• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1463-1474
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• 2008

In order to investigate stabilization effect and sustainability on As-contaminated farmland soils which were affected the abandoned mine site and stabilized by zerovalent iron(ZVI) and industrial by-products, batch-scale and pilot-scale tests were carried out. In batch tests, ZVI and industrial by-products(blast furnace slag, steel refining slag and oyster shell powder) were used in treatment materials to reduce the As leaching. Industrial by-products were mixed with As-contaminated soils, in the ratio of 1%, 3%, 5% and 7% on the weight base of dried soil. The results of batch-scale tests was shown that the reduction of As concentration was observed in all samples and it was expected that ZVI and steel refining slag were more effective than other treatment materials to stabilize As compounds. In pilot-scale tests, columns were filled with untreated soils and treated soils mixed with ZVI and steel refining slag in the same mixing ratio of 3%. Distilled water was discharged into the columns with the velocity of 0.3 pore volume/day. During the test, pH, EC, Eh and As concentration were measured in the regular term(1pore volume). after six months, pilot-scale tests were retested to investigate sustainability of treatment materials. As a result, It was shown that the leachate from control column was continuously released during the test period and its concentration was greater than $100ug{\cdot}L^{-1}$ which was exceeded the national regulation of water discharged to river or stream ($50ug{\cdot}L^{-1}$). On the other hand, soil treated with ZVI and steel refining slag showed that the concentrations of leachate were lower than national regulation of water discharged to river or stream. Therefore it was expected that ZVI and steel refining slag could be applied to the farmland site as the alternative treatment materials.

• Geomechanics and Engineering
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• 제10권6호
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• pp.757-774
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• 2016

Soils are usually weak in tension therefore different materials such as geosynthetics are used to address this inadequacy. Worldwide annual consumption of geosynthetics is close to $1000million\;m^2$, and the value of these materials is probably close to US$1500 million. Since the total cost of the construction is at least four or five times the cost of the geosynthetic itself, the impact of these materials on civil engineering construction is very large indeed. Nevertheless, there are several significant problems associated with geosynthetics, such as creep, low modulus of elasticity, and susceptibility to aggressive environment. Carbon fiber reinforced polymer (CFRP) was introduced over two decades ago in the field of structural engineering that can also be used in geotechnical engineering. CFRP has all the benefits associated with geosynthetics and it boasts higher strength, higher modulus, no significant creep and reliability in aggressive environments. In this paper, the performance of a CFRP reinforced retaining wall is investigated using the finite element method. Since the characterization of behavior of soils and interfaces are vital for reliable prediction from the numerical model, soil and interface properties are obtained from comprehensive laboratory tests. Based on the laboratory results for CFRP, backfill soil, and interface data, the finite element model is used to study the behavior of a CFRP reinforced wall. The finite element model was verified based on the results of filed measurements for a reference wall. Then the reference wall simulated by CFRP reinforcements and the results. The results of this investigations showed that the safety factor of CFRP reinforced wall is more and its deformations is less than those for a retaining wall reinforced with ordinary geosynthetics while their construction costs are in similar range.

• 한국물환경학회지
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• 제32권2호
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• pp.135-141
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• 2016

This study investigated changes of hydrology, soil characteristics, riparian vegetation communities, and geomorphology in sandbars before and after sand-mining to determine the effect of sand-mining at upstream of Guemgang and Bochungcheon streams in Korea. Sand-mining events affected the mining area. They supplied organic matters and nutrients during flood. Sediment deposition caused soil texture change and expansion of vegetation area. However, riverbeds were stabilized after the disturbance. According to the analyses of aerial photographs, the vegetation area was significantly expanded in both dam-regulated streams and dam-unregulated streams after sand-mining. Willow shrubs advanced in disturbed area at an average of 10 years after sand-mining. It took willows trees 10.6 years to become dominant communities. Therefore, it took a total of 20.6 years for new riparian forest to form in sandbar after sand-mining. Our results confirmed that stream flow condition were dependent on vegetation recruitment in dam-regulated streams and dam-unregulated streams. For willow recruitment in unregulated streams, calculation of water level below dimensionless bed shear stress is important because low water level variation is a limiting factor of vegetation recruitment.

• 대한토목학회논문집
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• 제42권1호
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• pp.23-33
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• 2022

상시미동의 수직성분에 대한 수평성분 스펙트럼비(HVSR)는 부지 공명주파수를 파악하는데 활발히 사용되고 있다. HVSR의 가장 큰 비율을 가지는 주파수는 부지 공명주파수와 일치한다. 상시미동은 부지 주변에 존재하는 미세진동을 의미하기 때문에 직접적인 진동원을 파악할 수 없으며, 또한 조절할 수 없다. 따라서 신뢰적인 상시미동 HVSR을 구하기 위해서는 상시미동 측정에 충분한 시간적 여유와 주변 환경의 파악 또한 필요하다. 본 연구에서는 신뢰적인 HVSR 분석에 필요한 상시미동 측정 최소시간과 지진계와 인위적인 진동 사이의 이격거리의 영향을 알아보았다. 토사 부지의 경우 센서 설치 후 5분 이내에 안정화가 되었으나, 암반 부지의 경우 안정화까지 1시간 이상이 소요되었다. 또한 상시미동 관측 시 발걸음 진동이 지진계 10 m 이내에 존재할 경우 HVSR결과에 큰 영향을 미치는 것을 확인하였다. 이러한 결과는 현장에서 상시미동의 HVSR측정에 필요한 가이드라인을 제공할 것으로 기대된다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1991년도 추계학술발표회 논문집 지반공학에서의 컴퓨터 활용 COMPUTER UTILIZATION IN GEOTECHNICAL ENGINEERING
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• pp.123-132
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• 1991

The GEOKST program was used to solve the tunnel example problem. The package can solve such geotechnical problem as excavation, embankment, foundations, etc., in which the soil can be modeled by various elastoplastic geomaterial models. The main objective was to consider the effects of excavation depth to the face of the tunnel on the stability of the ground and support system. Depended on the strength of the ground materials, the limit excavation depth without any support system could be established by analyzing three-dimensional excavation problem. In this given example problem, the strengths of the ground materials were enough for the stability of the tunnel without any support system up to fairly deep excavation and the maximum tunnel section displacement was stabilized as the excavation proceed. The asymptotic value was approximately the same as that of the plane strain analysis. Thus, assuming the plain strain condition and simulation the actual excavation procedure, the maximum tunnel section displacement was caculated after final step. The maximum calculated displacement occured at the top section of the tunnel geometry and was about 8mm.

• 한국환경복원기술학회지
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• 제13권1호
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• pp.112-120
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• 2010

This study was carried out to develop the environmental friendly restoration technique for various disturbed slopes using native plants seed chips. As the result of the separated seeding using the developed seed chips of native plant combination, average germination rate and survival rate of trees, shrubs, and herbs were higher than those of the direct seeding, as 79~70%, 83~73%, and 59~53% or so, respectively. Also, the germination rates and the survival rates of trees, shrubs, and herbs in the separated seeding by the native plants seed chips were 10~15 times higher than those of the direct seeding. Numbers of plants survived were at least 10 times of that of the simple seeding. The native plants seed chip technique is more efficient in soil slopes compared with stone slopes. The application of the native plants seed chip technique makes the restoration stabilized through the herbs dominant vegetation to the woody dominant 1 within 3 years, and the Landscapes also changed from herbs to variously combined herbs and woody. The technique using native plants seed chips that can be applicable to various disturbed slops is more efficient than conventional restoration techniques in the respect of economics and landscape.

• 미생물학회지
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• 제33권3호
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• pp.187-192
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• 1997

토양으로부터 biosurfactant를 생산하는 미생물을 분리하여 Tsukamurella sp. 26A로 동정하였다. Biosurfactant 생산을 위한 최적 배지 조성은 n-hexadecane 7%, $NaNO_{3}$ 0.2%, $K_2HPO_4$ 0.001%, $MgSO_{4}$ center dot $7H_{2}O$ 0.02%, $CaCl_2$ center dot $2H_{2}O$ 0.02%, yeast extract 0.02%(pH 6.8-7.0, 30^{\circ}C.$ )이었으며 배양액의 최저 표면장력과 계면장력은 각각 30mN/m, 1.5mN/m였다. 유화기질로서 hydrocarbon류, edible oil류, 그리고 petroleum oil등에 작용시켰을 경우 비교적 높은 유화활성과 유화 안정도를 나타내었다.

• Geomechanics and Engineering
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• 제17권5호
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• pp.429-438
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• 2019

Microbially induced carbonate precipitation (MICP) is an innovative soil improvement approach utilizing metabolic activity of microbes to hydrolyze urea. In this paper, the shear response and the erodibility of MICP-treated sand under axial compression and submerged impinging jet were evaluated at a low confining stress range. Loose, poorly graded silica sand was used in testing. Specimens were cemented at low confining stresses until target shear wave velocities were achieved. Results indicated that the erodibility parameters of cemented specimens showed an increase in the critical shear stress by up to three orders of magnitude, while the erodibility coefficient decreased by up to four orders of magnitude. Such a trend was observed to be dependent on the level of cementation. The treated sand showed dilative behavior while the untreated sands showed contractive behavior. The shear modulus as a function of strain level, based on monitored shear wave velocity, indicated mineral debonding may commence at 0.05% axial strain. The peak strength was enhanced in terms of emerging cohesion parameter based on utilizing the Mohr-Coulomb failure criteria.

• 한국토양비료학회지
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• 제18권4호
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• pp.392-406
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• 1985

인삼재배(人蔘栽培) 예정지(豫定地) 토양(土壤)에 산야초퇴비(山野草堆肥) 및 미원(味元) 유기질비료(有機質肥料)(아미노산 부산비료박(副産肥料粕) 처리구(處理區)와 유기질비료(有機質肥料)를 생산성분량(生産性分量)으로 2.5, 5, 10, 20, 30, 40kg/10a를 각각(各各) 시용(施用)하고 부족(不足)되는 산소성분량(酸素成分量)을 산야초퇴비(山野草堆肥)로 혼합(混合)한 후(後) 처리(處理)한 후(後) 기경(起耕)하면서 토양(土壤)의 이화학적(理化學的) 성질(性質)의 변화(變化)를 경시적(經時的)으로 조사(調査)하였으며, 예정지(豫定地) 관리후(管理後) 묘삼(苗蔘)을 이식(移植)하여 생육상태(生育狀態) 및 유효성분의 함량(含量)을 비교(比較)하였다. 1.예정지(豫定地)를 관리(管理)함에 따라 토양(土壤)의 가비중(假比重)은 감소(減少)되는 경향(傾向)이었고, 40일(日)까지의 감소(減少)는 경운(耕耘)에 의한 물리적(物理的)인 개량효과로 보였으며, 40일(日) 이후(以後) 부터는 유기질(有機質)의 효과로 생각되었다. 진비중(眞比重)도 같은 경향(傾向)이었고 공극률(孔隙率)은 증가하였다. 2. 토양산도(土壤酸度)는 예정지(豫定地) 관리후(管理後) 40일경까지는 낮아졌다가 그 후 높아지는 경향(傾向)이었고, CEC는 대체적으로 증가하는 경향(傾向)이었으며,$NH^+_4-N$는 20일(日)경에 $NO^-_3-N$는 40일(日)경에 최고(最高)로 증가하다가 감소(減少)하는 경향(傾向)이었다. 3. 질내실험(窒內實驗)을 통(通)한 각(各) 처리(處理)에 따른 유기물(有機物)의 경시적(徑時的) 분해속도(分解速度)는 20일(日)까지 처리후(處理後) 왕성하였다가 그 이후(以後)에는 완만하였다. 4. 인삼근중(人蔘根重)은 산야초퇴비(山野草堆肥)로서 질소성분량(窒素成分量) 30kg/10a와 유기질비료(有機質肥料)로서 질소성분량(窒素成分量) 10kg/10a(비료(肥料)로서 250kg/10a) 혼합시용(混合施用)한 처리구(處理區)에서 유의성(有意性)있는 증가를 보였다. 5. 각(各) 처리(處理)에서 재배(栽培)된 인삼근중(人參根中)의 Saponin 함량(含量)은 산야초퇴비(山野草堆肥)만을 처리(處理)한 구(區)에서 가장 많았고, 산야초퇴비(山野草堆肥)로서 질소성분량(窒素成分量) 20kg/10a와 유기질비료(有機質肥料)로서 2kg/10a 질소성분량(窒素成分量) 그 이상(以上)을 처리(處理)했을 때는 감소(減少)하는 경향(傾向)이었다.

• 한국토양비료학회지
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• 제5권2호
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• pp.59-64
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• 1972

담수상태하(湛水狀態下)에서 수종(數種) 규산물질(珪酸物質)의 입도별(粒度別) 토양산도교정능력(土壤酸度矯正能力)을 시기별(時期別)로 비교(比較)하고 EDTA 용액(溶液)과 NaOAc 용액(溶液) 침출(浸出)알카리분(分)이 이들 물질(物質)의 토양산도교정능력(壤酸度矯正能力)을 가늠할 수 있는지 검토(檢討)한 결과(結果) 1. 용성인비(熔成燐肥)는 pH5.5에 이르는 기간(期間)이 60일(日) 보다 작은 입자(粒子)는 20일(日), 40~48일(日)에서는 34일(日), 20~25일(日)은 84일(日)이 소요(所要)됐으며 같은 크기의 석회석립자(石灰石粒子)의 교정산도(矯正酸度)보다 pH 치(値)가 약 1.0~0.5 정도(程度) 낮았다. 2. 광재(鑛滓) I(Basic reduction furnace slag)는 100보다 작은 입자(粒子)는 pH5.5까지 교정(矯正)되나 이보다 큰 입자(粒子)는 pH $4.5{\pm}0.5$ 범위(範圍)에서 머물고, 규회석(珪灰石)은 25일(日) 보다 큰 입자(粒子)는 효과가 없고 40일(日)보다 작은 입자(粒子)는 pH 4.5~5.0 까지 밖에 미치지 못하며, 광재 II(Blast furnace slag)는 입도(粒度)의 크기에 큰 영향(影響)을 받지 않고 매우 미약(微弱)한 효과를 보였다. 3. 각재료(各材料) 및 입도별(粒度別) 교정산도(矯正酸度)와 EDTA 용액(溶液) 및 NaOAc 용액(溶液) 침출(浸出)알카리분(分)과의 관계(關係)는 NaOAc 용액(溶液) 침출(浸出)알카리분(分)이 EDTA 용액침출(溶液浸出)알카리분(分)보다 토양교정산도(土壤矯正酸度)와 더욱 밀접(密接)한 관계(關係)를 나타내며, 시기별(時期別)로 NaOAc 침출(浸出)알카리분(分)은 담수후(湛水後) 8일(日), EDTA 침출(浸出)알카리분(分)은 16일(日) 이후(以後)에 상관계수(相關係數)가 고정(固定)되었다.