Geotechnical Evaluation of Xanthan Gum Biopolymer-Based Soil Treatment for Backfill and Slope Surface Protection
- 주제(키워드) Biopolymer , Geotechnical engineering , MSE wall , Slope protection , Thermal conductivity , Xanthan gum
- 주제(DDC) 690
- 발행기관 아주대학교 일반대학원
- 지도교수 장일한
- 발행년도 2026
- 학위수여년월 2026. 2
- 학위명 박사
- 학과 및 전공 일반대학원 건설시스템공학과
- 실제URI http://www.dcollection.net/handler/ajou/000000036031
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
As social demands for climate change response and low-carbon infrastructure increase, the need for sustainable technologies that can replace cement-based soil improvement methods is also growing in the field of geotechnical engineering. Cement has substantial carbon dioxide emissions characteristics, which, despite its superior engineering performance, poses limitations that conflict with long-term climate crisis mitigation goals. In this background, the aims of this study were to assess the geotechnical applicability of biopolymer-based soil treatment (BPST) using xanthan gum (XG-BPST), an environmentally friendly material, and to verify its feasibility as a low-carbon, multi- functional soil improvement method. To that purpose, XG-BPST was applied to geotechnical structures with a variety of engineering requirements, including underground power cable backfill, mechanically stabilized earth (MSE) wall backfill, and slope surface protection, and its performance was comprehensively evaluated. A thermal conductivity test was performed using a thermal needle probe to assess XG- BPST's applicability as an underground power cable backfill. The heat transfer improvement effects of air replacement in the void with additives such as graphite, fly ash, and recycled aggregate, as well as the combined effect with XG, were compared and analyzed. Furthermore, the water retention characteristics in the unsaturated region were investigated using the Fredlund-type soil water characteristic curve (SWCC) apparatus and the van Genuchten model. This allowed for the identification of a relationship with the pendular, funicular, and capillary regimes, which are thermal conductivity change sections. XG-BPST has a possibility to delay the development of dry areas inside the backfill by enhancing water retention capacity in the void. Furthermore, it was proven that long-term operational stability may be achieved by maintaining steady heat transfer paths even under unsaturated conditions. This means that a complex application of additives may improve both the void-filling effect and the heat transfer mechanism. The applicability of XG-BPST as MSE wall backfill was assessed using laboratory-scale soil tank tests and reinforcement pullout tests. The lateral earth pressure measurements under active displacement conditions revealed that the layer reinforced with XG-BPST significantly reduced active earth pressure when compared to untreated condition. GeoPIV image analysis quantitatively found that shear deformation and failure wedge development were effectively controlled in the reinforced area. Furthermore, pullout tests were performed on the geogrid encapsulated with XG-BPST, and the interface shear strength, apparent friction coefficient, and interaction coefficient ratio were all improved. This indicates that the internal stability of the MSE wall is improved through enhancing the geogrid pullout resistance. This suggests that XG-BPST may be used as a reinforcing strategy to ensure MSE wall stability even under constrained construction conditions. The applicability of XG-BPST for slope surface protection was investigated using laboratory-scale tests and numerical analysis to verify the hydraulic and mechanical stabilizing mechanisms. The relationship was derived to estimate compaction and strength by measuring the cone index using a soil pocket penetrometer, and its potential utility as an indication of field quality management was proposed. Laboratory rainfall simulator tests resulted in XG-BPST efficiently controlling surface erosion and particle loss induced by rainfall infiltration by improving the bond between soil particles and the void structure. Furthermore, the findings of plant growth tests and direct shear tests demonstrated that XG- BPST had no adverse impact on plant development. Rather, it was demonstrated that it increased apparent cohesion and improved shear resistance by forming soil-root composites. To assess variations in slope stability over time after rainfall, transient seepage analysis and limit equilibrium stability analysis based on unsaturated hydraulic characteristics were performed. The numerical analysis results showed that slopes with XG-BPST efficiently restricted the development of unsaturated areas induced by rainfall infiltration. This demonstrated a tendency to mitigate the reduction in shear strength and secure slope stability over time. In conclusion, this study experimentally and numerically analyzed XG-BPST to demonstrate that it is a multifunctional, low-carbon soil improvement method that simultaneously enhances various performances such as thermal, mechanical, and hydraulic properties. The findings of this study suggest a novel approach in carbon-reducing geotechnical design through lowered cement consumption. It is also projected to provide foundational data for a paradigm shift toward sustainable geotechnical engineering design that addresses climate change.
more목차
CHAPTER Ⅰ INTRODUCTION 1
1.1 Background 1
1.2 Scope-Organization 3
CHAPTER Ⅱ BIOPOLYMER-BASED SOIL TREATMENT (BPST) LITERATURE REVIEW 5
2.1 Introduction 5
2.2 Geotechnical engineering behaviors by XG-BPST 6
CHAPTER Ⅲ ASSESSMENT OF XG-BPST APPLICABILITY AS A THERMAL BACKFILL FOR UNDERGROUND POWER CABLES 8
3.1 Introduction 8
3.2 Materials 10
3.2.1 Main soil 10
3.2.2 Additive 11
3.2.3 Binder 12
3.3 Methodology 13
3.3.1 Thermal conductivity measurement apparatus 13
3.3.2 Thermal conductivity test procedure 15
3.3.3 Analysis of unsaturated soil behavior 19
3.4 Thermal conductivity test results using thermal needle probe 20
3.4.1 The influence of void-filling additive on the thermal conductivity of backfill 20
3.4.2 Thermal conductivity modification owing to additive and binder combination 25
3.4.3 SWCC-based assessment of water retention and thermal performance of XG-BPST backfill 33
3.5 Discussion 36
3.5.1 Relationship between water retention regimes and thermal conductivity function using SWCC 36
3.5.2 Practical issues in backfill applications of graphite and XG- BPST mixtures 38
3.6 Summary 39
CHAPTER Ⅳ ASSESSMENT OF BPST-GEOGRID COMPOSITE INTERNAL STABILITY AND BEHAVIOR MECHANISMS AS MSE WALL BACKFILL 42
4.1 Introduction 42
4.2 Literature review 45
4.2.1 Literature review on methods to reduce lateral earth pressure 45
4.2.2 Literature review for improving geosynthetic pullout resistance · 47
4.3 Materials 48
4.3.1 Jumunjin sand 48
4.3.2 Xanthan gum biopolymer (XG) 49
4.3.3 Geogrid 50
4.4 Experimental program to assess lateral earth pressure 50
4.4.1 Soil tank and measurement system 50
4.4.2 Model ground conditions 52
4.4.3 Image analysis: GeoPIV 52
4.4.4 Test procedure 53
4.4.5 Mechanical properties of XG-BPST 55
4.5 Experimental program to assess geogrid pullout resistance 56
4.5.1 Pullout test apparatus 56
4.5.2 Test conditions 57
4.5.3 Laboratory test procedure 59
4.6 Test results and analysis 60
4.6.1 Lateral earth pressure behavior induced by active displacement · 60
4.6.2 The relationship between lateral earth pressure behavior and GeoPIV image analysis 65
4.6.3 Interface shear strength parameters at pullout 70
4.6.4 Apparent friction coefficient and interaction coefficient ratio between soil and geogrid 73
4.7 Discussion 75
4.7.1 Stability assessment of MSE wall backfill reinforced with XG- BPST 75
4.7.2 Addressing MSE wall backfill limits using XG-BPST reinforcement 77
4.8 Summary 78
CHAPTER Ⅴ ASSESSMENT OF XG-BPST FEASIBILITY FOR SLOPE SURFACE PROTECTION 81
5.1 Introduction 81
5.2 Materials 83
5.2.1 Main soil 83
5.2.2 Soil conditioner 84
5.2.3 Xanthan gum biopolymer (XG) 84
5.2.4 Geotechnical properties of improved soil 85
5.3 Methodology 87
5.3.1 Soil pocket penetrometer (SPP) 87
5.3.2 Laboratory rainfall simulator 88
5.3.3 Plant growth test of improved soil 91
5.4 Test results and analysis 94
5.4.1 Relationship between SPP cone index and compaction 94
5.4.2 Strength verification of improved soil and the relationship of SPP cone index 96
5.4.3 Verification of improved soil erosion mitigation through laboratory rainfall simulator 100
5.4.4 Plant growth characteristics based on soil conditioner 110
5.4.5 Shear behavior of XG-BPST with plant roots 113
5.5 Discussion 117
5.6 Summary 128
CHAPTER Ⅵ CONCLUSIONS 132
6.1 Conclusions on the engineering applicability of XG-BPST for sustainable geotechnical structures 132
6.2 Future research needs for field application of XG-BPST 135
REFERENCES 137
국문 초록 155
