• Environmental Engineering Research
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• 제25권3호
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• pp.356-365
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• 2020

The aqueous carbonation efficiencies of basic oxygen furnace (BOF) and ladle slags at various pressures, temperatures, and liquid-to-solid (L/S) ratios were investigated to determine optimum conditions. The maximum CO₂ carbonated concentrations in slag (0.584 mmol/g for BOF slag and 1.038 mmol/g for ladle slag) was obtained at 10 bars, 40℃, and L/S = 5 mL/g-dry. The L/S ratio was the most critical parameter for carbonation. The effect of carbonated slag amendment on the immobilization of heavy metals in two field-contaminated soils was also investigated. The immobilization efficiencies evaluated by using the toxicity characteristic leaching procedure (TCLP) and the Standards, Measurements and Testing Programme (SM&T) were above 90% for both raw and carbonated slags for all soils. The TCLP-extractable heavy metals concentrations were below the criteria (5.0, 1.0 and 5.0 g/L for Pb, Cd, and Cr, respectively) after immobilizations with both slags except for Pb in soil B. The SM&T analysis showed the decrease in the exchangeable phase but the increase in residual phase after immobilization with raw and carbonated slags. The results of this study imply the promising potential of the carbonated slags on the immobilization of heavy metals in the field-contaminated soils.

• 한국환경과학회지
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• 제25권10호
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• pp.1433-1444
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• 2016

South Korea is a maritime nation, surrounded by water on three sides; hence, it is important to preserve in a sustainable manner. Most areas, especially those bordering the East Sea, have been suffering from severe coastal erosion. Information on the sediment yield of a river basin is an important requirement for water resources development and management. In Korea, data on suspended sediment yield are limited owing to a lack of logistic support for systematic sediment sampling activities. This paper presents an integrated approach to estimate the sediment yield for ungauged coastal basins by using a soil erosion model and a sediment delivery rate model in a geographic information system (GIS)-based platform. For applying the sediment yield model, a basin specific parameter was validated on the basis of field data, that, ranging from 0.6 to 1.2 for the 19 gauging stations. The calculated specific sediment yield ranged from 17 to $181t/km^2.yr$ in the various basin sizes of Korea. We obtained reasonable sediment yield values when comparing the measured data trends around the world with those in Korean basins.

• Geomechanics and Engineering
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• 제10권6호
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• pp.827-836
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• 2016

The rate of softening is an important factor to determine whether the failure occurs along localized shear band or in a more diffused manner. In this paper, strength loss and softening rate effect depending on sensitivity are investigated for weakly cemented clays, for both artificially cemented high plasticity San Francisco Bay Mud and low plasticity Yolo Loam. Destructuration and softening behavior for weakly cemented sensitive clays are demonstrated and discussed through multiple vane shear tests. Artificial sensitive clays are prepared in the laboratory for physical modeling or constitutive modeling using a small amount of cement (2 to 5%) with controlled initial water content and curing period. Through test results, shear band thickness is theoretically computed and the rate of softening is represented as a newly introduced parameter, ${\omega}_{80%}$. Consequently, it is found that the softening rate increases with sensitivity for weakly cemented sensitive clays. Increased softening rate represents faster strength loss to residual state and faster minimizing of shear band thickness. Uncemented clay has very low softening rate to 80% strength drop. Also, it is found that higher brittleness index ($I_b$) relatively shows faster softening rate. The result would be beneficial to study of physical modeling for sensitive clays in that artificially constructed high sensitivity (up to $S_t=23$) clay exhibits faster strain softening, which results in localized shear band failure once it is remolded.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2381-2384
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• 2008

The heat exchange between the Borehole Heat Exchanger(BHE) and the surrounding ground depends directly on ground thermal conductivity k at the certain site. The k is thus a key parameter in designing BHE and coupled geothermal heat pump systems. Currently, although a thermal hydraulic Response Test(TRT) is mostly used in practice, the thermal hydraulic TRT needs additional power and is generally time-consuming. A new, simple wireless probe for hi-speed k determination was introduced in this paper. This technique using a wireless probe is less time-consuming and requires no external source of energy for measurement and predicts local thermal properties by measuring soil temperatures along the depth. Measured temperature data along the depth was analyzed. As a result, the electronic wireless probe can replace the conventional hydraulic TRT method after carrying out the additional research on a lot of local heat flow, etc.

• 한국지반공학회논문집
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• 제19권2호
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• pp.179-187
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• 2003

모래다짐말뚝과 쇄석말뚝 등 연직방향의 보강재를 이용한 방법은 지반의 지지력을 증가, 침하를 감소 등을 기대할 수 있는 효과적인 연약지반 개량공법이다. 이번 연구에서는 지반거동 특성을 이해함에 있어 탄소성이론을 이용하여 복합지반의 등가특성치(E,$\mu,\phi,c$)를 얻을 수 있는 이론식을 제시하였으며, 이론식을 토대로 사례별 등가특성치들을 산정하였다. 또한 산정된 등가특성치를 지반 해석프로그램인 SAGE CRISP을 사용하여 2차원 해석을 수행하여 그 결과를 원지반 특성치로 수행한 해석결과와 비교 분석하였다. 연구결과 원지반 특성치를 대신하여 이론식을 통해 얻은 등가특성치를 이용하여도 비슷한 결과를 얻을 수 있었다. 결과적으로 탄소성이론을 근거로 한 이론식에서 얻은 등가특성치들이 예비설계 단계에서 유용하게 사용될 수 있음을 제시하였다.

• Geomechanics and Engineering
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• 제5권1호
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• pp.57-70
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• 2013

Constant rate of strain (CRS) consolidation tests were conducted for undisturbed Ariake clay samples from three boreholes in Saga Plain of Kyushu Island, Japan. The coefficients of consolidation ($c_{\nu}$) were interpreted from the CRS test results by small- and large-strain theory. Large-strain theory was found to interpret smaller $c_{\nu}$ values and less strain rate effect on $c_{\nu}$ than that by small-strain theory. Comparing the theoretical strain distributions within a soil specimen to those obtained by numerical simulation shows that the small-strain theory can be used only for the dimensionless parameter $c_{\nu}/\dot{\varepsilon}H_0^2{\geq}50$ (where $\dot{\varepsilon}$ is strain rate and $H_0$ is the specimen height), and the large-strain theory can be used for a larger range of strain rates. Applying the criterion to undisturbed Ariake clay with a $c_{\nu}$ value of about $1{\times}10^{-7}\;m^2/s$, it is suggested that the large-strain theory should be adopted for calculating the $c_{\nu}$ value when $\dot{\varepsilon}$ > 0.03%/min.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2008년도 춘계 종합학술대회 논문집
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• pp.788-791
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• 2008

본 연구에서는 한강수계의 소유역을 24개로 분할하였고 강우의 공간 분포를 작성하기 위해 151개의 강우관측소를 이용하여 강우자료를 정리하였다. 한강수계의 주요 제어지점으로 소양강댐, 충주댐, 충주조정지댐, 횡성댐, 화천댐, 춘천댐, 의암댐, 청평댐, 팔당댐을 선정하였다. SSARR(Streamflow Synthesis and Reservoir Regulation) 모형을 기반모형으로 선정하여 모형의 입력자료를 작성하고 2002년의 수문자료를 이용하여 매개변수의 민감도분석을 수행하였다. 민감도 분석 결과, 유역유출과 관련된 매개변수 중 토양습윤상태별 유출율, 침투량별 지하수유입률 및 지표수와 복류수를 분리하는 매개변수가 비교적 큰 민감도를 나타내었다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2015년도 학술발표회
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• pp.175-175
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• 2015

기후변화로 인한 환경문제가 심각하게 대두되고 있는 상황에 하천으로 유입되는 토사에 대한 저감공법에 대한 연구가 활발히 이루어지고 있다. 토사 유출양을 산정하기 위해서는 여러 수문모형을 사용하고 있으며 이에 따른 입력자료에 대한 정확성을 요구하고 있는 실정이다. 하지만 입력 자료 중 DEM의 규격에 따른 특별한 규제가 없어 정량화된 규격을 사용하지 않고 있다. 이에 본 연구에서는 수문모형의 입력자료인 DEM의 셀 사이즈 크기 변화에 따른 토사유출 모의 결과의 변화를 확인하고자 한다. DEM의 셀 사이즈의 크기 변화에 따른 토사유출 모의를 위해 선정된 지역은 미국 위스콘신 주의 산악지형을 가지는 소유역 2곳과 평지지역을 가지는 소유역 2곳을 선정하여 연구를 진행했다. 토사유출량을 산정하기 위해 사용된 모형은 미국 농무성에서 개발되어 공급하고 있는 Arc SWAT을 사용하여 모의하였으며 사용된 DEM의 셀 사이즈는 10m, 30m, 50m, 100m의 규격으로 진행하였다. 모의된 결과를 대표적인 보정 및 검증 모형인 SWAT-CUP을 사용하여 보정 및 검증을 진행하였다. SWAT-CUP을 이용하여 추출해낸 Best parameter를 모든 조건에 동일하게 적용한 뒤 검정을 진행한 결과 DEM의 셀 사이즈 변화에 따른 토사 유출량에 많은 차이가 나타났으며 셀 사이즈크기가 작아질수록 좀 더 많은 양의 토사 유출량을 산정하는 것으로 확인하였다. 본 연구를 통해 DEM 셀 사이즈의 정량화의 필요성을 확인하였으며, 앞으로 진행될 토사 유출 관리를 위한 연구에 많은 도움을 줄 것이라 판단된다.

• Geomechanics and Engineering
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• 제11권6호
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• pp.771-785
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• 2016

The thermal conductivity of soils is an important property in energy-related geotechnical structures, such as underground heat pumps and underground electric power cable tunnels. This study explores the effects of geotechnical engineering properties on the thermal conductivity of soils. The thermal conductivities of quartz sands and Korean weathered silty sands were documented via a series of laboratory experiments, and its variations with effective stress, porosity, and water saturation were examined. While thermal conductivity was found to increase with an increase in the effective stress and water saturation and with a decrease in porosity, replacing air by water in pores the most predominantly enhanced the thermal conductivity by almost one order of magnitude. In addition, we have suggested an improved model for thermal conductivity prediction, based on water saturation, dry thermal conductivity, saturated thermal conductivity, and a fitting parameter that represents the curvature of the thermal conductivity-water saturation relation.

• Earthquakes and Structures
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• 제16권4호
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• pp.487-499
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• 2019

Energy-based seismic design of structures has gradually become prominent in today's structural engineering investigations because of being more rational and reliable when it is compared to traditional force-based and displacement-based methods. Energy-based approaches have widely taken place in many previous studies and investigations and undoubtedly, they are going to play more important role in future seismic design codes, too. This paper aims to compute the maximum earthquake energy input to elastic single-degree-of-freedom (SDOF) systems for selected real ground motion records. A data set containing 100 real ground motion records which have the same site soil profiles has been selected from Pacific Earthquake Research (PEER) database. Response time history (RTH) analyses have been conducted for elastic SDOF systems having a constant damping ratio and natural periods of 0.1 s to 3.0 s. Totally 3000 RTH analyses have been performed and the maximum mass normalized earthquake input energy values for all records have been computed. Previous researchers' approaches have been compared to the results of RTH analyses and an approach which considers the pseudo-spectral velocity with Arias Intensity has been proposed. Graphs of the maximum earthquake input energy versus the maximum pseudo-spectral velocity have been obtained. The results show that there is a good agreement between the maximum input energy demands of RTH analysis and the other approaches and the maximum earthquake input energy is a relatively stable response parameter to be used for further seismic design and evaluations.