• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.61-68
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• 2006

Cemented Sand and Gravel(CSG) is a material made by simple mixing of rock-based raw materials such as excavated soil and riverbed gravel together with cement and water. The use of CSG methodl for cofferdam and large dam is gradually increasing in Japan because a quarry and aggregate plants can be diminished. Also, the CSG method can reduce dam construction cost, construction duration and destruction of environment. In this paper, field test and test construction of CSG method was conducted on Hwabuk Dam. The mechanical properties of CSG, such as compressive strength, extention strength and field permeability test were investigated. From the results of the experimental study, application study of CSG method was discussed.

• 한국건설순환자원학회논문집
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• 제4권4호
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• pp.111-116
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• 2009

선별토사와 관행농토를 혼합하여 물리역학시험을 실시한 결과 일반 성 복토재로써 물리적 성능이 일반토양과 유사하여 활용이 가능할 것으로 판단된다. 토양분석시험 결과 산도가 강알칼리성을 보였고 유효인산 성분이 다소 부족하였으며, 치환성 양이온 중 Ca의 성분의 과잉으로 인하여 생육 저하 현상이 발생할 가능성이 있는 것으로 사료된다. 또한 상층토 50cm를 걷어내고 하층토 부분을 선별토사로 치환 후 걷어낸 상층토를 관행농토로 복토하여 생육 분석한 결과, 생육 장해 요인이 거의 없는 것으로 판단된다. 따라서 선별토사를 활용하는데 있어서 선별토사를 근권의 영향권인 유효토심에 사용하는 경우에는 작물의 생육을 저해할 가능성도 있기 때문에 객토와 같은 유효토심에 직접적으로 사용하기 보다는 근권에 대한 영향이 상대적으로 적은 하층토에 대해 대체하는 방안이 유효할 것으로 사료된다. 또한 선별토사를 세척하는 기술이나 산도의 중화, 유기물 공급 등의 방법을 강구해야 하며, 선별토사의 재료원이 일정치 않은 특성상 품질이 균질하지 않기 때문에 품질확보를 위해서는 품질에 따라 1급, 2급, 3급 등으로 나누고 사용용도 기준을 각각 정하여 품질의 확보를 위한 인증제도의 도입이 필요할 것으로 사료된다.

• 한국환경농학회지
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• 제42권1호
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• pp.28-34
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• 2023

Nitrogen fertilizers applied to agricultural lands for crop cultivation can be volatilized as ammonia. The released ammonia can catalyze the formation of ultrafine dust (particulate matter, PM2.5), classified as a short-lived climate change pollutant, in the atmosphere. Currently, one of the prominent methods for fertilizer application in agricultural lands is soil surface application, which comprises spraying the fertilizers onto the soil surface, followed by mixing the fertilizers with the soil. Owing to the low nitrogen absorption rate of crops, when nitrogen fertilizers are applied in this manner, they can be lost from land surfaces through volatilization. Therefore, investigating a new fertilization method to reduce ammonia emissions and increase the fertilizer utilization efficiency of crops is necessary. In this study, to develop a method for reducing ammonia emissions from nitrogen fertilizers applied to soil surfaces, deep fertilization was conducted using a newly developed deep fertilization device, and ammonia emissions from barley, garlic, and onion fields were examined. Conventional fertilization (surface application) and deep fertilization (soil depth of 25 cm) were conducted for analysis. The fertilization rate was 100% of the standard fertilization rate used for barley, and deep fertilization of N, P, and K fertilizers was implemented. Ammonia emissions were collected using a wind tunnel chamber, and quantified subsequently susing the indole-phenol blue method. Ammonia emissions released from the basal fertilizer application persisted for approximately 58 d, beginning from approximately 3 d after fertilization in conventional treatments; however, ammonia was not released from deep fertilization. Moreover, barley, garlic, and onion yields were higher in the deep fertilization treatment than in the conventional fertilization treatment. In conclusion, a new fertilization method was identified as an alternative to the current approach of spraying fertilizers on the soil surface. This new method, which involves injecting nitrogen fertilizers at a soil depth of 25 cm, has the potential to reduce ammonia emissions and increase the yields of barley, garlic, and onion.

• Geomechanics and Engineering
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• 제28권4호
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• pp.385-396
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• 2022

The accurate determination of the subgrade reaction modulus (K_s) of soil is an important factor for geotechnical engineers. This study estimated the K_s of soft soil improved with floating deep cement mixing (DCM) columns. A novel prediction model was developed that emphasizes the accuracy of identifying the most significant parameters of K_s. Several multi-layer perceptron (MLP) models that were trained using the Levenberg Marquardt (LM) backpropagation method were developed to estimate K_s. The models were trained using a reliable database containing the results of 36 physical modelling tests. The input parameters were the undrained shear strength of the DCM columns, undrained shear strength of soft soil, area improvement ratio and length-to-diameter ratio of the DCM columns. Grey wolf optimization (GWO) was coupled with the MLPs to improve the performance indices of the MLPs. Sensitivity tests were carried out to determine the importance of the input parameters for prediction of K_s. The results showed that both the MLP-LM and MLP-GWO methods showed high ability to predict K_s. However, it was shown that MLP-GWO (R = 0.9917, MSE = 0.28 (MN/m²/m)) performed better than MLP-LM (R =0.9126, MSE =6.1916 (MN/m²/m)). This proves the greater reliability of the proposed hybrid model of MLP-GWO in approximating the subgrade reaction modulus of soft soil improved with floating DCM columns. The results revealed that the undrained shear strength of the soil was the most effective factor for estimation of K_s.

• 한국농공학회지
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• 제39권2호
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• pp.62-73
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• 1997

The application of nutrients and pesticides to agricultural lands has been reported to contribute to groundwater contamination, which can be explained by preferential flow in lieu of convective-dispersive flow. An one-dimensional numerical model depicting preferential water and solute movement was modified to describe multi-layer flows. The model is based on a piecewise linear conductivity function. By combining conservation of mass and Darcy's law and using the method of characteristics a solution is obtained for water flow in which water moves at distinct velocities in different flow regions instead of an average velocity for the whole profile. The model allows transfer ofqr solutes between pore groups. The transfer is characterized by assuming mixing coefficients. The model was applied to undisturbed soil columns and an experiment site with structured sandy clay loam soil. Chloride, bromide, and 2, 4-D were used as tracers. Simulated solutes concentrations were in good agreement with the soil column data and field data in which preferential flow of solute is significant. The proposed model is capable of describing preferential solute transport under laboratory and field conditions.

• 한국농공학회논문집
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• 제49권4호
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• pp.63-70
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• 2007

The soil samples used in this study were prepared with the residual granite soils passed through the #4 sieve and obtained from Pocheon in Gyeonggi-Ki do. Specifically, five types of samples were prepared. Sample A which is a natural state soil was classified as SM according to the uses. Samples of B, C, D, and E were prepared by mixing Sample A with bentonite and were classified as SC according to the uses. The plasticity indexes of samples B, C, D, and E were 15, 25, 30, and 40, respectively. The specimens, whose dimensions are 100mm by 127.5mm, were prepared by A method of ASTM D 698 with the Proctor mold. In experiments, the loading with the 1%/min was applied. Four different disk diameters, 13mm, 26mm, 38mm, and 52mm were used in the Improved Unconfined Penetration (IUP) tests. To compare the tensile strengths, the split tensile tests were also conducted on the same specimens used for the IUP tests. To find out the effects of moisture contents, plasticity Index of specimens on the tensile strength, six different water contents were used for making a specimen.

• 한국약용작물학회지
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• 제17권6호
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• pp.415-420
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• 2009

This study was carried out to select economical byproduct composts as the substitute for the traditional organic fertilizer, Yacto, in the cultivation of ginseng seedlings, and to investigate the application method of a selected compost. Among tested byproduct composts, popped rice hull compost was the best substitute for Yacto, while the application of domestic animal manure composts resulted in red skinned roots of ginseng seedlings. Optimal mixing ratio of the popped rice hull compost with virgin soil (fine sand) were 3~4 : 1 in bulk, showing the same root yield compared to that of conventional seedbed soil. When the popped rice hull compost was lower than $1\;{\pm}\;0.1%$ in nitrogen content, the expeller cake of oil seed was added to seedbed soil to rise nitrogen content until $1\;{\pm}\;0.1%$.

• 환경영향평가
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• 제21권1호
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• pp.63-69
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• 2012

Sediment has been increasingly acknowledged as a carrier in water system and an available contamination. For this reason, dredging of sediment in reservoir to remediate water quality and secure storage capacity is conducted annually. However, disposal of numerous dredged sediment is necessary as a secondary problem. Currently, in Korea, dredged sediment is classified as waste to be reclamated or recycled into sandy soil, however, they are still in trouble because of spacial and environmental problem. Therefore, rather than simple disposal or reuse into sandy soil, it is necessary to research on method to manage main cause of pollution and increase the value as a resource. In this study, we intend to develop a recycle technology for numerous dredged sediment produced by dredging in deteriorated reservoirs using solidificator (stabilizer). To achieve this, we will consider utilization of dredged sediment and evaluation of use possibility as natural recycle by analysis the characteristics of soil-solidificator mixture in terms of physicochemical properties and the mixing ratio between sediment and solidificator.

• 한국지반공학회논문집
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• 제26권4호
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• pp.5-14
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• 2010

본 연구에서는 새로운 동상 억제제로서 폐타이어 파우더의 활용가능성을 검토하기 위해 폐타이어 분말 혼합토와 미혼합토를 대상으로 3년간 일본 토마코마이에서 야외실험 수행하였다. 야외실험 결과, 폐타이어 파우더를 20% 혼합함에 의해 현저한 동상억제 효과가 발생함을 확인하였으며, 관련 동상억제 효과를 동상량, 동상율, 열전도율, 투수성, segregation potential 이론 등을 중심으로 정량적으로 검토하였다.

• 농약과학회지
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• 제9권4호
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• pp.437-441
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• 2005

본 연구는 국내토착 토양세균인 Pasteuria penetrans 내생포자의 처리방법에 따른 땅콩뿌리혹선충(Meloidogyne arenaria) 방제효과를 파악하고자 수행하였다. 이를 위해 P. penetrans 내생포자의 농도($3{\times}10^4$, $3{\times}10^5$ 및 $3{\times}10^6$ endospores/5 g medium)별로 500마리 땅콩뿌리혹선충에 각각 부착한 후 기주식물인 토마토 뿌리에 접종하여 14주 후 뿌리에 형성된 뿌리혹 개체 수로 농도에 따른 선충방제 효과를 파악하였다. 그 결과 80%이상 방제효과를 보인 $3{\times}10^5$ 수준의 P. penetrans 내생포자를 500마리의 선충만을 접종한 토양과 혼합하여 처리한 시험구(토양혼화처리)와 토양표면에 처리한 시험구(토양표면처 리)로 구분하여 방제효과를 비교하였다. 이 중 방제효과가 높았던 토양혼화처리 방법을 이용하여 P. penetrans와 일본 상품인 $PASTORIA^{(R)}$그리고 국내에 등록된 살선충제인 선충탄(fosthiazate)과의 방제효과를 상호 비교하였다. 실험결과 P. penetrans의 농도가 높고 토양과 혼합하여 처리할 시 방제효과가 높았으며, P. penetrans 처리가 일본 제품보다는 우수한 방제효과를 보였고 국내 시판 화학방제제와는 유사하였다.