• The Journal of Engineering Geology
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• v.32 no.4
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• pp.483-498
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• 2022

Soil moisture is defined as water in the pores of the soil's unsaturated zone, and it is closely related to various hydrological processes. This study aims to provide meaningful data by identifying factors affecting soil moisture through comparing soil moisture content and soil permeability in a study area covering six different land use types in an agricultural region that is highly dependent on groundwater. We conduct auto-correlation analysis, spectral density analysis, and cross-correlation analysis using time-series data. Soil moisture content shows to have weak auto-correlation and memory effects, and precipitation appears to have a substantial influence on soil moisture content. Saturation hydraulic conductivity does not vary markedly with changing land use, and instead appears to be affected by the inhomogenous soil structure.

• Journal of the Korean Institute of Gas
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• v.26 no.2
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• pp.1-8
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• 2022

The purpose of this study is to prepare GPTMS((3-Glycidoxypropyl) trimethoxysilane)-SiO₂ nanofluid and analyze the effect of nanofluid injection on carbonate reservoirs. Structural analysis of silica nanoparticles modified by GPTMS was investigated by FTIR(Fourier transform infrared spectroscopy). C-H stretching vibrations at 2,950 cm^-1 indicating the silica surface modification with GPTMS were observed when the silane feed was over 0.5 mmol/g. Also, the coreflooding test by nanofluid injection on the aged limestone and dolomite plug samples was carried out with different particle concentration and flow rate. The incremental oil recovery was up to 18.9%, and contact angle and permeability of carbonate samples were changed by the effect of nanoparticle adsorption on pore which caused wettability alteration and pore size change. Therefore, the prepared nanofluid will be utilized as an injection fluid for enhancing oil recovery and modifying fluid flow properties such as change of rock wettability and permeability in carbonate reservoirs.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.127-127
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• 2023

지표수와 하상 경계층에서 발생하는 흐름 교환은 하천, 호소, 연안, 해안 등 자연계에 존재하는 수환경시스템에서 일반적으로 나타나는 수리학적 특성으로서, 흐름 교환이 발생하는 경계층 아래 하상층 영역을 혼합대(hyporheic zone)라 부른다. 수질오염사고 등에 의해 외부의 오염물질이 하천 내 유입될 경우, 혼합대 흐름에 의해 하상층으로 침투되고 지표수 대비 유속이 느린 하상 내 공극 흐름에 의해 거동함에 따라 이들의 하천 내 체류시간이 증가하게 된다. 따라서, 본 연구에서는 지표수와 하상 흐름을 연계한 수치해석 방법을 적용하여 혼합대가 지표수 내 용질 체류시간에 미치는 영향을 분석하였다. 먼저 연직 2차원 Reynolds 평균 Navier-Stokes(RANS) 방정식과 Darcy 방정식을 연계하여 지표수와 하상 내 흐름을 해석하였다. 지표수 영역은 RANS 방정식을 이용하여 모의하였고, 지표수 흐름해석에서 얻어진 하상의 압력장을 경계조건으로 하여 Darcy 방정식과 함께 하상 내 흐름을 모의하였다. 여기서 하상의 형태는 자연계 하천에서 일반적으로 관찰되는 사련하상(Ripple bed)으로 모사하였다. 이후, 지표수-하상 연계모의를 통해 얻어진 흐름 결과를 바탕으로 지표수-하상 경계층에서 용질거동을 모의하였다. 흐름 모의결과를 과거 실험자료와 비교한 결과, 지표수 영역 내연직흐름 분포를 정확하게 재현하였고, 동시에 혼합대 흐름 구조에 큰 영향을 미치는 지표수-하상 경계층 압력 분포 역시 관측값과 유사하게 나타났다. 용질거동 해석을 통해 얻어진 용질의 체류시간을 분석한 결과, 혼합대 흐름이 고려된 경우(투수성 하상)와 고려되지 않은 경우(불투수성 하상)를 비교했을 때 전자에서 체류시간 분포의 감수곡선이 길어지고 첨두농도가 감소하는 것으로 나타났다. 아울러, 지표수 영역의 유입부 경계의 평균 유속이 증가함에 따라 최대 체류시간이 감소하는 것으로 나타났는데, 이는 지표수-하상 경계층에서의 압력 경사가 커져 혼합대 내 유속이 증가함에 기인하는 것으로 분석되었다.

• Clean Technology
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• v.16 no.2
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• pp.145-152
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• 2010

Various technical methods are applied for removing water from the water-retaining media, and the energy efficiency is the main concern in those methods. The electroosmotic process is studied as an efficient way for dewatering. An experimental electroosmotic reactor is designed and used for evaluating the effects of operational variables. The operational variables such as the electrical fields and the structure of water-retaining medias were studied. Three different shapes of polarized electric fields in ranges of 0-100 V/cm and 0-10 kHz are used as the source of electric voltage. The effect of electroosmotic process with respect to the structural variation is estimated by filling the electroosmotic reactor with the glass beads in 0.18 mm, 0.35 mm and 1.2 mm in diameters. 6% of water removal is obtained in the simulating electroosmotic reactor of glass beads. The estimated energy consumption in the simulating electroosmotic was 330~490 cal/g-water.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.45-45
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• 2020

하천 횡단구조물 하류부에서는 고유속 및 ±압력에 의해 하상재료가 유실되는 세굴현상이 발생한다. 이러한 세굴을 방지하기 위해 횡단구조물 하류부에는 석재, 콘크리트 및 콘크리트 블록 등을 설치 및 포설하여 하상보호공을 설치한다. 하상보호공을 설치하면 설치된 부분은 세굴이 방지 되지만, 하상보호공 끝단 이후에는 지반이 노출되어 있어 노출된 지반에서 고유속 흐름 및 압력변화에 의한 세굴이 발생하는 경우가 많다. 이에 본 연구에서는 하상보호공 끝단 즉, 하상이 노출된 지반에서 압력변화에 따라 하상재료가 유실되므로 압력에너지를 감쇄시키기 위한 하상보호장치를 개발하였다. 개발한 하상보호장치는 본래 다수개가 열을 지어 메트릭스 형태로 설치되도록 하여야 하지만 실험 여건상 단일체로 수리실험을 진행하였다. 하상보호장치는 상판과 하판이 조립된 형태이며 상판과 하판 사이에 이격공간이 구비되어있다. 하상보호장치 검증을 위해 상판과 하판에 쓰이는 판은 수로재질과 같은 아크릴로 제작하였으며, 하상재료의 공극률을 반영하여 다공성 판으로 제작하였다. 다공판의 전체 구멍 면적 대비 판 면적은 35 % 로 동일하다. 상판 구멍 지름 15.0 mm, 4.5 mm 2가지로 제작하였으며, 하판 구멍 지름 3.0 mm 으로 동일하다. 압력변화가 큰 곳에서 작은 곳으로 물이 이동하게 되므로 고유속 수리조건에서 상판과 하판 사이에서의 압력변화를 측정하기 위해 판 중간에 압력계를 설치하였다. 하상보호장치 설치지점 앞 0.3 m 부근에 PIV를 설치하여 유속을 측정하였다. 실험결과 상판의 구멍 직경(15.0 mm)이 클 경우 상판부 압력이 하판부로 전달되어 하판에서 측정되는 압력이 증폭 되었으며, 상판의 다공성 구멍 직경(4.5 mm)이 작을 경우 상판부에서 하판부로 전달되는 압력이 감소하여 하판에서 측정되는 압력이 감소하였다. 상판과 하판의 다공성 구멍의 직경을 적절한 사이즈로 조절하면 상판부의 압력이 하판부로 전달되는 것을 막고 압력에 의해 하상에서 흡출되는 유사를 막을 수 있는 것으로 판단되며 추후 상판과 하판의 다공성판 구멍 직경의 상대적 차이에 따른 압력 감소효율에 관한 연구가 필요하다고 판단된다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1B
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• pp.91-96
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• 2009

Layered double hydroxide is synthesized and used in the arsenate adsorption experiments. The shapes of two materials analyzed by TEM showed that unheated material is amorphous in shape, micro-sized while heat treated material showed more crystallized in shape and nano-sized. X-ray diffraction showed this result more obvious. $N_2$ adsorption-desorption results showed that the materials are mesoporous and the specific surface area of the heated material is more than two times larger than the unheated material. Adsorption of As(V) is expected to be more in the heated material than the unheated material. Kinetic test of arsenate adsorption showed very fast reaction. The reactivity of Fe with As(V) might be the main factor for this result. The reaction kinetic of the heated and the unheated materials were similar and even the adsorption isotherms showed similar results for both materials. Both materials are found to be useful in remediation of soil and groundwater polluted by waste mine tailings consist of high concentration of As(V).

• The Korean Journal of Petroleum Geology
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• v.12 no.1
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• pp.27-33
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• 2006

The possibility of oil reserve has been conformed because the oil has been produced by 450 barrel per day in the West Korea Bay basin of the North Korea. There is also possibility of giant oil reserve since it is geographically close to one of the biggest oil fields of Bohai Basin, China. Based on the on-going oil exploration and the present condition of investment, the areas of ongoing oil exploration are three: West Korea Bay B&C prospect explored by Swedish Taurus, the north of West Korea Bay and Anju basin explored by Canadian SOCO, and East Korea Bay explored by Australian Beach Petroleum. However, there is little or no possibility of oil reserve in the rest sea areas of three. Even though oil reserves were discovered in the some parts of land areas such as Kilju and Myungcheon, it was presumed to have no economical efficiency. Geology in West Korea Bay off the North Korea is similar to that in Bohai Bay off China. The basement consists of thick carbonate rock of the Late Proterozoic and Early Paleozoic overlain by Mesozoic ($6,000{\sim}10,000\;m$) and Cenozoic ($4,000{\sim}5,000\;m$) units. Source rocks are Jurassic black shale (3,000 m or more), Cretaceous black shale ($1,000{\sim}2,000\;m$), and pre-Mesozoic carbonates (several thousand meters). Reservoir rocks are Mesozoic-Cenozoic sandstone with high porosity and pre-Mesozoic fractured carbonate rocks. Petroleum raps are of the anticline, fault sealed, buried hill, and stratigraphic types. It absolutely needs to take up a positive attitude, the activation of ocean science and technology exchange, and the joint research and development of modern MT (Marine Technology) considering the state of establishing new international ocean order forcing on building up 200 nautical mile EEZ (exclusive economic zone) among coastal nations. Both South and North Koreas should extend the ocean jurisdiction and contiguity, and MT development dealing with the same sea areas. It is more urgent problem to find a way to have the North Korea participated in, and then to develop ocean management and ocean industry individually.

• Journal of the Korea Institute of Building Construction
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• v.9 no.4
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• pp.63-73
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• 2009

Recently, the use of lightweight panels in building structures has been increasing. Of the various lightweight panel types, styrofoam sandwich panels are inexpensive and are excellent in terms of their insulation capacity and their constructability. However, sandwich panels that include organic material are quite vulnerable to fire, and thus can numerous casualties in the event of a fire due to the lack of time to vacate and their emission of poisonous gas. On the other hand, lightweight foamed concrete is excellent, both in terms of its insulation ability and its fire resistance, due to its Inner pores. The properties of lightweight concrete is influenced by foaming agent type. Accordingly, this study investigates the insulation properties by foaming agent type, to evaluate the possibility of using light-weight foamed concrete instead of styrene foam. Our research found thatnon-heating zone temperature of lightweight foamed concrete using AP (Aluminum Powder) and FP (animal protein foaming agent) are lower than that of light-weight foamed concrete using AES (alkyl ether lactic acid ester). Lightweight foamed concrete using AES and FP satisfied fire performance requirements of two hours at a foam ratio 50, 100. Lightweight foamed concrete using AP satisfied fire performance requirements of two hours at AP ratio 0.1, 0.15. The insulation properties were better in closed pore foamed concrete by made AP, FP than with open pore foamed concrete made using AES.

• Economic and Environmental Geology
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• v.44 no.3
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• pp.229-238
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• 2011

S-wave, which provides lithology and pore fluid information, plays a key role in estimating gas-hydrate saturation. In general, P- and S-wave velocities increase in the presence of gas-hydrate and the P-wave velocity decreases in the presence of free gas under the gas-hydrate layer. Whereas there are very small changes, even slightly increases, in the S-wave velocity in the free gas layer because S-wave is not affected by the pore fluid when propagating in the free gas layer. To verify those velocity properties of the BSR (bottom-simulating reflector) depth in the gas-hydrate prospect area in the Ulleung Basin, P- and S-wave velocity profiles were derived from multi-component ocean-bottom seismic data which were acquired by Korea Institute of Geoscience and Mineral Resources (KIGAM) in May 2009. OBS (ocean-bottom seismometer) hydrophone component data were modeled and inverted first through the traveltime inversion method to derive P-wave velocity and depth model of survey area. 2-D multichannel stacked data were incorporated as an initial model. Two horizontal geophone component data, then, were polarization filtered and rotated to make radial component section. Traveltimes of main S-wave events were picked and used for forward modeling incorporating Poisson's ratio. This modeling provides S-wave profiles and Poisson's ratio profiles at every OBS site. The results shows that P-wave velocities in most OBS sites decrease beneath the BSR, whereas S-wave velocities slightly increase. Consequently, Poisson's ratio decreased strongly beneath the BSR indicating the presence of a free gas layer under the BSR.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.5
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• pp.21-29
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• 2017

Cold joint caused by construction delay is vulnerable to shear stress and it allows more rapid chloride penetration and diffusion. In the paper, investigation of chloride diffusion coefficient is performed for 1-year cured concrete considering compressive and tensile loading level and cold joint. The results are compared with the previous results in 91-day cured concrete. In the 1-year cured concrete without loading, 10.7% and 10.5% of diffusion reduction are evaluated for those in 91-day cured concrete, respectively. The reduction ratios are almost similar however the result in cold joint concrete shows much higher values. The results in 1-year cured concrete under 30% and 60% of compressive loading show reduction of chloride diffusion by 10.9% and 5.8% compared with 91-day cured results, which is caused by steady hydration of cement particles, so called, time effect. In the case of tensile loading, the differences in results are not significant regardless of time effect and cold joint since micro cracks which is weak point of concrete is much dominant despite of long term curing.