• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.1094-1103
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• 2010

The safety of pile foundation is getting declined when the pile foundation acting on lateral load is exposed by dredging. So appropriate reinforcement is needed for stability secure. Thus, in this study, the stability variation and reinforcement range caused by dredging is estimated on the basis of down scale test. The scale effect is determined by real scale numerical analysis. the behavior of pile by dredging stages is estimated by load control type. The credibility is verified through the comparison between down scale model test and numerical analysis.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1147-1157
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• 2009

Recently this country has carried out the coast reclamation centering on the west and south coast for effective practical use of a country, considering purchase of materials and environmental problem, and carrying into effort the reclamation method after dredging the ground in the ocean. In this large scale ocean dredging reclaiming work, prediction the ground subsidence after reclaiming is very important for not only expense lose by overestimation or underestimation but also hereafter the best suited project establishment. this study carries out sedimentation and self weight consolidation in each cases and searches the features to analyze effect on kinds of soil of ground before dredging, abandonment height when it abandons momentary, void ratio, difference of abandonment height when it abandons by stages and difference of particle content of spoil.

• Journal of Environmental Science International
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• v.22 no.9
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• pp.1115-1129
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• 2013

The study area is located on the western coast, and the inner development construction has been ongoing since 2011. The purposes of current study are to effectively simulate and quantitatively predict a temporal and spatial distributions of water temperature and salinity due to the stages of inner development construction in saemangeum reclaimed area. The transient-state numerical modeling using EFDC model is done, and the numerical simulation results are validated reasonably by repetitive numerical model calibration procedures with respect to field measurements of water temperature and salinity. The spatial distributions of water temperature and salinity show similar trends before and after construction of the dikes. In spring season, the salinity has maximum value of 21 psu, while, in summer season, the salinity shows 7 psu in a whole modeling domain. Thus, it is clearly observed that salt water is replaced by freshwater. However, the salinity and temperature reach their initial conditions at the end of the year. The salinity after construction of the dikes is lower than that before construction of them at Mankyeong area. On the other hands, after construction of the dikes, the salinity after dredging operations is higher than that before dredging. Because drastical increasing of water volume in Saemangeum Lake leads to increasing of stagnation time at bottom layer, and salt water is easily intruded to the two estuaries. Therefore, it may be concluded that hydrodynamic characteristics on Saemangeum are dominated by either Mankyeong and Dongjin discharge or sluice gates in/out-flow amounts, and thus they must be properly considered when rigorous and reasonable predictions of water temperature and salinity according to the stages of inner development construction.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.11c
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• pp.143-155
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• 1999

An experimental study has been carried out to investigate the reinforcing effect of marine dredging clay(MDC) mixed with the Micro-Fiber(MF). A series of laboratory tests was performed using specimens of MDC alone and MDC with MF by means of uniaxial and triaxial compression test. In the test programme, three stages of water content of MDC were chosen according to the elapsed time after dredging, and content and length of MF were considered as important factors for reinforcing effect. And the developed strength due to curing was measured both in MDC and composite. The enhancement of strength of composite was found to be increased with the increasing content and length of MF, and curing time, and with decreasing water content of MDC. An additional study has been made for in-situ trafficability on the soft reclaimed ground by MDC due to high water content. It was found that the waste lime was to be applicable for this purpose to get a reinforcing effect of MDC. A further study would lead to the better understanding of the reinforcing mechanism of the composite.

• Journal of the Korean Institute of Landscape Architecture
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• v.36 no.3
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• pp.52-62
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• 2008

By analyzing specific plant distributions and physicochemical characteristics of topsoil in a reclaimed dredging area, baseline data was found of natural landscape planting sites, and developing dredged fill ground. The reclaimed dredging area is five different stands (1, 2, 3, 4 and 5) which were examined in this research. They are located from sea level to 15 meters in altitude and exhibited typical characteristics of the salt marsh in Gwangyang Bay. Species with high constancy in the vegetation on the reclaimed soil were classified into four stages. A total of 12, 15, 22, 27 and 35 different plant species were found and also increased in stands 1, 2, 3, 4 and 5, respectively. Moving from stand 1 to 5, halophytes decreased and non-halophytes increased. Desalination at each stage of the reclaimed dredging area was a driving force affecting the performance and distribution of halophytes and non-halophytes. Overall, 35 quadrats of soil were selected and analyzed for specific physicochemical characteristics of topsoil between O${\sim}$20cm. Results of the physicochemical analysis such as altitude, slope, vegetation and kind of reclaimed dredging soil, exhibited irregular increases or decreases. As survey areas moved from stand 1 to 4, desalination areas, soil acidity, electric conductions, content of salinity, available phosphorus, potassium, chlorine, calcium, and magnesium indicated decreasing patterns; however, total nitrogen, silt, and clay content increased. Cluster analysis and PCA by environmental data within the stands clearly showed five distinct vegetation patterns on the tested reclaimed area. These results indicate that the differences of performance and distribution of vegetation are due to the SAR in the reclaimed soil and related to the natural survival strategy at the given hostile habitat.

• Journal of Environmental Science International
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• v.23 no.8
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• pp.1523-1536
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• 2014

Restoration is the process of reducing or reversing damage to an ecosystem so that it can function in its original manner. However, many restoration programs do not achieve this. In the Nakdong Estuary, the largest migratory nesting site in the center of the East Asian-Australasian flyway, an estuarine barrage was constructed in the 1980s that required site restoration following its completion in 1987 and the expansion of several large industrial complexes(Noksan and Jangrim) and a residential development(Myeongji). The goal of the restoration was to restore the function of the wetland to its pre-disturbance state. To achieve this, a restoration program was designed consisting of three stages. The first stage(1993-1995), saw the construction of three artificial wetlands(Shinhori, Daemadeung, and Eulsuk), the second(2003-2005) involved the dredging and returning of farmed lands to their natural state, and the third(2008-2012) focused on the rehabilitation and vegetation development of the wetlands. However, the project has not achieved all of the desired goals, and it is an example of the lapses in ecological restoration following anthropogenic disturbance. Issues that resulted in an incomplete restoration included the timing of the stages, noncompliance with the restoration plan, not directly monitoring the restoration or continuing the monitoring following completion of the development project, and the political subversion of the restoration plan. For the success of the restoration plan, it is necessary to avoid mistakes such as inconsistent monitoring, unequal levels of stakeholder involvement, and political interference.

• Journal of the Korean Geotechnical Society
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• v.21 no.7
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• pp.63-72
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• 2005

Grounwater level applied on dredged and reclaimed clay layer was assumed to be the same value under design criterion as field test one, but actually differences are found through the monitoring test. In this study, a case study of measuring residual groundwater level is performed in ground improvement construction of Gwangyang container terminal and hinterland. With priority given to residual groundwater level measured during construction and management period of 9 years, it is investigated that residual groundwater level (R. GWL) could be applied reasonably to the design, construction, and use stages of the container harbor and land development.

• Journal of the Korean GEO-environmental Society
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• v.10 no.6
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• pp.89-98
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• 2009

In this research, settling tests with marine clays in Korea and extensive literature review were performed to investigate the characteristics of sedimentation and consolidation so that their behaviors during dredging and reclamating could be evaluated. Design parameters related to Yano's method (1985), one of experimental approaches having been used widely in Korea to estimate sedimentation and consolidation, were analyzed and their proprieties were reassessed. For samples from four different sites of south and west coasts in Korea respectively, settling tests with 1m height of columns were carried out, changing initial water content and height of sample in order to evaluate settling and consolidation characteristics of them from analyzing test results. More reliable regression curves than values from literature review were obtained as analyzing test results of estimating coefficient of sedimentation/ consolidation and initial setting velocity with changing initial water content. Relation between height of soil solid and surface height of slurry at the stages of initiation and termination of consolidation was also assessed. Finally, for marine clays of south and west coasts of Korea, ranges and average values of these design parameters were evaluated and typical empirical equations between these design parameters were also proposed. On the other hand, comparisons of characteristics of sedimentation and consolidation between marine clays from south coast and them from west coast were also performed.

• Magazine of the Korean Society of Agricultural Engineers
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• v.35 no.1
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• pp.50-58
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• 1993

The sedimentation patterns at a reservoir, important to the reservoir capacity curve were simulated using a depth averaged, two-dimensional sediment transport model, that is capable of depicting velocity distributions and sediment transportation. The Banweol reservoir, whose stage capacity relationships have been surveyed before and after the construction, was selected and the daily inflow rates and stages were simulated using a reservoir operation model(DI-ROM). The applicability of the transport model was tested from the comparisons of simulated sedimentation patterns to the surveyed results. The simulated inflow rates and water level fluctuations at the reservoir during twenty-one years from 1966 to 1986, showed that water levels exceeding 80 percent of the total capacity occurred for 70 percent of the periods and inflow rates less than 5000rn$^3$/day sustained for 54 percent of the spans. Dorminant flow directions were simulated from two streamflow inlets to the dam site. And simulated sediment concentrations were higher near the inlets and lower at the inside of the reservoir. Sediment was deposited heavily near the inlets, and portions of sediments were distributed along the flow paths within the reservoir. The comparisons between the simulation results and the surveyed depositions were partially matched. However, it was not possible to compare two results at the upper parts of the reservoir where dredging was carried out few times for the purpose of reservoir maintenance. This study demonstrates that sedimentation patterns within the reservoir are closely related to incoming sediment and flow rates, water level fluctuations, and flow circulation within the reservoir.

• Journal of the Korean Geosynthetics Society
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• v.1 no.1
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• pp.13-21
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• 2002

Geotextile tubes hydraulically or mechanically filled with dredged materials have been applied in hydraulic and coastal engineering in recent years(detached breakwater, groins and jetty). The geotextile tubes are made of sewn geosynthetics sheets. If the sandy soil is use to fill material, these inlets should be spaced closely to assure uniform filling of the tubes because sandy soil and geosynthetic is very pervious. However, the clayey soil or contaminated slurry is used, the inlets can be located relatively long distance. The fine clayey particles tend to rapidly blind the fabric slowing down water escape through the geotextile. This paper presents a field test result of a geotextile tube in the land reclamation project for the Songdo New City construction site. The dredged silty clay was dredged by the dredging ship and hydraulically pumped into the geotextile tube. The height of geotextile tube was measured at every filling stage and also measured width and diameter of geotextile tube with the elapsed time. Based on the test results, if the clayey filling material is used, the pumping step must be divided 3~4 stages for drainage and sediment. After complete drainage, the height of the geotextile tube reduces by approximately 50%.