PURPOSES : In this study, a numerical clogging model that can be used to realistically visualize the movement of particles in cylindrical permeability test equipment was proposed based on the system coupling of computational fluid dynamics with the discrete element method and experimental permeability test results. This model can also be used to simulate the interaction of dust particles with bedding particles. METHODS: A 4-way system coupling method with multiphase volumes of the fluid model and porous media model was proposed. The proposed model needs to consider the influence of flow on the dust particles, interaction between the dust particles, and interaction between the dust particles and bedding layer particles. The permeability coefficient of the bedding layer in cylindrical permeability test equipment was not calculated by using the permeability test result, but was estimated by using the particle packing model and Ergun model. RESULTS : The numerical simulation demonstrated a good agreement with the experimental test results in terms of permeability and drain time. Additionally, the initial movement of particles due to the sudden drain hole opening was successfully captured by the numerical model. CONCLUSIONS : A 4-way coupling model was sufficient to simulate the water flow and particle movement in cylindrical permeability test equipment. However, additional tests and simulation are required to utilize the model for more realistic block pavement systems.

PURPOSES : In this study, a series of fundamental falling head permeability tests were conducted on a binary particle mix bedding to determine the minimum water level, bedding layer thickness, and amount of dust that can result in the stable permeability with high repeatability. The determined condition is used to develop a CFD-DEM coupled clogging model that can explain the movement of dust particles in flowing water of a block pavement system. METHODS: A binary particle mixture is utilized to experimentally simulate an ideal bedding layer of a block pavement system. To obtain a bedding layer with maximum packing degree, the well-known particle packing degree model, i.e., the modified Toufar model, was utilized. The permeability of the bedding layer for various water levels, bedding layer thicknesses, and amounts of dust was calculated. The permeability for a small water level drop was also plotted to evaluate the effect of dust on the bedding layer clogging. RESULTS: It was observed that a water level of 100 mm, bedding depth of 70 mm, and dust amount of 0.3 g result in a stable permeability condition with high repeatability. The relationship between the minimum dust amount and surface clogging of the bedding layer was suggested based on the evaluation of the volumetric calculation of the particle and void and the permeability change in the test. CONCLUSIONS: The test procedure to determine the minimum water level, bedding thickness, and dust amount was successfully proposed. The mechanism of clogging on the surface of the bedding layer was examined by relating the volumetric characteristics of dust to the clogging surface.

Two step rapid filter system as a pre-treatment for the injected water into aquifer storage and recovery (ASR) in Korea was developed to reduce physical blockage and secure the volume of the injected water. First, single rapid sand filters with three different media sizes (0.4~0.7, 0.7~1.0 and 1.0~1.4 mm) were tested. Only two sizes (0.4~0.7 and 0.7~1.0 mm) satisfied target turbidity, below 1.0 NTU. However, they showed the fast head loss. To prevent the fast head loss and secure the volume of the injected water, a rapid anthracite filter with roughing media size (2.0~3.4 mm) were installed before a single rapid sand filter. As results, both the target turbidity and reduction of head loss were achieved. It was determined that the media size for a rapid sand filter in two step rapid filter system (i.e. a rapid anthracite filter before a rapid sand filter) was 0.7~1.0 mm. In addition, the effects of coagulant doses on the removal of natural organic matter (NOM), which might cause a biological clogging, were preliminarily evaluated, and the values of UV254, dissolved organic carbon (DOC) and SUVA were interpreted.

In order to provide the mechanism of nozzle clogging, recovered nozzles for high strength steel grade were examined carefully after continuous casting. The thickness of clogged material in SEN is increased in the following order: from the bottom to the top of the nozzle, upper part of slag line, and the pouring hole. Nozzle clogging material begins to form due the adhesion of metal to nozzle wall, the decarburization, and reduction of oxide in the refractory by Al and Ti in the melt. The reduction of oxide in the refractory by Al and Ti improves the wettability of the melt on the refractory and forms a thin Al-Ti-O layer. Metal containing micro alumina inclusions is solidified on the Al-Ti-O layer, and the solid layer grows due to the heat evolution through the nozzle wall. Thermodynamic calculation has been made for the related reactions. The effect of superheat to the nozzle clogging is discussed on ultra low carbon steel and low carbon steel.

NATM터널의 경우 대부분 산악지역에 위치함에 따라 배수형 터널이 지배적이다. 그러나 NATM 터널에서의 배수기능 저하와 수압작용, 이에 따른 라이닝 변상(누수, 백태 등)이 다수 보고되었으며, 매년 내구성과 사용성 확보를 위한 유지관리 비용이 투입되고 있다. 본 연구에서는 고속철도 NATM 터널을 대상으로 최근 실시한 정밀안전진단 결과를 활용하여 횡배수관 막힘 현상과 지보패턴과의 상관관계 분석사례를 소개하고 향후 개선방안에 대한 연구방향을 제시하고자 한다.

터널은 지하수 처리방법에 따라 배수형 및 비배수 방수형식으로 구분된다. 배수형 방수형식 터널은 콘크리트 라이닝 배면의 지하수에 대한 수압을 고려하지 않으므로 대단면 터널 및 얇은 라이닝 콘크리트 두께 등 터널형상 선정에서 자유롭고 경제적인 장점이 있다. 하지만 터널의 배수시스템에 문제가 생기는 경우 라이닝 콘크리트 배면에 지하수로 인한 수압으로 장기적인 측면에서 터널의 구조적 안전성에 영향을 주기 때문에 터널의 내구연한 동안 배수시스템에 대한 유지관리와 문제 발생 시 적절한 보수, 보강 방법의 적용이 필요한 실정이다.

The clogging of transverse drainage pipes in NATM tunnel is attributed to the hydraulic pressure generated on the outside of lining concrete and affects the safety of the whole structure in the long term, necessitating a keen attention in terms of its maintenance. Accordingly, this paper will introduce an analysis on the effect of the clogging of transverse drainage pipes on the lining structure based on the comparison between the inspection of the clogging of transverse drainage pipes and the visual inspection (leakage, efflorescence).

The latest precise inspection for safety and diagnosis has found the clogging of transverse drainage pipes in NATM tunnel, resulting in hydraulic pressure generated on the outside of lining concrete that poses a safety threat to the tunnel structure. Accordingly, this paper aims to conduct a safety analysis on using NATM tunnel that currently suffers the clogging of transverse drainage pipes based on its numerical analysis.

In this study, The correlation between drainage clogging of drain tunnel and leakage of lining was analyzed. As a result of analysis, the position of clogged drainage hole, leakage and efflorescence location are similar. When repairing leakage of lining, the maintenance method should be selected considering the clogging of tunnel drainage.

Clogging of the filter media which is brought by physical, chemical, and biological factors tend to reduce the lifespan of filters and remains a challenge. In this study, a laboratory column test method was used to investigate the evolution of physical and biological clogging in a non-vegetated filter media system with layers of sand, gravel, and woodchip. Blank column tests using either sand or gravel were conducted and investigated. Several column setups with varying arrangements and particle sizes of sand and gravel were also prepared to identify the best filter media combination that is least susceptible to clogging without compromising the treatment capacity. Artificial stormwater runoff was introduced in the system at a specific hydraulic loading rate (HLR) and influent characteristics. The degree of clogging was quantified by monitoring the variations in the hydraulic head at different levels of the columns. Water samples were also collected, tested, and analyzed at the end of each test run in order to measure the treatment efficiency of the filter. The insights and results of this study can justify the physical and biological clogging formation in filter media and therefore be used to suggest some filter media particle size modifications that can help to improve the sediment removal and treatment performance. Moreover, it can also aid to reduce the maintenance frequency and costs of a stormwater filter system.

최근 설계빈도 이상의 집중호우 발생시 배수로에 퇴적된 토사 및 유송잡물은 배수로의 통수능력을 감소시켜며 배수로 월류로 인한 토양의 습윤량 증가는 산사태의 발생가능성을 향상시킨다. 2011년 우면산과 2014년 부산의 산사태 발생은 토사 및 유송잡물등에 의한 주거지역 및 주요시설물 지역등에 직접적인 피해를 발생시켰으며 비슷한 토사재해의 사례가 반복적으로 발생하고 있다. 그러나, 현재 배수로 설계기준에서는 토사 및 유송잡물 퇴적으로 인한 배수로 통수단면적 감소의 저감기준이나 저감대책등은 전무한 실정이며 배수로 막힘방지를 위한 저감시설이나 침사지등의 시설은 계획되지 않았다. 배수로 설계시 배수로의 단면여유를 20%정도만을 고려하였을 뿐 명확한 토사퇴적에 대한 대비체계는 검토되지 않았다. 산사태 발생시 토사 및 유송잡물에 의한 피해가 급증하고 배수 및 통수불능에 의한 2차적 피해가 크므로 이에 대한 저감대책 수립이 필요하며 토사 및 유송잡물등의 퇴적을 고려한 배수로 설계가 진행되어야 한다. 본 연구에서는 배수로 막힘방지를 위한 토사 및 유송잡물의 거름시설의 설치를 통해 배수로로 유입하는 토사 및 유송잡물을 포착하고 배수로의 통수능력을 확보하여 재해예방을 통한 인명피해 및 재산피해를 저감하고자 한다.

지하유류비축기지의 수리안정성 평가를 위하여 비축기지 내 관측공을 포함한 공동 주변 지하수의 지화학분석을 수행하였으며, 결과를 근거로 광물학적 클로깅의 가능성을 평가하고, 아울러 미생물학적인 클로깅 가능성을 함께 고려하여 보았다. 물시료들은 대부분 Ca-HCO3에서 Ca-HCO3-SO4 유형에 속하며 물시료의 유형에 따른 차이를 보이지 않는다. 주요 클로깅 유발광물인 방해석은 모든 관측공 및 공동운영수 시료에서 불포화상태로서 탄산염 광물에 대해 침전하지 않는 지화학 환경이다. Fe, Mn은 대부분 낮은 함량을 보이지만 포화지수계산결과에 의하면 대부분 철-산화/수산화 광물에 대해 포화-과포화 상태를 보여주며 높은 용존산소 농도를 보여주기 때문에 장기적으로는 이들에 의한 클로깅의 가능성을 지시한다. 일부 지상 관측공 물시료의 경우에는 철-산화/수산화 광물과 더불어 미세한 열극을 충전할 수 있는 점토광물에 대하여 높은 포화 지수를 보여주어 이들 광물의 침전에 의한 클로깅 가능성을 지시하고 있다. 통계분석 결과, 광물들의 침전/용해 정도는 주로 pH, Eh, DO에 의해 좌우된다. 미생물 분석결과는 대부분의 물시료에서 호기성 미생물과 점액성 세균이 우세하며 황환원세균 등의 혐기성균은 대부분 아주 적거나 검출이 되지 않았다. 클로깅을 유발시키는 미생물로 알려져 있는 점액성 세균은 모든 시료에서 105 CFUs/mL 이하의 값을 나타내고 있지만, 일부 관측공들에서 점액성세균이 우점하고 있기 때문에 장기적 관점에서는 이들이 클로깅의 원인으로 작용할 수 있으며 철 수산화/산화 광물의 침전가능성과 함께 고려하면 클로깅 가능성이 더욱 상승되는 효과를 가져올 수 있기 때문에 지하유류비축기지의 안정적인 운영을 위하여 클로깅 평가와 관련된 체계적이고 장기적인 프로그램이 필요하다.