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Response of Flexible Pipe Subjected to Increasing Overburden Stress

Permanent Link: http://ufdc.ufl.edu/UFE0045484/00001

Material Information

Title: Response of Flexible Pipe Subjected to Increasing Overburden Stress
Physical Description: 1 online resource (112 p.)
Language: english
Creator: Konn, Victor
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2013

Subjects

Subjects / Keywords: aluminum -- box -- construction -- corrugated -- fdot -- flexible -- hdpe -- inspection -- overburden -- pipe -- pressure -- roadway -- soil -- steel -- transportation -- trench
Civil and Coastal Engineering -- Dissertations, Academic -- UF
Genre: Civil Engineering thesis, M.E.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: For flexible pipes installed under roadways, the Florida Department of Transportation requires inspection when backfill reaches 3 feet above the pipe crown or after placement of the stabilized subgrade.  This research aims to help identify pipes whose deflections are within the 5% specification tolerance at time of inspection but may ultimately exceed this tolerance at the time of project acceptance. The flexible pipes targeted in this project are HDPE, corrugated aluminum, corrugated steel, and HDPE with trench box installation.  These pipes were tested using the Soil Box, a large geotechnical testing enclosure, located at the University of Florida.
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 Victor Konn.
Thesis: Thesis (M.E.)--University of Florida, 2013.
Local: Adviser: Thieke, Robert J.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2013
System ID: UFE0045484:00001

Permanent Link: http://ufdc.ufl.edu/UFE0045484/00001

Material Information

Title: Response of Flexible Pipe Subjected to Increasing Overburden Stress
Physical Description: 1 online resource (112 p.)
Language: english
Creator: Konn, Victor
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2013

Subjects

Subjects / Keywords: aluminum -- box -- construction -- corrugated -- fdot -- flexible -- hdpe -- inspection -- overburden -- pipe -- pressure -- roadway -- soil -- steel -- transportation -- trench
Civil and Coastal Engineering -- Dissertations, Academic -- UF
Genre: Civil Engineering thesis, M.E.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: For flexible pipes installed under roadways, the Florida Department of Transportation requires inspection when backfill reaches 3 feet above the pipe crown or after placement of the stabilized subgrade.  This research aims to help identify pipes whose deflections are within the 5% specification tolerance at time of inspection but may ultimately exceed this tolerance at the time of project acceptance. The flexible pipes targeted in this project are HDPE, corrugated aluminum, corrugated steel, and HDPE with trench box installation.  These pipes were tested using the Soil Box, a large geotechnical testing enclosure, located at the University of Florida.
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 Victor Konn.
Thesis: Thesis (M.E.)--University of Florida, 2013.
Local: Adviser: Thieke, Robert J.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2013
System ID: UFE0045484:00001


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1 RESPONSE OF FLEXIBLE PIPE SUBJECTED TO INCREASING OVERBURDEN STRESS By VICTOR KONN A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ENGINEERING UNIVERSITY OF FLORIDA 2013

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2 2013 Victor Konn

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3 To my mother and f ather

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4 ACKNOWLEDGMENTS I thank Dr. David Bloomquist and Dr. Raphael Crowley for aiding my development as a researcher an d engineer. I thank the Coastal Engineering Laboratory personnel especially Ryan Mackey and Vik Adams, for their hard work and dedication to my project. Finally, I thank my wife Carrie Pimentel who has supported me endlessly thr oughout my undergraduat e and graduate school education.

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5 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ .. 4 LIST OF TABLES ................................ ................................ ................................ ............ 7 LIST OF FIGURES ................................ ................................ ................................ .......... 8 LI ST OF ABBREVIATIONS ................................ ................................ ........................... 11 ABSTRACT ................................ ................................ ................................ ................... 12 CHAPTER 1 BACKGROUND ................................ ................................ ................................ ...... 13 1.1 P urpose ................................ ................................ ................................ ............ 13 1.2 Soil Box Design ................................ ................................ ................................ 13 1.3 Approach ................................ ................................ ................................ .......... 13 1.3.1 Loading M echanism ................................ ................................ ................ 13 1.3.2 Earth Pressure Cells ................................ ................................ ................ 14 1.3.3 Soil Displacement ................................ ................................ .................... 14 1.3.4 Pipe Deflection ................................ ................................ ........................ 14 1.3.5 Simulation of Overburden ................................ ................................ ........ 15 1.3.6 Boundary Friction ................................ ................................ .................... 15 1.3.7 Saturation ................................ ................................ ................................ 15 1.3.8 Flexible Membrane System ................................ ................................ ..... 15 1.3.9 Finite Element Modeling ................................ ................................ .......... 16 1.4 Basis of Development ................................ ................................ ....................... 16 1.5 Previous Tests ................................ ................................ ................................ .. 16 2 PROCEDURE ................................ ................................ ................................ ......... 22 2.1 Pipe Preparation ................................ ................................ ............................... 22 2.2 Soil Box Preparation ................................ ................................ ......................... 22 2.3 Testing Procedure ................................ ................................ ............................. 23 3 36 INCH HDPE PIPE WITH TRENCH BOX AND 36 INCH ALUMINUM PIPE TEST ................................ ................................ ................................ ....................... 32 3.1 Trench Box Purpose ................................ ................................ ......................... 32 3.2 Test Modifications ................................ ................................ ............................. 32 3.3 Saturation Failure ................................ ................................ .............................. 33 3.4 Lift Bag Failure ................................ ................................ ................................ .. 33 3.5 Results ................................ ................................ ................................ .............. 34

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6 4 24 INCH HDPE PIPE TEST ................................ ................................ .................... 48 4.1 Test Modifications ................................ ................................ ............................. 48 4.2 Lift Bag Failure ................................ ................................ ................................ .. 48 4.3 Results ................................ ................................ ................................ .............. 49 5 24 INCH STEEL PIPE TEST ................................ ................................ .................. 59 5.1 Test Modifications ................................ ................................ ............................. 59 5.2 Results ................................ ................................ ................................ .............. 59 6 CONCLUSION ................................ ................................ ................................ ........ 66 APPENDIX A .............. 78 Nuclear Density Test Locations ................................ ................................ .............. 78 Earth Pressure Cell Locations ................................ ................................ ................ 82 B ................................ ................................ ............................ 89 Nuclear Density Test Locations ................................ ................................ .............. 89 Earth Pressure Cell Locations ................................ ................................ ................ 93 C ................................ ................................ ......................... 100 Nuclear Density Tes t Locations ................................ ................................ ............ 100 Earth Pressure Cell Locations ................................ ................................ .............. 104 LIST OF REFERENCES ................................ ................................ ............................. 111 BIOGRAPHICAL SKETCH ................................ ................................ .......................... 112

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7 LIST OF TABLES Table page 2 1 Loading sequence and deflection reading timing. ................................ ............... 25 3 1 Simulated overburden for 36 inch HDPE with trench box and aluminum pipe test. ................................ ................................ ................................ ..................... 36 4 1 Simulated overburden for 24 inch HDPE pipe test. ................................ ............ 50 5 1 Simulated overburden for 24 inch steel pipe test. ................................ ............... 60

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8 LIST OF FIGURES Figure page 1 1 The Soil Box lo cated at the University of Florida ................................ ................ 17 1 2 Soil Box loading mechanism. ................................ ................................ .............. 17 1 3 Steel plates and lift bags for loading mechanism. ................................ ............... 18 1 4 Regulators used to control lift bag pressure. ................................ ...................... 19 1 5 Laser profiling system. ................................ ................................ ........................ 19 1 6 Exploded view of flexible membrane system. ................................ ..................... 20 1 7 Alternate view of flexible membrane system. ................................ ...................... 21 2 1 E xample pipe pre deflected to 4%. ................................ ................................ ..... 26 2 2 Side wall flange. ................................ ................................ ................................ 26 2 3 Installed lubricated polyethylene sheets. ................................ ............................ 27 2 4 Soil being placed with front end loader. ................................ .............................. 27 2 5 First lift during compaction. ................................ ................................ ................. 28 2 6 First lift after compaction. ................................ ................................ ................... 28 2 7 Properly positioned pipe before flexible membrane system installation. ............. 29 2 8 Install ed flexible membrane system. ................................ ................................ ... 29 2 9 Fastening of Soil Box end partition. ................................ ................................ .... 30 2 10 Loading mechanism. ................................ ................................ .......................... 30 2 11 Top partition hoisted onto Soil Box via lift truck. ................................ ................. 31 2 12 Installed laser profiling system. ................................ ................................ ........... 31 3 1 Aluminum pipe end modification. ................................ ................................ ........ 37 3 2 HDPE pipe end modification. ................................ ................................ .............. 37 3 3 Rerouted pressure cell cabling. ................................ ................................ .......... 38 3 4 Hoisting trench box into Soil Box. ................................ ................................ ....... 38

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9 3 5 Installed trench box. ................................ ................................ ........................... 39 3 6 Removal of trench box walls. ................................ ................................ .............. 39 3 7 Voids from removal of trench box walls. ................................ ............................. 40 3 8 Void formed from flexible membrane b reach. ................................ ..................... 40 3 9 Top view of void (circle showing HDPE pipe). ................................ .................... 41 3 10 Lift bag failure locations. ................................ ................................ ..................... 42 3 11 overburden. ................................ ................................ ................................ ........ 43 3 12 urden over time. ..... 44 3 13 ......................... 45 3 14 deflection versus simulated overburden. .... 46 3 15 24 hours. ................................ ................................ ................................ ............ 47 4 1 Shaved corrugation on HDPE pipe prior to flexible membrane installation. ........ 51 4 2 Installed flexible membrane system. ................................ ................................ ... 51 4 3 Purchased laser for 24 inch pipe testing. ................................ ............................ 52 4 4 Modified laser. ................................ ................................ ................................ .... 52 4 5 Lift bag failure location. ................................ ................................ ....................... 53 4 6 overburden. ................................ ................................ ................................ ........ 54 4 7 d overburden over 24 hours. ................................ ................................ ................................ ............ 55 4 8 overburden. ................................ ................................ ................................ ........ 56 4 9 Deflectio over 24 hours. ................................ ................................ ................................ ..... 57 4 10 ................................ ........................ 58 5 1 .. 61

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10 5 2 24 hours. ................................ ................................ ................................ ............ 62 5 3 .. 63 5 4 simulated overburden over 24 hours. ................................ ................................ ................................ ............ 64 5 5 ................................ ........................... 65 6 1 Deflection comparison of tested pipe s. ................................ ............................... 68 6 2 Stress distribution before and after saturation for 36 inch HDPE with trench box and 36 inch aluminum pipes. ................................ ................................ ....... 69 6 3 St ress distribution at 0 psi and 20 psi for 36 inch HDPE with trench box and 36 inch aluminum pipes. ................................ ................................ ..................... 69 6 4 Stress distribution 40 psi and 60 psi for 36 inch HDPE with trench box and 36 inch alu minum pipes. ................................ ................................ .......................... 70 6 5 Stress distribution at 80 psi and 100 psi for 36 inch HDPE with trench box a nd 36 inch aluminum pipes. ................................ ................................ .............. 70 6 6 Stress distribution at 120 psi and 130 psi for 36 inch HDPE with trench box and 36 inch aluminum pipes. ................................ ................................ .............. 71 6 7 Stress distribution at 0 psi and 20 psi for dual 24 inch HDPE pipes. .................. 72 6 8 Stress distribution at 40 psi and 60 psi for dual 24 inch HDPE pipes. ................ 72 6 9 Stress distribution at 80 psi and 100 psi for dual 24 inch HDPE pipes. .............. 73 6 10 Stress distribution at 120 psi and 130 psi for dual 24 inch HDPE pipes. ............ 73 6 11 Stress distribution at 0 psi and 20 psi for dual 24 inch steel pipes. ..................... 74 6 12 Stress distribution at 40 psi and 60 psi for dual 24 inch steel pipes. ................... 74 6 13 Stress distribution at 80 psi and 100 psi for dual 24 inch steel pipes. ................. 75 6 14 Stress distribution at 120 psi and 130 psi for dual 24 inch steel pipes. ............... 75 6 15 Contour plot pressure cell layout for 36 inch HDPE with trench box and 36 inch aluminum pipes. ................................ ................................ .......................... 76 6 16. Contour plot pressure cell layout for dual 24 inc h HDPE and steel pipes. ........... 77

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11 LIST OF ABBREVIATIONS AASHTO American Association of State Highway and Transportation Officials FDOT Florida Department of Transportation FE M Finite Element Modeling HDPE High Density Polyethyle ne OSHA Occupational Safety and Health Administration PSI Pounds per Square Inch PVC Polyvinyl Chloride SGH Simpson, Gumpertz, and Heger

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12 Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfil lment of the Requirements for the Degree of Master of Engineering RESPONSE OF FLEXIBLE PIPE SUBJECTED TO INCREASING OVERBURDEN STRESS By Victor Konn May 2013 Chair: Robert J. Thieke Major: Civil Engineering For flexible pipes installed under roadway s t he Florida Department of Transportation requires inspection when backfill reaches 3 feet above the pipe crown or after placement of the stabilized subgrade. This research aims to help identify pipes whose deflections are within the 5% specification toler ance at time of inspection but may ultimately exceed this tolerance at the time of project acceptance. The flexible pipes targeted in this project are HDPE, corrugated aluminum, corrugated steel and HDPE with trench box installation These pipe s were tes ted using the Soil Box, a large geotechnical testing enclosure, located at the University of Florida.

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13 CHAPTER 1 BACKGROUND 1.1 Purpose For pipes installed under roadways, the Florida Department of Transportation (FDOT) requires inspection when backfill r eaches 3 feet above the pipe crown or after placement of the stabilized subgrade (FDOT 2013). The purpose of this project was to assist the Florida Department of Transportation in the understanding of pipe soil interaction by gathering deflection data of f lexible pipes when subjected to overburden stress. These data will ultimately be used to identify pipes whose deflection are within the 5% specification tolerance at the time of inspection but may exceed this tolerance at the time of project acceptance. 1. 2 Soil Box Design The steel Soil Box ( Figure 1 1 ) is 20 feet long 10 feet wide 8 feet tall and is capable of test ing full scale buried pipes. It is comprised of multiple partitions bolted together and reinforced wi th I beams to prevent deflection s of l ess than two millimeters when subjected to a geostatic earth pressure of 118 pounds per square inch (150 ft. of overburden) Observation portals located along the length of the Soil Box allow for 1.3 App roach 1.3.1 Loading Mechanism The loading mechanism consist ed of ten three quarter inch thick steel plates that lie on the surface of the soil These plates were overlain by pressurized lift bags that appl ied simulate d overburden pressure s A chain link fence was placed in between the

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14 steel plates and soil surface to help uniformly distribute the stress to the soil. The loading mechanism can be seen in Figure s 1 2 and 1 3 A main regulator fed ten additional regulators that controlled the pressure to the lift bags (Figure 1 4) Six of these regulators controlled the large lift bags and the remaining four controlled the small li ft bags. 1.3.2 Earth Pressure Cells Earth pressure cells were strategically placed throughout the Soil Box to measure the stress distribution within the soil during testing. The cell location s varied slightly for each test due to different pipe diameter s and the use of trench box installation (trench box installation will be discussed in Chapter 3) These locations are specified fo r each tested pipe in the chapters that follow. The collected soil pressure data was used in the finite element modeling (FEM) analysis. 1.3.3 Soil Displacement Vertical displacement in the soil was measured using a settlement plate located near each pipe invert The plate was connected to a string potentiometer that record ed the vertical movement of the soil mass Soil displacement data was collected to aid in the FEM analysis. 1.3.4 Pipe Deflection Pipe deflection was measured using a laser profiling s ystem consisting of a displacement laser mounted to a fixed trolley. The laser was directed through the pipe such that it measures vertical deflection for each loading increment. The laser profiling system can be seen in Figure 1 5

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15 1.3.5 Simulation of O verburden Six 42 inch square lift bags and eight 21 inch by 25 inch lift bags were utilized to apply the simulated overburden pressures. Simulated overburden was calculated using pressure data from the earth pressure cells located directly above the pipe crown and from nuclear density test results recorded at various locations within the Soil Box. The location and results of the nuclear density tests are specified for each pipe in the chapters that follow 1.3.6 Boundary Friction Boundary friction between the soil mass and side walls was minimized by placing two layers of lubricated polyethylene sheet in between the soil wall interface. 1.3.7 Saturation The soil backfill was saturated with water and drained prior to lo ading to simulate variable high ground water conditions expected in Florida To prevent water from seeping out of the Soil Box during saturation, the interior joints of the Soil Box were seal ed using marine grade sealant. A French drain is placed in the Soil Box to allow drainage after satura tion. 1.3.8 Flexible Membrane System The interface between the pipe ends and the Soil Box side walls was sealed using a flexible membrane system. This system was comprised of a rigid steel angle bolted to the Soil Box wall, two steel hose clamps, and a fl exible rubber membrane. This prevent ed soil and water from escaping through the observation portals while allow ing the pipe to deflect freely. This system can be see n in Figure s 1 6 and 1 7

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16 1.3.9 Finite Element Modeling Using data collected as part of th is study, Dr. Timothy McGrath of Simpson, Gumpertz, and Heger (SGH) is programming a finite element model (FEM) to simulate Soil Box conditions using ABAQUS. Results from this computational model will be presented in a future FDOT publication. 1.4 Basis of Development The development of the Soil Box design and testing approach were based on tests previously performed in a laboratory setting (Brachman et al. 2000 and 2001 ). 1.5 Previous Tests Brachman et al. ( 2001 ) performed testing of small diameter bu ried pipes subject to biaxially compressive earth pressures in a laboratory facility. Issues such as simulation of overburden pressures, boundary stiffness of the testing chamber, and influence of side wall friction were discussed. He reported the overal l effects on the pipe from the idealized laboratory model were small. Faraone (2012) measured deflections of a 36 inch HDPE pipe with trench box installation using the Soil Box and an identical approach. He concluded the trench box installation techniqu e ha d a major e ffect on the performance of the HDPE pipe The trench box test appeared to show the largest deflections of the pipes tested, including the 36 inch HDPE without trench box The 36 inch HDPE pipe with trench box installation examined in this thesis will be compared to the results reported by Faraone. This thesis is a continuation of previous research performed on other flexible pipes for the same FDOT project. These pipes, all of which were 36 inches in diameter, included two HDPE pipes, t wo PVC pipes, two corrugated steel pipes, and one HDPE pipe with trench box installation.

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17 Figure 1 1 The Soil Box located at the University of Florida Photo credit: Z Faraone. Figure 1 2 Soil Box l oading mechanism. Pho to credit: V. Konn.

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18 Figure 1 3. Steel plates and lift bags for l oad ing mechanism.

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19 Figure 1 4. Regulators used to control lift bag pressure. Photo credit: Z. Faraone. Figure 1 5 Laser profiling system.

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20 Figure 1 6 Exploded view of flexible membra ne system.

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21 Figure 1 7 Alternate view of flexible membrane system.

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22 CHAPTER 2 PROCEDURE 2.1 Pipe Preparation The pipes were cut slightly smaller than the ten f oot Soil Box width and their ends were modified to enable assembly to the flexible membrane sy stem. The details of each pipe end modification are discussed in the chapters that follow The pipes were pre deflected 4% of the ir nominal diameter s by extending turnbuckles between two channels placed along the interior length of the pipe As the turn buckles were extended measurements of the pipe diameter were taken until the diameter reach e d 4% deflection An example pre deflected p ipe can be seen in Figure 2 1. 2.2 Soil Box Preparation First, the interior joints of the Soil Box were sealed with mar ine grade sealant The rigid steel angles as part of the flexible membrane system, were then fastened to the Soil Box ( Figure 2 2 ) Next, a polyethylene sheet was placed on the side walls, lubricated with silicone grease and followed by a second polyet hylene sheet (Figure 2 3). A 12 inch layer of soil was placed into the Soil Box via a front end loader ( Figure 2 4 ) The soil was leveled manually and compacted wit h a vibratory plate compactor. T he soil during and after compaction are shown in Figures 2 5 and 2 6 respectiv ely. Nuclear density tests were performed at multiple locations in the first layer for use in FEM analysis The first set of e arth pressure cells were then placed in their appropriate locations below the pipes The pipes were placed in the Soil Box via fork lift rolled into their proper position and t he flexible membrane system is installed on each pipe end (Figures 2 7 and 2 8).

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23 The Soil Box end partition was then fastened to the Soil Box and its joints were sealed as shown in Figur e 2 9 T wo lubricated polyethylene sheets were placed on the inside wall partition and the remaining s oil for the first 12 inch layer was placed and manually compacted. A concrete bucket was filled with soil, hoisted above the box, emptied into the box, and manually evenly distributed with shovels. This was repeated in 18 inch lift increments until the Soil Box is filled. The e arth pressure cells were place d while soil was added and nuclear density tests were performed after each lift Refer to the app endices for each test for the locations of the nuclear density te sts and earth pressure cells The Soil Box was then saturated and followed by a final nuclear density test. After saturation, the loading mechanism was installed (Figure 2 1 0 ) After instal ling the loading mechanism the three top Soil Box partitions were fastened to the Soil Box Each section was hoisted onto the box via a lift truck and secured with nuts and bolts ( Figure 2 11 ) The turnbuckles were removed and the laser profiling system was installed in each pipe ( Figure 2 12 ) 2.3 Testing Procedure The loading sequence was comprised of five pound per square inch increments E ach increment was hel d for one hour before d eflection readings were recorded. The increments were increased unt il they reached 130 pounds per square inch because this was the maximum amount of pressure the lift bag s could tolerate without failure. For every third loading increment (45 pounds per square inch 90 pounds per square inch and 130 pounds per square inc h respectively), the load was held for 24 hours and deflection readings were taken at one hour, four hour, eight hour, and 24 hours to test the creep characteristics of the pipes. Table 2 1 displays the loading sequence and

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24 deflection reading tim es As the load was increased, pipe deflection was monitored and the lift bag regulators were adjusted to maintain uniform deflection along the pipes length After the loading sequence was concluded, the unloading sequence began This sequence consist ed of re ducing the pressure in the same increments in which it was increased. Each increment was held for an hour Throughout the loading and unloading sequence, pressure cell readings and soil de flection readings were recorded.

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25 Table 2 1. Loading sequence and deflection reading timing. Pressure Applied to Main Regulator ( PSI ) Deflection Readings taken x hours after pressure is applied 0 1 5 1 10 1 15 1 20 1 25 1 30 1 35 1 40 1 45 1, 4, 8 24 50 1 55 1 60 1 65 1 70 1 75 1 80 1 85 1 90 1, 4, 8 24 95 1 100 1 105 1 110 1 115 1 120 1 125 1 130 1, 4, 8, 24

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26 Figure 2 1. Example pipe pre deflected to 4%. Photo credit: V. Konn. Figure 2 2 Side wall flange. Photo credit: Z. Faraone.

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27 Figure 2 3 Installed lubricated polyethylene sheets Photo credit: V. Konn. Figure 2 4 Soil being placed with front end loader Photo credit: V. Konn.

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28 Figure 2 5 First lift during compaction Photo credit: V. Konn. Figure 2 6. First lift after compaction Photo credit: V. Konn.

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29 Figure 2 7. Properly positioned pipe before flexible membrane system installation. Photo credit: V. Konn. Figure 2 8 Installed f lexible membrane system. Photo credit: V. Konn.

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30 Figure 2 9 Fastening of Soil Box end partition. Photo credit: V. Konn. Figure 2 10. Loading mechanism. Photo credit: V. Konn.

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31 Figure 2 11. Top partition hoisted onto Soil Box via lift truck. Photo credit: Z. Faraone. Figure 2 12. Installed laser profiling system. Photo credit: V. Konn.

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32 CHAPTER 3 36 INCH H DPE PIPE WITH TRENCH BOX AND 36 INCH ALUMINUM PIPE TEST 3.1 Trench Box Purpose A trench box is a structure that protects workers within it and withstands the forces imposed on it by a cave in during trench excavation (OSHA 1926.650). When laying pipe a trench box is placed in the excavated trench while workers install a pipe section. T he trench box is then pulled forward and this procedure is repeated until the pipe laying is complete. Strength of flexible pipe is based upon passive soil pressures developed at the sides of the pipe when sub jected to overburden stress When pulling the trench box forward during pipe installation the voids left by the trench box are supposed to be filled and compacted. This test aims to trench box for pipe i nstallation on the most backfill sensitive pipe, HDPE 3.2 Test Modifications Several modifications were required for the trench box test An aluminum ring was riveted on each end of the aluminum pipe and one corrugation was removed on each end of the HDP E pipe (Figures 3 1 and 3 2) This allow ed the pipes to connect to the flexible membrane system To prevent damage, the pressure cell cables were rerouted underneath the trench box. These cables were buried before the installation of the trench box as sh own in Figure 3 3. The trench box was installed after the placement of the remaining soil for the first 12 inch layer The trench box was hoisted over the box via a lift truck and placed around the HDPE pipe as shown in Figure s 3 4 and 3 5.

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33 T he lift capa city of the lift truck was exceeded by the estimated force on the trench box due to the soil Therefore, as the Soil Box was filled, the trench box cross bars were removed to allow individual removal of the trench box walls (Figures 3 6 and 3 7). The voi ds left by the trench box removal were then filled The locations of the nuclear density tests and earth pressure cells are shown in Appendix A. 3.3 Saturation Failure During saturation, soil began flowing out of the HDPE pipe observation portals A fter examining the failure, it was apparent that the flexible membrane was breached. A void formed at the top of the Soil Box down through the observation portals exposing the HDPE as shown in Figures 3 8 and 3 9. The performance of flexible pipes is directly related to lateral passive pressures developed by the soil pipe system The se passive pressures were not developed due to the reduction in soil density from trench box removal and as the HDPE pipe deflected the stress on the flexible membrane increased ultimately caus ing its failure To remedy this issue, the membrane failure was sealed by placing an inflat able inner tube inside the HDPE pipe The void was filled and saturation was completed This failure is identical to flexible membrane failure of th e previously tested HDPE pipe with trench box installation (Faraone 2012) 3.4 Lift Bag Failure Two lift bag failures occurred during testing. The first failure occurred in a small lift bag located in the N ortheast corner of the Soil Box ( Figure 3 10 ) T he lift bag was leaking air through a small tear first observed during the early stages of the loading sequence. When the loading sequence reached 90 pounds per square inch the lift

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34 bag appeared to be leaking significantly. T o avoid overstressing the a ir compressor, the air supply to the lift bag was removed. T he second lift bag failure occurred during the 110 pounds per square inch load increment in a large lift bag located in the center e ast side of the Soil Box ( Figure 3 10 ) This lift bag ruptured without warning The rupture resulted in immediate pressure loss Although the failed lift bags were not located directly over the pipes, the failures caused a discontinuity of surcharge in the Soil Box which ultimately reduced the simulated overburden pr essure These lift bags were utilized through several loading and unloading sequences and most likely failed due to fatigue. 3.5 Results The HDPE pipe with trench box appeared to show the largest deflections of the pipes tested. A plot of deflection vers us simulated overburden for three points (mid span and 18 inches from each end) in the pipe can be seen in Figure 3 11. As shown, the mid span point appears to indicate the highest deflection reading. This may indicate the flexible membrane s ystem did no t perform as expected The flexible membrane was designed to prevent soil from exiting the Soil Box while allowi ng for free deformation of the pipe This difference of deflection between the three points may be caused by a partially fixed boundary condit ion at the pipe and wall interface. T he re is a small amount of creep deflection in the HDPE pipe (Figure 3 12). A plot of the two tested HDPE pipes with trench box can be seen in Figure 3 1 3 The simulated overburden for this test yielded lesser depths than previously tested HDPE pipe with trench box. This result is most likely due to the lift bag failures during testing.

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35 The aluminum pipe yielded deflections less than the HDPE pipe with trench box. This was expected because aluminum is a st iffer material than HDPE. The deflection of three points in the aluminum pipe versus simulated overburden is shown in Figure 3 14. T here does not appear to be any significant creep of the aluminum pipe (Figure 3 15) Table 3 1 displays the simulated ove rburden depth results HDPE pipe with trench box and aluminum pipe.

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36 Table 3 1. Simulated o verburden for 36 inch HDPE with trench box and aluminum pipe test. Pressure Applied to Main Regulator ( PSI ) Deflection Readings taken x hours after pressure was appli ed Simulated Overburden Over HDPE Pipe (f ee t) Simulated Overburden Over Aluminum Pipe (f ee t) 0 1 2.2 4. 9 5 1 2.5 5.5 10 1 3.3 7.0 15 1 3.9 8.3 20 1 4. 6 9. 7 25 1 4. 9 10.7 30 1 5. 6 12.1 35 1 6.2 13.3 40 1 6. 8 14.5 45 1, 4, 8 24 6. 8 15.2 50 1 7.0 15.9 55 1 7. 8 16.6 60 1 8.2 17.0 65 1 8.6 17.8 70 1 8. 4 18.1 75 1 9.0 18.6 80 1 9.4 19.1 85 1 9. 8 19.5 90 1, 4, 8 24 9.3 19.5 95 1 9.2 20.6 100 1 9. 6 21.4 105 1 9. 9 2 2.0 110 1 10. 2 22.0 115 1 9. 6 21.3 120 1 9.8 21.7 125 1 10.1 22. 2 130 1, 4, 8, 24 9. 9 22. 8

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37 Figure 3 1. Aluminum pipe end modification Photo credit: V. Konn. Figure 3 2. HDPE pipe end modification. Photo credit: V. Konn.

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38 Figure 3 3. Rerouted pressure cell cabling. Photo credit: V. Konn. Figure 3 4. Hoisting trench box into Soil Box Photo credit: V. Konn.

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39 Figure 3 5. Installed trench box Photo credit: V. Konn. Figure 3 6. Removal of trench box walls. Photo credit: V. Konn.

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40 Figure 3 7. Voids from removal of trench box walls. Photo credit: V. Konn. Figure 3 8 Void formed from flexible membrane breach. Photo credit: V. Konn.

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41 Figure 3 9 Top view of void (circle showing HDPE pipe). Photo credit: V. Konn.

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42 Figure 3 10. Lift bag failure locations

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43 Figure 3 1 1 T hree points in HDPE pipe with trench box deflection versus simulated overburden.

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44 Figure 3 over time

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45 Figure 3 1 3 D eflection c omparison of HDPE pipe with trench box tests

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46 Figure 3 1 4 Three point

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47 Figure 3 pipe under 19.5 ft of simulated overburden over 24 hours

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48 CHAPTER 4 24 INCH HDPE PIPE TEST 4.1 Test Modifications Several modifications were required f or the 24 inch diameter HDPE pipe test. The location s of the pressure cells were modified to account for the smaller pipe diameter ; these locations are shown in Appendix B The flexible membrane system was modified to fit the 24 inch pipes. A replacem ent rigid steel angle was fabricated painted, and bolted to the Soil Box wall. A single corrugation on each end of the HDPE pipes was removed to allow assembly to the flexible membrane system ( Figures 4 1 and 4 2 ) The laser previously used to measure di splacements of the 36 inch pipes did not have adequate precision to measure displacements of the 24 inch pipes. A new ILD1700 250VT laser was purchased from Micro Epsilon T wo aluminum plates were e properly mounted on the laser profiling system (Figures 4 3 and 4 4). 4.2 Lift Bag Failure A lift bag failure occurred during the 110 pounds per square inch load increment in a small lift bag located in the Northeast corner of the Soil Box ( Figure 4 5 ) Although the failed lift bag was not located directly over the pipes, it caused a discontinuity of surcharge in the Soil Box which ultimately reduced the simulated overburden. This may explain the difference in simulated overburden of the two HDPE pipes shown in Table 4 1. The lift bag was utilized through several loading and unloading sequences and most likely failed due to fatigue.

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49 4.3 Results The North HDPE pipe appeared to produce approximately uniform deflection along its length (Figure 4 6 ). Resu lts appear to show creep deflections in this pipe over a 24 hour time period (Figure 4 7 ). A deflection versus simulated overburden plot of three points in the South HDPE pipe displays a 2% deflection discrepancy between each end of the pipe (Figure 4 8 ). The creep characteristics for the South HDPE pipe over a 24 hour time period displays a similar upward trend (Figure 2 9). The North pipe consistently deflected ab out 2% more than the South pipe during the loading sequence (Figure 4 1 0 ). This deflection appears to conflict with the overburden simulations calculated for both pipes (Table 4 1) The simulated overburdens for the South pipe versus the North pipe are higher but the deflections recorded in the South pipe versus the North pipe are smaller. A possible reason for this discrepancy is the variation of the soil density in the Soil Box and variable contact areas between the lift bags and their corresponding load plates During the loading sequence, the load plate settles with the soil causing a red uction in contact area between the lift bag and load plate. This reduction in contact area decreases the simulated overburden pressure applied to the soil.

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50 Table 4 1. Simulated overburden for 24 inch HDPE pipe test. Pressure Applied to Main Regulator ( PS I ) Deflection Readings taken x hours after pressure was applied Simulated Overburden Over North HDPE Pipe (f ee t) Simulated Overburden Over South HDPE Pipe (f ee t) 0 1 3.8 4. 2 5 1 4. 4 4.7 10 1 5.6 6.3 15 1 5.7 6. 8 20 1 6.4 7.5 25 1 8. 9 10. 3 30 1 9.5 1 1.0 35 1 1 1 0 12.9 40 1 12. 4 14.6 45 1, 4, 8 24 12.9 1 5.0 50 1 13.3 15.5 55 1 14.7 17.3 60 1 15.0 17.5 65 1 15.4 17.8 70 1 16.6 19.4 75 1 16.6 19. 2 80 1 17.2 20.0 85 1 18.6 21.6 90 1, 4, 8 24 19.1 22.0 95 1 1 9 0 21. 8 100 1 19.8 22. 8 105 1 20.8 23.9 110 1 21.8 25.1 115 1 21.6 23.7 120 1 22.3 24. 6 125 1 2 3 0 25.3 130 1, 4, 8, 24 23.4 26. 2

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51 Figure 4 1. Shaved corrugation on HDPE pipe prior to flexible membrane installation. Photo credit: V. Konn. Figure 4 2. Installed flexible membra ne system. Photo credit: V. Konn.

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52 Figure 4 3. Purchased laser for 24 inch pipe testing. Photo credit: V. Konn. Figure 4 4 Modified laser. Photo credit: V. Konn.

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53 Figure 4 5 Lift bag failure location.

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54 Figure 4 6 e, deflection versus simulated overburden.

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55 Figure 4 7 Deflection of N

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56 Figure 4 8 Three points in S

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57 Figure 4 9 Deflecti on of S

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58 Figure 4 1 0 Deflection c omparison of 24 HDPE pipes

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59 CHAPTER 5 24 INCH STEEL PIPE TEST 5.1 Test Modifications Similar modifications to the 24 inch diameter HDPE pipe test were required for the 24 inch diameter steel pipe test. The locations of the pressure cells were modified to account for the smaller pipe diameter; these locations are shown in Appendix C. A steel ring was spot welded onto each end of the steel pipes to allow assembly to the flexible membrane system. 5.2 Results The North steel pipe appeared to produce approximately uniform deflection along its length (Figure 5 1). Results appear to show creep deflections in this pipe over a 24 hour time period (Figure 5 2). A deflection versus simulated overburden plot of three points in the South steel pipe displays a 1.5 % deflection discrepancy between each end of the pipe (Figure 5 3 ). The creep characteristics for the South HDPE pipe over a 24 hour time period displays a si milar upward trend (Figure 5 4 ). A comparison of the North and South pipe deflections appear s to be approximately equal during the loading sequence (Figure 5 5).

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60 Table 5 1. Simulated overburden for 24 inch steel pipe test. Pressure Applied to Main Regula tor ( PSI ) Deflection Readings taken x hours after pressure was applied Simulated Overburden Over North Steel Pipe (f ee t) Simulated Overburden Over South Steel Pipe (f ee t) 0 1 6.6 7.3 5 1 8.3 9.3 10 1 10.0 11.3 15 1 12.0 13.4 20 1 13.5 14.9 25 1 15.3 16.8 30 1 17.2 18.9 35 1 19.0 20.7 40 1 20.8 22.8 45 1, 4, 8 24 22.7 25.0 50 1 24.4 26.5 55 1 25.9 28.2 60 1 27.8 30.3 65 1 29.7 32.4 70 1 30.5 33.1 75 1 32.2 35.0 80 1 33.3 36.1 85 1 35.0 38.0 90 1, 4, 8 24 37.2 40.4 95 1 39.0 42.1 100 1 40.4 43.5 105 1 42.1 45.2 110 1 43.5 46.6 115 1 44.5 47.7 120 1 45.9 49.1 125 1 47.6 51.0 130 1, 4, 8, 24 48.5 51.6

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61 Figure 5

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62 Figure 5 2 eel pipe under 48.5ft of simulated overburden over 24 hours.

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63 Figure 5 3

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64 Figure 5 4 Deflection of ft of simulated overburden over 24 hours.

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65 Figure 5

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66 CHAPTER 6 CO NCLUSION The deflection data for the 36 inch HDPE pipe with trench box, 36 inch aluminum pipe, and 24 inch HDPE and steel pipes displayed trends expected for their specified material type. The greatest deflections occurred in t he 36 inch HDPE pipe with trench box installation followed by the 24 inch HDPE pi pes. The 36 inch aluminum pipe and 24 inch steel pipes deflected the least. The differences in simulated overburden as shown in Figu re 6 1, can be attributed to the density variability of the soil backfill and the variable contact stresses in the loading mechanism. C ontour plot s of each test at various loading increments can be seen in Figures 6 2 through 6 1 4 These plots display th e stress variation in the Soil Box at eight inches above the pipe crown. The location of the pressure cells used in the contour p lots can be seen in Figures 6 15 and 6 1 6 The more flexible pipes (HDPE) measured deflections much greater than the stiffer pi pes (steel) and resulted in smaller overburden pressures. During the loading sequence, the steel load plates settle with the soil. This causes a smaller contact area between the lift bags and load plates therefore reducing the simulated overburden. The use of multiple lift bags to apply simulated overburden resulted in an unknown pressure distribution across the soil surface. This uncertainty was diminished by monitoring the pressure cells placed throughout the Soil Box and deflection measurements recorded during loading. A n improvement to this loading mechanism would be to use single rubber membrane across the entire surface area of the Soil Box. Overall, the results obtained through this research show good development of flexible pipe response subjected to overburden stress. Pending a comparison with the

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67 FEM analysis, the results can better aid the FDOT identify pipes whose deflections are within the 5% specification tolerance at time of inspection but may ultimately exceed this tolerance at the time of project acceptance

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68 Figure 6 1. Deflection comparison of tested pipes.

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69 A B Figure 6 2. Stress distribution before and after saturation for 36 inch HDPE with trench box and 36 inch aluminum pipes A B Figure 6 3. Stress distribution at 0 psi and 2 0 psi for 36 inch HDPE with trench box and 36 inch aluminum pipes

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70 A B Figure 6 4. Stress distribution 40 psi and 60 psi for 36 inch HDPE with trench box and 36 inch aluminum pipes A B Figure 6 5. Stress distribution at 80 psi and 100 psi for 36 inch HDPE with trench box and 36 inch aluminum pipes

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71 A B Figure 6 6. Stress distribution at 12 0 psi and 1 3 0 psi for 36 inch HDPE with trench box and 36 inch aluminum pipes.

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72 A B Figure 6 7. Stress distribution at 0 psi and 20 psi for dual 24 in ch HDPE pipes. A B Figure 6 8. Stress distribution at 40 psi and 60 psi for dual 24 inch HDPE pipes.

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73 A B Figure 6 9. Stress distribution at 80 psi and 100 psi for dual 24 inch HDPE pipes. A B Figure 6 10. Stress distribution at 120 psi and 1 30 psi for dual 24 inch HDPE pipes.

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74 A B Figure 6 11. Stress distribution at 0 psi and 20 psi for dual 24 inch steel pipes. A B Figure 6 12. Stress distribution at 40 psi and 60 psi for dual 24 inch steel pipes.

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75 A B Figure 6 13. Stress distr ibution at 80 psi and 100 psi for dual 24 inch steel pipes. A B Figure 6 14. Stress distribution at 120 psi and 130 psi for dual 24 inch steel pipes.

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76 Figure 6 1 5 Contour plot pressure cell layout for 36 inch HDPE with trench box and 36 inch alumin um pipes.

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77 Figure 6 1 6 Contour plot pressure cell layout for dual 24 inch HDPE and steel pipes.

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78 APPENDIX A Nuclear Density Test Locations

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82 Earth Pressure Cell Locations

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89 APPENDI X B Nuclear Density Test Locations

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93 Earth Pressure Cell Locations

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100 APPENDIX C Nuclear Density Test Locations

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111 LIST OF REFERENCES Brachman, R. W. I. Moore, I. D., and Rowe, R. K. 200 0 The d esign of a laboratory f acility for e valuating the s tructural r esponse of s mall d iameter b uried p ipes. Canadian Geotech nical Journal, 37 : 281 2 95. Brachman, R. W. I., Moore, I. D., and Rowe, R. K. 2001. The perform ance of a l aboratory f acility for e valuating the s tructural r esponse of s mall d iameter b uri ed p ipes. Canadian Geotech nical Journal, 38 : 260 2 75. Faraone, Z. 2012. Flexible Pipe Response T o Increasing Overburden Stress. University of Florida, Gainesville, F L. Florida Department of Transportation. 2013. Standard Specifications for Road and Bridge Construction. Section 430 4.8. Occupational Safety and Health Administration. 201 2 Authority for 1926 Subpart P. United States Department of Labor, Washington, DC.

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112 BIOGRAPHICAL SKETCH Victor Konn was born in 1988 in New York New York. He was raised in Teaneck, New Jersey before moving to Wellington, Florida at the age of 15. While in school, Victor e xcelled in the math and sciences and a fter graduating high scho ol he decided to pursue a career in engineering He worked part time while enrolled at Palm Beach Community College before transferring to the University of Flori da to study civil engineering. While earning his undergraduate degree, Victor developed a str ong interest in geotechnic al and structural engineering. In the summer of 2010, he worked as an undergraduate assistant researching epoxy creep and anchorage failure. In the 2010 l mechanics course until graduating in December 2011. After graduating at the top of his class with a Bachelor of Science in Civil Engineering, Victor received the opportunity to become a research assistant and pursue a Master of Engineering degree special izing in geotech nical engineering Due to his strong interest in structural engineering, Victor split his graduate coursework between geotechnical and structural design Upon completing his Master of Engineering degree, Victor plans to begin a career util izing his strong geotechnical and structural education designing bridge or building structures