• Journal of the Korean Geotechnical Society
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• v.17 no.4
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• pp.49-55
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• 2001

본 논문에서는 서해안 폐기물 매립지 하부의 점성토와 고화차수재를 재료로 수행된 확산시험 결과와 현장 조건을 적용하여 오염물이동성에 대한 수치해석을 수행하였다. 무기화합물이 하부 차수재와 원지반퇴적층으로 이동되는 일차원 이동 특성을 대상으로 하였으며 일차원 용질이동해석 프로그램 CDFD(convection-dispersion finite difference)를 현장의 비균질한 지층에 이용할 수 있도록 수정하여 적용하였다. 그 결과 원지반점성토를 통한 용질이동 메카니즘에 확산이 기여하는 정도가 50%로 매우 큰 영향을 갖고 있음을 보여주며 원지반 투수계수가 클수록 인공차수층의 필요성이 증대됨을 알 수 있었다.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.3
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• pp.265-269
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• 2006

This study was to investigate the effect of acidic leachate on the landfill liner system and healing of cracks by using industrial by-products; BFS(Blast Furnace Slag) and FA(Fly Ash). From the results of pH measurement, for OPC(Ordinary Portland Cement) and DM(Dredged Mud) mixtures immersed acidic leachate, the initial pH($4.5{\sim}5.5$) was heavily increased to approximately 10 after 60 days experiment due to the production of 2 mole $OH^-$ which was occurred by hydrolysis of CaO and MgO etc.. Meanwhile, the initial pH of acidic leachate immersed DM mixtures with BFS and FA respectively was lasted for longer period as compared to the comparison. The reason was that production of low Ca C-S-H hydrates which stabilized in acidic liquid. The physical properties(compressive strength, hydraulic conductivity) of DM mixtures added BFS and FA was improved. It was concluded that the dissolution of hydrates was disturbed by high alkalinity of BFS and FA.

• Journal of the Korean Geosynthetics Society
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• v.7 no.2
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• pp.49-52
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• 2008

Most of waste sludge has generally been disposed in landfill site or dumped in the ocean, which will be banned by the content of its heavy metals according to London Dumping Convention in Korea. Therefore, environmentally friend methods are urgently required for the treatment and disposal of the sewage sludge. Thermal hydrolysis is one of the good treatment methods to solve the sludge problems. In this study, the physical and environmental testing was conducted to evaluate the feasibility of by-product cake from the thermal hydrolysis as liner or cover materials in landfill.

• Journal of the Korean Geotechnical Society
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• v.21 no.6
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• pp.147-154
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• 2005

This study deals with the calibration of low-frequency water content reflectometer for measuring the volumetric water content of soils in landfill final cover layer, and the validity of calibrations was evaluated by electrical conductivity and index properties of the soils. Linear calibrations concerning volumetric water content to WCR period provided good agreement with the data. Analysis of the calibration data indicates that the slope of the calibration decreases as the electrical conductivity of the soil increases. Lower slopes correspond to soils with greater clay content, organic content, liquid limit, and plasticity index, which typically have higher electrical conductivity. It could be well explained that WCR can operate in a lower frequency range.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.5
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• pp.1083-1096
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• 2015

This study utilised Computational Fluid Dynamics(CFD) for preliminary assessment of mixing efficiencies of 2-phase fluids in a pipe at which a slurry flow and an injected solidifier join, for the purposes of reducing trial-and-error-based instances of physical experiments and conducting the overall research in an economical way. Using OpenFOAM$^{(R)}$, we simulated behavior of 3-phase fluids under 18 different settings generated by changing diameters of a dredged soil transportation pipe, a quality improving material injection pipe and the confluence angle. While difference in mixing efficiencies amongst the instances was insignificant, discernible boundary layers amongst the materials were observed in all of the instances. In order to break the boundary layers, we designed a substructure inside a pipe and found out that it could remarkably improve mixing efficiencies particularly for short distance applications.

• The Journal of the Korea Contents Association
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• v.16 no.4
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• pp.114-122
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• 2016

Concrete is cost-benefit and high-durable construction material, however durability problem can be caused due to steel corrosion under chloride attack. Recently deicing salt has been widely spread in snowing season, which accelerates micro-cracks and scaling in surface concrete and the melted deicing salt causes corrosion in embedded steel. The previous governing equation of Fick's 2nd Law cannot evaluate the deteriorated surface concrete so that another technique is needed for the surface effect. This paper presents chloride penetration analysis technique for concrete subjected to deicing salt utilizing multi-layer diffusion model and time-dependent diffusion behavior. For the work, field investigation results of concrete pavement exposed deicing salt for 18 years are adopted. Through reverse analysis, deteriorated depth and increased diffusion coefficient in the depth are evaluated, which shows 12.5~15.0mm of deteriorated depth and increased diffusion coefficient by 2.0 times. The proposed technique can be effectively applied to concrete with two different diffusion coefficients considering enhanced or deteriorated surface conditions.

• Korean Journal of Optics and Photonics
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• v.9 no.5
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• pp.307-314
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• 1998

We have studied the effects of interface on polarization dependence of waveguide and designed the polarization independent 2-dimensional waveguides on InP for arrayed waveguide grating. To figure out the effects of interface on polarization dependence, we have solved the 1-dimensional wave equation using a transfer matrix method. It is shown that the birefringence becomes stronger as the number of interfaces increases. In order to design polarization independent 2-dimensional waveguides, we have used effective index method. The structures considered are ridge type, raised strip type, and buried type waveguide. In the cases of ridge and raised strip type, conventional effective index method was used. In the case of buried type corrected effective index method was used. We have determined the height and width of waveguides such that the waveguides become polarization independent.

• The Journal of Engineering Geology
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• v.17 no.3
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• pp.367-379
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• 2007

This study intended to evaluate hydrogeological characteristics in relation to subsurface geology data obtained from borehole, groundwater level, borehole flowmeter test, and field hydraulic tests. The regression equation of groundwater level (Y) versus ground elevation (X) is expressed by Y=0.75X-7.00 with quite high correlation coefficient of 0.78. Relationship between groundwater level and thickness of landfill, alluvium, and weathered zone results in higher correlation of groundwater level (Y) versus natural log value of weathered tone (A) than other correlations, with the regression equation Y= exp(9.974A)-14.155. The result of groundwater flow measurement in the boreholes indicates that groundwater flows towards between south and southwest, and this approximately agree with regional distribution of groundwater levels.

• Journal of the Korean Geotechnical Society
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• v.21 no.10
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• pp.41-48
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• 2005

The gravitational consolidation behavior of the dredged ground with horizontal drains is analyzed using a finite difference program developed for self-weight consolidation analysis with horizontal drains. The influence of area and direction of horizontal drains on the consolidation time and settlement is analyzed. Various field conditions such as the non-treated ground below horizontal drain installed ground, the accumulation of drained water at the end of horizontal drains, are also included in the analyses. It was found that a slight decrease of consolidation time is resulted in the twice increase of the sectional area of drains. Installing drains vertically can reduce the consolidation time more significantly than installing drains horizontally. The analyses showed quantitatively that the non-treated ground below the horizontal drain installed ground has much influence on long term consolidation settlement, and the accumulation of hydraulic head at the end of horizontal drains results in the increase of consolidation time and insufficient consolidation.

• Journal of the Korean Geosynthetics Society
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• v.19 no.4
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• pp.1-9
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• 2020

This study analyzes contaminant movement under transient flow in a rubble mound revetment offshore waste landfill barrier system that prevents contaminant runoff. The barrier system consists of bottom layer and side barrier. For the bottom layer system, impermeable clay layer is used. For the side barrier system, the HDPE barrier sheet (primary element) plays the main role, and the intermediate protection layer (supplementary element) is responsible for the barrier. Seepage, advection, dispersion numerical analysis was carried out using SEEP / W and CTRAN / W programs. As a result, under abnormal conditions considering the fluctuation in tidal range, the volume and direction of the flow velocity vector of the pore water change with time and the dispersion concentration of the contaminant changes. When comparing the case of 2 m tidal range and 8 m tidal range, the larger the tide value, the higher the concentration of contaminant under abnormal conditions. It was found that the rate of change of the concentration of the contaminant changed depending on the change in the tidal range, and as a result, the outflow of the pollutant was smaller than that in the steady flow state.