SOLID WASTE Introduction A major element in modern sanitary landf ill design is a slope stability evaluation of the proposed landfill configur ation and specified materials. In addition to assessing slope stability associated with the interfaces of different soil, geosynthetic, and waste layers, the internal stability of the dis posed waste itself r equires evaluation. Slope stability evaluation of compac ted municipal solid waste (MSW) requires estimating waste mechanical properties, with much im portance placed on the internal angle of friction. Research investi gating appropriate MSW internal friction angles has been reported, with most values r eported in the range of 15 to 35 (Kavazanjian et al. 1995; Kavazanjian et al. 1999; Sadek et al. 2001; Machado et al. 2002; Mahler and Netto 2003; Harris et al. 2006; G abr et al. 2007; Zhan et al 2007; Zekkos et al. 2007; Kavazanjian 2008; Zekkos et al. 2008; Reddy et al. 2009). The wide range is attributed to the heterogeneous compositio n of waste samples and diffi culties associated with the testing procedures. Geotechnical characteriza tion of MSW for internal friction angle is inherently more difficult than testing for soil, as MSW is heterogeneous in material composition, size, and mechanical properties. Considering the importance of internal friction angle as an input in the landfill design process, additional research to assess the impacts of waste composit ion and friction angle testing protocols is warranted. The composition of MSW varies wi th geographical, cultural, and seasonal differences. Food waste content, for example, can vary dramatically among countries. The food waste content of U.S. MSW is approximately 12. 5% on a wet-weight basis (USEPA, 2005), while that of China has been reported as up to 73% (The World Bank, 96

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1999; Wang and Nie, 2001). This difference results from dissimilar material consumption practices, packaging, waste management practices, and socio-economic conditions. In some cases the composit ion of landfilled MSW varies due to regionspecific policies and regulations. The Korean regulatory agency, for example, currently bans non-processed food waste from being dis posed of in an MSW landfill (Ministry of Environment of Republic of Korea, 2006). This study investigated the relationshi p between the MSW internal friction angle and food waste content. While it is expected that increa sing food waste content will decrease the MSW internal friction angle, t he magnitude of this relationship has not been measured. In addition to the value of such data to landfill design engineers assessing slope stability, friction angle data ar e also useful when evaluating mechanical MSW compaction efficiencies. Most of the previously reported data referenced earlier were determined for waste from western countries. As other parts of the world with different waste compositions begin to utiliz e large engineered sanitary landfills, it is important to better understand how different waste compositions (e.g., high food waste contents) might impact waste com paction and geotechnical stability. The impact of food waste c ontent on friction angle was in vestigated by conducting direct shear strength tests on synthetic MS W at a wide range of f ood waste contents (0 to 80% by wet weight). In addi tion to tests using a standard small-scale laboratory direct shear device designed for characterizing soil, a large-scale shear device was constructed and used. Given the wide range of results previously reported for MSW internal angle of friction as a whole, the re sults are intended to provide a clearer picture on the impact waste composition on this important design parameter. 97

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Methods and Material MSW Specimen Preparation In this study, synthetic MSW specim ens were created to represent waste characteristics expected upon initial landfi ll disposal (prior to the onset of biodegradation). Eight repres entative components were se lected: food waste, paper, plastic, metal, wood, textile, glass, and ash. MSW composition data from mainland China was used to represent waste with a hi gh initial food waste content; composition data from nine Chinese cities (as present ed by Wang and Nie (2001)) were averaged, for a resulting food waste content of 58% Three additional target MSW specimen compositions were selected by altering t he food waste content (0, 40, and 80% by wet weight) while maintaining a constant ra tio among other components (Table 5-1). The corresponding specimen weights for the 0, 40 58, and 80% food wast e conditions were 100, 180, 200, and 210 g for the sm all-scale direct shear test s (SSDSTs) and 25, 49, 55, and 60 kg for the large-scale direct shear tests (LSDSTs). Specimen weight increased with a larger food waste content as result of food wastes greater density compared to other waste components. The target sizes, methods of size reduc tion, and average moisture contents for the different waste components are summarized in Table 5-2. Food waste was collected from a local restaurant specializing in Chinese food. The food waste consisted primarily of discarded cooked foods (meats, rice, noodles, and vegetables), cooking oil, and discarded uncooked vegetables and fruits; bones and shells were removed prior to use. The food waste was collected periodically throughout the project as needed, and a visual observation was used to ascertain t hat the general characteristics remained the same throughout. For all SSDSTs, a total of 5 kg of food waste was pulped and 98

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homogenized using a food grinder (High-Speed Blender Mixing Syst em, Magic Bullet Express, California, US). Fo r the LSDSTs, 20 to 50 kg of food waste was used for each test, and size reduction was not performed (bones and shells were removed). The paper component consisted of 50% office paper and 50% newspaper by wet weight. Plastics used for the LSDSTs consisted of 50% plastic bottles and 50% film plastic by wet weight (only plastic bottles were used fo r the SSDSTs because of limitations in sizereducing the film plastic to a uniform si ze). Aluminum beverage cans served as the metal waste component for both tests. Ch ipped wood mulch of appropriate sizes for both tests was collected from a local waste transfer stat ion. Discarded clothes were used for the textiles. Crushed glass bottles we re used for the LSDSTs without sieving, while crushed and sieved (No. 4) glass was us ed for the SSDSTs. Coal ash from a local coal-fueled power plant (Gainesville Regional Utilities, FL US) served as the ash source. For SSDST specimens, all waste components were mixed by hand. For LSDST specimens, mixing was accomplished in four batches to promote a more homogenous composition throughout the large shear device. Waste mixt ures representing 25% of the target weight of each test were mixed individually using shovels in a stainless steel pan, and these mixtures were placed and compacted in the large-scale shear box until the target weight was reached. The moisture content (wet weigh bas is) of each component and specimen was determined by drying the specimens at 110 C (ASTM D2216-98). The average moisture content of each waste com ponent and specimen is presented in Tables 5-2 and -3, respectively; the average moisture content of each component was used to estimate the initial moisture content of each specimen before consolidation. 99

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Direct Shear Test Direct shear tests were conducted using two separate devices; one device was at a scale normally used for characterizing soils and another was fabricat ed to allow larger samples to be characterized. For the SSD STs, a Direct/Residual shear machine (Humboldt HM-2700, Humboldt Manufacturing Company, Illi nois, U.S.) with a 10-cmdiameter and 5-cm-height shear box was used. The maximum displacement level is approximately 18% of the shear box diameter (1.8 cm of hor izontal displacement). The SSDST apparatus is designed for a disp lacement-controlled test, and a horizontal displacement rate of 0.076 cm/min wa s used. The SSDSTs were performed in conformance with the ASTM standard method for soils under consolidated drained conditions (D 3080-04). For the LSDSTs, a stress-controlled direct shear box was designed as shown in Figure 5-1 (Stewart & Associates Manufac turing Corporation, Gainesville, Florida, U.S.); the photograph of the LSDST device is presented in Figure B-31. For normal stress and shear stress applications, hydraulic jacks equipped with hand pumps (SIMPLEX P42 and P82, Broadvie w, Illinois, U.S.) and pressure gauges (GD1 SIMPLEX, Broadview, Illinois) were used. The large-scale shear box includes an upper fixed shear box (43-cm length 43-cm width 46-cm height) and a movable lower shear box (43-cm length 43-cm width 16-cm height). The maximum displacement level of the large-scale dev ice is approximately 40% of the shear box length (17 cm of horiz ontal displacement). Each direct shear test was initiated by placing and compacting a well-mixed MSW specimen into the shear test box. The norma l stresses applied for the SSDSTs were 48, 97, 145, 194, and 290 kPa, and those for t he LSDSTs were 96, 192, and 287 kPa. Because all tests were performed under drai ned conditions, the applied normal stresses 100

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were treated as the effective normal st resses. Specimens of both scales were consolidated under each effective normal stress for 4 to 30 hours until vertical deformation rates were less than 0.5% per hour for the LSDSTs and 2% per hour for the SSDSTs. For the LSDSTs, the normal stress was continuously monitored and adjusted during the consolidation of an MSW specimen. Densities of the specimens for the LSDSTs after consolidation and before shear ing are provided in Ta ble 5-3. Dry density was calculated by subtracting the moisture weig ht from the total weig ht of a specimen. Density was not monitored for SSDST specimens. Data Analysis Two data interpretation methods were used to estimate shear-strength parameters (internal friction angle and cohesi on). First, the internal fric tion angles of both scales of tests were estimated using peak (ultimat e) shear strength va lues produced in the available displacement of each shear testing device: 1.8 cm (18% displacement level) for SSDSTs and 17.2 cm (40% displacement level) for LSDSTs. The Mohr-Coulomb failure criterion expressed as Equation 51 was used to calculat e the shear strength parameters. To develop a Mohr-Coulomb failure criterion envelope for each set of SSDST and LSDST data, a best-fit linear r egression was conducted. For all 20 SSDSTs, duplicate tests were conducted at each normal stress and food waste content, and in some cases, triplicate tests were perform ed (in cases where the difference in shear strength values of the duplicates was larger than normal). All of the replicate data points for each set of SSDSTs were used for the bes t-fit linear regression s. Because of the scale, replication was not conducted for the LSDSTs. Although the internal friction angle is the focus of this study, the cohesion va lues were also calc ulated and are reported briefly later. 101

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= c + tan( ) (5-1) Where = (Effective) shear stress (kPa); c = (Effective apparent) cohesion (kPa); = (Effective) normal stress (kPa); = (Effective, or drained) angle of internal friction (degree). In the second data interpretation method, the mobilized shear strength, cohesion and internal friction angle at various displacement levels were calculated to investigate the relationship between disp lacement level and mobiliz ed shear-strength parameters. Based on the stress-displacement response dat a, mobilized internal friction angles of MSW were estimated at 5 (5%), 10 (10%), 15 (15%), and 18 mm ( 18%) of horizontal displacement for the SSDSTs and 22 (5%), 43 (10%), 65 (15%), 86 (20%), 108 (25%), and 129 mm (30%) of horizontal displacement fo r the LSDSTs. To remain consistent, the horizontal displacement level will be presented as both a magnitude (mm) and percentage in the re mainder of the paper. Results and Discussion Stress-Displacement Response with Different Food Waste Contents The stress-displacement response plots of SSDSTs showed relatively well-defined peak (ultimate) shear strengths at all tested food wast e contents; stress-displacement curves are presented in Figures B-32 to B39. Twenty eight out of 48 SSDSTs showed the fully mobilized, well-defined peak shear strength. In the re maining 20 SSDSTs, the stress-displacement response curves were cl ose to their peak shear strengths at the maximum displacement of 18 mm (18%). For these tests the maximum shear strength values at a displacement of 18 mm (18%) were consider ed as the peak shear strength and those were used to develop Mohr-Coulomb failure criteria envelopes later. Figure 52 presents examples of each type of stre ss-displacement response of the SSDSTs. 102

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Stress-displacement response plots of the 40 and 80% food waste specimens show shear stresses that approach their peak shear strengths, while the 0 and 58% food waste specimens were fully mobiliz ed at 14 mm (14%) and 10 mm (10%) of displacement, respectively. These stress-di splacement response plots are similar to typical stress-displacement responses of direct shear tests on a loose-soil sample (Budhu, 2000; McCarthy, 2007). All LSDST stress-displacement response plots resulted in well-defined mobilized peak shear strength. Figure 5-3 shows examples of stress-displacement response plots produced from LSDSTs with 0, 40, 58, and 80% food waste content s under a stress of 192 kPa. Nine out of 12 LSDSTs showed peak shear strengths that were mobilized between 86 mm (20%) and 129 mm (30%) of di splacement, while the rest were mobilized at approximately 65 mm (15%) of displacement. This suggests that a displacement of 129 mm (30%) is enough to mobilize a peak shear strength using the wastes and apparatus tested. The peak shear strength of most of the SSDSTs wa s mobilized at smaller displacement levels (%) than the LSDSTs. O ne possibility is that the large sizes of fibrous materials used for the LSDSTs i nduced stronger reinforcement effect and required greater displacement level of LS DST specimens to mobilize their peak shear strengths. Reinforcement effect by fibrous ma terials is discussed more in a later section of the paper. Unlike the results of this study, which consistently show the relatively well-defined peak shear strengths, other res earch has reported various ty pes of displacement-stress responses (Harris et al. 2006; Gabr et al. 2007; Reddy et al. 2008). For example, in their 103

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small-scale (100-mm-diameter-by-50-mm-thick ness) direct shear tests Gabr et al. (2007) reported a particular type of stress-displacement res ponse plot that had an initial peak followed by a residual and then a cont inuous increase in shear stress with displacement. The stress-disp lacement response difference between this study and other studies may be attributed to factors such as the composition, size, and preparation method of the waste components. Stress-strain response curves of triaxial shear tests on MSW in the literature show even upward curvilinear curves (Machado et al. 2002; Zekkos et al. 2007; Zhan et al. 2008). Sadek et al. (2001) pointed out that the shear strength of MSW might be mobilized at smaller displacement levels in a direct shear test than in a triaxial shear test. This is because the failure surface of a direct shear test is pre-determined during the sample preparation; most fibrous material is placed parallel to the failure surface. The mobilized peak shear strength under a given normal stress increased as food waste content decreased. For example, with the SSDST and under a stress of 290 kPa, the mobilized peak shear strength decreased from 245 to 39 kPa as the food waste content increased from 0 to 80 %. This trend was consistent ly observed during all tests on both scales. As the ratio of food to other components became more dominant, shear strength decreased but the extent of this decrease declined as normal stress decreased. For example, in the SSDST s the difference in the m obilized peak shear strength between 0 and 80% food waste specimens under an effective normal stress of 48 kPa was only 20 kPa, while that under a stress of 290 kPa was 206 kPa. Change in Mobilized Internal Fr iction Angle with Food Waste Content Figure 5-4 presents Mohr-Coul omb criteria envelopes plotted using the mobilized peak shear strength values produced from (a) SSDSTs and (b) LSDSTs. The linear 104

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regressions showed a range of R squared va lues from 0.81 to 0.99 for SSDSTs and from 0.94 to 0.99 for LSDSTs. In both sca les, the Mohr-Coulomb failure criteria envelopes showed that mobilized internal fr iction angles increased with decreasing food waste content, but the magnitude of the increase varied in different food waste content or with scales of testing. The mobilized in ternal friction angles of SSDSTs decreased from 39 to 31o by increasing food waste content from 0 to 40% while the angles decreased more dramatically from 31 to 7 with an increase in the food waste content from 40 to 80%. The mobilized internal friction angles of LSDSTs decreased from 36 to 26o by increasing the food waste content fr om 0 to 40%. There was no considerable change in internal friction angle as food waste content increased from 40 to 58%. However, the mobilized internal friction angles dropped from 24 to 15 as food waste content increased from 58 to 80% in LSDSTs. Overall, the extent of decrease in the internal friction angle with increasing food waste content of SSD STs was greater than that of LSDSTs. One possible explanation is t hat the large size of the fibrous materials (metal, plastics, wood, and textile) used for the LSDSTs compared to the SSDSTs causes more additional shear resistance. Zekkos et al. (2007 and 2008) indicated that the increase in shear strength is attributed to the reinforcem ent effect of large fibrous material (> 20 mm). These re sults suggest that the food wa ste content has a greater impact on friction angle for processed waste (size-reduced) compared to non-processed waste. Because the food waste for the SSD STs was pulped, the contribution of the food waste as a fibrous (reinforcement) materi al might be reduced. Film plastic was not used as a part of plastic waste component fo r the SSDSTs. This might induce slightly different shear behavior of the SSDSTs and LSDSTs. 105

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The values of the mobilized internal fr iction angle and the mobilized cohesion at different displacement levels with differ ent food waste contents are presented in Table 5-4. At each displacement level of both scale s (except at the 15% di splacement level of LSDSTs), the internal fric tion angle decreased with increasing food waste content. As shown in Table 5-4, when the displacem ent level increased from 5 to 10%, the mobilized internal friction angles of all tests (except LSDSTs with the specimens of 80% of food waste content) increas ed. However, at the other displacement levels, no correlation between the mobilized internal fr iction angle and the displacement level was found. This differs from the resu lts from Zhan et al. (2008) who reported that the internal friction angle increased with strain based on the results of triaxi al tests on MSW. Cohesion values overall increased with increasing displacement level except LSDSTs with 80% food waste content. The great est cohesion among t he tested conditions occurred at the 58% food waste content in SSDSTs and at the 40% food waste content in the LSDSTs. Comparison of Internal Friction Angles with Previous studies In Figure 5-6, the internal friction angle and the cohesion of the current study were compared to those from previous studies (Kavazanjian et al. 1999; Sadek et al. 2001; Machado et al. 2002; Harris et al. 2006; Zhan et al. 2008; Reddy et al. 2009). Reported internal friction angles ranged from 14 to 39 and cohesion ranged from 0 to 70 kPa as shown in Figure 5-6. The wide range of value can be attributed to differences in the test methods for shear strength employed, wast e composition and proc essing, and age or level of decomposition of the waste samples. Again, this illustrates the need additional research to better understand the factors th at impact waste shear strength parameters and how possible future changes to the waste stream might impact t hese parameters. 106

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Internal friction angle values of 20 to 40 are often considered as a typical range for MSW from western countries where t he waste is more dominated by packaging materials and discarded domestic goods, and less by food waste. The design engineer would use an internal friction angle estimate as an input for a landfill design. Thus a natural question that would co me up in the design of a landf ill with a much larger food waste content, such as might be currently encountered in some parts of China, is whether typical friction angle values used for the design of a landfill in the U.S. would be appropriate or not. The re sults here suggest that food waste contents greater than typically seen in western countries would still have an internal angle of friction within the typical range, but t hat at very high food waste contents, friction angle does decrease to levels lower than expected for wastes with lowe r food contents. The re sults of testing at both scales suggest that at a f ood waste content up to 40%, t he friction angle falls within a typical range, with contents up to 60% close the lower end of typical ranges for design. The data here provide the design engineer with some guidance for better selecting input parameters for engineering applications. Clearly large food waste contents do impact friction angle and thus must be factored in the des ign of landfills containing this type of waste. As previously mentioned, the f ood waste content in some regions has been reported as high as 70% (The Worl d Bank, 1999; Wang and Nie, 2001). Summary and Conclusions The impacts of changing food waste content on the mobilized internal friction angle of MSW were investigated by conducting direct shear tests with small-scale and large-scale direct-shear testing devices. The stress-displacement response plots of SSDSTs showed relatively well-defined peak (ultimate) shear strengths in all tested 107

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108 food waste content. In 28 out of 48 SSDSTs and all 12 LSDSTs, well-defined peak shear strengths were observed. The s hear stress approached the peak shear strength in the remaining 20 SSDSTs. In both scales of tests, the mobiliz ed peak shear strength increased with a decrease in food waste content under a given normal stress. Also, decreasing food waste content resulted in in creasing the internal friction angles. A greater decrease in the internal friction ang le with increasing food waste content was observed in SSDSTs than in LSDSTs, which is lik ely a result of the greater sizes of the waste components in the LSDSTs which cause additional shear resistance (reinforcement effect). As food waste content increased from 0 to 80%, the mobilized internal friction angles decreased from 39 to 7 in SSDSTs and from 36 to 15 in LSDSTs. Internal frictions angles at food waste contents up to 40% for the SSDSTs and 58% for the LSDSTs were measured in the range of typical magnitu des reported in the literature; larger food waste contents resulted in below ty pical angles. In most of the tests, the mobilized internal friction ang le increased with increasing horizontal displacement level from 5% to 10%, but di splacement level increases beyond this were not found to change the internal friction angle estimate. Thes e results suggest that the impact of high food waste content on the internal friction angle of MSW should be considered when designing for landfill slope stability.

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Table 5-1. Composition of MSW specimens for LSDSTs and LSDSTs Component Content (%) by wet weight Food 0.0 40.0 57.6 80.0 Paper 24.0 14.4 10.2 4.8 Plastic 22.3 13.4 9.5 4.6 Metal 4.0 2.4 1.7 0.8 Wood 11.2 6.7 4.7 2.2 Glass 6.2 3.7 2.6 1.2 Textile 8.7 5.2 3.7 1.7 Ash 23.7 14.2 10.0 4.7 Table 5-2. Size and moisture content (MC) of each waste component for SSDST and LSDST Component SSDST LSDST Size limit Size reduction method MC (%) Size limit Size reduction method MC (%) Food Pulp a Food grinder 61.6 No size reduction 63.0 Paper 47 mm 7 mm Paper shredder 7.5 140 mm 220 mm Scissors 8.8 Plastic 10 mm 10 mm Scissors 0.7 < 150 mm Scissors 1.5 Metal 10 mm 10 mm Scissors 0.4 < 150 mm Scissors 0.2 Wood < 10 mm 8.3 < 150 mm 17.3 Glass < 4.75 mm Hammer 0.0 < 150 mm Hammer 0.1 Textile 10 mm 10 mm Scissors 5.0 < 150 mm Scissors 8.2 Ash No size reduction 0.7 No size reduction 15.3 a Food waste for SSDSTs was pulped by grinding. 109

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110 Table 5-3. Average moisture contents and dry densities (kg/m3) of the specimens Food waste content Moisture content (%) Dry density (kg/m3)c (LSDST) SSDST LSDST Normal stress Initiala Final b Initial Final 96 kPa 192 kPa 287 kPa 0% 3.5 4.5 8.9 10.4 358.5 462.3 508.5 40% 26.7 20.7 30.0 27.4 425.8 465.6 701.2 58% 37.0 30.0 39.1 42.8 467.6 456.6 651.6 80% 50.0 47.0 51.7 53.4 492.1 522.3 579.7 a Measured before consolidation. b Measured after testing shear strength. c Measured after consolidation and before shearing. Density was not monitored for SSDST.

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Table 5-4. Mobilized internal friction angle and cohesion values Displacementa Parameter SSDST Food Waste LSDST Food Waste 0% 40% 58% 80% 0% 40% 58% 80% 5% Angle ( ) 30 27 20 6 25 24 23 13 Cohesion (kPa) 5 6 17 6 0 12 6 5 10% Angle ( ) 36 30 21 7 33 26 24 12 Cohesion (kPa) 1 10 23 7 0 21 13 9 15% Angle ( ) 39 31 20 7 37 24 25 13 Cohesion (kPa) 2 12 27 7 0 34 18 7 18% 20%c Angle ( ) 39 30 18 7 38 25 24 15 Cohesion (kPa) 3 13 31 8 2 36 24 3 25% Angle ( ) 37 25 21 15 Cohesion (kPa) 9 38 31 1 30% Angle ( ) 36 24 21 19 Cohesion (kPa) 15 37 26 2 Peakb Angle ( ) 39 31 21 7 36 26 24 15 Cohesion (kPa) 4 13 28 8 17 37 24 4 a Displacement represents the relative horizontal displacement of a specimen. b The shear-strength parameter s estimated using the fu lly mobilized shear-strength values of each shear test. c 18% for SSDSTs and 20% for LSDSTs 111

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Hydraulic jack (normal stress) Hydraulic jack (Shear stress) Steel wheel Lower box (moveable) Upper box (fixed) Compressor carriage Figure 5-1. Large-scale direct shear test device 112

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Horizontal displacement (mm) 0 5 10 15 20 Shear stress (kPa) 0 20 40 60 80 100 120 140 0% 40% 58% 80% Figure 5-2. Stress-displacement response cu rves of SSDSTs with 0, 40, 58, and 80% food waste specimens under 145 kP a of effective normal stress Horizontal displacement (cm) 0246810121416 Shear stress (kPa) 0 50 100 150 200 0% 40% 58% 80% Figure 5-3. Stress-displacement response curves of LSDSTs with 0, 40, 58, and 80% of food waste specimens under 191 kP a of effective normal stress 113

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Normal stress (kPa) 050100150200250300350 Shear stress (kPa) 0 50 100 150 200 250 300 0% Food Waste 40% Food Waste 58% Food Waste 80% Food Waste R2=0.99 R2=0.95 R2=0.81 R2=0.88A Normal stress (kPa) 050100150200250300350 Shear stress (kPa) 0 50 100 150 200 250 300 R2=0.99 R2=0.94 R2=0.97 R2=0.96B Figure 5-4. Mohr-Coulomb failure envelopes of A) SSDSTs and B) LSDSTs. Data points correspond to peak shear strengths under each effective normal stress and at each waste composition; each line was derived by a best-fit linear regression. 114

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Food waste content (%) 02 04 06 08 0 Internal friction angle ( o ) 0 10 20 30 40 5% 10% 15% Relative displacementA Food waste content (%) 02 04 06 08 0 Internal friction angle ( o ) 0 10 20 30 40 5% 10% 15% 20% 25% 30% Relative displacementB Figure 5-5. Impact of food waste contents in synthetic fresh MSW on friction angles at different displacement levels: A) SSDSTs and B) LSDSTs 115

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116 Internal Friction Angles ( o ) 01 02 03 04 05 0 Cohesion (kPa) 0 20 40 60 0 % LSDST 40% LSDST 58% LSDST 80% LSDST 0 % SSDST 40% SSDST 58% SSDST 80% SSDST Reddy et al. (2009); fresh waste Harris (2008); < 2 years Harris et al. (2006); >10 years Machdo et al. (2002); about 15 years; at 20% strain Kavazanjian et al. (1999); 11-35 years Zhan et al. (2008); < 3 years; at 20% strain Zhan et al. (2008); 9-13 years; at 20% strain Figure 5-6. Comparison of values of inter nal friction angle and cohesion values in this study to those of in previous studie s; each error bar indicates positive or negative standard deviation

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CHAPTER 6 SUMMARY AND CONCLUSIONS Pore pressure variation resulting fr om liquids addition was monitored in a bioreactor landfill equipped with horizontal liqu id distribution trenches. To measure pore pressure in the landfill, piezometers were installed in liquids-introducing bedding media trenches and in the surrounding waste. This study consisted of two experiments. In Experiment 1, liquids were added at constant flow rates of 0.057 m3/min (conducted by Kumar (2009) in 2007). In Ex periment 2, liquids were a dded at a rate of 0.076 m3/min (conducted by the author in 2010). Added liqui ds were successfully transmitted to the ends of the crushed glass and the shredded tire trenches without considerable head loss. While the added liquids spread out fr om the trenches, pressure dropped sharply near the trenches and then gradually with in creasing horizontal distance; this would suggest that for a slope stability analysis for a landfill with a horizontal liquid addition trenches the rapid pore pressure drop near the bedding media trenches needs to be considered. Using analytical models presented by Townsend (1995) and t he aforementioned pore pressure measurements, Kx and Ky values of the landfill ed waste surrounding the horizontal trenches were estimate to be in the ranges of 7.0-4 to 3.0-3 cm/sec and 1.0-6 to 1.9-5 cm/sec, respectively. These estimated Kx and Ky values fell within a range reported in liter ature. Thus, it is concluded that the analytical models can be used as useful tools to roughly estimate hydraulic conductivities of waste in a bioreactor landfill equipped with horizontal liquids addition lines. The values of anisotropy were estimated to be in the range of 37 to 277. 117

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Surcharge-induced settlement of landfill ed waste with high moisture content (approximately 40%) was inve stigated using a settlement profiling sensor. Settlement profiling was conducted by inserting the sens or into 10-cm diameter HDPE pipes placed over the top surface of t he study landfill prior to addi tional waste placement. It was hypothesized that the settlement of the landfilled waste with high moisture content might be similar to consolidation settlement. As a result of consolidat ion, average monthly leachate generation increased fr om approximately 200 to 1100 m3 after additional waste placement. Based on the hypothesis, relative ly wide ranges of compression parameters (Cc, mv, and cv) were estimated and found typicall y within ranges reported in the literature: Cc (0.1 1.7), mv (3.0-4 7.3-3 m2/kN), and cv (0.89-2 to 1.44-2 cm2/sec). Ky values of the landfilled waste were estimated in the range of 4.6-7 to 9.8-6 cm/sec; these values were calculated using the estimated mv and cv values. During the settlement profiling period, the average settlement rate of 3.76% per year was approximately 1.4 times gr eater than the settlement rate prior to waste placement (2.66% per year). Settlement behavior of a landfill foundation was investigated in situ, using instrumentation consisting of eight pairs of TPCs and eight pairs of SSs installed under the bottom liner of a municipal solid wast e landfill. Settlement was monitored for 39 months from March 2007 to June 2010. Duri ng the study period, all sixteen TPCs and twelve out of the sixteen SSs worked proper ly. The readings of the TPCs near the landfill side slope toe were, on average, 3 times greater than predicted values [(predicted overburden pressu re) = (thickness of waste and cover soil) (bulk unit weight)] and1.3 times greater than those estimated using the Boussinesq influence 118

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factor charts. Settlement readings measur ed under the toe of t he side slope showed no relationship between overburden pressure and se ttlement while those under the interior area were found to generally increase with increasing overburden pressure. Settlement predictions were made using one-dim ensional elastic theory and Terzaghis consolidation model. Constrained moduli fo r elastic settlement predictions were estimated using SPT(N), CPT(N), and vari ous stress-strain (Youngs) modulus equations from Bowles (1996). The one-dimens ional settlement models did not provide reasonable settlement estimates of the ar ea beneath the landfill si de slope. Settlement predictions of the landfill cent ral body area were over predicted up to 2.6 cm. It should be noted that at one monitoring point settl ement was under predicted by approximately 2.7 cm. The impacts of food waste c ontent on the mobilized internal friction angle of MSW were investigated by conducting direct shear tests. Generally, mobilized peak shear strength increased with a decrease in food waste content under a given normal stress. Additionally, as food waste content decreased, internal friction angles increased. A greater decrease in the internal friction ang le with increasing food waste content was observed in SSDSTs compared to the LSDSTs, which might be due to the bulkier waste components in the LSDSTs; large fibrous material is generally considered to cause additional shear resistance (reinforcement effe ct). As food waste content increased from 0 to 80%, the mobilized internal friction ang les decreased from 39 to 7 in SSDSTs and from 36 to 15 in LSDSTs. The majority of friction angle measurem ents produced in this study fell within the range of those previously reported for MSW. 119

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120 APPENDIX A SUPPLEMENTAL TABLES Table A-1. Hydraulic conductivities and comp ression properties of waste in previous studies Cc' mv (m2/kN) cv (m2/sec) Kx (cm/sec) Ky (cm/sec) Reference 2.9-4 5-3 3.7-6 1.5-2 Powrie and Beaven (1999) 0.17 0.24 4-4 1.25-3 Landva (2000) 0.128 0.260 4.48-4 2.5-4 5.62-6 5.12-4 4.7-6 1.24-4 Durmusoglu et al. (2006) 0.1 0.41 Sowers (1973) 0.21 Machado et al. (2002) 0.17 0.23 Anderson et al. (2004) 3.0-6 4.0-6 Townsend (1995) 5.4-6 6.1-5 combined K Jain et al. (2006) 1.9-47.8-4 Larson (2007) represents no data. Cc represents modified primar y compressibility index. mv represents coefficient of volume change. cv represents coefficient of consolidation. Kx represents horizontal hydraulic conductivity. Ky represents vertical hydraulic conductivity.

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Table A-2. Summary of liter ature review and studies on landfill settlement behavior Site Study Period (yrs) Study Area (ha) Initial Ave. Depth (ft) Settlement (%) Settlement Rate (%/yr) Reference Crow Wing County, MN Bioreactor 5.0 5.7 NA 20.0 4.00 Bioreactor Performance, US EPA (2007) Victoria, Australia Dry 1.7 0.8 59.1 2.3 1.35 Yuen et al. (1997) Bioreactor 1.7 0.8 59.1 3.9 2.29 Mountain View, CA Dry 4.0 0.9 47.3 11.7 2.93 M. El-Fadel et al. (1999) Bioreactor-A 4.0 0.9 49.7 13.5 3.38 Bioreactor-B 4.0 0.9 47.1 13.7 3.43 Bioreactor-C 4.0 0.9 52.2 12.5 3.13 Bioreactor-D 4.0 0.9 47.7 7.8 1.95 Bioreactor-E 4.0 0.9 49.5 15.3 3.83 Meruelo, Spain Dry 3.0 3.0 1.00 Sanchez-Aliciturri et al (1995) A landfill, WI Dry 1.5 1.7 1.13 Edil et al. (1990) Site C Bioreactor 1.5 10.5 7.00 C.H. Benson et al. (2000) Site S Dry 2.7 4.1 1.50 C.H. Benson et al. (2000) Bioreactor 2.7 27.0 10.00 represents no data. 121

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Table A-3. Settlement (%) meas urements of the profiling pipe 1 Distance from the pipe entry (m) Waste below Pipe 1 (m) Waste above Pipe 1 (m) 5/9/2009 6/1/2009 8/31/2009 12/23/2009 3/3/2010 0 14.4 0.00 1.50 2. 22 2.39 2.61 2.94 5 14.8 0.44 1.80 2. 44 3.32 2.91 3.25 7 15.3 0.61 4.14 4. 77 5.22 5.07 5.39 10 15.9 0.80 5.84 6. 80 6.80 6.91 7.28 13 16.4 1.02 4.61 5. 21 5.58 5.67 6.15 16 16.7 1.33 4.03 4. 63 5.33 5.24 5.69 19 16.8 1.92 1.87 2. 50 3.07 3.15 3.63 22 16.9 2.37 1.30 1. 87 2.46 2.68 3.09 25 17.1 3.24 2.01 2. 54 3.08 3.22 3.59 28 17.32 3.77 2.20 2. 76 3.23 3.56 3.81 31 17.55 4.42 2.29 2. 89 3.44 3.75 4.06 34 17.65 5.21 1.95 2. 51 3.39 3.49 3.90 37 17.75 5.84 2.04 2. 38 3.23 3.50 3.87 40 17.9 6.75 2.22 2. 61 3.28 3.80 4.12 43 18.1 6.98 2.87 3. 36 4.21 4.61 4.69 46 18.2 8.07 2.49 2. 87 4.39 4.33 4.39 122

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Table A-4. Settlement (%) meas urements of the profiling pipe 2 Distance from the pipe entry (m) Waste below Pipe 2 (m) Waste above Pipe 2 (m) 5/9/2009 6/1/2009 8/31/2009 12/23/2009 3/3/2010 0 14.9 0.00 3.97 4. 89 5.40 5.26 5.89 3 15.2 0.00 1.36 1. 95 2.56 3.00 5.22 6 15.5 0.41 1.57 2. 33 2.78 2.78 6.01 9 15.9 0.57 2.21 3. 00 3.44 3.35 6.15 12 16.3 1.09 1.61 2. 46 2.79 2.82 5.53 15 16.6 1.32 2.08 2. 98 3.45 3.58 6.41 17 17.0 1.67 2.98 3. 78 4.13 4.08 6.94 20 17.4 2.04 1.93 3. 19 3.34 2.91 5.87 23 17.8 2.39 1.61 2. 86 3.26 2.97 5.55 27 18.1 2.81 1.77 2. 71 3.34 3.28 6.26 30 18.5 3.30 2.53 3. 30 4.34 4.00 6.80 33 18.8 3.51 2.64 3. 56 4.55 4.29 6.32 36 19.1 4.16 2.43 3. 38 4.56 4.31 5.43 39 19.1 5.29 1.58 2. 44 3.68 3.54 5.18 42 19.3 5.86 1.96 2. 78 4.64 3.95 5.14 45 19.4 6.52 1.76 2. 64 4.47 3.75 4.82 123

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Table A-5. Settlement (%) meas urements of the profiling pipe 3 Distance from the pipe entry (m) Waste below Pipe 3 (m) Waste above Pipe 3 (m) 5/9/2009 6/1/2009 8/31/2009 12/23/2009 3/3/2010 0 13.2 0.00 3.28 4. 17 3.97 4.00 4.12 3 13.6 0.00 3.43 4. 17 4.80 4.31 5.46 6 13.8 0.61 0.28 0. 88 1.24 1.05 3.78 9 14.0 1.01 2.12 2.71 3.21 6.14 12 14.4 1.32 4.14 4. 16 4.35 4.07 7.31 15 14.7 1.64 2.97 3. 49 3.81 3.64 6.46 18 15.0 2.02 3.09 3. 78 4.21 3.94 6.74 21 15.3 2.27 3.26 3. 94 4.45 4.25 7.10 23 15.6 2.06 3.19 4. 03 4.50 4.51 6.85 26 15.8 2.52 3.06 3. 84 4.44 4.50 7.49 29 16.1 2.89 3.96 4. 62 5.38 5.51 8.57 32 16.5 3.39 4.99 5. 85 6.68 6.72 9.33 35 16.7 3.96 3.94 4. 68 5.68 5.85 7.33 38 16.9 4.38 3.31 4. 18 5.03 5.17 7.61 41 17.2 4.64 3.32 3.98 4.90 7.04 44 17.4 5.24 3.60 4. 16 6.65 8.72 5.16 represents no data. 124

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Table A-6. Settlement (%) meas urements of the profiling pipe 4 Distance from the pipe entry (m) Waste below Pipe 4 (m) Waste above Pipe 4 (m) 5/9/2009 6/1/2009 8/31/2009 12/23/2009 3/3/2010 0 13.2 0.00 0.53 0. 66 1.01 1.84 2.30 4 13.6 0.56 2.39 2. 28 2.76 3.77 4.38 8 13.9 0.97 4.00 4. 02 4.50 5.51 5.94 10 14.2 1.27 7.24 4. 67 4.99 6.10 6.54 13 14.5 1.53 3.79 3. 85 4.26 5.35 5.92 16 14.9 1.80 3.80 3. 77 4.26 5.49 5.74 19 15.3 2.11 4.25 4. 31 4.91 5.93 6.43 22 15.4 2.68 3.12 3. 18 3.97 4.98 5.39 25 15.4 3.40 3.50 3. 71 4.33 5.16 5.64 29 15.6 4.02 3.74 3. 87 4.65 5.44 5.60 31 15.9 4.55 4.16 3. 92 4.74 6.09 6.25 34 16.2 4.91 4.18 3. 92 5.17 6.14 6.38 37 16.5 5.38 3.69 3. 63 4.74 5.93 6.30 40 16.6 5.18 3.57 3. 60 4.64 7.13 6.21 42 16.7 5.19 3.46 3.31 4.54 6.03 45 16.9 5.14 2.98 2.79 4.06 5.61 represents no data. 125

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126 Table A-7. Settlement (%) meas urements of the profiling pipe 5 Distance from the pipe entry (m) Waste below Pipe 5 (m) Waste above Pipe 5 (m) 5/9/2009 6/1/2009 8/31/2009 12/23/2009 3/3/2010 0 13.6 0.00 2.86 3. 11 3.50 3.59 4.31 3 14.0 0.00 2.46 2. 62 3.48 3.63 6.43 6 14.3 0.40 2.77 3. 09 3.34 3.88 6.09 9 14.4 0.68 3.68 3. 98 4.32 4.96 6.77 11 14.5 0.80 4.67 4. 99 5.29 6.14 6.94 14 14.6 1.02 3.87 4. 26 4.56 4.96 8.97 17 15.0 0.66 2.98 3. 37 3.84 8.27 5.96 20 15.1 0.59 4.85 5. 23 5.73 6.31 5.06 23 14.9 1.13 3.43 3. 99 4.34 4.92 3.87 26 14.7 1.50 3.08 3. 53 3.60 4.29 4.99 30 14.7 1.65 3.44 3. 81 3.80 4.32 5.08 35 14.7 1.85 3.72 4. 08 4.22 4.60 5.62 38 14.7 2.03 4.50 4. 91 5.02 5.65 5.74 41 14.7 2.01 3.31 3. 84 4.01 4.43 5.99 44 14.8 1.97 2.28 2. 64 2.99 3.08 4.58 47 14.9 1.96 3.68 4.07 4.64 4.96 represents no data.

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Table A-8. Compressibility properties and hy draulic conductivities estimated using the data obtained from Pipe 1 Distance from the pipe entry (m) Cc' cv (cm2/sec) mv (m2/kN) Ky (cm/sec) 0 0.0046 5 0.97 0.0065 7 1.43 0.0071 10 1.64 0.012 0.0042 5.62-6 13 1.02 0.014 0.0029 9.12-6 16 0.72 0.014 0.0011 9.84-6 19 0.28 0.011 0.0007 4.60-6 22 0.17 0.011 0.0007 3.08-6 25 0.18 0.012 0.0006 1.32-6 28 0.18 0.0005 31 0.16 0.012 0.0004 6.29-7 34 0.12 0.012 0.0003 4.88-7 37 0.11 0.014 0.0003 4.59-7 40 0.11 0.0004 43 0.13 0.0003 46 0.10 0.0046 represents no data. 127

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Table A-9. Compressibility properties and hy draulic conductivities estimated using the data obtained from Pipe 2 Distance from the pipe entry (m) Cc' cv (cm2/sec) mv (m2/kN) Ky (cm/sec) 0 3 6 1.03 0.009 0.0047 4.08-6 9 1.00 0.010 0.0044 4.18-6 12 0.45 0.010 0.0019 1.81-6 15 0.47 0.012 0.0019 2.24-6 17 0.49 0.0019 20 0.35 0.0013 23 0.28 0.0010 27 0.23 0.012 0.0008 9.56-7 30 0.25 0.0008 33 0.26 0.0008 36 0.21 0.0007 39 0.13 0.0004 42 0.13 0.0004 45 0.12 0.0003 represents no data. 128

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Table A-10. Compressibility properties and hydraulic conducti vities estimated using the data obtained from Pipe 3 Distance from the pipe entry (m) Cc' cv (cm2/sec) mv (m2/kN) Ky (cm/sec) 0 3 6 0.24 0.0012 9 0.47 0.0022 12 0.57 0.0026 15 0.40 0.0018 18 0.37 0.0016 21 0.35 0.0014 23 0.40 0.0016 26 0.32 0.0013 29 0.35 0.0013 32 0.39 0.0014 35 0.28 0.0010 38 0.23 0.0008 41 0.21 0.0007 44 0.20 0.0007 represents no data. 129

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Table A-11. Compressibility properties and hydraulic conducti vities estimated using the data obtained from Pipe 4 Distance from the pipe entry (m) Cc' cv (cm2/sec) mv (m2/kN) Ky (cm/sec) 0 4 0.67 0.0034 8 0.71 0.0035 10 0.65 0.0031 13 0.46 0.0021 16 0.40 0.0017 19 0.41 0.0017 22 0.25 0.0010 25 0.23 0.0009 29 0.21 0.0008 31 0.20 0.0007 34 0.19 0.0007 37 0.17 0.0006 40 0.17 0.0006 42 0.16 0.0005 45 0.13 0.0005 represents no data. 130

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Table A-12. Compressibility properties and hydraulic conducti vities estimated using the data obtained from Pipe 5 Distance from the pipe entry (m) Cc' cv (cm2/sec) mv (m2/kN) Ky (cm/sec) 0 3 6 1.29 0.0064 9 1.01 0.0049 11 1.09 0.0052 14 0.75 0.013 0.0035 4.52-6 17 0.91 0.0042 20 1.59 0.0073 23 0.65 0.012 0.0029 3.45-6 26 0.44 0.0020 30 0.43 0.0019 35 0.42 0.013 0.0018 2.40-6 38 0.46 0.0020 41 0.37 0.0016 44 0.26 0.0011 47 0.40 0.0017 represents no data. 131

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Table A-13. Profiles of the subsurface soils of the study site; the locations correspond to those in Figure 4-1. Depth Location m A&A' B&B'C&C' D&D' E&E' F&F'G&G' H&H' SILTY SAND TO SANDY SILT SAND SILTY SAND TO SANDY SILT SAND TO SILTY SAND SILTY SAND TO SANDY SILT SAND TO SILTY SAND SAND TO SILTY SAND SAND 2.5 GRAVELLY SAND TO SAND GRAVELLY SAND TO SAND SAND G.T.* SAND SAND TO SILTY SAND SAND TO SILTY SAND SILTY SAND TO SANDY SILT SAND TO SILTY SAND SAND SANDY SILT TO CLAYEY SILT 5.0 SAND SAND TO SILTY SAND HARD SILTY SAND SAND TO SILTY SAND SAND SAND 7.5 GRAVELLY SAND TO SAND GRAVELLY SAND TO SAND SAND SILTY CLAY to CLAY 10.0 SILTY CLAY to CLAY VERY STIFF FINE GRAINED CLAYS SAND TO SILTY SAND 12.5 SAND 15.0 SAND TO SILTY SAND G.T. represents ground water table. MEDIUM STIFF CLAYEY SAND GRAVELLY SAND TO SAND SAND SAND GRAVELLY SAND TO SAND LOOSE SAND CLAYEY SAND W/ PHOSPHATE SILTY SAND W/ LIMESTONE HARD CLAY SAND SAND SILTY SAND TO SANDY SILT SILTY SAND TO SANDY SILT CLAYEY SILT TO SILTY CLAY GRAVELLY SAND TO SAND SAND 132

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Table A-14. Summary of constrai ned moduli M of locations A and B Depth Layer Soil average (feet) Thickness Behavior N-value (feet)(TSF) (#) (#) 1 SILTY SAND TO SANDY SILT 7 2 SILTY SAND TO SANDY SILT 9 3 SILTY SAND TO SANDY SILT 10 4 SILTY SAND TO SANDY SILT 12 5 SILTY SAND TO SANDY SILT 11 660.24 SAND TO SILTY SAND 1110.00168.25679.7384.13 7 SAND 31 8 GRAVELLY SAND TO SAND 43 9 SAND 54 10 SAND 42 11 SAND 36 12 SAND TO SILTY SAND 29 13 SILTY SAND TO SANDY SILT 26 14 SAND TO SILTY SAND 27 1590.71 SAND 3936.33345.471051.90172.74 16 GRAVELLY SAND TO SAND 50 17 GRAVELLY SAND TO SAND 52 18 SAND 53 19 SAND 39 20 SAND TO SILTY SAND 32 21 SAND 37 22 SAND 53 23 SAND 54 24 SAND 59 25 SAND 63 26 GRAVELLY SAND TO SAND 57 27 SAND 56 28 SAND 53 29 SAND 46 30151.31 SAND 5650.67441.941254.47220.97 31 GRAVELLY SAND TO SAND 60 32 GRAVELLY SAND TO SAND 58 33 GRAVELLY SAND TO SAND 52 34 GRAVELLY SAND TO SAND 59 35 GRAVELLY SAND TO SAND 59 36 GRAVELLY SAND TO SAND 60 37 GRAVELLY SAND TO SAND 58 38 GRAVELLY SAND TO SAND 53 39 GRAVELLY SAND TO SAND 52 40 GRAVELLY SAND TO SAND 58 41 GRAVELLY SAND TO SAND 62 42 GRAVELLY SAND TO SAND 57 43 GRAVELLY SAND TO SAND 57 44142.03 GRAVELLY SAND TO SAND 6057.50539.751351.05243.96 45 SAND 56 46 SAND 52 47 SAND 44 48 SAND 35 49 SAND 28 5062.53 SAND TO SILTY SAND 2239.5366.81096.7183.4 Constrained modulus (TSF) CPT (N) oOC sand saturated sand Various eq.s CPT(N) represents a SPT(N) value estimated from CPT using a ratio of tip resistance (qc) to SPT(N) suggested by R obertson and Campanella (1983). 133

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Table A-15. Summary of constrained moduli M of locations C, D, E, and F Depth Layer Soil (feet) Thickness Behavior (feet)(TSF) (#) 12 LOOSE SAND 3121.1580.860.6 2 0.08 LOOSE SAND 32 MEDIUM STIFF CLAYEY SAND481.8594.963.9 4 MEDIUM STIFF CLAYEY SAND 52 MEDIUM STIFF CLAYEY SAND899.1651.577.4 6 MEDIUM STIFF CLAYEY SAND 72 MEDIUM STIFF CLAYEY SAND11112.0693.987.5 8 MEDIUM STIFF CLAYEY SAND 93 MEDIUM STIFF CLAYEY SAND10107.7679.784.1 10 MEDIUM STIFF CLAYEY SAND 113 MEDIUM STIFF CLAYEY SAND10107.7679.784.1 12 MEDIUM STIFF CLAYEY SAND 13110.44MEDIUM STIFF CLAYEY SAND36219.71047.2171.6 14 HARD SILTY SAND 15 HARD SILTY SAND 16 HARD SILTY SAND 175 HARD SILTY SAND 70538.41527.7286.0 18 HARD SILTY SAND 19 HARD SILTY SAND 20 HARD SILTY SAND 21 HARD SILTY SAND 225 HARD SILTY SAND 27538.4920.0141.3 23 HARD SILTY SAND 24 HARD SILTY SAND 25 HARD SILTY SAND 26 HARD SILTY SAND 27151.09 HARD SILTY SAND 18792.8792.8111.0 28 HARD SILTY SAND 29 CLAYEY SAND W/ PHOSPHATE 30 CLAYEY SAND W/ PHOSPHATE 31 CLAYEY SAND W/ PHOSPHATE 325 CLAYEY SAND W/ PHOSPHATE794.8637.374.0 33 CLAYEY SAND W/ PHOSPHATE 34 CLAYEY SAND W/ PHOSPHATE 35 CLAYEY SAND W/ PHOSPHATE 36 CLAYEY SAND W/ PHOSPHATE 3791.68CLAYEY SAND W/ PHOSPHATE13120.6722.194.2 38 SILTY SAND W/ LIMESTONE 39 SILTY SAND W/ LIMESTONE 40 SILTY SAND W/ LIMESTONE 41 SILTY SAND W/ LIMESTONE 42 SILTY SAND W/ LIMESTONE 4362.06SILTY SAND W/ LIMESTONE21835.2835.2121.1 44 HARD CLAY 45 HARD CLAY 46 HARD CLAY 475 HARD CLAY 27 48 HARD CLAY 49 HARD CLAY 5072.38 HARD CLAY 62 oSPT (N) Constrained modulus (TSF) Various eq.s OC sand saturated sand 134

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135 Table A-16. Summary of constrai ned moduli M of locations G and H Depth Layer Soil average (feet) Thickness Behavior N-value (feet)(TSF) (#) (#) 1 SILTY SAND TO SANDY SILT 10 2 SAND 17 3 SAND TO SILTY SAND 18 4 SILTY SAND TO SANDY SILT 8 550.20 SAND TO SILTY SAND 1413.4191.1727.895.6 6 SAND 34 720.46 SAND 3534.5333.11026.0166.6 8 GRAVELLY SAND TO SAND 47 9 GRAVELLY SAND TO SAND 47 1030.58 GRAVELLY SAND TO SAND 5048.0463.01216.8212.0 11 SAND 33 12 SAND TO SILTY SAND 32 13 SAND 49 14 SAND 42 15 SANDY SILT TO CLAYEY SILT 25 16 SILTY SAND TO SANDY SILT 37 17 SILTY SAND TO SANDY SILT 42 18 SAND 46 19 SAND 54 20 SAND 52 21 SAND TO SILTY SAND 47 22 SILTY SAND TO SANDY SILT 41 23 SILTY SAND TO SANDY SILT 34 24140.85 SAND 5742.2385.11135.0192.5 2511.22 GRAVELLY SAND TO SAND 6969.0632.61513.6282.7 2611.27 SAND 4747.0417.31202.7208.6 27 SILTY CLAY to CLAY 20 28 CLAYEY SILT TO SILTY CLAY 22 29 CLAYEY SILT TO SILTY CLAY 22 30 CLAYEY SILT TO SILTY CLAY 20 31 CLAYEY SILT TO SILTY CLAY 29 32 CLAYEY SILT TO SILTY CLAY 33 33 SILTY CLAY to CLAY 42 34 VERY STIFF FINE GRAINED 59 3591.52 CLAYS 41 3611.77 SAND TO SILTY SAND 3333.0323.01004.8161.5 37 GRAVELLY SAND TO SAND 58 38 GRAVELLY SAND TO SAND 67 39 GRAVELLY SAND TO SAND 63 40 GRAVELLY SAND TO SAND 65 41 GRAVELLY SAND TO SAND 65 42 GRAVELLY SAND TO SAND 54 43 GRAVELLY SAND TO SAND 54 44 GRAVELLY SAND TO SAND 58 4592.02 GRAVELLY SAND TO SAND 4558.8550.11369.1248.3 46 SAND 35 47 SAND 24 48 SAND 34 49 SAND 44 5052.37 SAND 4937.2351.31064.1175.7 oCPT (N) Constrained modulus (TSF) Various eq.s OC sand saturated sand CPT(N) represents a SPT(N) value estimated from CPT using a ratio of tip resistance (qc) to SPT(N) suggested by R obertson and Campanella (1983).

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APPENDIX B SUPPLEMENTARY FIGURES Figure B-1. Plan view of the study area of Chapter 2: the Phase II unit of the Polk Coun ty NCLF; Lines 82, 83, and 84 are the horizontal liquids addition lines with shredded-tire, excavate d waste, and crushed-glass bedding media, respectively. The drawing was made by Jones Edmonds and Associates, Inc., FL. 136

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137 Figure B-2. Cross-sectional view of the study area of Chapter 2: the Phase II unit of the Polk County NCLF; Lines 82, 83, and 84 are the horizontal liquids addition lines with shredded-ti re, excavated waste, and crushed-glass bedding media, respectively. The drawing was made by Jones Edmonds and Associates, Inc., FL.

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Figure B-3. Data-logger and pore pressure data downloading 138

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Figure B-4. Hydraulic conductivity versus effective stress. Samples from the Keele Valley Landfill, Material from 4 auger flights, *, sample 105B 105 depth; sample 105 C 105 depth, sample 120 A 120 depth; sample 120B 120 depth (adapted from Bl eiker et al., 1995) 139

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Horizontal distance from the source (m) 051015202530 Pore pressure (kPa) 0 5 10 15 20 25 30 35 40 45 50 Day 1 Day 3 Day 14 Model: (KxKy)0.5 = 1.68x10-4 cm/sec 21.3 mA Horizontal distance from the source (m) 051015202530 Pore pressure (kPa) 0 5 10 15 20 25 30 35 40 45 50 Day 1 Day 3 Day 14 Model: (KxKy)0.5 = 1.58x10-4 cm/sec 21.3 m B Horizontal distance from the source (m) 051015202530 Pore pressure (kPa) 0 5 10 15 20 25 30 35 40 45 50 Day 1 Day 3 Day 14 Model: (KxKy)0.5= 1.45x10-4 cm/sec 21.3 mC Horizontal distance from the source (m) 024681012141618 Pore pressure (kPa) 0 10 20 30 40 50 Model: (KxKy)0.5 = 1.40x10-4 cm/sec Day 1 Day 3 Day 12 5 kPa 11.4 m D Horizontal distance from the source (m) 024681012141618 Pore pressure (kPa) 0 10 20 30 40 50 Model: (KxKy)0.5 = 1.15x10-4 cm/sec Day 1 Day 3 Day 12 5 kPa 11.4 m E Figure B-5. Comparisons of pore pressure change as a func tion of a horizontal distance from the line source bet ween the field data and theoretical estimates for Experiment 1: A) shredded tire trench (rw = 0.3 m), B) shredded tire trench (rw = 0.45 m), C) shredded tire trench (rw = 0.6 m), D) crushed glass trench (rw = 0.3 m), and E) crushed glass trench (rw = 0.6 m). 140

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Horizontal distance from the source (m) 05101520253035 Pore pressure (kPa) 0 5 10 15 20 25 30 35 40 45 50 Day 1 Day 3 Day 11 Model: (KxKy)0.5 = 1.95x10-4 cm/sec 22.9 m A Horizontal distance from the source (m) 05101520253035 Pore pressure (kPa) 0 5 10 15 20 25 30 35 40 45 50 Day 1 Day 3 Day 11 Model: (KxKy)0.5= 1.75x10-4 cm/sec 22.9 m B Horizontal distance from the source (m) 05101520253035 Pore pressure (kPa) 0 5 10 15 20 25 30 35 40 45 50 Day 1 Day 3 Day 11 Model: (KxKy)0.5 = 1.65x10-4 cm/sec 22.9 m C Figure B-6. Comparisons of pore pressure change as a func tion of a horizontal distance from the line source bet ween the field data and theoretical estimates for Experiment 2: A) crushed glass trench (rw = 0.3 m), B) crushed glass trench (rw = 0.45 m), and C) cr ushed glass trench (rw = 0.6 m). 141

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Bioreactor Area Figure B-7. Plan view of t he study landfill of Chapter 3: the Ne w River Regional (adapted from as-built drawings prov ided by Jones Edmunds and Associates at Gainesville, Florida) 142

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MC (%) 510152025303540455055 Depth (m) 0 3 3 6 6 9 9 12 A MC (%) 152025303540455055 Depth (m) 0 3 5 8 9 12 B Mean value Standard deviations BMP (L CH4(g)/g VS) 0.000.050.100.150.200.250.300.35 Depth (m) 0 3 3 6 6 9 9 12 Mean value Standard deviation C BMP (L CH4(g)/g VS) 0.05 0.15 0.25 0.35 0.00 0.10 0.20 0.30 Depth (m) 0 3 5 8 9 12 D Figure B-8. Changes in waste properties with depth: A) moisture content (MC), 2002, B) MC, 2007, C) biochemical methane pot ential (BMP), 2002, and D) BMP, 2007. 143

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Settlement (m) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Bioreactor operation June, 2003 April, 2007 A Time (Year) 2002 2003 2004 2005 2006 2007 2008 2009 Settlement (%) 0 5 10 15 20 Stage 1: Rs = 1.15%/year Stage 2: Rs = 5.08%/year Stage 3: Rs = 2.11%/year Before surcharge B Figure B-9. Historic settlement records of the study landfill site of Chapter 3: A) settlement (m) time and B) settlement (%) time; the settlement (m) data was adapted from Kadambala (2 009) and re-plotted. 144

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Distance from pipe entrance (m) 01 02 03 04 0 5 0 Elevation (NGVD, m) 56 58 60 62 64 Inital 142 days 165 days 256 days 370 days 440 days Figure B-10. Elevation change over time at each settlement measurement location in settlement profiling pipe 2; NGVD represents U.S. Na tional Geodetic Vertical Datum 145

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Distance from pipe entrance (m) 01 02 03 04 0 5 0 Elevation (NGVD, m) 56 58 60 62 64 Initial 142 days 165 days 256 days 370 days 440 days Figure B-11. Elevation change over time at each settlement measurement location in settlement profiling pipe 3; NGVD represents U.S. Na tional Geodetic Vertical Datum 146

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Distance from pipe entrance (m) 01 02 03 04 0 5 0 Elevation (NGVD, m) 56 58 60 62 64 Initial 142 days 165 days 256 days 370 days 440 days Figure B-12. Elevation change over time at each settlement measurement location in settlement profiling pipe 4; NGVD represents U.S. Na tional Geodetic Vertical Datum 147

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Distance for pipe entrance (m) 01 02 03 04 0 5 0 Elevation (NGVD, m) 58 59 60 61 62 63 Inital 142 days 165 days 256 days 370 days 440 days Figure B-13. Elevation change over time at each settlement measurement location in settlement profiling pipe 5; NGVD represents U.S. Na tional Geodetic Vertical Datum 148

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Time (minutes) 1e+4 1e+5 1e+6 H (mm) 14600 14800 15000 15200 15400 15600 15800 16000 R100 = 14809 Rc = 15890 t50 = 156046 R50 = 15350 A Time (minutes) 1e+4 1e+5 1e+6 H (mm) 15400 15600 15800 16000 16200 16400 16600 R100 = 15496 Rc = 16396 t50 = 145062 R50 = 15946 B Time (minutes) 1e+4 1e+5 1e+6 H (mm) 15600 15800 16000 16200 16400 16600 16800 R100 = 15784 Rc = 16673 t50 = 153010 R50 = 16229 C Time (minutes) 1e+4 1e+5 1e+6 H (mm) 16200 16400 16600 16800 R100 = 16315 Rc = 16820 t50 = 203172 R50 = 16568 D Time (minutes) 1e+4 1e+5 1e+6 H (mm) 16400 16500 16600 16700 16800 16900 17000 R100 = 16555 Rc = 16942 t50 = 212109 R50 = 16749 E Time (minutes) 1e+4 1e+5 1e+6 H (mm) 16500 16600 16700 16800 16900 17000 17100 17200 R100 = 16616 Rc = 17118 t50 = 187813 R50 = 16867 F Figure B-14. Logarithm of time fitting model to estimate t50 (Pipe 1): data used was collected at A)10 m, B) 13 m, C) 16 m, D) 19 m, E) 22 m, and F) 25 m inside from the entry of Pipe 1. 149

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Time (minutes) 1e+4 1e+5 1e+6 H (mm) 16800 16900 17000 17100 17200 17300 17400 17500 17600 R100 = 17013 Rc = 17554 t50 =207011 R50 = 17184 A Time (minutes) 1e+4 1e+5 1e+6 H (mm) 17000 17100 17200 17300 17400 17500 17600 17700 R100 = 17059 Rc = 17649 t50 =199218 R50 = 17354 B Time (minutes) 1e+4 1e+5 1e+6 H (mm) 17000 17100 17200 17300 17400 17500 17600 17700 17800 R100 = 17173 Rc = 17746 t50 =180743 R50 = 17460 C Time (minutes) 1e+4 1e+5 1e+6 H (mm) 15000 15100 15200 15300 15400 15500 15600 R100 = 15067 Rc = 15497 t50 = 211119 R50 = 15282 D Time (minutes) 1e+4 1e+5 1e+6 H (mm) 15400 15600 15800 16000 R100 = 15371 Rc = 15919 t50 = 199218 R50 = 15645 E Time (minutes) 1e+4 1e+5 1e+6 H (mm) 15800 16000 16200 16400 R100 = 15834 Rc = 16283 t50 = 209153 R50 = 16059 F Figure B-15. Logarithm of time fitting model to estimate t50 (Pipes 1 and 2): data used was collected at A) 31 m, B) 34 m, and C) 37 m inside from the entry of Pipe 1 and D) 6 m, E) 9 m, and F) 12 m inside from the entry of Pipe 2. 150

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Time (minutes) 1e+4 1e+5 1e+6 H (mm) 16000 16200 16400 16600 R100 = 16180 Rc = 16638 t50 = 177226 R50 = 16409 A Time (minutes) 1e+4 1e+5 1e+6 H (mm) 17400 17500 17600 17700 17800 17900 18000 18100 18200 R100 = 17476 Rc = 18076 t50 = 213304 R50 = 17776 B Time (minutes) 1e+4 1e+5 1e+6 H (mm) 13800 14000 14200 14400 14600 14800 R100 = 13946 Rc = 14568 t50 =123610 R50 = 14257 C Time (minutes) 1e+4 1e+5 1e+6 H (mm) 14000 14200 14400 14600 14800 15000 R100 = 14325 Rc = 14920 t50 =147250 R50 = 14623 D Time (minutes) 1e+4 1e+5 1e+6 H (mm) 13800 14000 14200 14400 14600 14800 R100 = 14086 Rc = 14685 t50 =127846 R50 = 14386 E Figure B-16. Logarithm of time fitting model to estimate t50 (Pipes 2 and 5): data used was collected at A) 15 m and B) 27 m in side from the entry of Pipe 2 and C) 14 m, D) 23 m, and E) 35 m insi de from the entry of Pipe 5 151

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152 Figure B-17. Plan view of the identificati on of SPTs and CPTs locations at the study landfill of Chapter 4: the Phase III unit area of the Polk County NCLF (adapted from JEA, Inc.)

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Figure B-18. Cross-sectional view of the identification of SPTs and CPTs locations at the study landfill of Chapter 4: the Phase III unit area of the Polk County NCLF (adapted from JEA, Inc.) 153

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North Figure B-19. The topographic surveying of t he study landfill of Chapter 4(October 09, 2007): the Phase III unit of the Polk County NCLF 154

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North Figure B-20. The topographic surveying of t he study landfill of Chapter 4 (April 11, 2008): the Phase III unit of the Polk County NCLF 155

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North Figure B-21. The topographic surveying of the study landfill of Chapt er 4 (September 25, 2008): the Phase III unit of the Polk County NCLF 156

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North Figure B-22. The topographic surveying of the study landfill of Chapt er 4 (September 29, 2009): the Phase III unit of the Polk County NCLF 157

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Overburden pressure (kPa) 0 20 40 60 80 100 120 Measured overburden pressure (TPC-A) Measured overburden pressure (TPC-A') Estimated using Boussinesq chart Date 1/1/08 5/1/08 9/1/08 1/1/09 5/1/09 9/1/09 1/1/10 5/1/10 Vertical movement (cm) -5 0 5 10 15 20 Measured settlement (SS-A) Measured settlement (SS-A') Figure B-23. Variation of overburden pressure and settlement over time due to waste placement at location A: location A in Figure 4-1. 158

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Overburden pressure (kPa) 0 20 40 60 80 100 120 Measured overburden pressure (TPC-B) Measured overburden pressure (TPC-B') Estimated using Boussinesq chart Date 1/1/08 5/1/08 9/1/08 1/1/09 5/ 1/09 9/1/09 1/1/10 5/1/10 Vertical movement (cm) -10 -5 0 5 10 15 20 Measured settlement (SS-B) Measured settlement (SS-B') Figure B-24. Variation of overburden pressu re and settlement over time due to waste placement at location B: location B in Figure 4-1. 159

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Overburden pressure (kPa) 0 20 40 60 80 100 120 Measured overburden pressure (TPC-D) Measured overburden pressure (TPC-D') Estimated using Boussinesq chart Date 4/1/08 8/1/08 12/1/08 4/1/09 8/1/09 12/1/09 4/1/10 vertical movement (cm) -5 0 5 10 15 20 Measured settlement (SS-D) Figure B-25. Variation of overburden pressu re and settlement over time due to waste placement at location D; duplicate meas urements of settlement by D was malfunctioned and thus the data was not included: location D in Figure 4-1. 160

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Overburden pressure (kPa) 0 20 40 60 80 100 120 Measured overburden pressure (TPC-E) Measured overburden pressure (TPC-E') Estimated using Boussinesq chart Date 4/1/08 8/1/08 12/1/08 4/1/09 8/1/09 12/1/09 4/1/10 Vertical movement (cm) -5 0 5 10 15 20 Measured settlement (SS-F) E Figure B-26. Variation of overburden pressu re and settlement over time due to waste placement at location E; duplicate m easurements of settlement by E was malfunctioned and thus the data was not included: location E in Figure 4-1. 161

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Overburden pressure (kPa) 0 20 40 60 80 100 120 Measured overburden pressure (TPC-F) Measured overburden pressure (TPC-F') Estimated using Boussinesq chart Date 1/1/08 5/1/08 9/1/08 1/1/09 5/ 1/09 9/1/09 1/1/10 5/1/10 Vertical movement (cm) -5 0 5 10 15 20 Measured settlement (SS-F) Figure B-27. Variation of overburden pressu re and settlement over time due to waste placement at location F; duplicate m easurements of settlement by F was malfunctioned and thus the data was not included: location F in Figure 4-1. 162

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Date Overburden pressure (kPa) 0 20 40 60 80 100 120 Date 1/1/08 5/1/08 9/1/08 1/1/09 5/1/09 9/1/09 1/1/10 5/1/10 Vertical movement(cm) -5 0 5 10 15 20 SS-G SS-G' TPC-G TPC-G' Estimated using Boussinesq chart Figure B-28. Variation of overburden pressu re and settlement over time due to waste placement at location G: location G in Figure 4-1. 163

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Overburden pressure (kPa) 0 20 40 60 80 100 120 Measured overburden pressure (TPC-H) Measured overburden pressure (TPC-H') Estimated using Boussinesq chart Date 4/1/08 8/1/08 12/1/08 4/1/09 8/1/09 12/1/09 4/1/10 Settlement (cm) -5 0 5 10 15 20 Measured settlement (SS-H') Figure B-29. Variation of overburden pressu re and settlement over time due to waste placement at location H; duplicate m easurements of settlement by H was malfunctioned and thus the data was not included: location H in Figure 4-1. 164

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Figure B-30. Large-scale dire ct shear test device 165

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Relative displacement, % 01 02 03 04 0 Shear stress, kPa 0 20 40 60 80 100 0% 40% 58% 80% Figure B-31. Large-scale shear tests results under 96 kPa of normal stress Relative displacement, % 01 02 03 04 0 Shear stress, kPa 0 20 40 60 80 100 120 140 160 180 0% 40% 58% 80% Figure B-32. Large-scale shear tests re sults under 192 kPa of normal stress 166

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Relative displacement, % 01 02 03 04 0 Shear stress, kPa 0 50 100 150 200 250 0% 40% 58% 80% Figure B-33. Large-scale shear tests re sults under 287 kPa of normal stress Relative displacement, % 0 5 10 15 20 Shear stress, kPa 0 10 20 30 40 50 60 0%_1 0%_2 40%_1 40%_2 58%_1 58%_2 80%_1 80%_2 Figure B-34. Small-scale shear tests results under 48 kPa of normal stress 167

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Relative displacement, % 0 5 10 15 20 Shear stress, kPa 0 20 40 60 80 100 0%_1 0%_2 40%_1 40%_2 40%_3 58%_1 58%_2 58%_3 80%_1 80%_2 80%_3 Figure B-35. Small-scale shear tests results under 97 kPa of normal stress Relative displacement, % 0 5 10 15 20 Shear stress, kPa 0 20 40 60 80 100 120 140 0%_1 0%_2 40%_1 40%_2 58%_1 58%_2 58%_3 80%_1 80%_2 80%_3 Figure B-36. Small-scale shear tests results under 145 kPa of normal stress 168

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Relative displacement, % 0 5 10 15 20 Shear stress, kPa 0 20 40 60 80 100 120 140 160 180 0%_1 0%_2 40%_1 40%_2 40%_3 58%_1 58%_2 58%_3 80%_1 80%_2 Figure B-37. Small-scale shear tests results under 194 kPa of normal stress Relative displacement, % 0 5 10 15 20 Shear stress, kPa 0 50 100 150 200 250 300 0%_1 0%_2 40%_1 40%_2 58%_1 58%_2 58%_3 80%_1 80%_2 Figure B-38. Small-scale shear tests results under 290 kPa of normal stress 169

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APPENDIX C LANDFILL BULK DENSITY ESTIMATE METHODOLOGY 1. Estimate the mass of waste (MW) accepted in a certain period 2. Estimate the volume in crement of the landfill (VT) in the same period. 3. Assume the volume of cover soil (VC) (e.g. VC= 0.18VT) 4. Assume a density of cover soil ( C) 5. Calculate a bulk density and a unit weight: 0.15TcW B TVM V 170

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APPENDIX D UNIT CONVERSION OF PORE PRESS URE TRANSDUCER RAW DATA AND THERMAL IMPACT CORRECTION The raw data (Hz) of each pressure trans ducer was converted to pressure (kPa) using calibration factors provided by the ma nufacturer (Geokon, In c.). The calibration equation for the pressure transducer s was provided as follow: 21000 Hz R (2-1) P = G(R0-Ri) + K(Ti-T0) (2-2) where R = reading (digits); (Hz) = raw data of a pressure transducer; P = pressure (kPa); G = calibration factor (kPa/digits); R0 = initial reading (digits); Ri = reading at time i (digits); K = temperatur e correction factor (kPa/C); Ti = temperature at time i (C); T0 = initial temperature (C). For example, where the frequencie s (Hz) at times 0 and i are Hz0 = 2930.2 (Hz) and Hzi = 2901.3 (Hz), 22 0 2()(2930.2) 8586.3() 10001000 (2901.3) 8417.6(). 1000iHz R digits R digits If temperature m easurements are T0 = 62.0 oC, and Ti = 44.7 oC, then P = 0.200 kPa/digits (8586.3 8417.6) digits + 0.0298 kPa/oC (44.7 62.0)oC = 33 kPa where G = 0.200 kPa/digits and K = 0.0298 kPa/oC. 171

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APPENDIX E DERIVATION OF EQUATION 2-3 In this appendix, a method used to estima te vertical hydraulic conductivity of landfilled waste is explained. Townsend (1995) developed equatio ns based on uniform flow theory for saturated conditions to estimate the zone saturated by a horizontal line source with the following assumptions. 1. Steady state saturated flow. 2. Waste is homogeneous. 3. Anisotropic medium. 4. Axes of anisotropy correspond to the principal axes of the system. 5. The well can be treated as a horizontal line source. 6. The line source is subjected to the e ffect of gravity in the vertical downward direction. 7. The primary driving forces for liquid movement are the inje ction pressure and gravity. 8. Capillary force and dispersion effects are negligible. 9. Liquid movement in downw ard direction is not impeded. The governing equation for the ca se of steady plane flow is 22 220xyKK xy (E-1) where Kx = horizontal hydraulic conductivity (m/sec); Ky = vertical hydraulic conductivity (m/sec); = potential (m); x = distance in x-direction (m); y = distance in y-direction (m). The potential gradient in the gravity drainage scenario, t he potential gradient is 1. 172

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1 y ; 0 x (E-2) y (E-3) The potential function of the saturated flow is 22ln 4 x y xyqx KK KK y (E-4) By superposing Equation E-3 and Equation E-4, the potential function for a horizontal line source in an anisotropic medium (landfilled wast e) can be derived. 22ln 4xy xyqxy y KK KK (E-5) The stream function of the flow can be derived as follow. d dd dy x 222 1 4y xy xyy K dq ddx dx xy dy KK KK dx 22 02 4x y xy xyy K q dxx xy KK KK 22 01 2x xy yy x xyyKK q dxx KK xK y KK 173

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2 01 2 1y x x y y xK yK q dxx K K x yK 1tan 2y yxK qx x KyK (E-6) The boundary for the satura ted bulb occurs where 0 and this relationship may therefore be determined as 1tan 2y yxK qx x KyK (E-7) A schematic of the flow system eval uated is presented in Figure E-1. The value of Ymax may be determined where x = 0 and 0 d dy max2 x yq Y KK (E-8) The value of Xmax may be determined when y approaches max2yq X K (E-9) The value of Xwell may be determined at the boundary where y = 0. 4well yq X K (E-10) where xwell = horizontal maximum extent of satu rated zone at the elevation of the horizontal liquids addition line so urce (m); q= constant linear flow rate (flow rate per unit length of line source, m2/sec). The distances Xmax and Xwell are a function of the hydraulic conductivity in the vertical direction only. 174

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+y +x XwellXmax YmaxBoundary of saturated bulb Injection well At y Infinity Figure E-1. Saturated flow zone surrounding a horizontal line source under steady state conditions: adapted from Townsend (1995) 175

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APPENDIX F EXAMPLE CALCULATION OF THE HYDRAULIC CONDUCTIVITY AND ANISOTROPY OF LANDFILLED WASTE USING IN-SITU PORE PRESSURE MEASUREMENTS 1. Determination of Xwell based on in-situ pore pressure data: In Experiment 1, the increase in pore pressure measured by a pressure transducer at a distance of 11.4 m from the crushed glass trench was only 5 kPa while pore pressure in the trench increased up to 40 kPa. It was assumed that the hor izontal extent of the added liquids (saturated zone) was 11.4 m (= Xwell). 2. Estimation of Ky using Equation 2-3 4well yq x K (2-3) where q = constant linear flow rate (f low rate per unit length of line source, m2/sec); Xwell = horizontal maximum extent of sa turated zone at the elevation of the horizontal liquids a ddition line source (m) 62 58.6010/sec 1.8910/sec 4(11.4)xm Kc m m where Q = 0.057 m3/min and a length of the line = 110 m, the linear flow rate q = 8.6-6 m2/sec. 3. Estimation of (KxKy)0.5 using Equation 2-4 ()()()ln 2wRRr w xyq S r KK R (2-4) where S(R) = head drawdown (m); (R) = potential at a distance R (m); (rw) = potential in a horizontal trenc h (m); R = horizontal dist ance from a line source (m); rw = effective well radius (m); Kx = horizontal hydraulic conductivity (m/sec). 176

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A Kx value was determined by finding a theoretical S(R)-R curve closest to an actual S(R)-R curve plotted based on t he in-situ measurements; by varying (KxKy)0.5 values while keeping other par ameters constant, theoretical S(R)-R curves were developed and superimposed on an actual S(R)-R curve (Figure F1). R (m) 024681012141618 Pore pressure (kPa) 0 10 20 30 40 50 Model: (KxKy)0.5 = 1.10x10-4 cm/sec Day 12 Model: (KxKy)0.5 = 1.30x10-4 cm/sec Model: (KxKy)0.5 = 1.50x10-4 cm/sec Figure F-1. Example S(R)-R curve to determine (KxKy)0.5 Therefore, (KxKy)0.5= 1.30-4 cm/sec and Kx = 8.96-4 cm/sec 4. Estimation of anisotropy 4 58.9610 47 1.8910x yK K 177

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APPENDIX G ELEVATION MEASUREMENT USING A THEODOLITE The elevation (NGVD) of data collection lo cation in each settlement profiling pipe was estimated by measuring the elevation of each settlement profiler reference station using a laser leveling machine (Spectra Pr ecision Gplus, Trimble). Figure G-1 conceptually depicts how to determine the elevation of the reference station of the settlement profiler using the leveling machine. The elevation of the refer ence station of the settlem ent profiler was calculated using the following equation: R0212 1 n ii i H HHH (G-1) where HR = elevation of the refere nce station (ft, NGVD); H0 = elevation of the bench mark (ft, NGVD); H2i-1 = backward height of the leveling machine at the i th location; H2i = forward height of the leveling machine at the i th location. H1H2H4 Bench mark (H0 ft NGVD) Reference station (HRef)Example calculation for the height of the reference station of the settlement profilerHRef.= H0+ (H1 H2) + (H3 H4) H3 Leveling machine Settlement profilerreservoir Ruler Figure G-1. Elevation determinat ion using a leveling machine 178

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APPENDIX H UNIT CONVERSION OF SETTLEMENT PR OFILER RAW DATA AND SETTLEMENT ESTIMATION The elevation of a desired location in a settlement profiling pipe was estimated using the following equations pr ovided by the manufacturer. 2() 1000 H z R (3-1) E = Eref G(Ro Rc) (3-2) where R = reading (digits); (Hz) = raw data of a pr essure transducer; E = the elevation of the sensor (m); Eref = elevation of the re ference station (m); Ro = the reading at the reference station (digits); Rc = reading at a target location (digits); G = the calibration constant (meter per digits). Assuming the raw data at the reference station and a target location are Hz0 = 3067.40 (Hz) and Hzc = 3045.62 (Hz), 22 0 2()(3067.4) 9409.0() 10001000 (3045.62) 9275.8(). 1000cHz R digits R digits Where the reference stati on is set-up at an elevation 60.3 m (NGVD) and G = 0.00408 m/digits, E = 60.3 m 0.00408 m/digit(9409.0. 7-9275.8)digits = 59.7 m If the elevation of the ta rget location was measured to be 61.0 m in previous settlement profiling, then 1.3 m of settlement occurred during the period. 179

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APPENDIX I EXAMPLE CALCUATIONS OF COMPRESSION PROPERTIES AND HYDRAULIC CONDUCTIVITY OF LANDFILLED WASTE Based on a time-consolidation curve, the primary conso lidation period was determined (Figure I-1) ; data from Pipe 1 (31 m from the entry). Time (minutes) 1e+4 1e+5 1e+6 H (mm) 16800 16900 17000 17100 17200 17300 17400 17500 17600 R100 = 17013 Rc = 17554 t50 =207011 R50 = 17184 Primary consolidation Secondary consolidation Figure I-1. Example time-c onsolidation curve: log of time fitting method; Rc = initial thickness of an underlain waste layer; R50 = thickness of an underlain waste layer at t50; R100 = final thickness of an underlain waste layer after primary consolidation; t50 = time required to 50% ultimate primary consolidation. A modified primary compression index (Cc) of the landfilled waste was estimated using the following expression. log'cC (I-1) where = change in strain during the primary consolidat ion period (m); i, f = initial and final stress applied to the midpoint of the bioreacted waste layer, 0.5 Hi, (kPa). 180

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During the primary consolidat ion period, approximately 2.9% of strain occurred due to the increase in vertical stress fr om 105.3 kPa to 158.3 kPa. Therefore, log'cC 22.910 0.16 log(158.3)log(105.3) Coefficient of volume change (mv) of the landfilled waste was estimated using the following equation. 1 'v iV m V (I-2) where = change in volume (m3); = initial volume prior to pressure increment (m3); V iV' = pressure increment. By assuming no lateral deformation o ccurs, Equation I-2 can be rearranged. 1 'v iH m H (I-3) where = change in height (m); = initial height of a so il layer (m). Therefore, H iH 2 22.910 0.00055 '158.3105.3vm m kN kPakPa To estimate coefficient of consolidation (cv), the logarithm of time fitting method developed by Casagrande (1940) was used (Figure I-1). For example, t50 was determined to be 207,011 min fr om Figure I-1. Where Hi = 17.55 m and Hf = 17.04 m, 2 2 50 50 500.197v vTd d c tt (I-4) 4iHH df (I-5) 181

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17.5517.04 8.6 4d Therefore, 2 22 50.197(8.6) 7.05100.012 min sec 207,011vmc c m By rearranging an equation to estimate coefficient of consolidation (cv), hydraulic conductivity (K) of media can be estimated. y v vwK c m (I-7) yvvKcmw (I-8) Assumingw = unit weight of water (9.8 kN/m3), 22 5 37.05100.000559.8 minyvvwmm Kcm kN m k N m 774.010/min6.710/sec mc 182

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APPENDIX J UNIT CONVERSION OF SETTLEMENT SE NSOR RAW DATA AND BAROMETRIC PRESSURE AND THERMAL IMPACT CORRECTION Readings from each SS have a unit of frequency and thus were converted to proper units such as kPa or cm, respective ly. Unit conversion and calibration equations for the SSs are as follows: 2() 1000 H z R (4-1) E = G (Ro Ri) + Eres + K(Ti-T0) + {B0-Bi} (4-2) where R = reading (digits); (Hz) = raw data from settlement sensor; E = elevation of the sensor (cm); Eres = any change of the liquid level inside the reservoir sight glass (cm); Ro = initial sensor reading (digits); Ri = reading at time i (digits) ; G = calibration constant provided by the manufact urer (cm/digits); Ti = temperature at time i (C); T0 = initial temperature (C); K = temperature co rrection factor (cm/C) provided by the manufacturer; {B0-Bi} = barometric pressure corre ction for non-vented SSs (cm H2O). For example, the frequencies (Hz) readings at times 0 and i are Hz0 = 2573.8 (Hz) and Hzi = 2557.0 (Hz) can be converted as follow; 22 0 2()(2573.8) 6624.4() 10001000 (2557.0) 6538.2(). 1000iHz R digits Rd i g i t s If barometric pressure measurements are B0 = 29.86 in-Hg and Bi = 30.04 in-Hg, then P = 0.171 cm/digits(6624.4 6538.2) digits + 0.4 cm + 0.425 cm/oC(30.2 29.9)oC = 15.27 cm 183

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where G = 0.171 cm/digits, Eres = 0.4 cm, K = 0.425 cm/oC, Ti = 30.2oC, and To = 29.9oC. For non-vented SSs, barometric pressu re impact should be corrected. For example, if B0 = 29.89 in-Hg and Bi = 30.18 in-Hg, then P = 15.27 cm (30.18 29.89).53 cm /i n-Hg = 5.26 cm. 184

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APPENDIX K UNIT CONVERSION OF TOTAL PRESSURE CELL RAW DATA AND BAROMETRIC PRESSURE AND THERMAL IMPACT CORRECTION Unit conversion and calibration equations for the TPCs were as follow: 2() 1000 H z R (4-3) P = G(R0-Ri) + (B0-Bi) K(P) (4-4) where R = reading (digits); (Hz) = raw data from pressure transducer; P = pressure (kPa); G = calibration factor provi ded by the manufacturer (kPa/digits); R0 = initial reading (digits); Ri = reading at time i (digits); B0 = initial barometric pressure (kPa); B1 = current barometric pressure (kPa); K(P) = thermal impact correction equation derived from a best-fit regression of P versus (T0-Ti) data; Ti = temperature at time i (C); T0 = initial temperature (C). For example, the frequencies (Hz) readings at times 0 and i are Hz0 = 2890.6 (Hz) and Hzi = 2860.6 (Hz) can be converted as follow; 22 0 2()(2890.6) 8357.4() 10001000 (2860.6) 8183.3(). 1000iHz R digits R digits If G = 0.0927 kPa/digits, B0 = 29.86 in-Hg and Bi = 30.04 in-Hg, then P = 0.0927 kPa/digits (8357.4 8183.3) digits + 6.89 kPa/2.036 in-Hg(29.86 30.04)in-Hg = 15.5 kPa A thermal impact correction equation can be derived using a best-fit regression as shown in Figure K-1. 185

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T0-Ti (oC) 012345 6 P (kPa) 0 2 4 6 8 10 12 14 16 18 20 P = 0.392(T0-Ti)2 + 1.457(T0-Ti) R2=0.99 Figure K-1. Example best-fit regression to derive a ther mal impact correction equation for TPC P = 15.5 kPa {0.392(20.5 24.5)2 + 1.457(20.5 24.5)} kPa = 15.03 kPa where T0 = 22.3 oC and Ti = 30.8 oC. 186

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APPENDIX L EXAMPLE ESTIMATION OF LANDFILL FOUNDATION SETTLEMENT In Chapter 4, one-dimensional (vertica l) elastic and primary consolidation settlements of the subsurface soil layers under the study landf ill foundation were estimated using the following equations: teSSSc (4-7) 0 n vi ei i iSH M (4-8) ,0 0 ,0 1 0log 1n vivi i cc i vi i iH SC e (4-9) where = total settlement (m); = elastic settlement (m); = primary consolidation settlement (m); Hoi = thickness of soil layer i (m); tSeScS vi = overburden stress increase caused by the waste placement at midpoint of soil layer i; Mi = constrained modulus of soil layer i (MPa); Cci = primary compression index; eoi = initial void ratio of soil layer i; oi = initial overburden stress at t he center of soil layer i. To estimate elastic settl ement, constrained modulus of a soil layer should be determined first. Various equations introduced in Bowles (1996) were used to estimate the stress-strain (Youngs) modulus E of each soil layer with the CPT(N) and SPT(N) and then a constrained modulus M was determi ned using the E value. For example, for the gravelly sand to sand laye r at depths of 31 to 44 ft in Table L-1, Equation 4-14 was used to estimate a stress-strain modulus. E(kPa) = 600(N + 6) + 2000 for gravelly sand, N>15 (4-14) E(kPa) = 600(57.5 + 6) + 2000 = 40,100 kPa = 401 TSF 187

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Then, constrained modulus M was estima ted using the foll owing equation. 1 112 E M (4-15) where = Poissons ratio (effective); Poission s ratio of 0.3 was assumed (Budhu 2000). 1 401(10.3) 539.7 112(0.31)(120.3) E TSF M TSF Assuming 0.91 tsf of vertical stress increase, the elastic settlement of the layer is estimated to be 00.91 14 0.024 539.7v eTSF SHft ft MT S F Assuming Cc /(1+eo) = 0.002 for sand or silty sand (Conuto 2004), for example, the consolidation settlement of t he sand layer at depths of 45 to 50 ft in Table L-1 was estimated to be ,0 0 ,0 02.530.91 log 0.0026log 0.016 12 5 3vv cc vH TSFTSF SC ft ft eT S F 188

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Table L-1. Example settlement estimates at location A; the data used were collected on May 20, 2010. Layeraverage Constrained ThicknessN-value Modulus ElasticConsolidation (ft) (#) (ft)(#)(TSF) ( TSF )(ft)(ft) 1 SILTY SAND TO SANDY SILT 7 2 SILTY SAND TO SANDY SILT 9 3 SILTY SAND TO SANDY SILT 10 4 SILTY SAND TO SANDY SILT 12 5 SILTY SAND TO SANDY SILT 11 6 SAND TO SILTY SAND 11610.00.24168.30.0320.008 7 SAND 31 8 GRAVELLY SAND TO SAND 43 9 SAND 54 10 SAND 42 11 SAND 36 12 SAND TO SILTY SAND 29 13 SILTY SAND TO SANDY SILT 26 14 SAND TO SILTY SAND 27 15 SAND 39936.30.71345.50.0240.006 16 GRAVELLY SAND TO SAND 50 17 GRAVELLY SAND TO SAND 52 18 SAND 53 19 SAND 39 20 SAND TO SILTY SAND 32 21 SAND 37 22 SAND 53 23 SAND 54 24 SAND 59 25 SAND 63 26 GRAVELLY SAND TO SAND 57 27 SAND 56 28 SAND 53 29 SAND 46 30 SAND 561550.71.31441.90.0310.007 31 GRAVELLY SAND TO SAND 60 32 GRAVELLY SAND TO SAND 58 33 GRAVELLY SAND TO SAND 52 34 GRAVELLY SAND TO SAND 59 35 GRAVELLY SAND TO SAND 59 36 GRAVELLY SAND TO SAND 60 37 GRAVELLY SAND TO SAND 58 38 GRAVELLY SAND TO SAND 53 39 GRAVELLY SAND TO SAND 52 40 GRAVELLY SAND TO SAND 58 41 GRAVELLY SAND TO SAND 62 42 GRAVELLY SAND TO SAND 57 43 GRAVELLY SAND TO SAND 57 44 GRAVELLY SAND TO SAND 601457.52.03539.70.0240.004 45 SAND 56 46 SAND 52 47 SAND 44 48 SAND 35 49 SAND 28 50 SAND TO SILTY SAND 22639.52.53366.80.0150.002 Total Settlement(ft)0.1250.028 (cm)3.820.84 CPT (N) o Depth Soil Behavior Settlement 189

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BIOGRAPHICAL SKETCH Youngmin Cho was born in 1976 in S outh Korea to In-ok Hwang and Myung-hyun Cho. He enrolled in the Chungnam National University, South Korea, in March 1995, and graduated with a Bachelor of Engineering in environm ental engineering in February 2003. He had served in the military army of South Korea from January 1997 to March 1999. He also enrolled in the Johns Hopkin s University, Baltimore, United States, in August 2006 and graduated with a Master of Science and engineering in geography and environmental engineering in May 2007. 196