Title Page
ABSTRACT
국문 초록
PREFACE
Contents
CHAPTER 1. INTRODUCTION 26
1.1. Background 26
1.2. Scope 27
CHAPTER 2. OPTIMIZED TIME DOMAIN REFLECTOMETRY PROBE FOR ESTIMATING ELECTRICAL PROPERTIES OF CONDUCTIVE MATERIAL 28
2.1. Introduction 28
2.2. Experimental Setup 29
2.2.1. Principle of time domain reflectometry 29
2.2.2. Time domain reflectometry probe 32
2.2.3. Measurement system 32
2.3. Experimental Results 33
2.3.1. Coating materials 33
2.3.2. Electrodes 34
2.4. Analyses and Discussion 35
2.4.1. Sensitivity 36
2.4.2. Electrical characteristics 37
2.5. Summary and Conclusions 39
CHAPTER 3. EVALUATION OF DIELECTRIC AND ELECTRICAL PROPERTIES OF CEMENTITOUS MATERIAL 54
3.1. Introduction 54
3.2. Theoretical Background 56
3.2.1. Principle of time domain reflectometry 56
3.2.2. Electrical resistivity measurement 58
3.3. Experimental Study 60
3.3.1. Cementitious materials 60
3.3.2. Test setup 61
3.4. Results and Discussion 62
3.4.1. Dielectric constant 62
3.4.2. Electrical resistivity from ERP 64
3.4.3. Electrical resistivity from TDR 65
3.4.4. Comparison 66
3.5. Summary and Conclusions 68
CHAPTER 4. CHARACTERIZATION OF SLIME MIXTURE USING TIME DOMAIN REFLECTOMETRY 87
4.1. Introduction 87
4.2. Material and Methods 89
4.2.1. Slime mixture 89
4.2.2. Principle of time domain reflectometry 90
4.2.3. TDR sensors 92
4.2.4. Test setup 92
4.3. Experimental Results 93
4.3.1. Uniaxial compressive strength 93
4.3.2. Electromagnetic wave 94
4.4. Analyses and Discussion 96
4.4.1. Curing time effect 97
4.4.2. Slime ratio effect 98
4.4.3. Comparison 99
4.5. Summary and Conclusions 101
CHAPTER 5. EVALUATION OF LOCAL INTEGRITY OF PILES USING ELECTROMAGNETIC WAVES 124
5.1. Introduction 124
5.2. Theoretical Background 126
5.2.1. Transmission line theory 126
5.2.2. Time domain reflectometry 129
5.3. Experimental Setup 130
5.3.1. Model piles and transmission lines 130
5.3.2. Measurement system 132
5.4. Experimental Results 133
5.4.1. Transmission line without connector 133
5.4.2. Transmission line with one connector 134
5.4.3. Transmission line with two connectors 134
5.4.4. Transmission line with three connectors 135
5.5. Analyses and Discussion 136
5.5.1. Global velocity of EM wave in transmission line according to defect condition 137
5.5.2. Local velocity separated by defect and connectors 137
5.5.3. Local velocity separated by only connectors 139
5.5.4. Velocity according to the defect ratio 140
5.5.5. Defect estimation 141
5.6. Summary and Conclusions 144
CHAPTER 6. ADVANCED ELECTROMAGNETIC WAVE-BASED METHOD FOR CHARACTERIZING DEFECTS IN CEMENT-BASED STRUCTURES USING TIME DOMAIN REFLECTOMETRY 157
6.1. Introduction 157
6.2. Time Domain Reflectometry 159
6.3. Experimental Setup 161
6.3.1. Model plate 161
6.3.2. Transmission line configuration 161
6.3.3. Wave measurement 162
6.4. Results and Discussion 163
6.4.1. Electromagnetic waveform 163
6.4.2. Electromagnetic wave velocity 164
6.4.3. Area of reflection coefficient 165
6.4.4. Attenuation correction 166
6.4.5. Centroid of defect zone 167
6.4.6. Length of defect zone 168
6.5. Summary and Conclusions 170
CHAPTER 7. SUMMARY AND CONCLUSIONS 186
REFERENCES 194
VITA 210
Table 2.1. Equations of electrical conductivity with characteristic voltages. 41
Table 3.1. Chemical components of ordinary Portland cement. 70
Table 3.2. Index properties of soil. 71
Table 3.3. Weight fractions of cement paste. 72
Table 3.4. Weight fractions of cement paste-slime mixture. 73
Table 3.5. Relationship between electrical conductivity and factors in TDR waveform. 74
Table 4.1. Chemical components of ordinary Portland cement. 103
Table 4.2. Slime ratios and weight fractions of five slime mixtures. 104
Table 4.3. Model parameters for the relationship between uniaxial compressive strength and curing time. 105
Table 4.4. Model parameters for the relationship between dielectric constant and curing time. 106
Table 4.5. Model parameters for the relationship between slime ratio and dielectric constant obtained from the conventional probe. 107
Table 4.6. Model parameters for the relationship between slime ratio and dielectric constant obtained from the electrical wire. 108
Table 4.7. Parameters for the relationship between dielectric constant with compressive strength. 109
Figure 2.1. Equivalent circuit model of signal and return paths in TDR probe. 42
Figure 2.2. Typical electromagnetic signal measured by time domain reflectometry. 43
Figure 2.3. Schematic drawing of TDR probes with different number of electrodes. 44
Figure 2.4. Typical electromagnetic signals with different coating materials: (a) single-coated epoxy; (b) double-coated epoxy; (c) top-coat; (d) varnish. 45
Figure 2.5. Voltages at the travel time of 150ns from different coating materials with respect to copper concentration. 46
Figure 2.6. Typical electromagnetic signals with different number of electrodes: (a) 2; (b) 3; (c) 4; (d) 7. 47
Figure 2.7. Voltages at the travel time of 150ns from different number of electrodes with respect to copper concentration. 48
Figure 2.8. Sensitivities with respect to copper concentration: (a) coating materials; (b) number of electrodes. 49
Figure 2.9. Electromagnetic signals from optimized TDR probe in water with various salinities. 50
Figure 2.10. Estimated electrical conductivity from suggested equations versus measured electrical conductivity. 51
Figure 2.11. Electromagnetic signals from optimized TDR probe penetrated into the simulated seabed with various copper concentrations. 52
Figure 2.12. Estimated electrical conductivity from suggested equations with respect to copper concentration. 53
Figure 3.1. Typical waveform of electromagnetic signal obtained from time domain reflectometry. 75
Figure 3.2. Schematic of the experimental cell incorporated with a TDR probe and an electrical resistivity probe: (a) TDR probe; (b) electrical resistivity probe (Wenner... 76
Figure 3.3. Measurement system for electromagnetic waves using TDR and electrical resistivity probes. 77
Figure 3.4. Typical calibration result between electrical resistance and resistivity. 78
Figure 3.5. TDR waveforms with curing time in two different cement pastes with the water-cement ratios of (a) w/c=0.45; (b) w/c=1.5. 79
Figure 3.6. Dielectric constant computed from TDR waveforms according to the curing time: (a) cement paste; (b) cement paste-slime mixture. 80
Figure 3.7. Electrical resistivities estimated from the electrical resistances of (a) cement paste and (b) cement paste-slime mixture. 81
Figure 3.8. Electrical resistivity of cement paste estimated from TDR waveforms using previous studies: (a) Giese and Timann (1975); (b) Dalton et al. (1984); (c)... 82
Figure 3.9. Electrical resistivity of cement paste-slime mixture estimated from TDR waveforms using previous studies: (a) Giese and Timann (1975); (b) Dalton et al.... 83
Figure 3.10. Comparison between measured and computed electrical resistivities: (a) Giese and Timann (1975); (b) Dalton et al. (1984); (c) Topp et al. (1988); (d) Yanuka... 84
Figure 3.11. Relationship between characteristic voltages in TDR waveform: (a) V₁ and V₂; (b) V₁ and Vf; (c) V₂ and Vf.[이미지참조] 85
Figure 3.12. Error norm versus voltage: (a) Dalton et al. (1984); (b) Yanuka et al. (1988). 86
Figure 4.1. Particle size distribution curve of soil used in this study. 110
Figure 4.2. Typical electromagnetic signal obtained from time domain reflectometry. 111
Figure 4.3. Schematic drawings of a MC Nylon mold incorporated with two TDR sensors: (a) conventional probe and electrical wire; (b) design of MC Nylon mold... 112
Figure 4.4. Electromagnetic wave measurement system. 113
Figure 4.5. Typical stress-strain curves of two different slime mixtures obtained from uniaxial compression test. 114
Figure 4.6. Uniaxial compressive strength with the curing time for five slime mixtures. 115
Figure 4.7. Electromagnetic signals acquired from the conventional probe according to the curing time: (a) slime ratio of 0.38; (b) slime ratio of 0.72. 116
Figure 4.8. Electromagnetic signals acquired from the electrical wire according to the curing time: (a) slime ratio of 0; (b) slime ratio of 0.35. 117
Figure 4.9. Electromagnetic wave velocities determined from the conventional probe. 118
Figure 4.10. Electromagnetic wave velocities determined from the electrical wire. 119
Figure 4.11. Dielectric constants of five slime mixtures with the curing time determined from (a) conventional probe and (b) electrical wire. 120
Figure 4.12. Dielectric constants of five slime mixtures with the slime ratio determined from (a) conventional probe and (b) electrical wire. 121
Figure 4.13. Relationship between dielectric constants measured from two TDR sensors. εw and εp indicate dielectric constants determined from electrical wire and...[이미지참조] 122
Figure 4.14. Relationship between uniaxial compressive strengths and dielectric constants determined from (a) conventional probe and (b) electrical wire. 123
Figure 5.1. Conceptual model of a transmission line: (a) electrical wire; (b) equivalent circuit on transmission line composed of two electrical wires. R, L, G, and C denote... 146
Figure 5.2. Model concrete piles with: (a) defect filled with air; (b) defect filled with sands; (c) defect filled with water. 147
Figure 5.3. Combination of transmission lines in model piles. 12 combinations were configured using 4 types of transmission lines in 3 types of model piles. 148
Figure 5.4. Measurement system. 149
Figure 5.5. Reflection coefficients of model piles with various types of defects for: (a) 0 connector; (b) 1 connector; (c) 2 connectors; (d) 3 connectors. 150
Figure 5.6. Signature of reflection coefficient for travel time selection method. 151
Figure 5.7. Reversely plotted reflection coefficient from the pile toe for: (a) 0 connector; (b) 1 connector; (c) 2 connectors; (d) 3 connectors. 152
Figure 5.8. Global velocity of electromagnetic waves according to defect conditions. 153
Figure 5.9. Local velocity of electromagnetic waves in transmission line separated by: (a) defect and 0 connector; (b) defect and 1 connector; (c) defect and 2 connectors; (d) defect and 3 connectors. 154
Figure 5.10. Local velocity of electromagnetic waves in the transmission line separated by: (a) 0 connector; (b) 1 connector; (c) 2 connectors; (d) 3 connectors. 155
Figure 5.11. Local velocity of electromagnetic waves according to the defect ratio. 156
Figure 6.1. Typical electromagnetic waveforms recorded in time domain reflectometer. Red and blue lines denote the signals for sound plate and plate with an... 173
Figure 6.2. TDR waveforms for sound and defective concrete structures with similar travel time. 174
Figure 6.3. Schematic drawing of two cement-based plates used in this study: (a) sound plate; (b) defective plate. 175
Figure 6.4. Configuration of transmission lines installed in the cement-based plates. 176
Figure 6.5. TDR waveforms from cement-based plates: (a) without connectors; (b) with one connector; (c) with two connectors; (d) with three connectors. 177
Figure 6.6. Electromagnetic wave velocities in two different plates. TL denotes transmission line. 178
Figure 6.7. Schematic description of calculating the area of reflection coefficient for defect zone in a TDR waveform. 179
Figure 6.8. Average areas of reflection coefficient under three defect conditions. 180
Figure 6.9. Variation in additional reflections induced by connectors in TDR waveforms along the number of connectors: (a) one connector; (b) two connectors;... 181
Figure 6.10. Variation in peak reflection coefficient of additional reflections induced by connectors along the distance to each connector. 182
Figure 6.11. Corrected area of reflection coefficient after excluding attenuation effect. 183
Figure 6.12. Estimated distance to the centroid of the defect zone from the starting point of wave propagation in the plate. 184
Figure 6.13. Length of defect zone estimated from transmission lines with measured one: (a) evaluated using defect ratio and wave velocities; (b) evaluated using time... 185