ポーラリメトリック・ボアホールレーダによる地下き裂の性状評価と水理性推定への応用

Tohoku University佐藤源之課

Mining Safety and Sustainability I

Safety and sustainability are becoming ever bigger challenges for the mining industry with the increasing depth of mining. It is of great significance to reduce the disaster risk of mining accidents, enhance the safety of mining operations, and improve the efficiency and sustainability of development of mineral resource. This book provides a platform to present new research and recent advances in the safety and sustainability of mining. More specifically, Mining Safety and Sustainability presents recent theoretical and experimental studies with a focus on safety mining, green mining, intelligent mining and mines, sustainable development, risk management of mines, ecological restoration of mines, mining methods and technologies, and damage monitoring and prediction. It will be further helpful to provide theoretical support and technical support for guiding the normative, green, safe, and sustainable development of the mining industry

침투실험을 통한 입도분포가 좋은 풍화토의 내부불안정성 평가

학위논문(박사) -- 서울대학교대학원 : 공과대학 건설환경공학부, 2022. 8. 정충기.Internal erosion is an important process that affects the stability of a fill dam. Suffusion and suffosion, also known as internal instability, are forms of internal erosion. Suffusion involves the selective erosion of fine particles from the matrix of coarse particles of an internally unstable soil through seepage flow, thereby removing the fine particles through the voids and leaving behind a soil skeleton formed by coarse particles. Suffosion is a similar process but results in volume changes. The erosion of fine particles increases the soil permeability, resulting in a decrease in shear strength and changes in hydraulic conditions. In turn, this scenario may cause various types of dam failures. Generally, gap-graded soil with two distinct grain sizes is vulnerable to internal instability. Such soils show clear manifestations of suffusion, such as the erosion of a significant quantity of fine particles and an increase in permeability and void ratio. Therefore, previous studies on seepage erosion problems commonly focused on gap-graded soils as the target. However, no study has shown whether the well-graded soils, used as fill dam materials in South Korea, are susceptible to suffusion. Moreover, the process and cause of internal instability in well-graded soils have not been investigated. In this dissertation, suffusion tests were performed on gap-graded and well-graded soils with different relative densities by using a newly developed suffusion test apparatus. In short-term tests, hydraulic gradient was increased stepwise, and the occurrence of internal instability were analyzed. In contrast to gap-graded soils, well-graded soils showed a continuous reduction in permeability before the initiation of internal instability. At the onset of internal instability, permeability and soil discharge suddenly increased. Additionally, when the relative density of well-graded soils increased, the hydraulic gradient required to reach an unstable state also increased. Long-term tests were carried out to analyze the progress and cause of the internal instability of well-graded soils at constant hydraulic gradients. Results revealed that well-graded soils in internally stable conditions had clogging of fine particles in the bottom, which reduces the overall permeability. Similar clogging was identified in internally unstable conditions, and subsequent unclogging resulted in a rapid increase in permeability and erosion rate with the collapse of soil structure. Consequently, the internal instability of well-graded soils developed in the form of suffosion. On this basis, the mechanism of internal instability and its progress in well-graded soils were proposed. Seepage tests with pore water pressure transducer were used to verify the above mechanism of internal instability in well-graded soils. The erosion of fine particles increased permeability and decrease the pressure, while the clogging of fine particles decreased permeability and increased pressure. Consequently, the test confirmed that the movement path of fine particles and verified the mechanism of internal instability in well-graded soils. Results indicated that the characteristics and development of the internal instability of well-graded soils differed from those of gap-graded soils. The findings can be used to deepen the understanding of the development of internal instability in well-graded soils.내부 침식은 성토댐의 안정성에 영향을 미치는 중요한 원인 중 하나이며, 내부불안정성으로 알려진 suffusion과 suffosion은 내부 침식의 한 형태이다. Suffusion은 부피 변화없이 침투압에 의해서 세립질이 조립질 사이를 이동하여, 선택적으로 침식되는 것으로 정의하고, Suffosion은 suffusion과 같은 메커니즘으로 발생한, 부피변화를 동반한다고 정의하고 있다. 내부불안정성이 발생하면 세립질이 유출되어 간극비가 증가하고, 이로 인해 투수계수가 증가하며, 흙의 전단강도가 감소할 수 있다. 또한, 후방침식, 침하, 사면붕괴의 원인이 될 수도 있다고 알려져 있다. Gap-graded soil은 양극화된 세립질과 조립질로 이루어진 흙으로, 일반적으로 내부불안정성에 취약하며, 세립질의 유출과 투수계수, 간극비의 증가와 같은 명확한 내부불안정성을 보인다. 따라서, 주로 gap-graded soil을 이용하여 내부불안정성에 대한 연구를 수행하였다. 그러나 국내 흙댐 제체재료와 같이 여러가지 입도분포가 혼합되어있는 well-graded soil에 대한 연구는 제한적으로 수행되었으며, 내부불안정성 발생 여부 및 형태, 원인에 대한 분석이 부족한 실정이다. 따라서, 본 논문에서는 새로 개발한 내부불안정성 실험 장치를 이용하여, gap-graded soil과 well-graded soil에 대하여 다양한 상대밀도와 동수경사에서 침투실험을 실시하였다. 단기실험에서는 동수경사를 단계적으로 증가시키며 실험을 수행하고, 흙의 유출량과 투수계수를 기준으로 내부불안정성의 발생을 분석하였다. 실험 결과, well-graded soil은 gap-graded soil과는 달리 내부불안정성이 시작되기 전에 투수계수가 감소하다 내부불안정성이 시작될 때 급격하게 투수계수와 흙의 유출속도가 증가하는 경향을 보였다. 또한, 상대밀도가 증가할수록 내부불안정성이 발생하는 동수경사가 증가하였다. 장기실험은 내부불안정성의 진행과정과 원인을 분석하기 위하여 동수경사를 일정하게 유지하면서 수행하였다. 내부적으로 안정한조건에서 well-graded soil은 하부에 세립분들이 막히면서 전체 투수계수를 감소시켰고, 내부적으로 불안정한 조건에서는 투수계수가 감소하다가 흙의 유출량과 투수계수가 갑자기 증가하는 경향을 보였다. 또한, 조립질과 세립질이 같이 유출되며 침하가 발생하는 suffosion의 형태로 내부불안정성이 진행되었다. 실험결과를 바탕으로 well-graded soil의 내부불안정성의 진행 메커니즘을 제안하였다. 제안된 내부불안정성 메커니즘을 검증하기 위하여 간극수압계를 설치한 침투실험을 실시하였다. 세립질이 유출되는 부분은 투수계수가 증가하고, 간극수압이 감소한 반면, 세립질이 쌓이는 부분은 투수계수가 감소하고, 간극수압이 증가하였다. 따라서, 간극수압을 측정하여 세립질의 이동을 조사하고 메커니즘을 검증하였다. 본 연구에서는 well-graded soil의 내부불안정성의 특성 및 진행과정이 gap-graded soil과 다름을 확인하였고, 그 원인에 대하여 분석하였다. 이 연구 결과는 well-graded soil에서 내부불안정성의 진행과정을 이해하고, 안정성을 평가하는 참고자료로 사용될 수 있을 것이다.Chapter 1. Introduction 1 1.1 Research Background 1 1.2 Objective and Scope of Research 7 1.3 Organization and Structure 9 Chapter 2. Literature review 11 2.1 Introduction 11 2.2 Conditions governing the internal instability 13 2.2.1 Geometric condition 13 2.2.2 Hydraulic condition 16 2.3 Previous studies on well-graded soil 22 Chapter 3. Research methods 26 3.1 Introduction 26 3.2 Testing materials 27 3.2.1 Particle size distributions and properties of specimens 27 3.2.2 Assessment of the internal instability 29 3.3 Experimental apparatuses 34 3.3.1 Apparatus for the short-term and long-term tests 34 3.3.2 Apparatus with pore pressure transducer 38 3.4 Experimental procedure and program 42 3.4.1 Short-term tests 42 3.4.2 Long-term tests 45 3.4.3 Tests with pore pressure transducer 46 Chapter 4. Short-term test results and analyses 48 4.1 Introduction 48 4.2 Short-term test results and analyses 49 4.2.1 Gap soil with a relative density of 78% 49 4.2.2 WG soil with a relative density of 50% 51 4.2.3 WG soil with a relative density of 65% 53 4.2.4 WG soil with a relative density of 80% 56 4.3 Assessment of internal instability 59 4.4 Summary 63 Chapter 5. Long-term test results and analyses 65 5.1 Introduction 65 5.2 Amount of eroded soil and erosion rate 68 5.3 Hydraulic conductivity 73 5.3.1 Gap soil 75 5.3.2 Internally stable WG soil 79 5.3.3 Internally unstable WG soil 84 5.4 Settlement 92 5.5 Mechanism of internal instability 98 5.6 Summary 103 Chapter 6. Test results with pore pressure transducer 106 6.1 Introduction 106 6.2 Hydraulic conductivity and pore water pressure 108 6.2.1 Internally unstable result 109 6.2.2 Internally stable result 114 6.3 Verification of mechanism of internal instability in WG soil 118 6.4 Summary 121 Chapter 7. Conclusions and Recommendations 122 7.1 Conclusions 122 7.2 Recommendations for further researches 130 List of References 131박

Environmental Hydraulics Research

This book aims to provide research and engineering applications related to water and hydraulic problems. It is comprised of scientific papers in all topics of hydraulics, in particular, on sustainable water management, environmental hydraulics, ecohydraulics, water–energy nexus, and systems protection and efficiency. Safety and innovation issues, interdisciplinary problems, and linkage of theory to experimental and field applications can also be found within. Solutions of water problems in the form of prediction models, flow simulations, engineering systems, monitoring, management strategies covering scientific investigations and/or experimental or field studies of flow behaviour, hydrodynamics, and climate changes effects and adaptation, new design solutions, innovative approaches in the field of environment, hydraulics, techniques, methods, and analyses to address the new challenges in environmental hydraulics are alo presented and explored. This topic is studied both from a technical and environmental point of view, with the objective of protecting and enhancing the quality of the environment. In a cross-disciplinary field of study, this book comprises open channel/river flows and pressurised systems, combining, among others, new technological, social, and environmental hydraulic challenges, working in water-related fields with available information, new concepts and tools, new design solutions, eco-friendly technologies, and the advanced materials necessary to address the increasing challenges of ensuring a sustainable water environment by promoting the adaptation, flexibility, integration, and sustainability of recognised environmental solutions

Corrosion and Degradation of Materials

Studies on the corrosion and degradation of materials play a decisive role in the novel design and development of corrosion-resistant materials, the selection of materials used in harsh environments in designed lifespans, the invention of corrosion control methods and procedures (e.g., coatings, inhibitors), and the safety assessment and prediction of materials (i.e., modelling). These studies cover a wide range of research fields, including the calculation of thermodynamics, the characterization of microstructures, the investigation of mechanical and corrosion properties, the creation of corrosion coatings or inhibitors, and the establishment of corrosion modelling. This Special Issue is devoted to these types of studies, which facilitate the understanding of the corrosion fundamentals of materials in service, the development of corrosion coatings or methods, improving their durability, and eventually decreasing corrosion loss

Advanced Underground Space Technology

The recent development of underground space technology makes underground space a potential and feasible solution to climate change, energy shortages, the growing population, and the demands on urban space. Advances in material science, information technology, and computer science incorporating traditional geotechnical engineering have been extensively applied to sustainable and resilient underground space applications. The aim of this Special Issue, entitled “Advanced Underground Space Technology”, is to gather original fundamental and applied research related to the design, construction, and maintenance of underground space

Book of Abstracts

no abstrac

Experimental, Numerical and Field Approaches to Scour Research

This book presents fourteen state-of-the-art research papers prepared by research scientists and engineers around the world. They explore the subject of scour related to bridge piers, monopiles, propellers, turbines, weirs, dams, grade-control structures, and pipelines. Their works are based on three different research methodologies, namely experimental, numerical, and field approaches

River Ecological Restoration and Groundwater Artificial Recharge

Three of the eleven papers focused on groundwater recharge and its impacts on the groundwater regime, in which recharge was caused by riverbed leakage from river ecological restoration (artificial water replenishment). The issues of the hydrogeological parameters involved (such as the influence radius) were also reconsidered. Six papers focused on the impact of river ecological replenishment and other human activities on river and watershed ecology, and on groundwater quality and use function. The issues of ecological security at the watershed scale and deterioration of groundwater quality were of particular concern. Two papers focused on water resources carrying capacity and water resources reallocation at the regional scale, in the context of the fact that ecological water demand has been a significant topic of concern. The use of unconventional water resources such as brackish water has been emphasized in the research in this issue