• 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 the Korean Society for Marine Environment & Energy
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• v.5 no.1
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• pp.3-10
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• 2002

Quantifying the settling velocities of fine-cohesive sediments is very essential in the study of ocean pollutions as well as sedimentations. Settling properties of fine-cohesive sediments are influenced largely by aggregation which occurs as a consequence of interparticle collision and cohesion of particles. Since the degree of cohesion of fine-cohesive sediments depends on physico-chemical properties such as grain size distribution, percentage of organic materials, and mineralogical compositions, and these physico-chemical properties varies regionally, the settling velocities of fine-cohesive sediments for a specific site should be determined through field or laboratory experiment. Recently, settling velocities of fine-cohesive sediments in Saemankeum coasts and Kunsan Estuary have been measured through laboratory experiments. Using these data, the previously proposed well-known settling velocity equations for fine-cohesive sediments are examined and a new equation is developed for better representation of the measured data in this study. The newly developed settling velocity equation is simpler in the form and easier in determining the related coefficients than the previous well-known equations.

• Journal of Ocean Engineering and Technology
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• v.19 no.4 s.65
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• pp.42-48
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• 2005

The sediment of Shihwa Lake contains an abundant quantity of cohesive sediments. The transport processes of the cohesive sediments are complex and difficult to predict, quantitatively. The cohesive sediments are the primary reason for the pollution of the environment and water quality in the coastal region. In this study, a column test has been performed. In order to quantify the settling velocities of sediment from Shihwa Lake, an experiment was conducted using a specially designed 1.8m tall settling column. A series of settling tests and physico-chemical property tests on Shihwa Lake cohesive sediments has been conducted to investigate the correlation between settling properties and their physico-chemical properties, which are represented as grain size distribution, mineralogical composition, and percentage oj organic contents. Experimental results of physico-chemical property tests show that Shihwa Lake sediments are relatively large in average grain $size(74\mu m)$ contain very small organic $material(6\%)$, and are dominantly composed of Quarts, which has relatively low cohesion. Thus, Shihwa Lake sediments might be specified as those whose settling properties are more influenced by gravity than cohesion. It is concluded that the magnitude of settling velocities of muddy sediments can be quite different, regionally, and it implies that field or laboratory experiments for settling velocity measurement should be preceded over the numerical modeling of muddy sediment transport, in order to obtain the reliable prediction results for a given specific site.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.3
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• pp.159-165
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• 2012

In this study, a series of deposition tests have been performed using an annular flume and depositional parameters of natural cohesive sediments have been estimated domestically for the first time. The natural cohesive sediments for deposition tests have been collected from Kwangyang Bay and total 18 deposition tests have been carried out on different bed shear stress respectively but with the same initial concentration. Test results for natural cohesive sediments of Kwangyang bay show that minimum bed shear stress ${\tau}_{bmin}$, standard deviation ${\sigma}_1$, and time scale parameter $({\tau}_b^*-1)_{50}$ are $0.11N/m^2$, 0.68 and 0.85, respectively. Through the comparison with results of previous studies for other sediments, the results of this study are shown to be good enough to verify.

• Journal of Korea Water Resources Association
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• v.41 no.5
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• pp.473-482
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• 2008

The purpose of this study is to quantitatively estimate the erosional properties for cohesive sediment from Saemankeum artificial lake. A series of erosion tests were conducted with Chonbuk annular flume, which is the first one constructed in this country and verified with validities. Each erosion tests were conducted under a uniform bed condition but a different bed density respectively, and its critical shear stress for erosion(${\tau}_{ce}$) as well as the erosion rate coefficient (${\varepsilon}_M$) were determined quantitatively. Since the erosional properties of the cohesive sediments vary largely depending in the physico-chemical properties, such properties of Saemankeum sediments were also estimated and their effects on the erosional properties were analyzed. For Saemankeum sediments, it can be seen that ${\tau}_{ce}$ increases from $0.26N/m^2$ to $0.52N/m^2$ and ${\varepsilon}_M$ decreases exponentially from $14.28mg/cm^2\;hr$ to $6.02mg/cm^2\;hr$, as the bed density varies from $1.17g/cm^3$ to $1.34g/cm^3$. The erosional parameters of Saemankeum sediments are found to be remarkably different in quantity as compared with those for cohesive sediments from other sites. Particularly, ${\tau}_{ce}$ for Saemankeum sediments is known to be larger than that of Kunsan sediments but similar with that of Shihwa sediments, while ${\varepsilon}_M$ for Saemankeum sediments is shown to be smaller than that for Kunsan sediments.

• Journal of Ocean Engineering and Technology
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• v.22 no.1
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• pp.37-45
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• 2008

The purpose of this study is to quantify the settling velocities of cohesive sediments from Han estuary and to evaluate their local variation within Han estuary. This study also includes an estimation of their spatial variation, for which the settling velocities of cohesive sediments from Han estuary arecompared with those for sediments from other regions. At the same time, physical-chemical properties, such as grain size distribution, the percentage of organic contents, mineralogical composition etc are measured in this study in order to examine their correlation with settling velocities and their effect on settling velocities. Results from settling tests shaw that the settling velocities of Han estuary mud varies in the range of two orders of magnitude(from 0.01 to 1.5 mm/sec) over the corresponding concentration range of 0.1 to 80 g/L, and a feature of the settling velocity profile is quite different in quantity as compared to those of previous studies for muds from other regions. Particularly in the flocculated settling region, the settling velocity for Han estuary muds is shown to be larger than that of Saemankeum and Keum estuary sediments, while in the hindered settling region all three sediments are shown to have a similar settling velocity. However, local variability of the settling velocities within Han estuary is shown to be insignificant.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1B
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• pp.125-135
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• 2008

The purpose of this study is to quantify the erosion parameters of cohesive sediments in Keum Estuary. This study also involves the examinations on the local/seasonal variation of them in Keum Estuary and on their spatial variation comparing with those of other sites. As erosional properties of cohesive sediments are in general influenced largely by the physico-chemical properties of cohesive sediments themselves, this study also involves the qualitative analyses on the impact by the physico-chemical properties. Erosion tests have been performed under the uniform bed condition using the Chonbuk annular flume and total 16 tests have been carried out with various bed densities and bottom shear stresses. Experimental results show that the critical shear stress for erosion varies in the range of $0.19{\sim}0.41N/m^2$ and the coefficient of erosion rate varies in the range of $54.26{\sim}7.70mg/cm^2{\cdot}hr$, over the corresponding bulk-density range of $1.14{\sim}1.38g/cm^3$. While erosion parameters estimated for Keum estuary sediments are found to be remarkably different in quantity compared with those for cohesive sediments from other sites, their local/seasonal variabilities within Keum Estuary are found to be insignificant.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.3
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• pp.179-188
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• 2006

The purpose of this study is to quantitatively estimate the settling and erosional properties for cohesive sediments in Shihwa lake. Settling tests are conducted by multi-depth method using a specially designed 1.8 m tall settling column, and erosion tests are conducted with annular flume under the uniform bed condition. As result of settling tests, it is confirmed that the settling velocity of the cohesive sediments has the range of $0.002 for suspended sediments concentration of 0.1$0.19{\sim}0.55N/m^{2}$ for bed shear stress of $1.14{\sim}1.32g/cm^{3}$, and the erosion rate coefficient decreases with logarithmic function in a range of $18.4{\sim}3.9mg/cm^{2}{\cdot}hr$ with increase of bed shear stress.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.4
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• pp.283-293
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• 2006

The purpose of this study is to quantitatively estimate the erosional properties for cohesive sediments on Keum Estuary. Then the spatial variation was evaluated, through analyzing and comparing the seasonal variation of the erosional properties in Keum Estuary with that of the erosional properties in the other sites. As erosional properties of cohesive sediments are also influenced largely by basic physico-chemical property of cohesive sediments themselves, the impact that the basic physico-chemical property has on the erosional properties is analyzed in this study. Erosional tests are performed under the condition of uniform beds. Total 8 times of tests using an annular flume are also conducted in a location, low times respectively by seasons: the fall, winter. Experimental results of erosional tests show that the critical shear stress for erosion varies in the range of $0.12{\sim}0.36N/m^2$ and the coefficient of erosion rate varies in the range of $120.91{\sim}6.72mg/cm^2{\cdot}hr$, over the corresponding bulk-density range $1.15{\sim}1.34g/cm^3$. Although the calculated parameters of erosional properties are remarkably different in quantity compared with those of other cohesive sediments(lake Okeechobee) and Kaolinite, their seasonal variabilities within Keum Estuary appear to be insignificant.

• 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.