• 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.

• Clean Technology
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• v.10 no.1
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• pp.1-7
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• 2004

In this study, the performance of Aluminium foil etching waste(PWF100) as a cohesive agent was estimated and the methods to commercialize it were investigated through comparison of physical properties between Aluminium foil etching waste(PWF100) and commercial cohesive agent(PAC17). The height of sediment bed was measured according ot the change of the concentration of BKN-100, BKR-110, and BKR-120 prepared by using PWF100. When the concentrations of BKN-100, BKR-110, and BKR-120 were increased, the heights of sediment bed were constant after decreased. Also, the density of sediment bed was investigated according to the change of the concentration of BKN-100. When the concentrations of BKN-100 were increased, the densities of sediment bed were decreased. In addition, based on the concentration of BKN-100, BKR-110, and BKR-120, the sediment rate was experimented. When the concentrations of BKN-100, BKR-110, and BKR-120 were increased, sediment rates were rapid and then slow. Moreover, the volumes of sediment bed were measured according to the change of the concentration of BKN-100. According to increasing the concentrations of BKN-100, the required time for getting to the minimum volume of sedment bed were reduced and then increased. Lastly, the required time for sedimentation based on the concentration of BKN-100, BKR-110, and BKR-120 was investigated. When the concentrations of BKN-100, BKR-110, and BKR-120 were increased, the required times for sedimentation were increased after decreased. From these results, it can be concluded that the PWF100 acts as a cohesive agent.

• Journal of Korea Water Resources Association
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• v.57 no.5
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• pp.347-357
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• 2024

Numerous prior studies have delineated the size distribution of noncohesive sediment in suspension, focusing on mean size and standard deviation. However, suspensions comprise a heterogeneous mixture of sediment particles of varying sizes. The transport dynamics of suspended sediment in turbulent flow are intimately tied to settling velocities calculated based on size and density. Consequently, understanding the grain size distribution becomes paramount in comprehending sediment transport phenomena for noncohesive sediment. This study aims to introduce a straightforward modeling approach for simulating the grain size distribution of suspended sediment amidst turbulence. Leveraging insights into the contrast between cohesive and noncohesive sediment, we have meticulously revised a stochastic flocculation model originally designed for cohesive sediment to aptly simulate the grain size distribution of noncohesive sediment in suspension. The efficacy of our approach is corroborated through a meticulous comparison between experimental data and the grain size distribution simulated by our newly proposed model. Through numerical simulations, we unveil that the modulation of grain size distribution of suspended sediment is contingent upon the sediment transport capacity of the carrier fluid. Hence, we deduce that our simplified approach to simulating the grain size distribution of suspended sediment, integrated with a sediment transport model, serves as a robust framework for elucidating the pivotal bulk properties of sediment transport.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2006.09a
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• pp.5-8
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• 2006

• Journal of Korea Water Resources Association
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• v.33 no.S1
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• pp.905-910
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• 2000

• Journal of Advanced Research in Ocean Engineering
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• v.2 no.2
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• pp.86-98
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• 2016

In this study, after the installation of a subsea pipeline, backfilling was performed in the trenched area. During these operations, a stability problem in the subsea pipeline occurred. The pipeline was directly impacted by environmental loading such as waves and currents that were caused by backfill material when scouring or sediment transport and siltation was carried out. Therefore, this study reviewed whether trenching was necessary, and conducted research into an indigenous seabed property that contains granular soil. A study of cohesive soil was also conducted in order to cross-correlate after calculating the values of the critical Shields parameter relevant to elements of the external environment such as waves and current, and the shear Shields parameter that depends on the actual shearing stress. In case of 1), sedimentation or erosion does not occur. In the case of 2), partial sedimentation or erosion occurs. If the case is 3), full sedimentation or erosion occurs. Therefore, in the cases of 1) or 2), problems in structural subsea pipeline stability will not occur even if partial sedimentation or erosion occurs. This should be reflected particularly in cases with granular and cohesive soil when a reduction in shear strength occurs by cyclic currents and waves. In addition, since backfilling material does not affect the original seabed shear strength, a set-up factor should be considered to use a reduced of the shear strength in the original seabed.

• Journal of Korea Water Resources Association
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• v.53 no.10
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• pp.917-928
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• 2020

The purpose of this study is to find the appropriate probability distribution representing the size distribution of suspended cohesive sediment. Based on goodness-of-fit test for a significance level of 5% using the Kolmogorov-Smirnov test, it is found that the floc size distributions measured in laboratory experiment and field study show different results. In the case of sample data collected from field experiments, the Gamma distribution is the best fitting form. In the case of laboratory experiment results, the sample data shows the positively-skewed distribution and the GEV distribution is the best fitted. The lognormal distribution, which is generally assumed to be a floc size distribution, is not suitable for both field and laboratory results. By using 3-parameter lognormal distribution, it is shown that similar size distribution with floc size distribution can be simulated.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1992.08a
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• pp.158-165
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• 1992

Bottom sediments, in various types of sediment transport models, have been usually assumed to be horizontally and/or vertically homogeneous. The assumption may be appropriate in well-sorted sedimentary environments including sand beaches and high turbid regions of fine grained cohesive sediments. (omitted)

• 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.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.2 no.2
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• pp.19-28
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• 1982

The development of unsteady, depth-averaged two dimensional sediment transport prediction model in estuaries and harbors by the Galerkin finite element technique is presented. The model consists of two submodels, flow induced circulation model and sediment transport model. The sediment transport submodel is formulated by incorporating sediment continuity equation and sediment diffusion equation. Numerical experiments of the model, which were carried out in one dimensional channel under different conditions for circulation and sediment transport, show the adaptability of the formulation for predicting the migration of both cohesive and noncohesive sediments. The model was applied to Busan harbor to simulate circulation and sediment transport for simplified conditions. Of the results by the model the flow pattern are shown to be similar to observed data.