Integrity Testing of Drilled Shafts Using Thermal Profiling a Thesis Presented to the Faculty of the Russ College of Engineering

Integrity Testing of Drilled Shafts Using Thermal Profiling

A thesis presented to

the faculty of the Russ College of Engineering and Technology of Ohio University

In partial fulfillment

of the requirements for the degree

Master of Science

Daniel E. Karch

May 2018

This thesis titled

Integrity Testing of Drilled Shafts Using Thermal Profiling

DANIEL E. KARCH

has been approved for

the Department of Civil Engineering

and the Russ College of Engineering and Technology by

Issam Khoury

Assistant Professor of Civil Engineering

Dennis Irwin

Dean, Russ College of Engineering and Technology 3

ABSTRACT

KARCH, DANIEL E., M.S., May 2018, Civil Engineering

Integrity Testing of Drilled Shafts Using Thermal Profiling

Director of Thesis: Issam Khoury

This thesis explores integrity testing of drilled shaft foundations by using a Digital

Temperature Sensor (DTS) in thermal profiling. Drilled shafts have become a popular

foundation in recent years and therefore their quality should be closely monitored. One

new method of monitoring them is by using thermal profiling.

Laboratory and field tests were conducted using a series of DTSs connected

together to obtain readings at set intervals. Thermocouples were also used to compare to the readings given by the DTSs. This data was analyzed and its variations were explored.

This study shows that these sensors can be used to thermally profile drilled shafts.

However, more protection is needed for these sensors so that they can continually take

readings. New protection methods were tested in the laboratory to be used in future field

work. These findings will provide value to owners, engineers, and contractors alike

because the DTSs are economical and can give accurate results.

DEDICATION

To my fiancée and family for your love and support for all these years

ACKNOWLEDGMENTS

I would like to thank the civil engineering faculty and staff here at Ohio

University. You have given me the knowledge and support I needed to succeed.

Specifically, I would like to express my gratitude to my advisor, Sam. I could not

have asked for a better person to guide me during my time here. He gave me the opportunity to grow as an engineer and as an individual.

I would also like to thank Dr. Masada. He was the instructor of the first civil engineering class I took here at Ohio University my freshman year of my undergraduate degree. He was also the instructor of the last class taken as part of my graduate degree.

His knowledge and wisdom will always be with me.

I would like to show appreciation my gratitude to Dr. Sargand and Dr. Savin of the Math department for agreeing to be on my committee.

I would also like to recognize Joshua Jordan for all his assistance during the testing portion of this research.

Finally, I would like to thank my fellow civil engineering student and friend Evan

Holcombe for his guidance. All the years of study and work were worth it. 6

TABLE OF CONTENTS

Page

Abstract ...... 3 Dedication ...... 4 Acknowledgments...... 5 List of Tables ...... 7 List of Figures ...... 8 Chapter 1: Introduction ...... 12 Chapter 2: Literature Review ...... 15 Chapter 3: Hydration of Concrete and Heat Transfer ...... 30 Chapter 4: Methodology ...... 38 Chapter 5: Results and Discussion ...... 65 Chapter 6: Digital Temperature Sensor Protection Methods ...... 85 Chapter 7: Conclusions and Recommendations ...... 92 References ...... 95 Appendix A: Field and Laboratory Test Results ...... 99

LIST OF TABLES

Page

Table 1. Density, Specific Heat, and Volumetric Heat Capacity of Common Soil Components at 20°C at 1 atm (van Wijk & de Vries, 1963) ...... 33 Table 2. Thermal Conductivities of Soil Related Materials (T in °C) (Bristow, 2002) .... 33 Table 3. Thermal Properties of Common Materials (Pauly, 2010) ...... 34 Table 4. Laboratory Concrete Mix Design ...... 49 Table 5. ODOT Class QC1 Concrete Requirements ...... 52 Table 6. DTS Readings, Laboratory Test, Stick 1 (°C) ...... 68 Table 7. DTS Readings, Laboratory Test, Stick 2 (°C) ...... 69 Table 8. DTS Readings, Field Test, Stick 1 (°C) ...... 80 Table 9. DTS Readings, Field Test, Stick 2 (°C) ...... 81 Table 10. Correction Factors for DTS Protection Methods ...... 91

LIST OF FIGURES

Page

Figure 1. Drilled Shaft (Drilled Shaft Construction)...... 15 Figure 2. Sonic Echo/Impulse Response Test (Olson Engineering, 2015)...... 17 Figure 3. Cross-Hole Sonic Logging (Paiksowsky et al., 2000)...... 21 Figure 4. Infrared Probe (Mullins & Winters, 2011)...... 24 Figure 5. Thermal Wires (Robinson, 2012)...... 25 Figure 6. Temperature Variation in a Drilled Shaft (Robinson, 2012)...... 26 Figure 7. Rebar Cage Alignment (Robinson, 2012)...... 27 Figure 8. DS18S20 Sensor...... 39 Figure 9. Sonotube...... 41 Figure 10. Marking Pipe at 1’ Intervals...... 42 Figure 11. Drilling Holes in Pipe...... 43 Figure 12. DTSs and Ribbon Cable with Connectors...... 43 Figure 13. Coating Sensors with Dow Corning 748 Non-Corrosive Sealant...... 45 Figure 14. Sensors Connected to Arduino Board...... 46 Figure 15. Forming Artificial Voids...... 47 Figure 16. Laboratory Test Assembly...... 48 Figure 17. Spacers Attached to Sensor Sticks...... 50 Figure 18. Sensor Sticks with Spacers and Thermocouples in Sonotube...... 51 Figure 19. Construction of Sensors for Field Test...... 53 Figure 20. Fully Constructed Field Sensors...... 54 Figure 21. I-Beam Clamp Fastened to Beam...... 55 Figure 22. Sensor Stick Attached to Beam...... 56 Figure 23. Lifting of Beam...... 57 Figure 24. Plumbing of Beam...... 57 Figure 25. Welding of Guardrail Lagging...... 58 Figure 26. Sensor Sticks in Shaft...... 58 Figure 27. Pouring Concrete into Shaft...... 59 Figure 28. Completed Shaft...... 59 Figure 29. Data Acquisition Systems...... 60 Figure 30. Burned Wires...... 60 Figure 31. Model Program Input Page (Ballim and Graham, 2004)...... 63 Figure 32. Model Program Output (Ballim and Graham, 2004)...... 64 Figure 33. Temperature vs. Time, Stick 1, Depth of 2'...... 67 Figure 34. Temperature vs. Time, Stick 2, Depth of 2’...... 67 Figure 35. Depth vs. Temperature, Stick 1, 12.5 hr...... 71 Figure 36. Depth vs. Temperature, Stick 2, 12.5 hr...... 71 Figure 37. Temperature vs. Time, Stick 1, All Depths...... 73 Figure 38. Temperature vs. Time, Stick 2, All Depths...... 73 Figure 39. Temperature vs. Time, North Side, All Depths...... 76 9

Figure 40. Temperature vs. Time, South Side, All Depths...... 78 Figure 41. Depth vs. Temperature, North Side, 12.5 hr...... 82 Figure 42. Depth vs. Temperature, South Side, 12.5 hr...... 83 Figure 43. Sensor Protection Test 1, Thermocouple, Oil...... 86 Figure 44. Sensor Protection Test 1, Thermocouple, Silicone...... 87 Figure 45. Sensor Protection Test 1, DS18S20, Oil...... 87 Figure 46. Sensor Protection Test 1, DS18S20, Silicone...... 88 Figure 47. Sensor Protection Test 2, Oil...... 88 Figure 48. Sensor Protection Test 2, Foil...... 89 Figure 49. Sensor Protection Test 2, No Treatment...... 89 Figure 50. Temperature vs. Time, Stick 1, 0.0'...... 99 Figure 51. Temperature vs. Time, Stick 1, 0.5'...... 100 Figure 52. Temperature vs. Time, Stick 1, 1.0’...... 100 Figure 53. Temperature vs. Time, Stick 1, 1.5'...... 101 Figure 54. Temperature vs. Time, Stick 1, 2.0'...... 101 Figure 55. Temperature vs. Time, Stick 1, 2.5'...... 102 Figure 56. Temperature vs. Time, Stick 1, 3.0’...... 102 Figure 57. Temperature vs. Time, Stick 1, 3.5'...... 103 Figure 58. Temperature vs. Time, Stick 1, 4.0’...... 103 Figure 59. Temperature vs. Time, Stick 2, 0.0’...... 104 Figure 60. Temperature vs. Time, Stick 2, 0.5’...... 104 Figure 61. Temperature vs. Time, Stick 2, 1.0’...... 105 Figure 62. Temperature vs. Time, Stick 2, 1.5’...... 105 Figure 63. Temperature vs. Time, Stick 2, 2.0’...... 106 Figure 64. Temperature vs. Time, Stick 2, 2.5’...... 106 Figure 65. Temperature vs. Time, Stick 2, 3.0’...... 107 Figure 66. Temperature vs. Time, Stick 2, 3.5’...... 107 Figure 67. Temperature vs. Time, Stick 2, 4.0’...... 108 Figure 68. Depth vs. Temperature, Stick 1, Initial...... 108 Figure 69. Depth vs. Temperature, Stick 1, 2.5 hr...... 109 Figure 70. Depth vs. Temperature, Stick 1, 5.5 hr...... 109 Figure 71. Depth vs. Temperature, Stick 1, 7.5 hr...... 110 Figure 72. Depth vs. Temperature, Stick 1, 9 hr...... 110 Figure 73. Depth vs. Temperature, Stick 1, 10 hr...... 111 Figure 74. Depth vs. Temperature, Stick 1, 11 hr...... 111 Figure 75. Depth vs. Temperature, Stick 1, 12 hr...... 112 Figure 76. Depth vs. Temperature, Stick 1, 13 hr...... 112 Figure 77. Depth vs. Temperature, Stick 1, 14 hr...... 113 Figure 78. Depth vs. Temperature, Stick 1, 15 hr...... 113 Figure 79. Depth vs. Temperature, Stick 1, 16 hr...... 114 Figure 80. Depth vs. Temperature, Stick 1, 17 hr...... 114 Figure 81. Depth vs. Temperature, Stick 1, 18 hr...... 115 Figure 82. Depth vs. Temperature, Stick 1, 19 hr...... 115 10

Figure 83. Depth vs. Temperature, Stick 1, 20 hr...... 116 Figure 84. Depth vs. Temperature, Stick 1, 21 hr...... 116 Figure 85. Depth vs. Temperature, Stick 1, 22 hr...... 117 Figure 86. Depth vs. Temperature, Stick 1, 23 hr...... 117 Figure 87. Depth vs. Temperature, Stick 1, 24 hr...... 118 Figure 88. Depth vs. Temperature, Stick 2, Initial...... 118 Figure 89. Depth vs. Temperature, Stick 2, 2.5 hr...... 119 Figure 90. Depth vs. Temperature, Stick 2, 5.5 hr...... 119 Figure 91. Depth vs. Temperature, Stick 2, 7.5 hr...... 120 Figure 92. Depth vs. Temperature, Stick 2, 9 hr...... 120 Figure 93. Depth vs. Temperature, Stick 2, 10 hr...... 121 Figure 94. Depth vs. Temperature, Stick 2, 11 hr...... 121 Figure 95. Depth vs. Temperature, Stick 2, 12 hr...... 122 Figure 96. Depth vs. Temperature, Stick 2, 13 hr...... 122 Figure 97. Depth vs. Temperature, Stick 2, 14 hr...... 123 Figure 98. Depth vs. Temperature, Stick 2, 15 hr...... 123 Figure 99. Depth vs. Temperature, Stick 2, 16 hr...... 124 Figure 100. Depth vs. Temperature, Stick 2, 17 hr...... 124 Figure 101. Depth vs. Temperature, Stick 2, 18 hr...... 125 Figure 102. Depth vs. Temperature, Stick 2, 19 hr...... 125 Figure 103. Depth vs. Temperature, Stick 2, 20 hr...... 126 Figure 104. Depth vs. Temperature, Stick 2, 21 hr...... 126 Figure 105. Depth vs. Temperature, Stick 2, 22 hr...... 127 Figure 106. Depth vs. Temperature, Stick 2, 23 hr...... 127 Figure 107. Depth vs. Temperature, Stick 2, 24 hr...... 128 Figure 108. Temperature vs. Time, North Stick, 0’...... 129 Figure 109. Temperature vs. Time, North Stick, 1’...... 130 Figure 110. Temperature vs. Time, North Stick, 2’...... 130 Figure 111. Temperature vs. Time, North Stick, 3’...... 131 Figure 112. Temperature vs. Time, North Stick, 4’...... 131 Figure 113. Temperature vs. Time, North Stick, 5’...... 132 Figure 114. Temperature vs. Time, North Stick, 6’...... 132 Figure 115. Temperature vs. Time, North Stick, 7’...... 133 Figure 116. Temperature vs. Time, North Stick, 8’...... 133 Figure 117. Temperature vs. Time, North Stick, 9’...... 134 Figure 118. Temperature vs. Time, North Stick, 10’...... 134 Figure 119. Temperature vs. Time, South Stick, 0’...... 135 Figure 120. Temperature vs. Time, South Stick, 1’...... 135 Figure 121. Temperature vs. Time, South Stick, 2’...... 136 Figure 122. Temperature vs. Time, South Stick, 3’...... 136 Figure 123. Temperature vs. Time, South Stick, 4’...... 137 Figure 124. Temperature vs. Time, South Stick, 5’...... 137 Figure 125. Temperature vs. Time, South Stick, 6’...... 138 11

Figure 126. Temperature vs. Time, South Stick, 7’...... 138 Figure 127. Temperature vs. Time, South Stick, 8’...... 139 Figure 128. Temperature vs. Time, South Stick, 9’...... 139 Figure 129. Temperature vs. Time, South Stick, 10’...... 140 Figure 130. Depth vs. Temperature, North Stick, 7.5 hr...... 141 Figure 131. Depth vs. Temperature, North Stick, 8.5 hr...... 141 Figure 132. Depth vs. Temperature, North Stick, 9.5 hr...... 142 Figure 133. Depth vs. Temperature, North Stick, 10.5 hr...... 142 Figure 134. Depth vs. Temperature, North Stick, 11.5 hr...... 143 Figure 135. Depth vs. Temperature, North Stick, 12.5 hr...... 143 Figure 136. Depth vs. Temperature, North Stick, 13.5 hr...... 144 Figure 137. Depth vs. Temperature, North Stick, 14.5 hr...... 144 Figure 138. Depth vs. Temperature, North Stick, 15.5 hr...... 145 Figure 139. Depth vs. Temperature, North Stick, 16.5 hr...... 145 Figure 140. Depth vs. Temperature, North Stick, 17.5 hr...... 146 Figure 141. Depth vs. Temperature, North Stick, 20.5 hr...... 146 Figure 142. Depth vs. Temperature, North Stick, 21.5 hr...... 147 Figure 143. Depth vs. Temperature, North Stick, 22.5 hr...... 147 Figure 144. Depth vs. Temperature, North Stick, 23.5 hr...... 148 Figure 145. Depth vs. Temperature, North Stick, 24.5 hr...... 148 Figure 146. Depth vs. Temperature, North Stick, 25.5 hr...... 149 Figure 147. Depth vs. Temperature, North Stick, 26.5 hr...... 149 Figure 148. Depth vs. Temperature, North Stick, 27.5 hr...... 150 Figure 149. Depth vs. Temperature, South Stick, 7.5 hr...... 150 Figure 150. Depth vs. Temperature, South Stick, 8.5 hr...... 151 Figure 151. Depth vs. Temperature, South Stick, 9.5 hr...... 151 Figure 152. Depth vs. Temperature, South Stick, 10.5 hr...... 152 Figure 153. Depth vs. Temperature, South Stick, 11.5 hr...... 152 Figure 154. Depth vs. Temperature, South Stick, 12.5 hr...... 153 Figure 155. Depth vs. Temperature, South Stick, 13.5 hr...... 153 Figure 156. Depth vs. Temperature, South Stick, 14.5 hr...... 154 Figure 157. Depth vs. Temperature, South Stick, 15.5 hr...... 154 Figure 158. Depth vs. Temperature, South Stick, 16.5 hr...... 155 Figure 159. Depth vs. Temperature, South Stick, 17.5 hr...... 155 Figure 160. Depth vs. Temperature, South Stick, 20.5 hr...... 156 Figure 161. Depth vs. Temperature, South Stick, 21.5 hr...... 156 Figure 162. Depth vs. Temperature, South Stick, 22.5 hr...... 157 Figure 163. Depth vs. Temperature, South Stick, 23.5 hr...... 157 Figure 164. Depth vs. Temperature, South Stick, 24.5 hr...... 158 Figure 165. Depth vs. Temperature, South Stick, 25.5 hr...... 158 Figure 166. Depth vs. Temperature, South Stick, 26.5 hr...... 159 Figure 167. Depth vs. Temperature, South Stick, 27.5 hr...... 159

CHAPTER 1: INTRODUCTION

Due to increased demand stemming from rising population, roadways and larger buildings in the United States have seen a rise in traffic. This has necessitated the design of bridges on these roadways and foundations of these buildings to be able to handle the higher traffic rates and the greater loads which accompany them. A thorough design of any structure incorporates the foundation. Therefore, it is vital that the foundations of these structures are of high quality and with as few imperfections to safely support the structure through its anticipated design lift. A well designed and constructed foundation will be economically efficient because it will allow the uninhibited used of its superstructure for years to come.

Drilled shafts have become a popular foundation choice by engineers because of their ability to sustain high loads compared to their relatively low construction cost.

Drilled shafts are large concrete foundations which are cylindrical in shape. To build them, a hole of typically three to six feet in diameter is drilled in the ground using an auger drill bit, and this hole is subsequently filled with concrete after a rebar cage has been placed in it. Since these shafts are constructed in the ground, the construction process does not allow for good inspection of the concrete placed. This can result in some situations in which the concrete does not consolidate, an air or water pocket forms in the concrete, a volume of soil falls into the shaft, or necking or bulging of the shaft occurs. All of these situations result in an imperfect shaft, and are referred to as “flaws” or “defects”. 13

To assess the state of concrete within the shafts, engineers use a variety of tests to determine their presence, size, and location. One new method involves using the heat of hydration of the concrete as it cures to identify defects. This method has shown promising results in its ability to determine the quality of the shaft at a relatively low cost.

The objectives of this study are the following:

• Develop a system to use DS18S20 sensors to thermally profile drilled shaft

foundations.

• Conduct laboratory and field tests to evaluate the reliability of these sensors

• Analyze laboratory and field data to determine the quality of the shafts in

which they were implemented.

• Conclude whether these sensors are a dependable tool to thermally profile

drilled shafts.

The outline of this study is as follows:

• Chapter 1 introduces drilled shaft foundations and objectives of this

research.

• Chapter 2 provides a literature review and evaluation of the current methods

and practices for assessing the quality of drilled shafts.

• Chapter 3 discusses heat generation and transfer during the concrete

hydration process

• Chapter 4 shows the methods and materials used in the laboratory and field

settings to thermally profile drilled shafts using the DTSs. 14

• Chapter 5 analyzes the results of the laboratory and field tests and discusses

the meaning of these results.

• Chapter 6 introduces and discusses methods tested to protect DTSs

• Chapter 7 draws conclusions about the results and provides

recommendations for future studies on the use of these sensors for this type

of testing.

CHAPTER 2: LITERATURE REVIEW

With the ever-growing need for bigger and taller infrastructure in America due to increased demand, deep foundations have become a popular solution to the heavier loads which accompany them. Drilled shafts, also known as drilled piers and caisson foundations, are a type of deep foundation that are frequently used to support buildings and bridges. A schematic of a drilled shaft can be seen in Figure 1. Since these buildings and bridges are becoming larger and heavier due to increased demand, more and larger shafts are required to support them. It is critical to the integrity of these structures that the foundation be sound so that failure does not occur. Therefore, it is important to monitor and gauge the soundness of the foundations themselves. This chapter will review and asses the many types of quality control methods that exist for drilled shaft foundations.

Figure 1. Drilled Shaft (Drilled Shaft Construction). 16

2.1. Quality Control of Drilled Shaft Foundations

There are several different types of tests which can be conducted on drilled shafts.

These include static, dynamic, and non-destructive tests. Non-destructive tests have

become popular, because they have minimal effects on the structural integrity of the shaft. Static and dynamic tests are expensive, complicated and time-consuming tests that

might not be able to identify problems within these structures. Therefore, to save time

and money, it is wise to use non-destructive tests to identify flaws so that they can be

corrected without causing total failure of the shaft.

2.2. Non-Destructive Tests on Drilled Shaft Foundations

There are many types of non-destructive tests (NDTs), also called non-destructive

evaluations (NDEs), which evaluate the integrity of drilled shafts. While these tests are

looking for imperfections in the foundations, nearly all use different methods and

approaches to yield their results. Many of these tests result in varying shaft

characterizations, making it difficult to compare. In the following sections, the most

popular NDTs for drilled shafts are listed and evaluated.

2.2.1. Sonic Echo Test

The sonic echo test (SET) was first used to test the integrity of driven precast

piles in the 1970s (Mullins, Johnson, & Winters, 2007). However, it has also been

applied to drilled shafts. In this test, a hammer is used to induce stress waves into the

shaft which are then read upon return by a geophone mounted on the surface of the shaft.

The geophone is connected to a computer which is equipped with a data collection

software. This set up can be seen in Figure 2. 17

Figure 2. Sonic Echo/Impulse Response Test (Olson Engineering, 2015).

The data is recorded as time of return of the reflected waves. The time of return of the wave is proportional to the depth of the reflection surface. According to Mullins et al. (2007), the waves are reflected when they encounter an anomaly or defect in the shaft, a change in cross section, or a change in soil stiffness along the shaft. In theory, if the depth to the toe of the shaft is known, then defects should be detectable by this method since reflections will occur above the depth of the toe.

The SET is the most economical of all integrity tests currently used on drilled shafts. However, there are some major drawbacks which prevent it from being frequently used. This method does not provide any information about the size of defects if they are detected. It only shows that a defect exists at a certain depth. It also does not provide any information about the horizontal location of the defect or anomaly. This test also 18

cannot detect any defects existing below another defect since the returning waves will not

be strong enough to be picked up by the geophone (Mullins et al., 2007). Also, it is

difficult to read any wave reflections within the upper 10 feet of the shaft. According to

Mullins et al. (2007), this is because the impact of the hammer produces Rayleigh waves

along with the compression waves. Another drawback is that changes in cross section

and changes in soil stiffness both cause waves to be reflected. However, a distinction

cannot be made between these waves and waves reflected from a defect. In addition,

defects located near the bottom of the shaft often go undetected since the reflection time

corresponds to that of the toe of the shaft. Finally, large length to diameter ratios can

cause dissipation of the waves into the surrounding soil, resulting in no wave returning

from the bottom. Therefore, any defect located beneath the point at which complete

wave attenuation occurs will remain undetected (Mullins et al., 2007). Because of these

disadvantages, Mullins et al. (2007) argues that the SET should be used exclusively for

precast piles because drilled shafts frequently show variations in cross section (as cited in

Finno & Prommer, 1994).

2.2.2. Impulse Response Method

The impulse response (IR) method is also known in literature as the transient

response and pile integrity test. There are some small variations between the equipment and results of this test and the sonic echo test, but the procedure used to conduct them is relatively the same. For the IR test the equipment used consists of a hammer, an accelerometer or geophone, and a processing unit (Rausche, 2004). The top of the shaft is struck with the hammer and the resulting waves are then gauged by the accelerometer 19

or geophone which then transmits them to the processing unit, usually a computer.

Massoudi & Teferra (2004) explained that a strain gauge is sometimes fitted to the head of the hammer so that the impact force can be found. The results are plotted as the velocity of the top of the shaft vs. time (Rausche, 2004). An experienced operator, knowing the length and diameter of the shaft, should be able to detect defects in the foundation from the shape of this curve. This method is very inexpensive and can detect large defects in the shaft. However, there are many weaknesses to the method. Rausche

(2004) explains that some test results are simply inconclusive, defects existing below larger defects are not detected, and no information about horizontal location of the flaws can be obtained from the test. Massoudi & Teffera (2004) added that the surface of the pile must be prepared before being struck by the hammer and the soil surrounding the shaft must not dampen the wave so much that they cannot be detected upon return. These papers agree that assumptions about the material properties of the shaft must be made.

This is done so that the wave speed can be computed and compared to the results. The papers disagree about the length to diameter ratio (L/D) requirements of the drilled shaft, however. Massoudi & Teffera (2004) state that the L/D should be less than 30 for accurate results, while Rausche (2004) asserts that the L/D needs to be 60 or less.

More recently, there have been attempts made to refine the impulse response method using new data interpretation techniques. One of the most popular ways of doing this is to filter the results using a Fourier transform. Shdid and Hajali (2015) showed that using a Fast Fourier Transform (FFT), which is an efficient Discrete Fourier Transform

(DFT), the locations and sizes of the anomalies are very accurately determined. 20

However, these results were obtained in a lab using very controlled conditions and scale

sized shafts. It is difficult to say whether this method could be useful in practice. Ni et al. (2011) used finite element modeling to estimate the size of flaws within a drilled shaft and their effects on its capacity. It was found in this study that the actual flaw sizes and

flaw sizes produced from the model differed by ±10% (Ni et al., 2011). Also, for the

model to run successfully, the length to diameter ratio of the shaft had to be between 10

and 30 (Ni et al., 2011). In this study, there were other factors which also needed to be

controlled so that the model could work properly. These were the soil layers surrounding

the shaft and their properties and the flaw size and location. In practice however, the flaw parameters would not be able to be controlled.

2.2.3. Cross-Hole Sonic Logging/Single-Hole Sonic Logging

The most common NDT is the cross-hole sonic logging (CSL) method.

Paikowsky, Chernauskas, Hart, Ealy, & DiMillio (2000) explained that in this test two opposing transducers are lowered to the bottom of the drilled shaft through access tubes installed prior to concrete pouring. Then a signal is sent from one transducer and picked up by the other. The transducers are then raised through the tubes at an equal rate.

Signals are sent between the two during the time they are being raised. The time between the signals being sent by one and picked up by the other is recorded. The travel velocity of the signal can then be found since the distance between the tubes is known. Therefore, defects are found if large variation in this signal velocity are found. This method can be

repeated for all tube arrangements in the shaft to give a better picture of the concrete

conditions. Figure 3 shows a typical test assembly. 21

Figure 3. Cross-Hole Sonic Logging (Paiksowsky et al., 2000).

Using this test, Rausche (2004) explained that there is no length or diameter

limitation as with the impulse response method. Also, defects can be found in real time

as the test is being performed. The greatest advantage of this test is that the dimensions

of the flaw in the shaft can be determined. This information can then be used to find the

actual shaft capacity.

While there are some benefits of using this method, disadvantages exist for this

test as well. Rausche (2004) and Paikowsky et al. (2000) expressed that the access tubes must be installed before the placement of concrete. Also, straight tube alignment in shafts in which there is no reinforcement cage is very difficult. Straight tube alignment is necessary because constant access tube spacing allows for constant signal travel time.

Any variation in distance between the access tubes could give false positive results of a 22

defect being present. These papers also state that only the areas between the tubes can be checked for defects. Therefore, if flaws exist on the outer walls of the piles, they will not be detected. Finally, debonding can occur between the concrete and the access tubes after a certain number of days (Paikowsky et al., 2000). This debonding results in the space between the concrete and tube being interpreted as a void by the test results.

Olson, Aouad, and Sack (1998) state that many government agencies require this test be performed within 10 days of concrete placement for PVC access tubes and within 45 days for steel access tubes.

The single-hole sonic logging (SHSL) method is very similar to the CSL method.

In this method described by Paikowsky et al. (2000), both transducers are lowered into the same hole and the CSL procedure is then followed. This test can only find flaws which are located directly next to the tube (Paikowsky et al., 2000). But, this test is less expensive that the CSL method because there are fewer tubes, and therefore, fewer tests.

Therefore, this test would be best suited for foundations with many redundant small diameter shafts in which only one or two access tubes have been installed.

2.2.4. Cross-Hole Tomography

Cross-hole tomography (CT) is a method which is generally used along with CSL.

Once the latter has found voids within this shaft, the CT method is then used to determine the exact dimensions of the defect or void. Instead of raising both transducers at the same rate as with the CSL, either the transmitter or receiver is kept stationary while the other is slowly raised from the bottom of the defect to the top (Mullins et al. 2007).

Doing this in different access tubes allows for a 3D model of the void to be generated 23

(Olson, 2003). Engineers can then determine whether the void needs to be corrected by coring and refilling with concrete.

2.2.5. Gamma-Gamma Logging

Gamma-gamma logging (GGL) is a method that is sometimes used to also gauge the soundness of the drilled shafts. This method is similar to that of the CSL and SHSL, but instead of using a pulse signal, radioactive material is used (Rausche, 2004). The radioactive material is cesium 137 (Robinson, 2012). This material emits radiation in the form of photons (Rausche, 2004). Some of these photons penetrate the surrounding concrete, while some are reflected back to the receiver. The number of photons that return are counted by a computer, and this data is translated to give the density of the concrete (Rausche, 2004). If the density is within range of the type of concrete used, then that section of the drilled shaft most likely does not have a flaw. However, if there are significant differences between signals, then an imperfection is most likely present. This method of quality control can only be used on one hole at a time. Therefore, the results are like those of the SHSL, in that only the concrete immediately surrounding the access tube can be verified. It is estimated that a radius of about 3 inches around the tube can be measured (Robinson, 2012). For this reason, this method is good for determining the quality of concrete around the rebar cage (Rausche, 2004). Another drawback of this test is that it requires the handling and storing of radioactive materials (Rausche, 2004). Also if gamma-gamma logging is the only verification test performed, then many access tubes are required to obtain accurate results (Robinson, 2012). Too many tubes in a single shaft can adversely affect the shaft’s capacity. Another disadvantage is that since the 24

probe houses radioactive material, it must be retrieved after the test is completed, which

can be difficult if the access tube is bent from concrete pouring (Robinson, 2012).

2.2.6. Thermal Integrity Profiling

Thermal integrity profiling (TIP) is another method which has been recently developed to monitor the quality of drilled shafts. In this method, access tubes are once again needed to be installed in the shaft before the pouring of the concrete. The number of tubes depends on the diameter of the shaft being analyzed. It is recommended that the same number of tubes be used for TIP as for CSL, which is about one tube for every one foot of shaft diameter spaced evenly about the reinforcement cage (Olson, Aouad, &

Sack, 1998). There are currently two methods to apply the TIP method. In the first

method, an infrared probe is then lowered into each of the tubes and measurements of the

surrounding concrete temperature are taken along the length of the shaft (Mullins &

Winters, 2011). Second, thermal wires are used to measure the temperature profile

(Robinson, 2012). Each of these sensors can be seen in Figures 4 and 5.

Figure 4. Infrared Probe (Mullins & Winters, 2011).

Figure 5. Thermal Wires (Robinson, 2012).

These wires have temperature sensors embedded along their length at a certain spacing, typically about one foot between each sensor. As the concrete hydrates and heats up, the readings are recorded by the sensors and interpreted by the operator or supervising engineer. An average temperature of the concrete should be available at this point. Mullins and Winters (2011) explained that if there are regions in the shaft which are significantly different from the average, then these indicate the presence of flaws.

Cooler regions suggest regions in which there is a lack of concrete, such as a reduction in diameter or void, while warmer regions are a sign of excess concrete, such as a bulge

(Mullins & Winters, 2011). An example of a lower temperature in a drilled shaft can be seen in Figure 6. This would indicate a void on the left side of the shaft. 26

Figure 6. Temperature Variation in a Drilled Shaft (Robinson, 2012).

An advantage of using this method is that the entire shaft can be examined.

Unlike the previous methods, the areas outside of the access tubes can also be studied. It is also easy to detect flaws because the temperature readings will show them in each tube, but they will be more obvious in the tubes which are located closer to the flaw itself

(Mullins & Winters, 2011). Even the alignment of the rebar cage can be determined. If two readings on opposing sides of the shaft are equally higher and lower than the average temperature, respectively, then it is likely that the rebar cage is shifted at that depth in the direction of the sensor with a lower temperature since the highest temperature in the shaft is at the center. An example of this is shown in Figure 7. 27

Figure 7. Rebar Cage Alignment (Robinson, 2012).

One problem with using the thermal probe, however, is the temperature readings

should be taken during the time that the maximum temperature of the concrete has been

reached. Ashlock and Fotouhi (2014) used the TIP and CSL methods in drilled shafts

and compared their results. It was found in this study that the minimum flaw size to be

detectable by TIP is 8% of the shaft’s cross-sectional area. They found that the CSL had better resolution overall, but they noted that the TIP test was conducted before the maximum concrete temperature had been reached. This was known because there were thermocouples within the shaft that were reading continually during all phases of testing

(Ashlock & Fotouhi, 2014). It is explained that fly ash and slag aggregates were used in the concrete mix for the shafts. It is known that these components slow down the rate of hydration of concrete. According to Mullins and Winters (2011), a drilled shaft should be tested with TIP between 20 to 24 hours after initial mixing of the concrete. This is based on a computer program called Heat Source Calculator (HSC). Once some basic 28

parameters of a concrete mix design are inputted, this program will give an optimal

testing window in which TIP should be conducted (Mullins & Winters, 2011). However,

the program does not account for hydration retarders or water reducers, so time must be

added to allow the concrete to reach its highest temperature if these are present in the mix

(Mullins & Winters, 2011).

Thermocouples can also be used to thermally profile drilled shafts.

Thermocouples are a common temperature sensor which take temperature readings near

the head of the sensor. They are each about the size of the head of a pin. Each

thermocouple requires one wire for each sensor. Also, each sensor requires one channel

of a data acquisition system for data collection. Some drilled shafts can be 90 feet or deeper, would could require hundreds of sensors to accurately thermally profiling.

Collecting data on hundreds of data acquisition channels could be a very cumbersome task. Therefore, using thermocouples to thermally profile drilled shafts would not be an attractive method to use.

All in all, when used individually, the sonic echo, impulse response, cross-hole tomographic, and gamma-gamma logging methods have many drawbacks, which outweigh the benefits because the results would be for local, isolated areas of the drilled shaft. The cross-hole sonic logging (CSL) test method is considered by many to be the most reliable NDE because it has been used for years and with success at determining flaws within shafts. However, thermal integrity profiling (TIP) has also shown to be a

reliable NDE and can even show other shaft characteristics such as rebar cage alignment 29

which the CSL method cannot. When used in conjunction, the CSL and TIP methods would provide the best results to gauge the integrity of a drilled shaft.

CHAPTER 3: HYDRATION OF CONCRETE AND HEAT TRANSFER

Thermal integrity profiling utilizes the heat generated by the hydration of curing concrete to produce readings which are analyzed and interpreted to determine the quality of the concrete within structures. The heat produced by the concrete comes from the concrete mix design, i.e., the amount of cementitious materials in each ingredient with respect to the total cementitious material in the mix (Mullins & Winters, 2011). The typical cementitious materials in concrete mixes are cement, fly ash, and slag. Although all produce heat while hydrating, they produce heat in different amounts and at different rates because of their varying chemical compositions. According to Schindler and

Folliard (2005), the total heat produced by a concrete mix is established by Equations 1

through 3.

= + 461 + (1)

𝑢𝑢 𝑐𝑐𝑐𝑐𝑐𝑐 𝑐𝑐𝑐𝑐𝑐𝑐 𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠 𝐹𝐹𝐹𝐹 𝐹𝐹𝐹𝐹 𝐻𝐻 𝐻𝐻 𝑝𝑝 𝑝𝑝 𝐻𝐻 𝑝𝑝

where Hu is the total heat produced by the system, is the heat produced by cement,

𝑐𝑐𝑐𝑐𝑐𝑐 is the heat produced by the fly ash, is the𝐻𝐻 percentage of cement by weight in the

𝐹𝐹𝐹𝐹 𝑐𝑐𝑐𝑐𝑐𝑐 mixture,𝐻𝐻 is the percentage of slag by𝑝𝑝 weight in the mixture, and is the

𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠 𝐹𝐹𝐹𝐹 percentage𝑝𝑝 by weight of fly ash in the mixture. The heat of slag hydratio𝑝𝑝 n is given

directly as 461 kJ/kg. The heat produced by cement and fly ash can be estimated by:

= 500 + 260 + 866 + 420 + 624 + 1186

𝑐𝑐𝑐𝑐𝑐𝑐 𝐶𝐶3𝑆𝑆 𝐶𝐶2𝑆𝑆 𝐶𝐶3𝐴𝐴 𝐶𝐶4𝐴𝐴𝐴𝐴 𝑆𝑆𝑆𝑆3 𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹 (2) 𝐻𝐻 𝑝𝑝 + 850 𝑝𝑝 𝑝𝑝 𝑝𝑝 𝑝𝑝 𝑝𝑝

𝑀𝑀𝑀𝑀𝑀𝑀 where , , ,𝑝𝑝 , , , are the percentages by weight of

𝐶𝐶3𝑆𝑆 𝐶𝐶2𝑆𝑆 𝐶𝐶3𝐴𝐴 𝐶𝐶4𝐴𝐴𝐴𝐴 𝑆𝑆𝑆𝑆3 𝐹𝐹𝐹𝐹 𝐹𝐹𝐹𝐹𝐹𝐹𝑠𝑠𝑆𝑆 𝑀𝑀𝑀𝑀𝑀𝑀 tricalcium𝑝𝑝 silicate,𝑝𝑝 𝑝𝑝 dicalcium𝑝𝑝 silicate,𝑝𝑝 𝑝𝑝 tricalcium𝑝𝑝 aluminate, tetracalcium aluminoferrite,

sulfuric annhydride, free lime, and magnesium oxide in the cement, respectively.

= 1800 (3)

𝐹𝐹𝐹𝐹 𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹 𝐻𝐻 𝑝𝑝

where is the percentage by weight of lime in the fly ash.

𝐹𝐹𝐹𝐹 𝐹𝐹𝑠𝑠𝑆𝑆 Accurate𝑝𝑝 information about the chemical constituents of the cement and fly ash used in

the mix are needed in Equations (2) and (3). These can usually be obtained from the

supplier of each of these materials.

After conducting many laboratory tests, Schindler and Folliard (2005) were able to fit a curve whose equation, shown in equation 4, described the rate of heat production in concrete with varying degrees of cementitious components by weight (Mullins &

Winters, 2011).

( ) = (4) 𝛽𝛽 𝑒𝑒 𝑢𝑢 𝜏𝜏 𝛼𝛼 𝑡𝑡 𝛼𝛼 𝑒𝑒𝑒𝑒𝑒𝑒 �− � 𝑒𝑒� � 𝑡𝑡 where is the degree of hydration at time te; and , , and are determined by

𝑢𝑢 Equations𝛼𝛼 5 through 7: 𝛼𝛼 𝛽𝛽 𝜏𝜏 32

1.031 / = + 0.5 + 0.3 1.0 (5) 0.194 + / 𝑤𝑤 𝑐𝑐𝑐𝑐 𝛼𝛼𝑢𝑢 𝑝𝑝𝐹𝐹𝐹𝐹 𝑝𝑝𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆 ≤ = . 181.4 . 𝑤𝑤 𝑐𝑐𝑐𝑐 . . ( 0.647 ) (6) 0 227 0 146 −0 535 0 558 𝐶𝐶3𝑆𝑆 𝐶𝐶3𝐴𝐴 𝑆𝑆𝑆𝑆3 𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆 𝛽𝛽 𝑝𝑝 ∙ 𝑝𝑝 ∙ 𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵 ∙ 𝑝𝑝 ∙ 𝑒𝑒𝑒𝑒𝑒𝑒 − 𝑝𝑝

= . 66.78 . . . −0 401 −0 154 −0 804 −0 758 (7) 𝐶𝐶3𝑆𝑆 𝐶𝐶3𝐴𝐴 𝑆𝑆𝑆𝑆3 𝜏𝜏 𝑝𝑝 ∙ (2𝑝𝑝.187 ∙+𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵9.5 𝐵𝐵 + ∙ 𝑝𝑝 )

𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆 𝐹𝐹𝐹𝐹 𝐹𝐹𝐹𝐹−𝐶𝐶𝐶𝐶𝐶𝐶 ∙ 𝑒𝑒𝑒𝑒𝑒𝑒 𝑝𝑝 𝑝𝑝 𝑝𝑝

where / is the ratio of water to cement in the concrete mix and is the surface 𝑤𝑤area𝑐𝑐𝑐𝑐 per unit volume of the cement. Cements with small individual𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵 particle sizes have higher surface areas than those with large particle sizes, which speeds hydration.

In general, the heat produced by the hydration of the concrete in the shaft is transmitted to the surrounding material. The subsurface conditions around the shaft have a great influence on the temperature of the shaft itself as it cures. Generally, more material in direct contact with the surface of the concrete allows more heat to flow from the shaft and into the soil, mostly through conductive heat flow. Simultaneously, however, more material requires more energy to transmit that heat because the extra

material needs more energy to be heated to the same temperature. Therefore, the two

mechanisms act in opposition to one another. The thermal conductivity of a soil,

shown in Equation 8, is the heat flow through a unit area A with a certain𝜆𝜆 temperature

gradient / (Mullins & Winters, 2011).

Δ𝑇𝑇 𝐿𝐿 33

= / (8) 𝑞𝑞 𝜆𝜆 Typical values for thermal conductivity𝐴𝐴 ∗ Δ of𝑇𝑇 subsurface𝐿𝐿 materials are presented below in Tables 1 and 2 below. Table 3 shows the thermal conductivities and specific heats of other common materials as a comparison to those in Tables 1 and 2.

Table 1. Density, Specific Heat, and Volumetric Heat Capacity of Common Soil Components at 20°C at 1 atm (van Wijk & de Vries, 1963) Volumetric heat Specific heat Soil component Density (Mg/m3) capacity (kJ/kg*K) (MJ/m3*K) Soil minerals 2.65 0.73 1.90 (average) Soil organic matter 1.30 1.90 2.50 (average) Water 1.00 4.18 4.18

Ice (0° C) 0.92 2.00 1.90

Air 0.0012 1.00 0.0012

Table 2. Thermal Conductivities of Soil Related Materials (T in °C) (Bristow, 2002) Material Thermal conductivity (W/m*K) Basalt 2.20 Granite 2.00 Quartz 8.80 Clay minerals 2.90 Organic matter 0.25 Water 0.552 + 2.34 x 10-3 T - 1.1 x 10-5 T2 Air 0.0237 + 0.000064 T Ice (0 ° C) 2.18 34

Table 3. Thermal Properties of Common Materials (Pauly, 2010) Material Thermal Conductivity (W/m*K) Specific Heat (MJ/kg*K) Dry Air 0.024 0.775 Saturated Air 0.100 0.940 Wood, Pine 0.147 0.240 Fresh Water 0.600 4.180 Salt Water 0.800 3.850 PVC Plastic 1.040 1.340 Concrete (w=44%) 1.900 0.850 Concrete (w=40%) 2.000 0.900 Concrete (w=36%) 2.300 1.100 Steel 14 0.470 Aluminum 250 0.900 Silver 429 0.233

Tables 3 shows a comparison between the thermal conductivities of concrete and air, both dry and saturated. Generally, concrete has a thermal conductivity around 2.000

W/m*K while air has a much lower thermal conductivity between 0.024 and 0.100

W/m*K. This means that concrete conducts heat between 20 and 83 times better than air.

Therefore, an air pocket within a concrete matrix greatly reduces the thermal conductivity of the concrete matrix in the area of the air pocket.

Most often, soils in the field are either partially or fully saturated. To compensate for this, the amount of water in the soil must be accounted for. 35

= (9) 1−𝑛𝑛 𝑛𝑛 𝑠𝑠𝑠𝑠𝑠𝑠 𝑠𝑠 𝑑𝑑 where is the thermal conductivity𝜆𝜆 of soil𝜆𝜆 when𝜆𝜆 saturated, is the thermal

𝑠𝑠𝑠𝑠𝑠𝑠 𝑠𝑠 conductivity𝜆𝜆 of the soil at its natural water content, is the thermal𝜆𝜆 conductivity of the

𝑑𝑑 dry soil, and is the volumetric fraction of water in𝜆𝜆 the soil.

Soil often𝑛𝑛 contains other foreign soil particles in it, such as clay being contaminated with sand. Equation 10 represents the thermal conductivity of a soil contaminated by a secondary soil.

= (10) 𝑞𝑞 1−𝑞𝑞 𝑠𝑠 𝑞𝑞 𝑜𝑜 𝜆𝜆 𝜆𝜆 𝜆𝜆

where is the fraction of secondary soil, is the thermal conductivity of the main soil,

𝑞𝑞 and 𝑞𝑞is the thermal conductivity of the secondary𝜆𝜆 soil.

𝑜𝑜 𝜆𝜆 Thermal conductivity is simply the ability of a soil to transfer heat. While the soil

transfers heat, it also resists being heated. This property, known as heat capacity, is the

energy required to heat a unit volume of the soil by one-degree.

= (11)

𝐶𝐶 𝜌𝜌 ∗ 𝑐𝑐

where is the density of the soil, and is the mass specific heat.

𝜌𝜌 𝑐𝑐 36

Since most soil materials are composed of soil, water, and air, the effective heat capacity of a soil is estimated as the volumetric fraction, of each and its heat capacity,

𝑖𝑖 . 𝑋𝑋

𝑖𝑖 𝐶𝐶 = + + (12)

𝑆𝑆 𝑆𝑆 𝑊𝑊 𝑊𝑊 𝐴𝐴 𝐴𝐴 𝐶𝐶 𝑋𝑋 𝐶𝐶 𝑋𝑋 𝐶𝐶 𝑋𝑋 𝐶𝐶

Thermal conductivity and heat capacity are two properties of a soil which seemingly act against one another. Combining these features results in a parameter called soil diffusivity, , which is the ratio of thermal conductivity to heat capacity.

𝑘𝑘

= (13) 𝜆𝜆 𝑘𝑘 𝐶𝐶

This term describes the ease at which heat can transfer from the hydrating shaft to the surrounding soil. The thermal conductivity, heat capacity, and diffusivity of the soil can be determined from boring logs, and the density of the soil can be found from the blow count (N60) of the SPT test (Pauly, 2010).

In general, soils distribute heat according to the governing equation for heat transfer in three dimensions.

= + + + 2 2 2 (14) 𝜕𝜕𝜕𝜕 𝑄𝑄 𝜕𝜕 𝑇𝑇 𝜕𝜕 𝑇𝑇 𝜕𝜕 𝑇𝑇 𝑘𝑘 � 2 2 2 � 𝜕𝜕𝜕𝜕 𝐶𝐶 𝜕𝜕𝑥𝑥 𝜕𝜕𝑦𝑦 𝜕𝜕𝑧𝑧 37

where is temperature, is time, is added heat from a source such as hydrating concrete,𝑇𝑇 C is the heat capacity𝑡𝑡 of 𝑄𝑄the soil, and k is the diffusivity of the soil. Equation 14 shows that the change in temperature of a soil with respect to time is proportional to the product of the diffusivity and the second derivative of temperature with respect to distance in the spatial directions, x, y, and z (Mullins and Winters, 2011).

The information and equations presented in this chapter provide an overview into

the processes and workings of models used to predict the heat produced within a shaft

during the curing process. Optimal times for thermal integrity testing can be determined

from these equations with information about the mix design, geometry of the shaft, and

subsurface materials. The results of this model can be compared with field data to gauge

the accuracy of the readings in the field with respect to the theoretical results.

The most important aspect of this chapter in relation to the remainder of this

thesis is the differences of the thermal properties between concrete and air. Concrete has a value of thermal conductivity which is comparable to those of some rocks, which is low. However, air has a very low value of density and thermal conductivity. This means that air conducts heat far less effectively than concrete. Therefore, when air and concrete are combined into one matrix, the concrete will dominate the heat transfer in the material.

An area of air will exhibit a much lower temperature than the surrounding concrete due to its thermal properties. Thus, air voids as small as three to four inches in diameter within a concrete matrix should be able to be detected with accurate temperature sensors.

CHAPTER 4: METHODOLOGY

This research consisted of three parts; laboratory testing, field testing, and

computer modeling. Computer modeling was conducted for both the laboratory portion

and field portion of this research. Each phase of testing was compared to the model to

verify the results. The following chapter discusses the details of each phase of the

materials and methods used during the research.

4.1. Digital Temperature Sensor

The Digital Temperature Sensor (DTS), also known as a DS18S20 sensor, is a temperature sensor which is about the size of the head of a pin and has an accuracy of

±0.5°C over the range of -10°C to 85°C (Maxim Integrated, 2015). A DS18S20 sensor can be seen in Figure 8. It was chosen for use in this research for a few reasons. First, any number of these sensors can be connected on a one wire bus, eliminating the need for each individual temperature sensor to be connected to its own wire. This saves the complication of having many wires connected to a data acquisition system in the laboratory or in the field. Secondly, the sensors are easy to use and a compatible with an

Arduino board. An Arduino board is a cheap, programmable device on which a user can upload software to perform a specific task. In this case, the Arduino board was programmed to read temperature data from the DTSs at a set interval. And lastly, the sensors are very inexpensive. All the materials used in relation to the DTSs cost less than

$200 to obtain at the time of this research. 39

Figure 8. DS18S20 Sensor.

4.2. Laboratory Testing

The laboratory testing was conducted in Stocker Center. Two tests were run about three weeks apart due to a malfunction in the data acquisition system during the first test. DTSs and thermocouples were used to collect the temperature at planned points within the Quik-Tube form. Quik-Tube forms are often used in residential deck construction as a foundation for vertical posts. They are cylindrical tubes composed of a stiff cardboard material. They were used in this experiment because of their geometry, affordability, and availability. The shape of the forms closely matches the shape of typical drilled shafts.

Thermocouples were used in this experiment because they are an established and reliable tool for reading temperature data. Their readings were compared with the readings of the DTSs to verify that the readings of the DTSs were accurate.

The DTSs were spaced evenly at six-inch intervals from the top to the bottom of the Quik-Tube form in PVC pipes. The sensors were mounted into holes drilled into the

PVC pipes and strung together with ribbon cable. The sting of sensors mounted in a PVC pipe were named “sensor stick”. The sensors sticks can be seen below in Figures 10 and

13. 40

Another aspect of the laboratory experiment was the introduction of artificial

voids into the Quik-Tube forms. This was done to determine if the readings of the

sensors in an ideal form differed from those in a form in which there were known voids present. The artificial voids were constructed of Styrofoam since it has a very low thermal conductivity, similar to that of air. Styrofoam spheres were two and three inches in diameter. The spheres were placed at various locations within one of the forms near the sensors and their locations were recorded.

The following two sections detail the processes of building the sensors for testing and the lab procedure followed to obtain the results for the laboratory portion of this research.

4.2.1 Laboratory Test 1

For the first test, two Quik-Tube forms were used to simulate the conditions of a drilled shaft. These Quik-Tube forms are shown in Figure 9. These tubes were 4’ in height with 1’ diameter. In Figure 9 it is shown that one of the tubes fits inside of the other. This is for ease of shipping and handling for the manufacturer. Therefore, one of the tubes has a slightly reduced diameter. 41

Figure 9. Sonotube.

The sensor sticks were constructed using two 5’ lengths by ¾” diameter PVC pipe, ribbon cable, and the DTSs. These pipes were sawed in half along their length using a band saw, resulting in four semicircular pieces of pipe. Each of the four halves were numbered; 6 and 7 for the white halves and 8 and 9 for the gray halves. These pieces were then marked off at one-foot intervals from the bottom and the marks were drilled using a drill. This is demonstrated in Figures 10 and 11. After the initial markings were completed, it was decided that the spacing of the sensors should be at 6” interval to give a better thermal profile of the Quik-Tube forms. After this step was completed, the DTSs were placed in the holes, one per hole. A ribbon cable was fitted 42

with connecting devices which allowed for connection between the cable and pins of the sensors simply by inserting the pins into the holes of the connectors, shown in Figure 8.

Figure 10. Marking Pipe at 1’ Intervals.

Figure 11. Drilling Holes in Pipe.

Figure 12. DTSs and Ribbon Cable with Connectors.

After the sensor heads were inserted into the holes, the pins of the sensors were bent and inserted into the connecting devices. Then each DTS was superglued into place using Kyowa CC-33A strain gage cement. Once this was completed, the line of sensors was connected to an Arduino board which was in turn connected to a computer with the

Arduino program installed. An Arduino board is a widely available and inexpensive computer system which can be customized and programmed to perform a variety of tasks.

In this case, the Arduino board was programmed to collect the temperature data from the

DTS at five-minute intervals. This program continually took readings from the sensors.

Each sensor was factory coded with its own serial number which was displayed in the program along with its temperature reading. The order of the sensors in the stick was recorded by warming them one at a time and reading the change in temperature on the program. The position of each sensor was recorded. Once all the sensors had been read, each sensor was covered with Dow Corning 748 non-corrosive sealant. This silicone material is designed specifically to protect electronic equipment and can be used from

-67° F to 350° F and is shown in Figure 13. After all the sensors had been coated, the silicone was allowed to cure for 24 hours, as illustrated in Figure 14. 45

Figure 13. Coating Sensors with Dow Corning 748 Non-Corrosive Sealant.

After the silicone had cured, the cable was again connected to a computer to test if the sensors were functioning properly. After good operation of the sensors was confirmed, the end of the cable which corresponded to the top of the sonotube was trimmed and soldered to another length of wire to add length and was then connected to the Arduino board. The Arduino board was connected to a battery, and the system was allowed to collect data overnight. While this experiment was in progress, six

thermocouple wires were employed. These thermocouples were attached to two 5’ #2

reinforcement steel, with three thermocouples for each piece of the rebar. One

thermocouple was placed at 6” from the top of the sonotube, one at the middle, and the

last 6” from the bottom. The thermocouples were attached to the rebar with duct tape. 46

Figure 14. Sensors Connected to Arduino Board.

To construct the artificial voids, a long sheet of styrofoam was cut into 2” and 3” squares. Three of these squares were stacked and glued atop of one another, forming styrofoam cubes, shown in Figure 15. A weight was placed on top of all of these cubes and the glue was allowed to cure overnight. Once this was completed, the edges of the cubes were cut off to form spheres. The spheres were attached to sensor sticks 8 and 9 at different heights to simulate voids that could form during construction. On sensor 8, a 2” sphere was installed on the sensor 1’ from the bottom, a 3” sphere 2’ from the bottom, and another 2” sphere 1’ from the top. On sensor 9, a 2” sphere was installed 1.5’ from the bottom, and a 3” sphere 6” from the top. No styrofoam spheres were attached to sensor sticks 6 or 7. The spheres were attached to the sticks using duct tape. 47

Once the artificial voids were attached to the sensor sticks, the sticks were attached directly to the sides of the sonotubes using duct tape. When these were secured, the reinforcement bars with the attached thermocouples were inserted into the middle of the sonotubes and secured with duct tape. The entire assembly is shown in Figure 16.

Figure 15. Forming Artificial Voids.

Figure 16. Laboratory Test Assembly.

With the assembly ready for testing, the DTSs were connected to the Arduino board with an SD card recording all data at five-minute intervals. Also, the thermocouples were connected to a Campbell Scientific CR7 data acquisition system which was collecting data every two minutes. To fill the tubes, a 0.25 yd3 motorized mechanical concrete mixer was used during mixing. The mix design used was as shown in Table 4. Once this batch was mixed, the concrete was placed into the first Quik-Tube form by hand using scoops. After every 6” in height achieved within the tube, the concrete was vibrated four times around the perimeter. This process continued until both

Quik-Tube forms were filled and then the top of the concrete was finished. The sensors were allowed to collect data for 24 hours. Leftover concrete was used to make three 6 x

12 cylinders instrumented with one thermocouple each. Two cylinders contained a 2” void and the other contained no void. 49

Table 4. Laboratory Concrete Mix Design Ingredient Design Weights Batch Weights

Coarse Aggregate 1595 lb/yd3 502.4 lb

Fine Aggregate 1260 lb/yd3 396.9 lb

Cement 510 lb/yd3 160.7 lb

Fly Ash (Class C) 90 lb/yd3 29 lb

Water Reducer 12 oz/lbd 23 oz

Water (w/c) 0.25 48 lb

When attempting to collect data from the DTSs, it became apparent that no data had been recorded onto the SD card. Therefore, this test had to be repeated.

4.2.2. Test 2

Many of the same materials and procedures using for Test 1 were also used and followed in Test 2. There were a few exceptions, however. Due to the lack of time, no artificial voids were installed in either Quik-Tube forms during this test. Another change was that instead of attaching the sensor sticks directly to the very edges of the Quik-Tube forms, wooden spacers were installed between them and the walls of the tube to simulate attachment to a rebar cage in a field situation, as shown in Figures 17 and 18 below.

Also, since no data was able to be collected during the first test, the terminal blocks on the Arudino board were changed for another set. This was due to the suspicion that the issue was due to the connection of the wires to the board because the sensors were 50

properly working when connected to the computer. A final change was that the thermocouples were attached directly to the sensor sticks instead of to a piece of rebar that ran through the middle of the tube, which is illustrated in Figure 18. This allowed to the local temperature around each of the sensors to be the same so that more correlation could be drawn between the readings of the thermocouples and the DTSs. The same mix design and procedure was used to mix and place the concrete in the Quik-Tube forms as in Test 1.

Figure 17. Spacers Attached to Sensor Sticks. 51

Figure 18. Sensor Sticks with Spacers and Thermocouples in Sonotube.

4.3 Field Testing

A field test was conducted on S.R. 139 at mile marker 3.15 outside of Jackson,

Ohio. This was done near a culvert where the ditch running into it along the road was deep and washing away the side of the roadway. Therefore, ODOT decided to install a drilled shaft soldier pile wall with guardrail lagging and asphalt milling backfill to reinforce the roadway. Along this test section, there were a total of 12 shafts to be installed, each being 2’ in diameter and 15’ in depth. A rock auger mounted on an excavator was used to dig the shafts, and an excavator mounted with a bucket was used to lift the W16 x 31 sections and set them in the open shafts. After ensuring the steel sections were plumb in both directions, guardrail lagging was welded to them. A total of 52

six guardrail lifts were necessary to achieve the height necessary to backfill to the height of the roadway. Starting from the bottom, the lowest section of guardrail was welded to the beams. Next, the lower portion of the next highest section was hammed over the upper portion of the lower section. This new section was then welded both to the lower section along with the steel beam. After the guardrail lagging had been completed, concrete was poured by freefall into the open shafts. The mix design used for these shafts was ODOT’s QC1 standard mix, which is available in the ODOT 2016

Construction and Material Specifications. Then after all concrete had been poured, haul trucks dumped recycled asphalt millings between the guardrail and the excavated wall on the shoulder of the roadway. Finally, the additional lengths of the beams extending above the top of the lagging wall were cut using an acetylene torch.

Table 5. ODOT Class QC1 Concrete Requirements Cementitious Permeability Air Design Content Aggregate Maximum Content Strength (psi) Minimum Requirements (Coulombs) (%) (lbs/cy)

4,000 at 28 2,000 520 Well-Graded 6±2 days

The sensors used for this test were constructed of the same material and in the same manner in which those for Test 2 in the lab were made. The only exception in this 53

case is that these sensors were 10’ in length as opposed to 4’ in the lab. The construction of the sensor sticks is shown below in Figure 19. They are displayed fully assembled with attached thermocouples in Figure 20.

Figure 19. Construction of Sensors for Field Test.

Figure 20. Fully Constructed Field Sensors.

Typically for drilled shafts, there is a rebar cage which surrounds the outer perimeter with about 2-3” of cover for protection. This rebar gives extra axial capacity to the shaft, but is mainly present to add flexural capacity since concrete is weak in tension.

Sensors could then easily be tied to the rebar cage with tie wire or zip ties to keep them in place during the concrete pour. However, the drilled shafts on this project used W16 x 31 steel beams to add flexural strength, so a different method had to be used to anchor these sensors to the beams. A swiveling I-beam clamp for pipe and conduit was used to fix the sensors to the beam, which is shown in Figure 21. A total of five of these clamps were used on each sensor stick to ensure proper security to the beam during pouring.

In the field, the beam to be instrumented were on site lying flat on the ground with the web of the beam running parallel to the ground surface. Figure 22 shows that

the first sensor stick was attached to the flange of the beam such that the sensor stick 55

would reside between the two flanges. The sensor was placed one foot from the end of the bottom of the beam to be placed at the bottom of the shaft. Once the first sensor stick was fastened, the beam was lifted with the excavator so that the second sensor stick could be fixed to the opposite side and flange. The sensors were turned facing outwards from the beam. Ideal readings would be taken such that the sensors would be facing the outer walls of the shaft and be mounted on the outside of the beams. However, this could not be done in this case since the diameter of the shafts was 2’ and the height of the beams was nearly 1.5’. The machinery on site that was used to lower the beams into the shafts did not provide enough fine motor control to avoid contact with the surrounding shaft, meaning the sensors would have made hard contact with the wall during this process.

This is the reason for the locations of the sensors on the beams.

Figure 21. I-Beam Clamp Fastened to Beam. 56

Figure 22. Sensor Stick Attached to Beam.

With the sensors securely attached to the beam, the beam was lifted and placed into the shaft, as shown in Figure 23. Once in the shaft, the beam was plumbed and guardrail was welded, as presented in Figures 24 and 25, respectively. Figure 26 shows a view of the sensors on the beam in the hole.

Figure 23. Lifting of Beam.

Figure 24. Plumbing of Beam. 58

Figure 25. Welding of Guardrail Lagging.

Figure 26. Sensor Sticks in Shaft. 59

Figure 27. Pouring Concrete into Shaft.

Figure 28. Completed Shaft. 60

Figure 29. Data Acquisition Systems.

Figure 30. Burned Wires. 61

When the above steps had been completed, concrete was poured directly down

shaft by free fall, shown in Figure 27. Figure 28 shows the finished shaft. Once the

thermocouples were confirmed to be properly reading and data collection had started, the

Campbell Scientific CR7 was connected to a large battery to provide enough power for

days. Also, the Arduino board was connected to an external battery to also provide

additional power for more days of data acquisition. The batteries and Arduino board

were placed in Campbell Scientific field boxes and shut tightly. Figure 28 presents the

way the boxes were stacked near the edge of the excavation near the instrumented shaft.

A problem did arise during the cutting of the beam. Some of the hot slag fell onto

the wires during this time and ignited them, which is shown in Figure 30. Upon return to the site, the status of the thermocouples was checked again. Since they were in working order, the burned wire was covered with heavy duty duct tape and fastened to the side of the beam to protect from possible rainfall. The data acquisition systems were then allowed to collect data for four days.

4.4. Computer Modeling

Thermal modeling of the heat of hydration of the concrete from the laboratory and field tests was performed using the equations discussed in Chapter 3. This modeling was done using a Microsoft Excel spreadsheet created by Ballim and Graham (2004). In this spreadsheet, parameters can be inputted such as the concrete mixture, structure geometry, concrete casting temperature, type of formwork, and environmental high and low temperatures during curing. The model uses a forward finite difference temperature model to predict the concrete hydration temperature in structures with a much larger z 62

dimension than its x and y dimensions, such as in drilled shafts (Ballim and Graham,

2004). The model is based on Equation 14 presented in Chapter 3. Equations 1 though 7

are incorporated into the model through various parameter inputs on the program’s main

page. However, Equations 8 through 13 are not integrated into the model. This is a

drawback of this model since the subsurface conditions have an influence on the

hydration of the concrete. Therefore, the model may not accurately predict the

experimental temperature. However, the general trend of the model should be similar to

the experimental trend. Also, the laboratory test used the Quik-Tube form as the

formwork with no soil surrounding it. This model did not allow for the selection of a

formwork type similar to the Quik-Tube form, so “Timber” was selected as the formwork. According to Ballim and Graham (2004), the model assumes the concrete is cast into bedrock and is open to the air on its top surface. This closely follows the field conditions in this research, except that the model assumes there is either timber or steel formwork surrounding the structure and not soil or rock.

The input and output pages of the model used in this research are shown in

Figures 31 and 32, respectively. The mix designs used in the laboratory and field experiments were modeled separately, using the parameters closest to that of ODOT standard 4000 psi bridge mix for the laboratory test and QC1 standard mix for the field test. Once the parameters were inputted into the program, the installed macro was run, and the output page appeared as shown in Figure 32. The time interval from each iteration are shown at the top of each individual table. The time interval was set to every

0.5 hours, and the total time of computation was set to 30 hours for both the laboratory 63

and field test so that many data points could be generated. The depth of the structure is shown on the leftmost column, and the radius of the structure is shown in the column just above the yellow tables. The radii selected for plotting were 0.20 m for the laboratory test and 0.40 m for the field test, which closely corresponded to the locations of the DTSs for each test.

CONCRETE DETAILS

80% CEM I + 20% FA Limestone

Binder Content 302.5 kg/m3 STRUCTURE AND ANALYSIS DETAILS Sand Content 747 kg/m3 Horizontal (x) Dimension of Structure 0.61 m Stone Content 946.3 kg/m3 Vertical (y) Dimension of Structure 4.572 m Water Content 75.64 kg/m3 Space interval (δx= δy= ∆ ) for Analysis 0.2 m Admixture Content 0.85 kg/m3 Time interval for Analysis 0.5 hours Time Duration of Analysis 28s hour CONSTRUCTION DETAILS Concrete Casting Time 10 Clock time (hh) Concrete Casting Temperature 18 oC Formwork Type TimberTimber Concrete age at Formwork removal 72 hours Maximum Day Temperature 25 oC Minimum Day Temperature 10 oC After entering the required data and selections, press "Ctrl + h" to run the model This temperature model is intended for use as a preliminary design tool. Please refer to Research Monograph 8: "A numerical model for UNIVERSITY OF THE predicting early age time- WITWATERSRAND - School of Civil & temperature profiles in large Environmental Engineering concrete structures" by Y Ballim Concrete Temperature Prediction and PC Graham Model: May 2005 for guidance on the use of the model Figure 31. Model Program Input Page (Ballim and Graham, 2004). 64

SECTION DETA ILS Casting (clock) Time= 10.00 hrs k = 3.1 W/m.K x= 0.6096 m Start Temp= 18.0 ºC Cp = 1021 J/kg.K y= 4.572 m Age at formw ork removal = 72 hrs Density = 2072.27 kg/m3 dx= 0.2 m 4.048 Nodes in the x direction Binder Content = 302.5 kg/m3 dy= 0.2 m 23.86 Nodes in the y direction h(min)= 5 W/m2.C h(max)= Number of time cycles = 60 Time interval = 0.5 hrs h = 5 UNIVERSITY OF THE WITWATERSRAND; School of Civil & Environmental Engineering Temperatu t = 0.00 hrs m 0.00 0.20 0.40 0.60 0.00 18.0 18.0 18.0 18.0 0.20 18.0 18.0 18.0 18.0 0.40 18.0 18.0 18.0 18.0 0.60 18.0 18.0 18.0 18.0 0.80 18.0 18.0 18.0 18.0 1.00 18.0 18.0 18.0 18.0 1.20 18.0 18.0 18.0 18.0 1.40 18.0 18.0 18.0 18.0 1.60 18.0 18.0 18.0 18.0 1.80 18.0 18.0 18.0 18.0 2.00 18.0 18.0 18.0 18.0 2.20 18.0 18.0 18.0 18.0 2.40 18.0 18.0 18.0 18.0 2.60 18.0 18.0 18.0 18.0 2.80 18.0 18.0 18.0 18.0 3.00 18.0 18.0 18.0 18.0 3.20 18.0 18.0 18.0 18.0 3.40 18.0 18.0 18.0 18.0 3.60 18.0 18.0 18.0 18.0 3.80 18.0 18.0 18.0 18.0 4.00 18.0 18.0 18.0 18.0 4.20 18.0 18.0 18.0 18.0 4.40 18.0 18.0 18.0 18.0 t = 0.50 hrs m 0.00 0.20 0.40 0.60 0.00 19.2 18.6 18.6 19.2 0.20 18.2 18.1 18.1 18.2 0.40 18.2 18.1 18.1 18.2 0.60 18.2 18.1 18.1 18.2 0.80 18.2 18.1 18.1 18.2 1.00 18.2 18.1 18.1 18.2 1.20 18.2 18.1 18.1 18.2 1.40 18.2 18.1 18.1 18.2 1.60 18.2 18.1 18.1 18.2 1.80 18.2 18.1 18.1 18.2 2.00 18.2 18.1 18.1 18.2 2.20 18.2 18.1 18.1 18.2 2.40 18.2 18.1 18.1 18.2 2.60 18.2 18.1 18.1 18.2 2.80 18.2 18.1 18.1 18.2 3.00 18.2 18.1 18.1 18.2 3.20 18.2 18.1 18.1 18.2 3.40 18.2 18.1 18.1 18.2 3.60 18.2 18.1 18.1 18.2 3.80 18.2 18.1 18.1 18.2 4.00 18.2 18.1 18.1 18.2 4.20 18.2 18.1 18.1 18.2 4.40 18.3 18.1 18.1 18.3 Figure 32. Model Program Output (Ballim and Graham, 2004).

CHAPTER 5: RESULTS AND DISCUSSION

The following chapter analyzes and discusses the results collected from the

laboratory and field tests. Graphs of temperature versus time for each DTS were plotted

with all thermocouples in each Quik-Tube form or drilled shaft. Also presented are graphs of the temperature profiles of the shaft at specific times during the hydration process. These graphs show the data collected from the DTSs along with the thermocouples. Also shown are the computer model results compared with the laboratory and field tests.

5.1. Laboratory Testing

As discussed in Chapter 4, there were two laboratory tests conducted for this experiment. Unfortunately, data was only able to be collected for one experiment.

Therefore, Test 1 is omitted in this chapter. The following section contains the results of

Test 2 and a discussion of these results.

5.1.1. Laboratory Test 2

For laboratory test 2, the results were first plotted as temperature versus time and depth versus temperature. Time was zeroed just before the concrete was poured into the

Quik-Tube forms. Consequently, an initial sudden in rise in temperature can slightly be seen from the thermocouple curves. The temperature after this point is the initial mixing and pouring temperature of the concrete, which was approximately 24.5° C, or 76.1° F.

The maximum temperature recorded in the middle of the Quik-Tube form by the DTS on

Stick 1 was 32.31° C 12.5 hours after pouring. The temperature recorded by the thermocouple at this same point in the concrete at this time was 36.19° C. This is a 66

difference of 11.38%. From the specification sheet of the DTSs, it is known that while

operating within -10° C to +85° C, the sensors are accurate to within ±0.5° C (Maxim

Integrated, 2015). Type T thermocouples, which were used in this experiment, are

accurate to ±1.0° C or ±0.75% of the reading, whichever is greater (Omega, 2017). But

even with these error compensations, the readings still to not fall within each other’s

ranges. However, the thermocouples were attached close the edge of the sticks, but some length was left and pointed to the middle. Therefore, the thermocouples were about an inch closer to the center of the Quik-Tube form than the DTSs. Figure 33 below shows

the plot of temperature versus time for the sensor directly in the center of sensor stick 1.

Figure 34 shows the same plot for the sensor at the center on sensor stick 2. These

figures also show the temperature predictions of the finite difference model. These

figures show that the DTSs on opposing sides of the form gave similar results of their

temperature readings. Also, the trend of the model and the sensor data is similar.

However, the model predicts a temperature well above the maximum temperature read by

the sensors and the thermocouples. The model, however, predicts temperatures based

upon drilled shaft underground. This shows that there may have been factors such as a

temperature controlled room that may have influenced the temperature of the concrete as

it cured, resulting in a lower overall temperature. Tables 2 and 3 below show a small

sample of the data corresponding to Figures 31 and 32, respectively. The readings from

stick 2 of -127.00° C are highlighted in purple and were omitted from all figures. These

incorrect readings occurred at times when the sensors malfunctioned.

35 C) ° 30

25 Temperature Temperature (

15 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 33:36 36:00 Time (hours)

DS18S20 Model Top Thermocouple 1 Mid Thermcouple 1 Bottom Thermocouple 1

Figure 33. Temperature vs. Time, Stick 1, Depth of 2'.

35 C) ° 30

25 Temperature Temperature (

15 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 33:36 36:00 Time (hours)

Model DS18S20 Top Thermocouple 1 Mid Thermcouple 1 Bottom Thermocouple 1

Figure 34. Temperature vs. Time, Stick 2, Depth of 2’.

Table 6. DTS Readings, Laboratory Test, Stick 1 (°C) Depth (ft) Time 0 0.5 1 1.5 2 2.5 3 3.5 4 0:00 20.75 21.06 21.31 21.75 21.87 21.81 21.81 21.87 21.81 2:29 20.44 21.94 22.31 22.37 22.44 22.44 22.50 22.50 22.12 2:34 20.44 22.00 22.37 22.37 22.44 22.44 22.50 22.56 22.12 2:39 20.50 22.00 22.44 22.44 22.44 22.50 22.56 22.56 22.19 2:44 20.44 22.06 22.44 22.44 22.50 22.50 22.56 22.62 22.19 2:49 20.44 22.06 22.50 22.50 22.56 22.56 22.62 22.69 22.19 2:54 20.44 22.12 22.56 22.56 22.56 22.62 22.62 22.69 22.25 2:59 20.50 22.12 22.56 22.62 22.62 22.69 22.75 22.75 22.25 3:04 20.50 22.19 22.62 22.69 22.69 22.69 22.75 22.75 22.31 5:29 21.56 24.31 25.19 25.19 25.19 25.19 25.25 25.19 24.00 7:33 22.81 26.69 28.00 28.12 28.12 28.06 28.12 27.87 26.12 7:58 23.00 27.12 28.62 28.75 28.69 28.69 28.69 28.31 26.50 8:03 23.12 27.25 28.75 28.87 28.81 28.81 28.81 28.44 26.56 8:08 23.12 27.31 28.81 29.00 28.94 28.94 28.94 28.56 26.69 8:13 23.19 27.44 28.94 29.12 29.06 29.00 29.06 28.69 26.75 8:18 23.25 27.50 29.06 29.19 29.19 29.19 29.19 28.75 26.81 8:23 23.31 27.62 29.19 29.31 29.31 29.25 29.31 28.87 26.87 8:28 23.37 27.69 29.31 29.44 29.44 29.37 29.44 29.00 26.94 8:33 23.44 27.81 29.37 29.56 29.56 29.50 29.50 29.06 27.06 8:38 23.56 27.87 29.50 29.69 29.69 29.62 29.62 29.19 27.12 8:43 23.56 27.94 29.62 29.81 29.81 29.69 29.75 29.25 27.19 8:48 23.62 28.06 29.75 29.87 29.87 29.81 29.81 29.37 27.25 8:53 23.69 28.12 29.81 30.00 30.00 29.94 29.94 29.50 27.37 8:58 23.75 28.25 29.94 30.12 30.12 30.06 30.06 29.56 27.44 9:03 23.75 28.31 30.06 30.25 30.25 30.19 30.19 29.69 27.50 9:08 23.81 28.37 30.12 30.37 30.31 30.25 30.25 29.75 27.56 9:13 23.87 28.44 30.25 30.44 30.44 30.37 30.37 29.81 27.69 9:18 23.94 28.56 30.31 30.56 30.56 30.50 30.50 29.94 27.75 9:23 23.94 28.62 30.44 30.69 30.62 30.56 30.56 30.06 27.81 9:28 24.00 28.69 30.50 30.75 30.75 30.69 30.69 30.12 27.87 9:33 24.06 28.81 30.62 30.87 30.81 30.75 30.75 30.19 27.94 9:38 24.06 28.87 30.75 30.94 30.94 30.87 30.87 30.25 28.00

Table 7. DTS Readings, Laboratory Test, Stick 2 (°C) Depth (ft) Time 0 0.5 1 1.5 2 2.5 3 3.5 4 0:00 20.75 21.12 21.37 21.44 21.75 21.69 21.75 21.75 21.75 2:29 20.44 21.94 22.31 22.19 22.44 22.50 22.56 22.44 22.00 2:34 20.37 21.94 22.44 22.25 -127.00 -127.00 -127.00 -127.00 -127.00 2:39 20.44 22.00 22.44 22.31 22.56 22.62 22.62 22.50 -127.00 2:44 20.44 22.00 22.50 22.31 22.56 22.62 22.62 22.56 22.06 2:49 20.44 22.00 22.50 22.37 22.62 22.69 22.69 22.56 22.12 2:54 20.44 22.06 22.56 22.44 -127.00 -127.00 -127.00 -127.00 -127.00 2:59 20.50 22.12 -127.00 -127.00 -127.00 -127.00 -127.00 -127.00 -127.00 3:04 20.50 22.12 -127.00 -127.00 -127.00 -127.00 -127.00 -127.00 -127.00 5:29 21.44 24.25 25.19 25.06 25.31 25.37 25.37 25.12 24.00 7:33 22.50 26.56 28.06 28.06 28.25 28.31 28.25 27.75 26.12 7:58 22.69 27.00 -127.00 28.69 -127.00 -127.00 -127.00 28.25 -127.00 8:03 22.75 27.06 28.69 28.75 -127.00 29.06 28.94 28.37 26.56 8:08 22.81 27.12 28.81 28.87 29.12 29.12 29.06 28.50 26.62 8:13 22.81 27.25 28.94 29.00 29.25 29.25 29.19 28.56 26.75 8:18 22.87 27.37 29.06 29.12 29.31 29.37 29.31 28.69 26.81 8:23 23.00 27.44 29.19 29.19 29.50 29.50 29.44 28.81 26.87 8:28 23.00 27.50 29.25 29.37 29.56 29.62 29.56 28.87 27.00 8:33 23.06 27.62 29.37 29.50 29.69 29.75 29.62 29.00 27.06 8:38 23.19 27.69 29.50 29.62 29.81 29.87 29.75 29.12 27.12 8:43 23.19 27.75 29.62 29.75 29.94 29.94 29.87 29.19 27.25 8:48 23.25 27.87 29.69 29.81 30.06 30.06 30.00 29.31 27.31 8:53 23.31 27.94 29.81 29.94 30.19 30.19 30.06 29.37 -127.00 8:58 23.37 28.00 29.94 30.06 30.25 30.31 30.19 29.50 -127.00 9:03 23.44 28.12 30.00 30.19 30.37 30.44 30.31 29.56 -127.00 9:08 23.50 28.19 30.12 30.25 30.50 30.50 30.37 29.69 -127.00 9:13 23.50 28.25 30.25 30.37 30.62 30.62 30.50 29.75 -127.00 9:18 23.56 28.37 30.31 30.50 30.69 30.75 30.62 29.81 -127.00 9:23 23.62 28.44 30.44 30.56 30.81 30.81 30.69 29.94 -127.00 9:28 23.69 28.50 30.50 30.69 30.87 30.94 30.81 30.00 -127.00 9:33 23.75 28.56 30.56 30.81 31.00 31.00 30.87 30.06 -127.00 9:38 23.81 28.69 30.69 30.87 31.06 31.12 30.94 30.19 -127.00

The DTSs did not take many readings during the initial 7 hours immediately

following pouring. They also stopped reading after 30 hours of curing. The reason for

the initial infrequency of readings is unknown. However, the latter issue could stem from

the concrete shrinkage. It is well known that concrete shrinks as it cures. It could be that

the concrete shrinks enough that it breaks the sensors. If just one of the sensors on the

string breaks or it shorted, the remaining sensors also will not read.

Figures 35 and 36 show plots of temperature versus depth within the Quik-Tube form for sticks 1 and 2 at the time of peak temperature. This gives a complete temperature profile of the Quik-Tube form. The temperature pattern here shows that the middle area of the tube remains about a constant temperature while the top and bottom show a decrease in temperature. Johnson (2016) explains that drilled shafts show a gradual temperature decrease in the top and bottom of the shaft beginning about one diameter length into the shaft. This is due to the added effect of the heat loss in the longitudinal direction along with the radial direction (Johnson, 2016). This means that around one diameter depth into the shaft on either side, the temperature will begin to decrease compared to the middle portion of the shaft which will remain mostly constant.

Under normal circumstances, the top of the shaft will be cooler than the bottom because the top is open to the air and the bottom is still insulated by the soil underneath. This effect can also be seen in the Figures 35 and 36. In this test, the cardboard used at the bottom of the Quik-Tube form to keep in the concrete provided a layer of insulation.

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples Model

Figure 35. Depth vs. Temperature, Stick 1, 12.5 hr.

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples Model

Figure 36. Depth vs. Temperature, Stick 2, 12.5 hr. 72

It is demonstrated in the above two figures that the readings from the DTSs in both sticks closely match one another. However, the thermocouples on stick 1 show readings that are about 6° C cooler than those on stick 2. The reason for this is unknown.

Also, the trends of increasing temperature towards the center of the Quik-Tube form from the DTSs and the thermocouples match in both cases. But the individual data points at the same depths are significantly different. In both cases, the model predicted higher temperatures than were obtained. However, the general trend of the of all data sets match well.

A good indication of the presence of voids in the form would be a large decrease in temperature in the middle area of the shaft where the temperature should be constant.

The profile of the concrete in this laboratory test is constant in this area. This is a good indication that there were no voids present after the concrete had been poured and consolidated. This is a good result because it shows that proper consolidation techniques were used. The lack of voids in concrete gives it the ability to support loads to its ultimate capacity as designed. If this shaft were to be used in the field, it is likely that it would be acceptable.

Shown in Figure 37 is a plot of the temperature variation over time of the stick 1 in the form. It is displayed that the highest temperature experienced occurs between the depths of 1.0’ to 3.0’ feet within the form. This agrees with the thermal profile of the shaft given by the readings of stick 1 in Figure 35. This is also in agreement with the literature in that the area within one diameter into the shaft displays a temperature decrease. 73

40 C)

° 35

25 Temperature Temperature (

15 0:00 4:48 9:36 14:24 19:12 24:00 28:48 33:36 Time (hours)

0.0' 0.5' 1.0' 1.5' 2.0' 2.5' 3.0' 3.5' 4.0' Model 2.0'

Figure 37. Temperature vs. Time, Stick 1, All Depths.

40 C)

° 35

25 Temperature Temperature (

15 0:00 4:48 9:36 14:24 19:12 24:00 28:48 33:36 Time (hours)

0.0' 0.5' 1.0' 1.5' 2.0' 2.5' 3.0' 3.5' 4.0' Model 2.0'

Figure 38. Temperature vs. Time, Stick 2, All Depths. 74

Figure 38 shows a plot of the temperature change over time of sensor stick 2.

This figure is in close agreement with Figure 36 as to the temperature at each depth over time. This confirms that the measurements from the sensors can be duplicated.

Therefore, this laboratory test was successful. It was a good sign that the DTSs themselves agreed with each other. However, it was still somewhat concerning those readings matched the readings of the thermocouples only some of the time. Shown in

Appendix A are the temperature profiles for the Quik-Tube form at different times after pouring. A pattern can be seen from these Figures 44 through 101. At 2.5 hours, the thermocouple readings are much higher than those of the DTSs. Then after 5.5 hours the readings from both sets of sensors match each other well. The readings continue to match well in stick 2 up until the 12.5-hour mark where the thermocouple readings become noticeably larger than the DTSs and continue to stay this way until the end of testing. In stick 1 however, from 7.5 hours to 12.5 hours, the readings from the thermocouples are much lower than the other sensors. Then from the 13-hour to 16-hour mark, the readings match well again. Then after the 17 hours, the thermocouples show much higher readings than the DTSs. The readings from stick 1 after 13 hours match better than those from stick 2 during the same time. It can be generally deduced from these graphs that the thermocouples tend to give higher readings than the DTSs. This again could be due to the thermocouples being located slightly closer to the center of the sonotube. This data is summarized in Table 2. Thermal profile plots for each hour after pouring are shown in Appendix A. Overall, it was confirmed that these sensors can measure the increase in temperature of the concrete with some confidence. 75

5.1.2. Field Test

Like the laboratory test, the field test results were plotted as temperature versus

time as well as depth versus temperature. The two sensor sticks in this test are called

north stick and south stick due to their position in the shaft. The north stick was placed

on the north facing side of the shaft and the south stick was positioned on the southern

facing side of the shaft. The following section contains the results of the field test and a

discussion of these results.

The DTSs again had issues collecting data sporadically. During the first seven

hours immediately following the concrete pour, the sensors did not function properly.

There were times in which they would only collect data for one point and then not again

for another hour or so. Other times, only about half of the sensors took readings. Also

during this time, some of the data points were clearly incorrect, either too high or too

low. Therefore, the data from the first seven hours is not shown in the plots.

The maximum temperature of the shaft occurred around the 12 hours following

the concrete pour. Figures 39 and 40 show that the temperature of the shaft is maximum at the top of the shaft and lowest at the bottom of the shaft at all times. This is due to the temperature of the limestone surrounding the shaft linearly decreasing in temperature

from top of bottom. Therefore, instead of constant temperature through the shaft as

described in the literature, the curing temperature of the concrete also linearly decreases

from top to bottom. This is even more so apparent in Figures 41 and 42, which illustrate

the temperature profile of the shaft at various times. Tables 4 and 5 show a small amount 76

of the data used for these figures. Highlighted in purple and red are readings that were not taken and are incorrect, respectively.

Sensor 9 at the depth of 9’ shows some variation of its reading in the initial portion of Figure 39. This displays the variability at times of the readings given by the sensors. Therefore, caution should be taken in accepting these readings as given. The concrete cures in a fashion that should result in a smooth curve. Therefore, if a sharp rise or fall in temperature occurs over a short amount of time, the reading is likely incorrect.

38 36 34 32 C) ° 30 28 26

Temperature Temperature ( 24 22 20 18 0:00 4:48 9:36 14:24 19:12 24:00 28:48 Time (hr)

0' 1' 2' 3' 4' 5' 6' 7' 8' 9' 10' Model

Figure 39. Temperature vs. Time, North Side, All Depths.

Figure 40 shows the temperature variation of the shaft over time at all depths of stick 2. The trends are like those of stick 1, but they are generally 2-3° C warmer than those stick 1. This could be due the concrete being more consolidated on the south side 77

of the shaft compared to the north side. Also, sensor 9 at a depth of 9’ clearly read

incorrectly during this test. Its results should have been between sensor 8 and sensor 10

like in stick 1. However, its readings were between sensors 1 and 2, and its last readings

were even above sensor 0 in a scatter pattern. This is a good indication that sensor 9 did

not function properly for the duration of the test. This could possibly be due to damage

caused to that sensor during the concrete pour. Perhaps some loose rock from the shaft or

some aggregate from the concrete struck the sensor with enough force to damage it. It

could also be a manufacturing error, but this is unlikely because all the sensors were

tested in the laboratory before being taken to the field. Therefore, sensor 9 did not have enough protection to provide quality data to this study. For this reason, the data from sensor 9 was excluded from all plots of depth versus temperature because they signified an unrealistic defect in the shaft.

The model predicts that the maximum temperature of hydration is reached at 27

hours after pouring. This is in stark contrast to the field data which shows that the

maximum temperature is reach at 12 hours. This is most likely due to the difference in

the assumptions of the model and the actual field conditions. The model assumes that the shaft is deep enough that no temperature variation existing in the surrounding material. It also does not consider the water table. In this field test, the shaft was within the upper 15 feet of the ground surface. The temperature of the material beneath the ground surface becomes constant around a depth of 30 feet and below. Also, the shaft was within the

water table which would raise the water to cement ratio and therefore reduce the overall 78

temperature increase from the hydration of the concrete. These factors could explain the variation between the field data and the model.

38 36 34 32 C) ° 30 28 26

Temperature Temperature ( 24 22 20 18 0:00 4:48 9:36 14:24 19:12 24:00 28:48 Time (hr)

0' 1' 2' 3' 4' 5' 6' 7' 8' 9' 10' Model

Figure 40. Temperature vs. Time, South Side, All Depths.

The best method to determine if voids or soil inclusions are present in the shaft is to plot the depth versus the temperature of the shaft at the time of maximum temperature.

Figure 35 shows a comparison between the temperatures recorded by the DTSs and the thermocouples on the north side of the shaft at 12.5 hours after pouring, which is the time of maximum temperature in this shaft. The general trend shows that the temperature linearly decreases from the top of the shaft to the bottom. This can be attributed to two factors. One being that temperature within the ground becomes constant at a depth of about 35’. This test was conducted above this height; therefore, a decrease in 79

temperature from top to bottom can be expected. The second factor is that this test was conducted within the water table. The water has a cooling effect on the temperature of the soil, more so on the soil which is near or below the water table. It should be noted that this test was conducted during the summer season. This is the reason that the temperature is higher at the surface than the bottom of the shaft. If this test were conducted in winter, the results would show the opposite with the top of the shaft having a lower temperature than the bottom of the shaft and a general linear trend of increasing temperature towards the bottom.

Since there were only three thermocouples, the temperature trend appears perfectly linear. The DTSs shows that the trend is generally linear, but there are some deviations. At a depth of 3’ there is a major drop in temperature. This is also shown in the same plots from the north sensor stick but at other times during the hydration process.

This is an indication that there is a significant void in this area of the shaft. It could be an area of concrete that did not consolidate, or it could be a rock or soil inclusion which fell into the shaft during the concrete pour. There is also the area at 9’ on this plot that shows an increase in temperature. This rise is not as sudden as the decrease at 3’. The sensors at 7’ and 8’ are both also above the idealized linear curve. This signifies as bulge in the cross section of the shaft at this point. Bulges, however, a generally not a concern in drilled shafts because they add capacity to the shaft. There is good correlation between the readings of the thermocouples and the DTSs, which denotes that the readings are accurate.

Table 8. DTS Readings, Field Test, Stick 1 (°C) Depth (ft) Time 0 1 2 3 4 5 6 7 8 9 10 0:00 19.19 19.44 19.06 18.75 18.12 18.31 17.87 17.62 17.12 16.62 16.12 0:05 19.00 19.37 18.87 18.56 18.00 18.00 17.69 17.37 16.87 16.44 16.00 0:10 18.87 19.25 18.69 18.37 17.81 17.81 17.44 17.12 16.69 16.25 15.88 0:15 18.75 19.12 18.56 18.19 17.62 17.56 17.25 16.94 16.50 16.12 15.81 0:20 18.75 19.06 18.44 18.00 17.44 17.37 17.06 16.81 16.37 16.00 15.75 0:25 18.75 19.00 18.37 17.87 17.31 17.25 16.94 16.62 16.19 15.88 15.69 0:30 18.75 18.94 18.19 17.69 17.19 17.06 16.75 16.50 16.12 15.81 15.63 0:35 18.81 18.87 18.06 17.50 17.00 16.94 16.62 16.37 16.00 15.75 15.50 0:40 18.94 18.94 18.06 17.50 16.87 16.75 16.50 16.25 15.94 15.63 15.50 0:45 18.94 18.94 18.00 17.37 16.81 16.62 16.44 16.12 15.81 15.56 15.44 0:50 18.94 18.87 17.87 17.25 16.69 16.50 16.31 16.06 15.75 15.56 15.44 0:55 19.00 18.81 17.81 17.12 16.62 16.44 16.25 16.00 15.69 15.50 15.44 0:59 18.81 18.69 17.75 17.06 16.50 16.31 16.12 15.88 15.63 15.44 15.38 1:04 18.75 18.50 17.62 17.00 16.44 16.25 85.00 15.81 15.63 15.44 15.44 7:34 28.62 28.50 28.50 26.37 26.87 26.12 25.00 24.56 24.06 24.62 21.37 7:39 28.75 28.62 28.62 26.44 26.94 26.19 25.06 24.62 24.12 25.12 21.44 7:44 28.87 28.75 28.75 26.56 27.06 26.31 25.12 24.69 24.19 25.62 21.50 7:49 29.00 28.87 28.87 26.69 27.12 26.37 25.25 24.75 24.25 26.37 21.50 - 7:59 29.25 127.00 29.06 26.87 27.31 26.56 25.37 24.87 24.37 27.25 21.56 8:14 nan nan nan 26.94 27.44 26.62 25.44 24.94 24.44 26.62 21.56 8:19 29.81 29.94 29.69 27.37 27.31 26.81 26.12 25.44 24.94 27.56 22.37 8:24 29.94 29.81 29.69 27.37 27.81 27.00 25.75 25.25 24.62 27.94 21.75 - - - 8:29 30.06 29.94 29.81 27.44 27.94 27.06 127.00 127.00 127.00 27.62 21.75 8:34 30.19 30.00 29.94 27.56 28.00 27.12 25.87 25.37 24.81 27.81 21.81 8:39 30.31 30.19 30.00 27.62 28.12 27.25 26.00 25.50 24.87 27.81 21.81 8:44 30.44 30.31 30.12 27.75 28.19 27.31 26.06 25.56 24.94 27.19 21.87 8:49 30.56 30.44 30.25 27.87 28.31 27.44 26.19 25.62 25.00 26.87 21.87 8:54 30.69 30.56 30.37 27.94 28.44 27.56 26.25 25.69 25.06 26.94 21.94 8:59 30.81 30.69 30.44 28.06 28.50 27.62 26.37 25.75 25.19 26.31 22.00

Table 9. DTS Readings, Field Test, Stick 2 (°C)

Depth (ft) Time 0 1 2 3 4 5 6 7 8 9 10 0:00 20.00 19.44 19.06 18.62 18.94 18.06 17.75 17.50 17.00 19.31 16.69 0:05 19.81 19.25 18.81 18.37 18.62 17.87 17.50 17.25 16.75 19.06 16.50 0:10 19.62 19.06 18.56 18.12 18.37 17.62 17.31 17.00 16.56 18.87 16.31 0:15 19.44 18.87 18.37 17.94 18.12 17.44 17.12 16.81 16.37 18.62 16.19 0:20 19.25 18.69 18.19 17.75 17.94 17.25 16.94 16.62 16.25 18.44 16.12 0:25 19.12 18.56 18.00 17.56 17.75 17.06 16.75 16.50 16.06 18.25 16.00 0:30 19.06 18.50 17.87 17.44 17.56 16.87 16.56 16.37 15.94 18.19 15.88 0:35 19.06 18.44 17.75 17.25 17.37 16.75 16.44 16.25 15.88 18.00 15.81 0:40 19.06 18.44 17.56 17.12 17.25 16.62 16.31 16.12 15.75 17.94 15.75 0:45 19.19 18.50 17.50 17.00 17.06 16.44 16.19 16.00 15.69 17.87 15.75 0:50 19.25 18.56 17.37 16.87 16.94 16.37 16.06 15.94 15.63 17.81 15.69 0:55 19.25 18.56 17.25 16.75 16.81 16.25 16.00 15.88 15.56 17.81 15.63 0:59 19.44 18.56 17.19 16.69 16.75 16.19 15.94 15.81 15.56 17.75 15.63 1:04 19.50 18.75 17.19 16.56 16.62 16.12 15.81 15.75 15.50 17.81 15.56 7:34 19.56 18.87 17.12 16.50 16.50 16.00 15.75 15.69 15.44 17.94 15.50 7:39 32.00 31.25 30.56 30.12 29.25 28.50 28.44 27.94 27.12 31.19 24.81 7:44 32.19 31.44 30.69 30.25 29.37 28.62 28.62 28.06 27.12 31.31 24.87 7:49 32.31 31.56 30.81 30.37 29.50 28.69 28.75 28.19 27.25 31.50 24.94 7:59 32.50 31.69 30.94 30.50 29.56 28.81 -127.00 28.31 -127.00 31.69 -127.00 8:14 32.81 32.06 31.19 30.62 29.69 28.94 28.81 28.56 27.37 31.81 25.00 8:19 32.81 32.06 31.19 30.62 29.69 28.94 28.81 28.56 27.37 31.81 25.00 8:24 32.81 32.06 31.19 30.62 29.69 28.94 28.81 28.56 27.37 31.81 25.00 8:29 33.63 32.75 31.87 31.37 30.37 29.50 29.06 28.94 27.87 32.56 25.25 8:34 33.75 32.88 31.94 31.50 30.44 29.62 -127.00 -127.00 -127.00 -127.00 -127.00 8:39 33.88 33.06 32.13 31.62 30.56 29.69 29.25 29.06 28.00 32.81 25.37 8:44 34.06 33.19 32.19 31.75 30.69 29.81 29.37 29.12 28.06 32.88 25.44 8:49 34.19 33.31 32.31 31.81 30.75 29.87 29.50 29.19 28.19 33.00 25.44 8:54 34.31 33.38 32.44 31.94 30.87 30.00 29.50 29.25 28.25 33.13 25.50 8:59 34.38 33.56 32.56 32.06 30.94 30.06 29.62 29.37 28.31 33.25 25.56

Depth (ft) 10

16 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

Model DS18S20 Thermocouples

Figure 41. Depth vs. Temperature, North Side, 12.5 hr.

Figure 42 shows the temperature variation of the south side of the shaft. The thermocouple data and DTS data match nearly perfectly at all depths within the shaft.

There is a slight indication of a bulge at a depth of 7’ which agrees with the signal from the north sensor that a bulge was present in this area. However, the increase in temperature is not significant enough to prove that in fact a bulge does exist on this side of the shaft. 83

Depth (ft) 10

16 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

Model DS18S20 Thermocouples

Figure 42. Depth vs. Temperature, South Side, 12.5 hr.

Comparing Figures 41 and 42, the south side of the shaft exhibits higher temperatures at all points of about 2-3° C, similar to the results from Figures 39 and 40.

This may be due to the concrete being more consolidated on the south side of the shaft.

However, this is unlikely because the concrete was poured into the shaft by freefall, so

the degree of consolidation of the concrete should generally be about the same

throughout the shaft. Since all of the readings are higher on this side of the shaft, this

points to the steel beam being positioned off center. It appears that for entirety of the

shaft, the beam is located closer to the northern side of the shaft. This results in the

readings from the north side being lower because those sensors are farther from the center

of the shaft. It also causes the readings from the south side to be higher because of the

greater temperatures experienced in the center of the shaft. 84

Located in Appendix A are additional figures showing results from this field test.

Plots of temperature versus time for each sensor compared to the thermocouples are given, along with plots of depth versus temperature at various times during curing. These figures signify that the temperature of the shaft increases smoothly from the time of pouring to the 12.5-hour mark. After this point, the temperature begins slowly decreasing until the 27-hour mark where the DS18S20 stopped recording. Since the sensors again stopped collecting data, this is yet another suggestion that the shrinkage of the concrete cause a failure of the sensors. In a drilled shaft of this size, it usually to take about 48 hours for the concrete to reach a constant temperature. It is good practice to collect data up to this point. Therefore, some more measures should be taken in future tests to prevent premature failure of the sensors.

CHAPTER 6: DIGITAL TEMPERATURE SENSOR PROTECTION METHODS

Most likely due to concrete shrinkage, the DTS sticks malfunctioned after about

29 hours in the laboratory test and about 27 hours in the field test. Typically, larger diameter (about 3 to 5 feet) shafts are used in practice than the 2-foot diameter shaft from this field test. For these larger shafts, the heating and cooling rates are generally slower than that of small shafts. Larger drilled shafts also experience a higher percentage of concrete shrinkage compared to small shafts, which could result in a higher chance of damage to the sensors. Temperature readings should be taken during the entire curing process to determine the presence or lack of defects within a shaft. For these reason, protection methods differing from those used previously in this research were attempted in the lab to make the sensors more durable. This chapter discusses the methods and results of these tests.

In the first laboratory test of sensor protection, two methods were used. One was a coating of Dow Corning 748 silicone and the other was a coating of form oil on the outside of the Dow Corning 748 silicone. Form oil is commonly used as a lubricant when casting concrete into 21 x 6 x 6-inch concrete molds for strength testing. It was used in this test because of availability and economy. The silicone was used to provide a flexible barrier between the sensors and the concrete while allowing good thermal conductivity between the two. The form oil was used to provide lubricant between the sensors and the concrete so as the concrete cured and shrank it would slide easily around the sensors. The experiment was conducted by using the DTSs and thermocouples 86

attached to their respective data acquisition systems. Two DTSs were connected on one string for each test method.

For this test, two 6X12 inch concrete cylinders were used to simulate drilled shafts. In each cylinder, two DSTs and one thermocouple were placed near the center of the cylinder. One cylinder contained the sensors coated with the silicone while the other cylinder contained the sensors coated with both silicone and form oil. Concrete was placed and rodded in each cylinder to ensure proper compaction.

In the second laboratory test, two protection methods and one control method were used. One was a coating of form oil, one was a covering of aluminum foil, and the last was no treatment. The process of this test was the similar to the first sensor protection test. Figures 43 through 49 show the results of these experiments.

30 C) ° 28

Termperature ( Termperature 24

20 0:00 2:24 4:48 7:12 9:36 12:00 14:24 Time (hr)

Thermocouple oil

Figure 43. Sensor Protection Test 1, Thermocouple, Oil. 87

30 C) ° 28

Temperature Temperature ( 24

20 0:00 2:24 4:48 7:12 9:36 12:00 14:24 Time (hr)

Thermocouple silicone

Figure 44. Sensor Protection Test 1, Thermocouple, Silicone.

C) 43 °

33 Temeperature Temeperature (

23 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 Time (hr)

DS18S20 1 oil DS18S20 2 oil

Figure 45. Sensor Protection Test 1, DS18S20, Oil.

C) 43 °

33 Temperature Temperature (

23 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 Time (hr)

DS18S20 1 silicone DS18S20 2 silicone

Figure 46. Sensor Protection Test 1, DS18S20, Silicone.

25.00

24.00

23.00 C) ° 22.00

21.00

Temperature ( 20.00

19.00

18.00 0:00 4:48 9:36 14:24 19:12 24:00 28:48 33:36 38:24 43:12 48:00 Time (hr)

DS18S20 oil 1 DS18S20 oil 2 Thermocouple oil

Figure 47. Sensor Protection Test 2, Oil.

25.00

24.00

23.00 C) ° 22.00

21.00

Temperature ( 20.00

19.00

18.00 0:00 4:48 9:36 14:24 19:12 24:00 28:48 33:36 38:24 43:12 48:00 Time (hr)

DS18S20 foil 1 DS18S20 foil 2 Thermocouple foil

Figure 48. Sensor Protection Test 2, Foil.

24.00

23.00

C) 22.00 °

21.00

20.00 Temperature (

19.00

18.00 0:00 4:48 9:36 14:24 19:12 24:00 28:48 33:36 38:24 43:12 48:00 Time (hr)

DS18S20 no treatment 1 DS18S20 no treatment 2 Thermocouple no treatment

Figure 49. Sensor Protection Test 2, No Treatment.

Figures 43 and 44 show that the thermocouples from sensor protection test 1 did

not perform well. This could be due to a loose connection to the data acquisition system.

Figures 45 and 46 show that the DTSs from the first test survived, which shows that using silicone and silicone and form oil may both be good protection methods.

Figures 47 through 49 indicate a good correlation between the readings from the thermocouples and the DTSs. However, there was some difference between the readings.

Table 10 shows the average difference between the readings from each sensor protection

method from test 2 and the recommended correction factor for each reading from the

DTSs.

Figure 48 shows sensor 2 gave readings steadily at the beginning and end of the

test, but only gave intermittent readings between 14 and 33 hours after mixing.

Therefore, using aluminum foil may not be a protection method that should be used in

future experiments. Figure 49 shows that the DTSs which received no protection

treatment survived the test. The indicates that the issue of obtaining continuous readings

from the DTSs may stem from another source other than the concrete shrinkage. It could

be due to a loose connection between the sensors and the connection devices which link

the DSTs to the ribbon cable and subsequently the Arduino board. However, exploring

this possibility was outside the scope of this research.

Table 10. Correction Factors for DTS Protection Methods Temperature Protection Survived? Difference Method (°C) Dow Corning Yes N/A 748 Oil Yes -1.58 Aluminum No +0.03 Foil No Treatment Yes -1.38

CHAPTER 7: CONCLUSIONS AND RECOMMENDATIONS

This chapter makes the final deductions on the results presented in the previous chapters. Conclusions and recommendations are made to develop knowledge about using

DTSs to thermally profile drilled shaft foundations. In all, this research has improved the knowledge and techniques to verify the quality of drilled shafts with this new non- destructive test.

Laboratory testing of materials, especially sensors used for a new test in which they have not previously been used, is critical to understanding how they will perform under ideal conditions. If the results come out well compared with established methods, then the sensors can be put through a field run. For this study, the readings of the temperature of curing concrete from thermocouples and the DTSs were compared in a laboratory setting. The results show that the readings from these two sets of sensors showed some variability. The readings were close most of the time, around 2-3° C between adjacent sensors. But there were instances where they had larger difference in readings, such as the readings from stick 2 at 9 hours after pouring where there was a 4°

C difference. Therefore, it is difficult to say that the sensors were very accurate during the laboratory test due to these differences.

Field testing of the DTS sticks was performed on S.R. 139 outside of Jackson, OH on a sheet pile lagging wall. The drilled shafts used to support the vertical beams were 2’ in diameter. The sensors were fastened to the inner flanges of the beam and the sensors faced outwards toward the shaft wall. After concrete was poured, data was collected for

29 hours because that is the point at which the sensors failed. The data shows that 93

temperature of the shaft gradually decreased from top to bottom. This is because the

surrounding limestone most likely exhibited this temperature gradient and influenced the temperature of the concrete during curing.

The most useful time to judge the integrity of a drilled shaft is when the concrete has reached maximum temperature. Using this information, it is evident that there some defect at the depth of 3 feet. It is also clear that this anomaly was closer to the northern side of the shaft because the north sensor at that depth showed a great temperature decrease than the sensors at that depth on the south side. Also, since the temperatures given by the southern sensors is generally higher than the northern sensors, the beam in the center of the shaft likely sits closer to the northern side of the shaft. Also, the thermocouple readings generally agree closely with those given by the DTSs. Therefore, these results are verified by the thermocouples.

During the both laboratory and field test, the sensors failed to record after about

28 hours. This was most likely due to the shrinkage of the concrete as it cured being enough that the sensors cracked or were dislodged from their connections to the wire.

For this reason, a series of lab tests were conducted to attempt to protect the sensors in a variety of ways.

The trend of the model used in this research matched the trend obtained from the laboratory data. This shows that the results of the laboratory test were within reason.

However, the model and the field data do not trend in a similar manner. The reason for this could be that the assumptions of the model were for idealized shaft conditions which was not close to the actual field conditions. For that reason, a field test should be 94

conducted in which the field conditions more closely resemble those assumed by the model. Or another model can be used which can take other field conditions into account.

Since the field test was conducted on a relatively small diameter shaft, it is recommended that the field test be repeated but with the instrumented shaft being one with at least a 3’ diameter with a rebar cage installed instead of an I-beam. This would allow a better understanding of how the sensors would respond to a typical field situation.

Also, it is recommended that more than two of the sensor sticks be made for this test so that a better thermal profile can be generated. Having an average temperate from at least four sticks would allow the identification of defects to be much easier and more accurate.

It is also recommended that other different methods be attempted to protect the sensors from the concrete shrinkage. Performing a field test with each stick using a different protection method would be a good indication of which methods perform well and which do not.

According the results of the sensor protection experiment, using silicone, silicone and oil, and no treatment were all successful sensor protection methods while using foil was not. It is recommended that a combination of silicone and oil be used to protect the sensors in the future to protect the DTSs because it provides the best chance for the sensors to survive. It also was indicated in these experiments that the data collection problems with the DTSs may not be from the concrete shrinkage but from a loose connection in the connecting device between the sensors and the ribbon cable.

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Olson Engineering. (2015). Sonic Echo/Impulse Response. Retrieved from

http://www.olsonengineering.com/images/pdf/methods/se_techbrief2.pdf?lbisphp

req=1

Omega Engineering. (2017). Revised Thermocouple Reference Tables. Retrieved from

https://www.omega.com/techref/pdf/z207.pdf

Paikowsky, S.G., Chernauskas, L.R., Hart, L.J., Ealy, C.D. & DiMillio, A.F.

(2000). Examination of a New Cross-Hole Sonic Logging System for Integrity

Examination of Drilled Shafts. S. Niyama & J. Beim (Eds.) Sixth International

Conference on the Application of Stress-Wave Theory to Piles Wave Theory to

Piles (pp. 223-230). Sao Paulo, Brazil.

Pauly, N. (2010). Thermal conductivity of soils from the analysis of boring logs. Master’s

Thesis, University of South Florida Department of Civil and Environmental

Engineering.

Rausche, F. (2004). Non-Destructive Evaluation of Deep Foundations. Proceedings

from the Fifth International Conference on Case Histories in Geotechnical

Engineering. New York, NY.

Robinson, B. (2012). Non-Destructive Testing of Drilled Shafts – Current Practices and

New Methods [PowerPoint slides]. Retrieved from

http://docs.lib.purdue.edu/cgi/viewcontent.cgi?article=1130&context=roadschool van Wijk W.R., de Vries D.A. (1963): Periodic temperature variations in a homogenous

soil. In: van Wijk W.R. (ed.): Physics of Soil Environment. North-Holland

Publishing Company, Amsterdam, 102–143. 98

Winters, Danny. (2014). Selected Topics in Foundations Design, Quality Assurance, and

Remediation. Retrieved from Google Scholar. 99

APPENDIX A: FIELD AND LABORATORY TEST RESULTS

Laboratory Test

Stick 1 – Temperature vs Time

35 C) ° 30

25 Temperature Temperature (

15 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 0:00 2:24 4:48 7:12 9:36 12:00 Time (hours)

DS18S20 Top Thermocouple 1 Mid Thermcouple 1 Bottom Thermocouple 1

Figure 50. Temperature vs. Time, Stick 1, 0.0'.

100

35 C) ° 30

25 Temperature Temperature (

15 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 0:00 2:24 4:48 7:12 9:36 12:00 Time (hours)

DS18S20 Top Thermocouple 1 Mid Thermcouple 1 Bottom Thermocouple 1

Figure 51. Temperature vs. Time, Stick 1, 0.5'.

35 C) ° 30

25 Temperature Temperature (

15 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 0:00 2:24 4:48 7:12 9:36 12:00 Time (hours)

DS18S20 Top Thermocouple 1 Mid Thermcouple 1 Bottom Thermocouple 1

Figure 52. Temperature vs. Time, Stick 1, 1.0’. 101

35 C) ° 30

25 Temperature Temperature (

15 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 0:00 2:24 4:48 7:12 9:36 12:00 Time (hours)

DS18S20 Top Thermocouple 1 Mid Thermcouple 1 Bottom Thermocouple 1

Figure 53. Temperature vs. Time, Stick 1, 1.5'.

35 C) ° 30

25 Temperature Temperature (

15 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 0:00 2:24 4:48 7:12 9:36 12:00 Time (hours)

DS18S20 Top Thermocouple 1 Mid Thermcouple 1 Bottom Thermocouple 1

Figure 54. Temperature vs. Time, Stick 1, 2.0'. 102

35 C) ° 30

25 Temperature Temperature (

15 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 0:00 2:24 4:48 7:12 9:36 12:00 Time (hours)

DS18S20 Top Thermocouple 1 Mid Thermcouple 1 Bottom Thermocouple 1

Figure 55. Temperature vs. Time, Stick 1, 2.5'.

35 C) ° 30

25 Temperature Temperature (

15 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 0:00 2:24 4:48 7:12 9:36 12:00 Time (hours)

DS18S20 Top Thermocouple 1 Mid Thermcouple 1 Bottom Thermocouple 1

Figure 56. Temperature vs. Time, Stick 1, 3.0’. 103

35 C) ° 30

25 Temperature Temperature ( 20

15 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 0:00 2:24 4:48 7:12 9:36 12:00 Time (hours)

DS18S20 Top Thermocouple 1 Mid Thermcouple 1 Bottom Thermocouple 1

Figure 57. Temperature vs. Time, Stick 1, 3.5'.

35 C) ° 30

25 Temperature Temperature (

15 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 0:00 2:24 4:48 7:12 9:36 12:00 Time (hours)

DS18S20 Top Thermocouple 1 Mid Thermcouple 1 Bottom Thermocouple 1

Figure 58. Temperature vs. Time, Stick 1, 4.0’. 104

Stick 2 – Temperature vs Time

35 C) ° 30

25 Temperature Temperature (

15 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 0:00 2:24 4:48 7:12 9:36 12:00 Time (hours)

DS18S20 Top Thermocouple 1 Mid Thermcouple 1 Bottom Thermocouple 1

Figure 59. Temperature vs. Time, Stick 2, 0.0’.

35 C) ° 30

25 Temperature Temperature (

15 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 0:00 2:24 4:48 7:12 9:36 12:00 Time (hours)

DS18S20 Top Thermocouple 1 Mid Thermcouple 1 Bottom Thermocouple 1

Figure 60. Temperature vs. Time, Stick 2, 0.5’. 105

35 C) ° 30

25 Temperature Temperature (

15 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 0:00 2:24 4:48 7:12 9:36 12:00 Time (hours)

DS18S20 Top Thermocouple 1 Mid Thermcouple 1 Bottom Thermocouple 1

Figure 61. Temperature vs. Time, Stick 2, 1.0’.

35 C) ° 30

25 Temperature Temperature (

15 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 0:00 2:24 4:48 7:12 9:36 12:00 Time (hours)

DS18S20 Top Thermocouple 1 Mid Thermcouple 1 Bottom Thermocouple 1

Figure 62. Temperature vs. Time, Stick 2, 1.5’. 106

35 C) ° 30

25 Temperature Temperature (

15 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 0:00 2:24 4:48 7:12 9:36 12:00 Time (hours)

DS18S20 Top Thermocouple 1 Mid Thermcouple 1 Bottom Thermocouple 1

Figure 63. Temperature vs. Time, Stick 2, 2.0’.

35 C) ° 30

25 Temperature Temperature (

15 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 0:00 2:24 4:48 7:12 9:36 12:00 Time (hours)

DS18S20 Top Thermocouple 1 Mid Thermcouple 1 Bottom Thermocouple 1

Figure 64. Temperature vs. Time, Stick 2, 2.5’.

107

35 C) ° 30

25 Temperature Temperature (

15 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 0:00 2:24 4:48 7:12 9:36 12:00 Time (hours)

DS18S20 Top Thermocouple 1 Mid Thermcouple 1 Bottom Thermocouple 1

Figure 65. Temperature vs. Time, Stick 2, 3.0’.

35 C) ° 30

25 Temperature Temperature (

15 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 0:00 2:24 4:48 7:12 9:36 12:00 Time (hours)

DS18S20 Top Thermocouple 1 Mid Thermcouple 1 Bottom Thermocouple 1

Figure 66. Temperature vs. Time, Stick 2, 3.5’.

108

35 C) ° 30

25 Temperature Temperature (

15 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 0:00 2:24 4:48 7:12 9:36 12:00 Time (hours)

DS18S20 Top Thermocouple 1 Mid Thermcouple 1 Bottom Thermocouple 1

Figure 67. Temperature vs. Time, Stick 2, 4.0’.

Stick 1 – Depth vs Temperature

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 68. Depth vs. Temperature, Stick 1, Initial. 109

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 69. Depth vs. Temperature, Stick 1, 2.5 hr.

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 70. Depth vs. Temperature, Stick 1, 5.5 hr. 110

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 71. Depth vs. Temperature, Stick 1, 7.5 hr.

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 72. Depth vs. Temperature, Stick 1, 9 hr.

111

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 73. Depth vs. Temperature, Stick 1, 10 hr.

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 74. Depth vs. Temperature, Stick 1, 11 hr.

112

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 75. Depth vs. Temperature, Stick 1, 12 hr.

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 76. Depth vs. Temperature, Stick 1, 13 hr.

113

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 77. Depth vs. Temperature, Stick 1, 14 hr.

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 78. Depth vs. Temperature, Stick 1, 15 hr.

114

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 79. Depth vs. Temperature, Stick 1, 16 hr.

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 80. Depth vs. Temperature, Stick 1, 17 hr.

115

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 81. Depth vs. Temperature, Stick 1, 18 hr.

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 82. Depth vs. Temperature, Stick 1, 19 hr.

116

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 83. Depth vs. Temperature, Stick 1, 20 hr.

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 84. Depth vs. Temperature, Stick 1, 21 hr.

117

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 85. Depth vs. Temperature, Stick 1, 22 hr.

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 86. Depth vs. Temperature, Stick 1, 23 hr.

118

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 87. Depth vs. Temperature, Stick 1, 24 hr.

Stick 2 – Depth vs Temperature

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 88. Depth vs. Temperature, Stick 2, Initial. 119

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 89. Depth vs. Temperature, Stick 2, 2.5 hr.

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 90. Depth vs. Temperature, Stick 2, 5.5 hr.

120

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 91. Depth vs. Temperature, Stick 2, 7.5 hr.

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 92. Depth vs. Temperature, Stick 2, 9 hr.

121

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 93. Depth vs. Temperature, Stick 2, 10 hr.

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 94. Depth vs. Temperature, Stick 2, 11 hr.

122

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 95. Depth vs. Temperature, Stick 2, 12 hr.

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 96. Depth vs. Temperature, Stick 2, 13 hr.

123

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 97. Depth vs. Temperature, Stick 2, 14 hr.

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 98. Depth vs. Temperature, Stick 2, 15 hr.

124

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 99. Depth vs. Temperature, Stick 2, 16 hr.

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 100. Depth vs. Temperature, Stick 2, 17 hr.

125

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 101. Depth vs. Temperature, Stick 2, 18 hr.

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 102. Depth vs. Temperature, Stick 2, 19 hr.

126

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 103. Depth vs. Temperature, Stick 2, 20 hr.

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 104. Depth vs. Temperature, Stick 2, 21 hr.

127

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 105. Depth vs. Temperature, Stick 2, 22 hr.

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 106. Depth vs. Temperature, Stick 2, 23 hr.

128

0.0

0.5

1.0

1.5

2.0

Depth (ft) 2.5

3.0

3.5

4.0 20 22 24 26 28 30 32 34 36 38 Temperature (°C)

DS18S20 Thermocouples

Figure 107. Depth vs. Temperature, Stick 2, 24 hr.

129

Field Test

North Side of Shaft - Temperature vs Time

25 C) ° 20

Temperature Temperature ( 10

0 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 Time (hours)

DS18S20 North Top Thermocouple North Mid Thermocouple North Bottom Thermocouple

Figure 108. Temperature vs. Time, North Stick, 0’.

130

25 C) ° 20

Temperature Temperature ( 10

0 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 Time (hours)

DS18S20 North Top Thermocouple North Mid Thermocouple North Bottom Thermocouple

Figure 109. Temperature vs. Time, North Stick, 1’.

25 C) ° 20

Temperature Temperature ( 10

0 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 Time (hours)

DS18S20 North Top Thermocouple North Mid Thermocouple North Bottom Thermocouple

Figure 110. Temperature vs. Time, North Stick, 2’. 131

25 C) ° 20

Temperature Temperature ( 10

0 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 Time (hours)

DS18S20 North Top Thermocouple North Mid Thermocouple North Bottom Thermocouple

Figure 111. Temperature vs. Time, North Stick, 3’.

25 C) ° 20

Temperature Temperature ( 10

0 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 Time (hours)

DS18S20 North Top Thermocouple North Mid Thermocouple North Bottom Thermocouple

Figure 112. Temperature vs. Time, North Stick, 4’. 132

25 C) ° 20

Temperature Temperature ( 10

0 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 Time (hours)

DS18S20 North Top Thermocouple North Mid Thermocouple North Bottom Thermocouple

Figure 113. Temperature vs. Time, North Stick, 5’.

25 C) ° 20

Temperature Temperature ( 10

0 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 Time (hours)

DS18S20 North Top Thermocouple North Mid Thermocouple North Bottom Thermocouple

Figure 114. Temperature vs. Time, North Stick, 6’. 133

25 C) ° 20

Temperature Temperature ( 10

0 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 Time (hours)

DS18S20 North Top Thermocouple North Mid Thermocouple North Bottom Thermocouple

Figure 115. Temperature vs. Time, North Stick, 7’.

25 C) ° 20

Temperature Temperature ( 10

0 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 Time (hours)

DS18S20 North Top Thermocouple North Mid Thermocouple North Bottom Thermocouple

Figure 116. Temperature vs. Time, North Stick, 8’. 134

25 C) ° 20

Temperature Temperature ( 10

0 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 Time (hours)

DS18S20 North Top Thermocouple North Mid Thermocouple North Bottom Thermocouple

Figure 117. Temperature vs. Time, North Stick, 9’.

25 C) ° 20

Temperature Temperature ( 10

0 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 Time (hours)

DS18S20 North Top Thermocouple North Mid Thermocouple North Bottom Thermocouple

Figure 118. Temperature vs. Time, North Stick, 10’. 135

South Side of Shaft – Temperature vs Time

30 C) ° 25

15 Temperature Temperature ( 10

0 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 Time (hours)

DS18S20 South Top Thermocouple South Middle Thermocouple South Bottom Thermocouple

Figure 119. Temperature vs. Time, South Stick, 0’.

30 C) ° 25

15 Temperature Temperature ( 10

0 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 Time (hours)

DS18S20 South Top Thermocouple South Middle Thermocouple South Bottom Thermocouple

Figure 120. Temperature vs. Time, South Stick, 1’. 136

30 C) ° 25

15 Temperature Temperature ( 10

0 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 Time (hours)

DS18S20 South Top Thermocouple South Middle Thermocouple South Bottom Thermocouple

Figure 121. Temperature vs. Time, South Stick, 2’.

30 C) ° 25

15 Temperature Temperature ( 10

0 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 Time (hours)

DS18S20 South Top Thermocouple South Middle Thermocouple South Bottom Thermocouple

Figure 122. Temperature vs. Time, South Stick, 3’. 137

30 C) ° 25

15 Temperature Temperature ( 10

0 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 Time (hours)

DS18S20 South Top Thermocouple South Middle Thermocouple South Bottom Thermocouple

Figure 123. Temperature vs. Time, South Stick, 4’.

30 C) ° 25

15 Temperature Temperature ( 10

0 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 Time (hours)

DS18S20 South Top Thermocouple South Middle Thermocouple South Bottom Thermocouple

Figure 124. Temperature vs. Time, South Stick, 5’. 138

30 C) ° 25

15 Temperature Temperature ( 10

0 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 Time (hours)

DS18S20 South Top Thermocouple South Middle Thermocouple South Bottom Thermocouple

Figure 125. Temperature vs. Time, South Stick, 6’.

30 C) ° 25

15 Temperature Temperature ( 10

0 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 Time (hours)

DS18S20 South Top Thermocouple South Middle Thermocouple South Bottom Thermocouple

Figure 126. Temperature vs. Time, South Stick, 7’. 139

30 C) ° 25

15 Temperature Temperature ( 10

0 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 Time (hours)

DS18S20 South Top Thermocouple South Middle Thermocouple South Bottom Thermocouple

Figure 127. Temperature vs. Time, South Stick, 8’.

30 C) ° 25

15 Temperature Temperature ( 10

0 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 Time (hours)

DS18S20 South Top Thermocouple South Middle Thermocouple South Bottom Thermocouple

Figure 128. Temperature vs. Time, South Stick, 9’. 140

30 C) ° 25

15 Temperature Temperature ( 10

0 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 24:00 26:24 28:48 31:12 Time (hours)

DS18S20 South Top Thermocouple South Middle Thermocouple South Bottom Thermocouple

Figure 129. Temperature vs. Time, South Stick, 10’.

141

North Side of Shaft – Depth vs. Temperature

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 130. Depth vs. Temperature, North Stick, 7.5 hr.

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 131. Depth vs. Temperature, North Stick, 8.5 hr. 142

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 132. Depth vs. Temperature, North Stick, 9.5 hr.

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 133. Depth vs. Temperature, North Stick, 10.5 hr.

143

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 134. Depth vs. Temperature, North Stick, 11.5 hr.

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 135. Depth vs. Temperature, North Stick, 12.5 hr.

144

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 136. Depth vs. Temperature, North Stick, 13.5 hr.

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 137. Depth vs. Temperature, North Stick, 14.5 hr.

145

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 138. Depth vs. Temperature, North Stick, 15.5 hr.

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 139. Depth vs. Temperature, North Stick, 16.5 hr.

146

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 140. Depth vs. Temperature, North Stick, 17.5 hr.

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 141. Depth vs. Temperature, North Stick, 20.5 hr.

147

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 142. Depth vs. Temperature, North Stick, 21.5 hr.

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 143. Depth vs. Temperature, North Stick, 22.5 hr.

148

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 144. Depth vs. Temperature, North Stick, 23.5 hr.

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 145. Depth vs. Temperature, North Stick, 24.5 hr.

149

6 Depth (ft) 8

12 19 24 29 34 39 Temperature (°C)

DS18S20 Thermocouples

Figure 146. Depth vs. Temperature, North Stick, 25.5 hr.

6 Depth (ft) 8

12 19 24 29 34 39 Temperature (°C)

DS18S20 Thermocouples

Figure 147. Depth vs. Temperature, North Stick, 26.5 hr.

150

6 Depth (ft) 8

12 19 24 29 34 39 Temperature (°C)

DS18S20 Thermocouples

Figure 148. Depth vs. Temperature, North Stick, 27.5 hr.

South Side of Shaft – Depth vs Temperature

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 149. Depth vs. Temperature, South Stick, 7.5 hr. 151

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 150. Depth vs. Temperature, South Stick, 8.5 hr.

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 151. Depth vs. Temperature, South Stick, 9.5 hr. 152

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 152. Depth vs. Temperature, South Stick, 10.5 hr.

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 153. Depth vs. Temperature, South Stick, 11.5 hr. 153

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 154. Depth vs. Temperature, South Stick, 12.5 hr.

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 155. Depth vs. Temperature, South Stick, 13.5 hr. 154

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 156. Depth vs. Temperature, South Stick, 14.5 hr.

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 157. Depth vs. Temperature, South Stick, 15.5 hr. 155

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 158. Depth vs. Temperature, South Stick, 16.5 hr.

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 159. Depth vs. Temperature, South Stick, 17.5 hr. 156

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 160. Depth vs. Temperature, South Stick, 20.5 hr.

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 161. Depth vs. Temperature, South Stick, 21.5 hr. 157

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 162. Depth vs. Temperature, South Stick, 22.5 hr.

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 163. Depth vs. Temperature, South Stick, 23.5 hr. 158

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 164. Depth vs. Temperature, South Stick, 24.5 hr.

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 165. Depth vs. Temperature, South Stick, 25.5 hr. 159

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 166. Depth vs. Temperature, South Stick, 26.5 hr.

6 Depth (ft) 8

12 20 22 24 26 28 30 32 34 36 38 40 Temperature (°C)

DS18S20 Thermocouples

Figure 167. Depth vs. Temperature, South Stick, 27.5 hr. ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !

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