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.

목 적: 간접적 안구 운동 검사 방법인 New York State Optometric Association King-Devick (NYSOAK-D) 및 Developmental Eye Movement (DEM) 검사를 수행하는 동안 직접적 안구 운동 검사 방법인 안구운동 추적 장치(Eye Movement Tracking Device, SMI, Co.)를 사용하여 측정된 안구 운동 변수가 두 검사수행에 미치는 영향력을 비교하고자 하였다. 방 법: 대학생 86명(22.60±1.68세)을 대상으로 NYSOA K-D 및 DEM 검사를 수행하는 동안 안구 운동추적 장치를 이용하여 주시, 홱보기 및 눈 깜박임 안구 운동 변수의 횟수 그리고 지속 시간을 측정하였다. 결 과: 안구 운동 추적 장치로 측정한 검사 수행 시간은 NYSOA K-D 하위 검사 1, 2 및 3에서 각각15.85±3.46 sec, 15.45±3.32 sec 및 15.69±3.16 sec로 서로 유의한 차이가 없었다. DEM 하위 검사 A, B 및 C에서 16.03±2.82 sec, 16.45±2.96 sec 및 15.69±3.19 sec로 시표가 수직 방향으로 배열된 하위 검사SA 및 SB에서는 유의한 차이가 없었다. NYSOA K-D 및 DEM 검사에서 주시 수행 시간이 홱보기 수행 시간보다 더 많았고, DEM 검사에서 수평 방향보다 수직 방향으로 배열된 시표에서 홱보기 수행 시간이 더 감소하였다. 결 론: NYSOA K-D 및 DEM 검사에서 주시운동의 수행시간이 홱보기보다 더 크고, 수직방향보다 수평방향의 시표에서 홱보기의 수행시간 비율이 상대적으로 증가하였다. 주시 및 홱보기 안구 운동 능력을 명확하게 평가하기 위해서는 다양한 연령과 안구운동이상자를 대상으로 수직 및 수평 배열 시표가 모두 포함된NYSOA K-D나 DEM 검사와 안구운동추적검사를 병행한 후속 연구가 필요하고 생각된다.

PURPOSES: Simulation of aggregate slump test using equivalent sphere particle in DEM and its validity evaluation against lab aggregate slump test METHODS : In this research, aggregate slump tests are performed and compared with DEM simulation. To utilize spheric particles in YADE, equivalent sphere diameter concept is applied. As verification measures, the volume in slump cone filled with aggregate is used and it is compared with volume in slump cone filled with equivalent sphere particle. Slump height and diameter are also used to evaluate the suggested numerical method with equivalent concept RESULTS : Simulation test results show good agrement with lab test results in terms of loose packing volume, height and diameter of slumped particle clump. CONCLUSIONS : It is concluded that numerical simulation using DEM is applicable to evaluate the effect of aggregate morphological property in loose packing and optimum gradation determination based on the aggregate slump test simulation result.