• Journal of Korea Water Resources Association
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• v.38 no.3 s.152
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• pp.223-233
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• 2005

In this study, a two-dimensional model for identifying areas of erosion and deposition over a basin was developed based on the mass balance principle in a distributed model. The program consists of three steps: (a) estimation of soil erosion; (b) determination of flow amount and direction; and (c) estimation of mass balance. Soil erosion was estimated with USLE. A single-direction (SF) and a multi-direction flow algorithm (MF) were applied to estimate slope length (L). The Maximum Downhill Slope Method (MDS) and the Neighborhood Method (NBH) were used to estimate the slope degree (S). Sediment transport resulting from eroded soil was estimated using Ferro's (1998) and Swift's (2000) sediment delivery ratio (DR). The model was validated by comparing the predicted sediment yields for three basins with measured data. The developed algorithm showed that Ferro's DR method combined with the MDS and MF produced the best agreement with the dredging records of three agricultural reservoir basins in Korea.

• Korean Journal of Agricultural Science
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• v.47 no.4
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• pp.803-814
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• 2020

Managing erosion control dams requires the annual average sediment yield to determine their storage capacity and time to full sediment-fill and dredging. The GeoWEPP (Geo-spatial interface for Water Erosion Prediction Project) model can predict the annual average sediment yield from various land uses and vegetation covers at a watershed scale. This study assessed the GeoWEPP to determine the annual average sediment yield for managing erosion control dams by applying it to five erosion control dams and comparing the results with field observations using ground-based LiDAR (light detection and ranging). The modeling results showed some differences with the observed sediment yields. Therefore, GeoWEPP is not recommended to determine the annual average sediment yield for erosion control dams. Moreover, when using the GeoWEPP, the following is recommended :1) use the US WEPP climate files with similar latitude, elevation and precipitation modified with monthly average climate data in Korea and 2) use soil files based on forest soil maps in Korea. These methods resulted in GeoWEPP predictions and field observations of 0 and 63.3 Mg·yr-1 for the Gangneung, 142.3 and 331.2 Mg·yr-1 for the Bonghwa landslide, 102.0 and 107.8 Mg·yr-1 for the Bonghwa control, 294.7 and 115.0 Mg·yr-1 for the Chilgok forest fire, and 0 and 15.0 Mg·yr-1 for the Chilgok control watersheds. Application of the GeoWEPP in Korea requires 1) building a climate database fit for the WEPP using the meteorological data from Korea and 2) performing further studies on soil and streamside erosion to determine accurate parameter values for Korea.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1C
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• pp.1-5
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• 2010

The river maintenance processing has revealed that the river beds in Korea have been significantly polluted in various ways for the last two decades. Thus, the dredging, transportation and landfilling of these contaminated materials are attracting public attention these days. In this study, electrokinetic method was applied in order to accelerate the settling processes of clay particles in suspension and evaluate the factors affecting the settling behaviour. It has been found from the testing results that the settling velocity under the influence of electrokinetics was much faster than the gravitational one, and the water content of slurry soil reduced significantly after the electrokinetic processing. The initial water content of slurry soil should be one of the important factors affecting the settling behaviour as well as variation of water content, and hence the electrokinetic processing would be the cost-effective method for the field application.

• Journal of the Korean Geotechnical Society
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• v.31 no.7
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• pp.5-12
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• 2015

In this study, the deposition of dredged soils from domestic rivers is simulated in the laboratory using a small soil box. In the tests, small sand with 0.002-0.85 mm, large sand with 0.85-2 mm, and gravel 4.75-5.6 mm are air or water-pluviated into the box. Such various deposition processes are simulated and their dry densities are measured. While dredging or piling such soils, their volume may change. The loss of such soils is calculated by a soil conversion factor C. The C value was determined as 0.91 for small sand, 0.96 for large sand, and 0.91 for gravel. The drainage through soil piles may occur and result in effective stress increase. This may cause the volume change of soils and in order to consider such effect it is necessary to recalculate C values. As a result, dry density increased by 5-12% when the drainage effect is considered. When the drainage effect is considered, the value of soil conversion factor C was 0.81 for small sand, 0.92 for large sand, and 0.82 for gravel. Eventually, the C value decreased up to 4-12%.

• Journal of the Korean GEO-environmental Society
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• v.12 no.9
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• pp.71-78
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• 2011

Cement treating technique, such as deep mixing method, has been used widely to stabilize the dredged clayey soil for many years. Despite of its effectiveness in treating soil by cement, several efforts have also been made to try to reduce the side effect of the cement that used to stabilize the dredged clay. However, authors considered that more detailed study on the physical and mechanical properties of lean-mixed soil-cement has been required to establish the design procedure to apply the practical problems. Therefore, in this study, the curing time and mixing ratio was used as key parameters to estimate the physical and mechanical properties including long-term behavior. The unconfined strength of lean-mixed soil-cement increase continuously during curing period, 270 days, while increasing rate becomes low in ordinary cement-treated dredged clay. We also concluded that cement-treated dredging clay shows apparent quasi overconsolidation behavior even in low cement proportion. By this study, fundamental approach was carried out for effective reuse of very soft dredged clayey soil both in mechanical and environmental aspect. It can be also expected that this study can propose a basic design data to use the lean-mixed soil cement.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.280-285
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• 2005

At present, there are several problems related with sand mat which is used as a way to accelerate consolidation settlement, act like an underground drainage layer and increase trafficability simultaneously. First of all, the unbalance oft he demand and supply of sand is the one of the biggest problems, which makes not only price advance of sand but also delays a term of total construction work. Secondly, the damage of ecosystem and scenery is triggered by thoughtless sand dredging or mining. So, the need that the sand for sand mat should be replaced with a new environmental friendly material has been increased. Fiber mat may be one of the proper materials that suits the need. Therefore, we intended to compare the drainage properties of sand mat with those of fiber mat by experimental model tests. On the basis of the test results, fiber mat took shorter period of consolidation than sand mat and it's amount of settlement showed a little bit bigger than the other. In conclusion, the substitutability of fiber mat for sand mat could be placed highly in view of drainage efficiency. Furthermore, when Fiber mat is used, it has an advantage that spoil soil of the construction site or nearby site can be used for the purpose of increasing trafficability in addition to a role of drainage layer.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• v.6 no.1
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• pp.22-29
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• 2003

This research aims at investigation of accuracy potential of RTK(Real-Time Kinematic) GPS in combination with Echo Sounder(E/S) for the coastal mapping. Apart from this purpose, the accuracy of ambiguity resolution with the OTF(On The Fly) method was tested with respect to the initialization time. The result shows that the accuracy is better than 1cm with 5-minute initialization in the distance of 10km baseline. The seaside topography was measured by the RTK GPS only, on the other hand the seafloor topography was surveyed in combination of RTK GPS and E/S. Comparing to the volume of seaside measured by RTK GPS and digital topographical map, the difference of only 2% was achieved. This indicates that the coastal mapping. As a result, it has been revealed that every possible noise in surveying could be corrected and the accuracy could be improved. The accuracy of GPS data acquired in real time was as good as that acquired by post processing. It is expected that it will be useful for the analysis of coastal geographic characteristics because DTM(Digital Terrain Model) can be also constructed for the harbor reclamation, the dredging, and the variation of soil movement in a river.

• Journal of Ocean Engineering and Technology
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• v.17 no.3 s.52
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• pp.13-20
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• 2003

This research aims at investigation of accuracy potential of RTK(Real-Time Kinematic) GPS in combination with Echo Sounder(E/S) for the coastal mapping. Apart from this purpose, the accuracy of ambiguity resolution with the OTF(On The Fly) method was tested with respect to the initialization time. The result shows that the accuracy is better than 1cm with 5-minute initialization in the distance of 10km baseline. The seaside topography was measured by the RTK GPS only, on the other hand the seafloor topography was surveyed in combination of RTK GPS and E/S. Comparing to the volume of seaside measured by RTK GPS and digital topographical map, the difference of only $2\%$ was achieved. This indicates that the coastal mapping. As a result, it has been revealed that every possible noise in surveying could be corrected and the accuracy could be improved. The accuracy of GPS data acquired in real time was as good as that acquired by post processing. It is expected that it will be useful for the analysis of coastal geographic characteristics because DTM(Digital Terrain Model) can be also constructed for the harbor reclamation, the dredging, and the variation of soil movement in a river.

• 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 Geotechnical Society
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• v.31 no.4
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• pp.13-18
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• 2015

Considering dredged ground is consolidated more than one meter, Compression index prediction is very important. But, UD-sampling and consolidation test are impossible because of high moisture content and weak shear strength. This paper demonstrates the compression index relation, $C_{c(d)}=F(e_d,C_c)$, between in-situ and dredged clay using N. Keith Tovey's Omega point and soil physical properties. Good relationship is confirmed between proposed formula and measured primary consolidation result on dredged ground in The Republic of Korea.