Title Page
Abstract
Contents
Chapter 1. Introduction 16
1.1. Research Background 16
1.2. Objective and Scope of Research 22
1.3. Organization and Structure 24
Chapter 2. Literature review 26
2.1. Introduction 26
2.2. Conditions governing the internal instability 28
2.2.1. Geometric condition 28
2.2.2. Hydraulic condition 31
2.3. Previous studies on well-graded soil 37
Chapter 3. Research methods 41
3.1. Introduction 41
3.2. Testing materials 42
3.2.1. Particle size distributions and properties of specimens 42
3.2.2. Assessment of the internal instability 44
3.3. Experimental apparatuses 49
3.3.1. Apparatus for the short-term and long-term tests 49
3.3.2. Apparatus with pore pressure transducer 53
3.4. Experimental procedure and program 57
3.4.1. Short-term tests 57
3.4.2. Long-term tests 60
3.4.3. Tests with pore pressure transducer 61
Chapter 4. Short-term test results and analyses 63
4.1. Introduction 63
4.2. Short-term test results and analyses 64
4.2.1. Gap soil with a relative density of 78% 64
4.2.2. WG soil with a relative density of 50% 66
4.2.3. WG soil with a relative density of 65% 68
4.2.4. WG soil with a relative density of 80% 71
4.3. Assessment of internal instability 74
4.4. Summary 78
Chapter 5. Long-term test results and analyses 80
5.1. Introduction 80
5.2. Amount of eroded soil and erosion rate 83
5.3. Hydraulic conductivity 88
5.3.1. Gap soil 90
5.3.2. Internally stable WG soil 94
5.3.3. Internally unstable WG soil 99
5.4. Settlement 107
5.5. Mechanism of internal instability 113
5.6. Summary 118
Chapter 6. Test results with pore pressure transducer 121
6.1. Introduction 121
6.2. Hydraulic conductivity and pore water pressure 123
6.2.1. Internally unstable result 124
6.2.2. Internally stable result 129
6.3. Verification of mechanism of internal instability in WG soil 133
6.4. Summary 136
Chapter 7. Conclusions and Recommendations 137
7.1. Conclusions 137
7.2. Recommendations for further researches 145
List of References 146
초록 150
Table 2-1. Criteria for suffusion 30
Table 2-2. Summary of previous studies on the hydraulic condition 36
Table 2-3. Summary of previous studies on well-graded soil 39
Table 3-1. Properties of specimens 43
Table 3-2. Criteria for suffusion and assessment results 46
Table 3-3. Experimental program for short-term tests 59
Table 3-4. Experimental program for long-term tests 61
Table 3-5. Experimental program for tests with pore pressure transducer 62
Table 4-1. Summary of the short-term test results 77
Table 5-1. Summary of the long-term test results 82
Table 5-2. Internal instability of test results 89
Table 5-3. Test results of WG soil (Dγ＝50%) at a hydraulic gradient of 15[이미지참조] 97
Figure 1-1. Schematic diagram of internal instability 17
Figure 1-2. Schematic diagram of gap-graded soils 18
Figure 1-3. Particle size distribution of fill dam materials in South Korea and schematic diagram of well-graded soils 19
Figure 2-1. Schematic drawing of testing apparatus in USACE (1953) 27
Figure 2-2. The coefficient of permeability calculated by the seepage velocity and hydraulic gradients in the test results of Liu et al. (2021) 40
Figure 3-1. Particle size distributions of specimens and fill dam materials in South Korea 43
Figure 3-2. Internal stability of the Gap and WG soils based on Kenney & Lau (1986) 47
Figure 3-3. Internal stability of the Gap and WG soils based on Burenkova (1993) 47
Figure 3-4. Internal stability of the Gap and WG soils based on Wan & Fell (2008) 48
Figure 3-5. Schematic design of experimental apparatus 51
Figure 3-6. Experimental apparatus 52
Figure 3-7. Constriction size of loose and dense particles 53
Figure 3-8. Schematic design of experimental apparatus with pore pressure transducer 55
Figure 3-9. Experimental apparatus with pore pressure transducer 56
Figure 3-10. Experimental procedure 59
Figure 4-1. Accumulative eroded soil and k of Gap soil according to the hydraulic gradients 65
Figure 4-2. Particle size distribution of Gap soil 65
Figure 4-3. Accumulative eroded soil and k of WG soil (Dγ＝50%) according to the hydraulic gradients[이미지참조] 67
Figure 4-4. Particle size distribution of WG soil (Dγ＝50%)[이미지참조] 68
Figure 4-5. Accumulative eroded soil and k of WG soil (Dγ＝65%) according to the hydraulic gradients[이미지참조] 70
Figure 4-6. Particle size distribution of WG soil (Dγ＝65%)[이미지참조] 70
Figure 4-7. Accumulative eroded soil and k of WG soil (Dγ＝80%) according to the hydraulic gradients[이미지참조] 72
Figure 4-8. Particle size distribution of WG soil (Dγ＝80%)[이미지참조] 72
Figure 4-9. Settlement according to hydraulic gradients 73
Figure 4-10. The assessment results of internal instability according to the hydraulic gradient 76
Figure 5-1. Accumulative eroded soil of all test results over time 86
Figure 5-2. Particle size distributions of tested and eroded soil 86
Figure 5-3. SEM images: (a) Gap soil; and (b) WG soil 87
Figure 5-4. Erosion rate of all test results with hydraulic gradients 87
Figure 5-5. Accumulative eroded soil and k of Gap soil at a hydraulic gradient of 3 91
Figure 5-6. Particle size distribution of Gap soil at a hydraulic gradient of 3 92
Figure 5-7. Accumulative eroded soil and k of Gap soil at a hydraulic gradient of 5 93
Figure 5-8. Particle size distribution of Gap soil at a hydraulic gradient of 5 93
Figure 5-9. Accumulative eroded soil and normalized k of WG soil (Dγ＝50%) at hydraulic gradients of 5 and 15[이미지참조] 96
Figure 5-10. Particle size distribution of WG soil (Dγ＝50%) at a hydraulic gradient of 15[이미지참조] 97
Figure 5-11. Accumulative eroded soil and normalized k of WG soil (Dγ＝65%) at a hydraulic gradient of 30 and WG soil (Dγ＝80%) at a hydraulic...[이미지참조] 98
Figure 5-12. Particle size distribution of WG soil (Dγ＝65%) at a hydraulic gradient of 30[이미지참조] 99
Figure 5-13. Accumulative eroded soil and k of WG soil (Dγ＝50%) at a hydraulic gradient of 17[이미지참조] 101
Figure 5-14. Accumulative eroded soil and k of WG soil (Dγ＝50%) at a hydraulic gradient of 25[이미지참조] 101
Figure 5-15. Particle size distribution of WG soil (Dγ＝50%) at a hydraulic gradient of 17[이미지참조] 102
Figure 5-16. Accumulative eroded soil and k of WG soil (Dγ＝65%) at a hydraulic gradient of 60[이미지참조] 103
Figure 5-17. Particle size distribution of WG soil (Dγ＝65%) at a hydraulic gradient of 60[이미지참조] 104
Figure 5-18. Accumulative eroded soil and k of WG soil (Dγ＝80%) at a hydraulic gradient of 120[이미지참조] 105
Figure 5-19. Particle size distribution of WG soil (Dγ＝80%) at a hydraulic gradient of 120[이미지참조] 106
Figure 5-20. Accumulative eroded soil and settlement of test results 108
Figure 5-21. Accumulative eroded soil and settlement of WG soil (Dγ＝50%) at a hydraulic gradient of 17[이미지참조] 108
Figure 5-22. Accumulative eroded soil and settlement of WG soil (Dγ＝65%) at a hydraulic gradient of 60 and WG soil (Dγ＝80%) at a hydraulic gradient...[이미지참조] 109
Figure 5-23. k and e of WG soil (Dγ＝50%) at a hydraulic gradient of 17[이미지참조] 111
Figure 5-24. k and e of WG soil (Dγ＝65%) at a hydraulic gradient of 60[이미지참조] 111
Figure 5-25. k and e of WG soil (Dγ＝80%) at a hydraulic gradient of 120[이미지참조] 112
Figure 5-26. Schematic diagram of the progression of internal instability in Gap soil 115
Figure 5-27. Schematic diagram of the progression of internal instability in WG soil 116
Figure 5-28. Schematic of internal instability behavior in WG soil 117
Figure 6-1. Schematic design of specimen and pore pressure transducer 124
Figure 6-2. Overall k and differential pore water pressure in each part 126
Figure 6-3. The distributions of total head (hT), elevation head (he), and pressure head (hp)[이미지참조] 126
Figure 6-4. The distribution of pressure head 127
Figure 6-5. Overall k and k at each part 127
Figure 6-6. Normalized k and settlement 128
Figure 6-7. Particle size distribution of internally unstable result 129
Figure 6-8. Overall k and differential pore water pressure in each part 130
Figure 6-9. Overall k and k at each part 131
Figure 6-10. Normalized k and settlement 131
Figure 6-11. Particle size distribution of internally stable result 132
Figure 6-12. Schematic diagram of the progression of internal instability in WG soil 135