• Proceedings of the Korea Water Resources Association Conference
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• 2003.05b
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• pp.659-662
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• 2003

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.393-398
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• 2005

Suspended fine mineral particles are deposited at the areas with low flow velocity and low transportation capacity in rivers, reservoirs and lakes. It can be contaminated by heavy metals. Examples of problem fields art dredging of sediment, water pollutants, and maintenance of navigation channels and construction works. To deal with the settling problems it is necessary to understand tile physico-chemical characteristics of cohesive sediment under varying density of particle and ion addition(NaOH, HCl, NaCl), which is dissolved in river, because fine-grained cohesive sediment can lead to flocculation with the physico-chemical influences and takes different characteristics. Experiments with fresh and saline water are followed with fine-grained sediments(alumina and quartz) in settling columns. Settling velocity of suspended fine particles in still water was measured with a pressure sensor(maximum 10 mbar). Until the initial concentration of 20,000 mg/1 of alumina and quartz the settling velocity was on the increase. Above this initial concentration was it on the decrease. In an acid condition, which causes strong flocculation, average settling velocity of quartz powder was high. In an alkaline water low average settling velocity of it was observed. However, alumina behaved exactly contrarily.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.2
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• pp.105-112
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• 2015

In this study, the erosional properties of deposit bed for the natural sediments are quantitatively estimated domestically for the first time using annular flume. Four erosion tests for Saemankeum sediments have been carried out on different consolidation time. Experimental results of erosional tests show that shear strength ${\tau}_s$ increases with the increases of consolidation time and bed depth. The erosion rate increases logarithmically with the increases of exceed shear strength ${\tau}_b-{\tau}_s$. But, the erosion rate decreases rapidly with the decreases of exceed shear strength under the $0.2N/m^2$. Experimental results of this study are found to be remarkably different in quantity as compared with those for results of previous study.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.722-726
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• 2012

각 해역의 부유 플록은 그 해역의 조건에 따라 각기 다르게 형성된 플록이므로, 부유 플록 자체의 특성(결합강도, 밀도 및 크기 등)은 현장특성에 따라 현저하게 다른 "site-specific"한 특성을 가질 뿐만 아니라, 동일 해역이라 하더라도, 조류 등에 의한 유속변화에 따른 흐름전단응력의 증감에 따라 플록의 특성 또한 시간적으로 크게 변화할 수 있다. 이에 현장의 플록 특성이 반영된 부유플록의 침강속도를 산정하기 위해 입도 측정원리중 하나인 BW방법을 응용한 전북대 Owentube를 자체 제작하여 연구가 수행되었으며, 본 연구를 통하여 도출된 현장에서의 점착성 부유 플록의 침강속도 산정 결과는 향후 퇴적물 이송 및 수질 예측을 위한 수치모형 적용시에 필수적으로 요구되는 침강 및 퇴적특성 입력자료로 유용하게 사용될 수 있을 것이다.

• Journal of Ocean Engineering and Technology
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• v.25 no.1
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• pp.14-21
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• 2011

The purpose of this study is to quantify the erosional parameters, such as the critical shear stress for erosion and the erosion rate coefficient for cohesive sediments from the Mokpo coast. Using Chonbuk annular flume, five erosion tests were conducted under the uniform bed condition but a different bed density respectively. Erosion test results for Mokpo sediments have shown increases in the range of $0.16{\sim}0.43\;N/m^2$ but decreases exponentially in the range of $272{\sim}4.64\;mg/cm^2{\cdot}hr$ for the given bed shear stress of $1.14{\sim}1.34\;g/cm^3$. The erosional parameters of Mokpo sediments are found to vary remarkably in quantity compared with those for cohesive sediments from other sites. On the whole, the value of Mokpo coast sediments appears to be similar to Kunsan sediments but smaller than Saemankeum and Okeechobee sediments. On the other hand, Mokpo sediments have been shown to be larger than Saemankeum and Okeechobee sediments but smaller than Kunsan sediments.

• Journal of Ocean Engineering and Technology
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• v.22 no.4
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• pp.20-26
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• 2008

The primary purpose of this study was to quantitatively examine whether there was a difference in the settling velocities of cohesive sediments in the Saemankeum artificial lake before and after the closure of the Saemankeum seadike. Through in situ sediment sampling and laboratory experiments, the settling velocities were estimated as a function of the suspension concentration and their physico-chemical properties, such as grain size distribution, the percentage of organic contents, mineralogical composition, etc. were also examined. In this study, their inter-relation with settling velocities were also analyzed qualitatively. The result of the settling tests for Saemankeum sediments showed that there was a big difference in the settling velocities before and after the closure of the Saemankeum seadike. Its settling velocities in a flocculated settling region became remarkably larger after the closure compared to those before the closure, while they were similar but relatively smaller in a hindered settling region. This was found to be mainly due to the difference in their grain size.

• Water for future
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• v.23 no.1
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• pp.119-127
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• 1990

The concentration of cohesive suspended sediment is determined by the circulation of water and the material dispersion. The equations of the two-dimensional, depth-integrated dispersive transport are the Reynolds equation, continuity equation, and advection-dispersion equation based on the Fick's law. A finite difference method has been applied to two models of circulation and dispersion transport. The circulation model is solved by the explicit scheme and the dispersion transport model is solved by multi-operational scheme. It is investigated wheter advective terms are included when the equation of circulation is applied to the model. For advection-dispersion equation, it was also investigated about variations of suspended sediment concentration with respect to the critical shear stresses.

• Journal of Convergence for Information Technology
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• v.10 no.7
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• pp.153-159
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• 2020

In order to find out the condition of flow in sewer pipes, this study investigated the characteristics of tractive force of sewage flow estimated using actual measured values of water level, velocity, and flowrate in sewers located at uppermost portion in a treatment area during dry weather periods. When the scene of sewage flow was taken by CCTV after cohesive and non-cohesive solids (tofu and sand) were put on the sewer invert, it was found that the solids could be flushed without significant interruption. In sewer with slope of 0.00319, the frequency exceeding the minimum tractive force of sewage during a weekday was zero, while it was 10 per day with slope of 0.00603. During the week of the field observation, the event to exceed the minimum tractive force occurred once, suggesting that sewer odor would potentially increase. Maximum tractive force in sewer with steep slope was 2.9-3.1 N/㎡, but with gentle slope it decreased to 1.6-1.7N/㎡. It was also observed that the interval of time maintained below the criterion of minimum tractive force increased, during weekends compared to weekdays and for the sewage including non-cohesive particles which could enter combined sewers during a storm period. This study found that the sewer sediments formed by direct feces input into sewers, through sewer pipes which were designed meeting the standard sewer design criteria, could be flushed without staying as deposited solids state for a long time.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.173-173
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• 2022

유기 퇴적 오염물은 다양한 형태로 호소 바닥에 축적되어 호소 환경 및 생태계에 악영향을 미치고 있으며 메탄가스와 같은 온실가스의 발생을 유발한다. 또한, 수력 산업, 관개, 이·치수 등 다양한 목적에 의해 수체의 형성이 활발하게 이루어지면서 하천 및 호소에 의한 탄소유출을 전지구적 탄소순환에 적극적으로 포함시켜야 한다는 필요성이 증가하고 있다. 따라서 하천 및 호소에서 발생하는 다양한 생지화학적 반응에 의한 메탄 발생 메커니즘 파악은 유역의 중요한 환경평가 지표를 나타내며 탄소 순환을 이해하는데 매우 중요하다. 수온, 수심, 유기물 조건에 따른 하천 및 호소의 메탄 발생을 분석한 연구들이 선행되었으나 생지화학적 특성을 정리하고 이에 따른메탄 발생을 정량화한 연구들은 거의 없는 상황이다. 본 연구는 호소 내 메탄을 발생시키는 기작을 판별하기 위해 수온과 호소 환경과 유사한 TOC(총유기탄소)와 TP(총인) 조건과 같은 유기물 조건을 설정하여 BMP Test를 수행하였다. 반응수조에서 발생한 가스를 포집한 후 GC(Gas Chromatograpghy) 분석을 통해 메탄 생성량을 산출하였고, 유기물 조건에 따라 이론적인 메탄 생성량 대비 실제 발생한 메탄 생성량을 나타내는 생분해도를 산출하여 호소 환경별 주요 기작에 따른 가스 발생을 정량화 하였다. 실험 결과 수온에 가장 큰 영향을 받았으며, 수온에 따라 TP, TOC 순으로 메탄 발생의 영향성을 확인하였다. 향후에는 호소 환경에서의 유기물 조건을 반영하기 위해 입도비, 점착성/ 비점착성 조건, 수체의 높이 조건을 포함한 추가 실험을 수행하고 메탄수율을 정량화하여 호소 내 유기퇴적물에 대한 생지화학적 및 수환경 영향 평가 기법 개발이 가능할 것으로 기대한다.

• Journal of Korea Water Resources Association
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• v.41 no.9
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• pp.863-872
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• 2008

In this study, a series of deposition tests have been conducted on saltwater condition(salinity 32 %o) using an annular flume, in order to estimate depositional properties of kaolinite sediments and to analyze the effect of the initial concentration on them. Total 37 deposition tests have been carried out in three different initial concentrations (1000, 5000, 15000 ppm) with varying the bed shear stress. From these test results, minimum shear stress (or critical shear stress for deposition; ${\tau}_{bmin}$) and the deposition rate parameters (${\sigma}_1,\;({\tau}^*_b-1)_{50},\;{\sigma}_2,\;t_{50}$) for kaolinite sediments have been quantified, and the effects of the initial concentration and salinity on depositional properties of cohesive sediments have been analyzed qualitatively. As the results, ${\tau}_{bmin},\;{\sigma}_1\;and\;({\tau}^*_b-1)_{50}$ are found to be 0.147, 0.74 and $0.65N/m^2$ respectively. Through comparing with results from previous studies, the performance of this study and tests results are shown to be good enough to verify.