• Geomechanics and Engineering
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• 제4권1호
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• pp.55-65
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• 2012

This paper presents the results of an experimental study on the effect of suction on compressibility and shear behaviour of unsaturated silty soil under various types of loading. A series of laboratory experiments were conducted in a double-walled triaxial cell on samples of a compacted silty soil. In the experiments the soil samples were subjected to isotropic consolidation followed by unloading and subsequent reloading under constant suction and prescribed overconsolidated ratio. The experimental results are presented in the context of an elasto-plastic model for unsaturated soil. The effects of suction on mechanical behaviour of unsaturated silty soil are presented and discussed. It is shown that increasing suction affects the shear behaviour of unsaturated soils, but there is a limit beyond which, further increase in suction will not result in any significant change in the behaviour.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.177-184
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• 2000

Geotube is a tube made of geotextile and hydraulically filled with dredged soil. This technological method has been widely used in the advanced countries of the world to build the shore protection embankment. The dredged contaminated sediments from the lake, river, and harbor can be pumped into the geotube by using the hydraulic pump. So, environments effects can be minimized and enhanced by using this method. This paper presents a field test result of a geotube in the land reclamation project for the Songdo New City construction site. The dredged silty clay was dredged by the dredging ship and hydraulically pumped into the geotube. The height of geotube was measured at every filling stage and also measured width and diameter of geotube with the elapsed time. The unit weight of soil and undrained shear strength of filled soil in a tube were measured at the various locations and heights of geotube with the elapsed time. Geotube technique can be effectively implemented for the silty clayey soil with using the dredging ship.

• Geomechanics and Engineering
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• 제27권6호
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• pp.595-604
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• 2021

With the advantages of high permeability and strength, pervious concrete piles can be suitable for ground improvement with high water content and low bearing capacity. By comparing the strength and permeability of pervious concrete with different aggregate sizes (3-5 mm and 4-6 mm) and porosities (20%, 25%, 30% and 35%), the recommended aggregate size (3-5 mm) and porosity (30%) can be achieved. The model tests of the pervious concrete piles in soft soil (silt and clay) foundations were conducted to evaluate the bearing characteristics, results show that, for the higher consolidation efficiency of the silty foundation, the bearing capacity of the silty foundation is 16% higher, and the pile-soil stress ratio is smaller. But when it is the ultimate load for the piles, they will penetrate into the underlying layer, which reduces the pile-soil stress ratios. With higher skin friction of the pile in the silty foundation, the pile penetration is smaller, so the decrease of the pile axial force can be less. For the difference in consolidation efficiency, the skin friction of pile in silt is more affected by the effective stress of soil, while the skin friction of pile in clay is more affected by the lateral stress. When the load reaches 4400 N, the skin friction of the pile in the silty foundation is about 35% higher than that of the clay foundation.

• 한국토양비료학회지
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• 제45권1호
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• pp.9-15
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• 2012

This study was performed to produce basic data for silty reclaimed tidal lands and to develop techniques of environmentally-friendly utilization in agricultural system. We chose the two sites in Saemangeum reclaimed tidal lands, one (Site I) has been treated with cultivating green manure and conducting the desalinization process through submergence since April, 2007 and the other (Site II) has been under natural condition without artificial treatment. In situ and ex situ physic-chemical properties were determined and comparisons were made for soil profiles examined at these two sites in April 2009. Surface soil of Site I had lower EC and higher field saturated hydraulic conductivity than those of Site II, uncultivated land. Especially, exchangeable sodium content was lowest in Site I Ap1 layer than in other layers. This is probably due to flooding desalination and green manure cultivation. Besides, Ap1 and A2 layers of soil profile in Site I showed brighter soil color and more root observation than those of Site II. This is probably due to green manure cultivation. By the large, for high cash upland crops and intensive agricultural use of silty reclaimed tidal land, site-specific soil ripening such as flooding desalination and green manure cultivation could be useful.

• Environmental Engineering Research
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• 제23권4호
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• pp.462-473
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• 2018

The uranium ore residues from the legacies of past uranium mining and milling activities that resulted from the less stringent environmental standards along with the uranium residues from the existing nuclear power plants continue to be a cause of concern as the final uranium residues are not made safe from radiological and general safety point of view. The deposition of uranium in ponds increases the risk of groundwater getting contaminated as these residues essentially leach through the upper unsaturated geological formation. In this context, a numerical model has been developed in order to forecast the $^{238}U$ and its progenies concentration in an unsaturated soil. The developed numerical model is implemented in a hypothetical uranium tailing pond consisting of sandy soil and silty soil types. The numerical results show that the $^{238}U$ and its progenies are migrating up to the depth of 90 m and 800 m after 10 y in silty and sandy soil, respectively. Essentially, silt may reduce the risk of contamination in the groundwater for longer time span and at the deeper depths. In general, a coupled effect of sorption and hydro-geological parameters (soil type, moisture context and hydraulic conductivity) decides the resultant uranium transport in subsurface environment.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.209-216
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• 2000

When subjected to earthquake shaking, saturated sandy soil may generate excess pore pressure. And a time may come when initial confining pressure will equal to excess pore pressure. Depending on the characteristics of the soil and the length of the drainage path, excess pore pressure was dissipated after earthquake. For this reason, it was induced settlement in grounds and fatal damage of various structures. In this study, settlement in silty sand grounds induced earthquake was evaluated using post-liquefaction constitutive equation between volumetric strain and shear strain from previous study. Using that, it was proposed that simplified estimation of settlement in silty sand grounds induced liquefaction.

• 한국토양비료학회지
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• 제50권5호
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• pp.336-344
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• 2017

The soil water characteristics curve (SWCC) represents the relation between soil water potential and soil water content. The shape and range of SWCC according to the relation could vary depending on soil characteristics. The objective of the study was to estimate SWCC depending on soil types and layers and to analyze the trend among them. To accomplish this goal, the unsaturated three soils were considered: silty clay loam, loam, and sandy loam soils. Weighable lysimeters were used for exactly measuring soil water content and soil water potential. Two fitting models, van Genuchten and Campbell, were applied. Two models entirely fitted well the measured SWCC, indicating low RMSE and high $R^2$ values. However, the large difference between the measured and the estimated was found at the 30 cm layer of the silty clay loam soil, and the gap was wider as soil water potential increased. In addition, the non-linear decrease of soil water content according to the increase of soil water potential tended to be more distinct in the sandy loam soil and at the 10 cm layer than in the silty clay loam soil and at the lower layers. These might be seen due to the various factors such as not only pore size distribution, but also cracks by high clay content and plow pan layers by compaction. This study clearly showed difficulty in the estimation of SWCC by such kind of factors.

• 한국지반신소재학회논문집
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• 제16권1호
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• pp.73-83
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• 2017

모래 및 실트 함유량이 우세한 서해안 저소성 지반(인천, 화성, 군산)에서 실시된 실내 및 현장시험으로부터 얻어진 비배수전단 강도를 이용하여 피에조콘계수(Nkt)를 분석한 후, 이에 대한 적용성을 평가하였다. 인천, 화성 및 군산지역에서 얻어진 일축압축 강도에 의한 콘계수(Nkt)는 19~23, 간이 CU 강도에 의한 값은 13~13.8, 현장베인강도에 의한 값은 11.6~13.1로 평가되었다. 이는 저소성 실트 지반조건에서 일축압축강도가 과소평가되는 원인에 의한 것으로 간이 CU 강도 적용조건과 비교했을 때 콘계수(Nkt)가 약 1.8배 전후로 커지며 분산되는 경향을 나타냈다. 저소성 실트 지반에서 수행된 CPTU 데이터를 이용하여 콘계수(Nkt)를 평가할 때에는 지반의 입도분포, 액소성한계 등의 물리적 특성, 지층 내의 sandseam 분포 등으로 인한 콘선단저항(qt) 및 주면마찰력(fs)의 불규칙한 분포, 간극수압계수(Bq)를 종합적으로 분석하여 수행하는 것이 바람직할 것으로 판단된다.

• 아시안잔디학회지
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• 제20권1호
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• pp.83-91
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• 2006

본 연구는 폐 타이어를 미사질 토양에 혼합하여 경기장 식재층으로서의 질을 향상 시키고자 실시하였다. 특히 본 실험을 통해 토양에 혼합되는 폐 타이어의 입경 크기와 혼합량에 따라 식재층의 토양 물리적 특성을 측정하고자 하였다. 실험에서 두 종류의 토양 [Arenzville silt loam(coarse-silty, mixed, nonacid, mesic Typic Udifluvents), Hosmer silty clay loam(fine-silty, mixed, mesic Typic Fragiudalfs)]과 입경 크기(3.5, 6.5, 9.5mm)에 따라 세 가지의 폐 타이어를 사용하였다. 각각 크기별 토양에 혼합된 폐 타이어의 혼합 비율은 0에서 0.4 $g{\cdot}g^{-1}$ 사이였다. 각각의 처리구에 대한 실험 진행 및 물리성 조사는 미국 골프협회 Green Section Record 의 기준 방법에 준해서 실시하였다. 본 실험의 결과 토양에 혼합된 폐 타이어의 비율이 증가 할수록 토양의 총 공극량은 감소하였다. 하지만 입경 크기와 상관없이 폐 타이어의 혼합량이 0.15 $g{\cdot}g^{-1}$ 이하인 경우에는 대공극과 포화투수계수에 차이가 없었다. 반면 폐타이어가 0.15 $g{\cdot}g^{-1}$ 이상으로 혼합된 토양은 대 공극, 포화 투수계수, 그리고 공기 투과율이 대조구에 비해 통계적으로 유의하게 개선되었다.

• 한국토양비료학회지
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• 제20권1호
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• pp.23-28
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• 1987

간척년수(干拓年數)에 따라 토층별(土層別) 토성(土性)이 다른 토양(土壤)에서 수종토양화학성분(數種土壤化學成分) 변화정도(變化程度)를 알고저 봉남통(鳳南統), 광활통(廣活統) 및 만경통(萬頃統)의 답토양(畓土壤)을 공시(供試)하여 시험(試驗)한 결과(結果)를 보면 다음과 같다. 1. 토양중(土壤中) 가리(加里), 석회(石灰), 고토(苦土), 소-다, 망간, 규산(硅酸) 및 양(陽)ion 치환용량등(置換容量等)은 간척년수(干拓年數)가 경과(經過)할수록 현저(顯著)한 감소(減少)를 보였음. 2. 토양유기물함량(土壤有機物含量)은 간척년수(干拓年數)의 경과(經過)에 따라 증가(增加) 되었는데 증가정도(增加程度)는 사질토양(砂質土壤)에서 현저(顯著)하였다. 그리고 우리나라 전국답토양(全國沓土壤) 평균치(平均値) 2.5%에 달(達)하기 위해서는 간척후(干拓後) 식질토양(埴質土壤)은 30년(年) 양질(壤質)과 사질토양(砂質土壤)은 약(約) 80년(年)이 경과(經過)되어야 할 것으로 예측(豫測)되어짐. 3. 토양중(土壤中) 가리활성도비(加里活性度比)는 토성(土性) 및 작토층위(作土層位)에 따라 상이(相異)했으나 일반답토양(一般沓土壤)의 평균(平均) 0.05~0.2 정도(程度)에 달(達)하기 위해서는 약(約) 50년(年)이 소요(消要)될 것으로 예측(豫測)되어짐. 4. $Na^{{+}{+}}$ion의 흡수율(吸收率), 흡착비등(吸着比等)은 간척년수(干拓年數)에 따라 현저(顯著)한 차이(差異)를 보였는데 특(特)히 사질토양(砂質土壤)에서 감소(減少)의 정도(程度)가 뚜렷하였음. 5. 간척년수(干拓年數)에 따른 점토함량변화(粘土含量變化)는 토층별(土層別)로 상이(相異)했는데 간척후(干拓後) 30년경(年頃)까지는 심토(深土)의 용탈(溶脫)이 현저(顯著)했으나 50년(年) 이후(以後)는 표토(表土)에서 용탈(溶脫)이 큰 경향(傾向)을 보였음.