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.

국내 투수 콘크리트 포장을 시공할 시 발생하는 주요 문제점으로는 포장의 다짐도 만족과 다짐형식 및 방법에 의해 표면 공극 막힘 현상이 발생하는 현상을 꼽을 수 있다. 본 연구는 이에 투수성 콘크리트 포장 을 다짐할 시 다짐 에너지의 영향과 다짐 롤러 타입이 공극막힘에 미치는 영향을 실험적으로 규명하고 그 에 따른 개선책을 제시하는 것에 목적을 두었다. 본 연구를 수행하기 위해 두 가지 실험을 진행하였다. 첫 번째, 하중 유도 진동 실험을 실시하여 동일한 크기의 하중을 재하하는 조건 하에 서로 다른 진동시간을 설정하여 다짐 에너지의 영향을 확인하였다. 두 번째, 실제 포장 슬래브를 모사하여 형식이 다른 다짐롤 러를 적용하여 표면 공극 막힘이나 압축강도, 마모저항성 그리고 투수계수를 측정하여 다짐에 의한 성능 변화를 비교하였다. 실험 결과는 다음과 같다. 다짐 에너지가 증가할수록, 단위중량과 압축강도는 증가하나, 공극률과 투수 계수는 감소하는 경향이 나타났다. 물 분사를 실시하면서 철제 표면을 가진 다짐롤러로 다짐을 진행하였 을 시에는 물/시멘트 비의 변화로 인하여 시멘트 페이스트가 발생하여 표면 공극 막힘 현상이 발생하였 다. 그러나 반면 롤러 표면을 오일로 코팅하였거나 고무 롤러를 적용하여 다짐을 실시한 경우, 슬래브 표 면 공극 막힘률이 기존 방법을 사용하였을 시보다 상당히 개선되었으며 시편의 압축강도와 마모저항성 및 투수 성능에 있어서도 더욱 높은 결과치를 나타내었다.

PURPOSES : In this study, an image analysis method is used to evaluate the pore structure characteristics and permeability of hybrid concrete. METHODS: The binder weight of hybrid concrete is set to 400 kg/m3, 370kg/m3, and 350 kg/m3, and for each value of binder weight, the pore structure and permeability of concrete mixture is evaluated. The permeability of hybrid concrete is evaluated using a rapid chloride penetration test(RCPT). RESULTS : The concrete pore structure characteristics of hybrid concrete reveals that as the binder weight is reduced, the entrained air is reduced and the entrapped air is increased. The permeability of the hybrid concrete for all values was measured to be below 1000 C, which indicates a "Very Low" level of permeability relative to the evaluation standard of KS F 2711. Additionally, as the binder weight is decreased, there is a significant increase in the permeability of chloride ions. CONCLUSIONS : In this study, the pore structure characteristics of hybrid concrete at different binder weights shows that as the binder weight is reduced, the entrained air is reduced and the entrapped air is increased. Consequently, chloride ion penetration resistance of the hybrid concrete is diminished. As a result, it is expected that this will reduce the concrete’s durability.

PURPOSES: This study is to evaluate the dynamic modulus changes of permeable asphalt mixtures by using non-destructive impact testing method and to compare the dynamic moduli of permeable asphalt mixtures through repeated freezing and thawing conditions. METHODS: For the study, non-destructive impact testing method is used in order to obtain dynamic modulus of asphalt specimen and to confirm the change of dynamic modulus before and after freezing and thawing conditions. RESULTS : This study has shown that the dynamic moduli of asphalt concrete specimens consisting of 10%, 15% and 20% porosity are reduced by 11.851%, 1.9564%, 24.593% after freezing and thawing cycles. CONCLUSIONS : Non-destructive impact testing method is very useful and has repeatability. Specimen with 15% porosity has high durability than others.