• Journal of the Korean GEO-environmental Society
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• v.10 no.5
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• pp.5-9
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• 2009

In this experiment, the cutter head was designed as the down-scaled shape from the cutter head of the Asan-3 of Hyundai Construction Company. The dredging simulation instrument was installed in the experiment water tank which has the dimension of $4.2m(L){\times}2.2m(W){\times}1.5m(H)$. The speed of all components were controlled manually through the hydraulic tool and motors to find the effective desilting condition. As the results, the experiment was conducted to find the optimate dredging cutter head operation rate. To compare the factors which effect on the dredging effectiveness, the dimensionless dredging volume ratio was introduced and it can be found the best effectiveness at 2.0 m/s suction speed, 8 cm dredging depth and 4~4.5 dimensionless dredging volume ratio. Therefore, in order to take the best effectiveness these 3 components factors should be adequately considered.

• Journal of Korean Society for Geospatial Information Science
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• v.21 no.4
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• pp.3-12
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• 2013

In order to evaluate dredging results scientifically the system which can manage and estimate working process by monitoring dredging process in real-time needs to be constructed. We constructed real-time dredging management system for guidance of a dredging vessel and for survey of dredging construction. This system was designed to have functions of dredger location by GPS, ship direction measurement by GPS/Gyroscope combination, Grab position measurement, dredging depth measurement and correction. In addition, we developed the programs for controlling and operating the constructed system. The system could induce the vessel to accurate position and conduct dredging according to plan and the effectiveness of the system was evaluated through the results of application to actual dredging construction site.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2000.05a
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• pp.41-45
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• 2000

Geotube is made of permeable but soil-tight geotextile, hydraulically filled with soil include dredged sand and mud, which has been successfully applied in hydraulic and coastal engineering projects. Ceotube method is getting popular and being used a lot in many countries of the world because of the simplicity of the placement and construction, cost effectiveness and minimum impact on the environment, and enable to store & isolate contaminated materials as obtained by harbor dredging. Laboratory tests and field construction were performed to determine the design methodology and construction procedures. From the results of laboratory and field construction, the retention ratio of solid particle is a minimum 86%. The minimum permeability and the tensile strength of geotextile are $\alpha$ x 10$^{-4}$ cm/sec and 20t/m, respectively Also, based on the environmental test results, it can be concluded that this method does meet the Korean EPA standards.

• Journal of Korea Water Resources Association
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• v.44 no.1
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• pp.31-40
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• 2011

In this study, the methods of sedimentation reduction for the estuary barrage were analyzed using the CCHE2D bed change model. Especially, the effectiveness of sediment dredging currently applied in the field was evaluated quantitatively and also the channel contraction method which is a substitute method was analyzed for the Nakdong River Estuary Barrage (NREB). The numerical model was calibrated and validated for the sediment transport equations and transport modes. In the NREB case, the Ackers and White formula and bed load type was the most similar to the field condition. As a results of the dredging simulation, there was the sedimentation reduction effect of 0.2 m in the bed changes. Furthermore, the analysis result of the channel contraction method represented that the sedimentation reduction effects of the average 0.4 m and the maximum 2.0 m were produced.

• Journal of the Korean GEO-environmental Society
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• v.23 no.5
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• pp.15-24
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• 2022

In order to improve dredged area, long time and high cost is needed because of bad engineering and physical conditions. And there is no suitable example of pipe mixing method at domestic site. Moreover, applicability and effectiveness of this method is uncertain and shows different results between site and laboratory test. In order to solve these problems, we determined proper grain size distribution and water content range using dredged soil and reformed material (standard sand & material controlling grain size distribution) in the laboratory test. As a result, we confirmed that coefficient of sediment consolidation is increased and there is an improvement about separation sedimentation. Undrained shear strength was derived by water content of reformed dredging soil through regression analysis of test results. We suggest the correlation equation for determining mixing ratio.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.460-460
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• 2021

각종 오염물질이 수계로 유입되어 침강하면 하상에 퇴적되는데 이 오염된 퇴적물 중 질퍽한 콜로이드상의 물질을 오니토라 일컫는다. 이 오염물은 저장소 및 물환경의 변화에 따라 수질 악화의 직접적인 원인이 될 수 있는 인, 질소 등의 영양염류를 수중으로 재용출시킬 수 있는 비점오염원 종류 중 하나이다. 하천 준설은 하천에서 저수용량 확보와 하상 유지관리 및 골재확보, 수질 개선을 위해 토사를 제거하고 그 토사를 운반선에 의하여 운반하여 지정된 투기장에 투기하는 일련의 공사를 말하며, 이를 통하여 비점오염원인 오니토를 직접적으로 제거할 수 있다. 준설의 필요성 판단 및 수질개선 효과를 모니터하기 위해서는 하천의 수질과 유량을 조사해야 한다. 이때 대상구간이 요구하는 수질 기준에 부합하지 않으면 오염퇴적물 준설 기준을 통해 준설이 필요한 구간 및 사업량을 결정한다. 준설 사업량의 경제적 타당성을 정량적으로 검증하기 위해 대상 구간을 준설을 하지 않을 시 오니토가 상시 용출된다는 가정하에 물재생시설로 이 오염물을 정화했을 때의 비용을 준설 사업비와 비교하였다. 본 연구에서는 하천공사 표준시방서(2007)에 제시된 오염퇴적물 준설 기준을 만족하는 서낙동강수계의 준설 계획 지구에 대한 계획 사업비와 해당 지구 하류에 위치한 물재생시설의 정화능력 및 운영비를 비교해 하천 준설 사업비에 대한 편익을 산정하였다.

• Journal of the Korean GEO-environmental Society
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• v.21 no.3
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• pp.5-11
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• 2020

Recently, ground pits that have been occurring frequently in urban areas are hindering traffic flow and causing property damages and loss of human life, acting as factors that are threatening the safety of citizens. Therefore, sunken ground must be quickly restored and provisions must be made for additional damage but current domestic detailed standards regarding ground pits and accurate definitions regarding causes and measures to be taken for reoccurrences are lacking. Restoration methods of sunken ground include backfilling by reusing sunken soil or other fill material and paving the road and while this is the most often used method, this only prevents ground from sinking temporarily and can not serve as a fundamental solution. Also, additional ground pits can occur on ground that is reinforced using this method due to faulty backfill material or faulty hardening. This study used Eco-friendly High-Strength Material (EHSM) as restoration material that can be used in the restoration of underground cavities that have occurred due to ground subsidence to analyze the engineered characteristics of modified dredging clay and test pieces made from changed ratios of EHSM and weathered granite soil were uniaxial compression tests were conducted and freezing-thawing tests were conducted to study strength properties according to environmental changes of restoration material, and after tests were concluded by each level, uniaxial compression tests and dynamic elasticity tests were conducted for intensity analysis. Also, to evaluate strength characteristics of the restored ground, dynamic plate load tests were conducted to verify the improvement effectiveness of the restored ground.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.11
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• pp.834-846
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• 2011

The objective of this study is to development of IDFIS system, that are consisted of hydrocyclone, rapid flocculation and inclined settler with chitosan coagulant. As the results of Jar test, a chitosan optimum dosage of 40 mg/L for river sediment, and 5 mg/L for tunnelling wastewater sediment, which these conditions leaves of residual turbidity of less than 5 NTU. Because of the effectiveness of chitosan in removing turbidity was independent on pH, the operation of IDFIS system would be simple. The synthesized turbidity was made with clay particles, river sediment, river suspended sediment, and tunnelling wastewater sediment. Results indicate that the mean overall removal efficiency of turbidity, SS, COD and TP were 98%, 99%, 85% and 95%, respectively. Chitosan is very efficient in removing turbidity in the entire turbidity range examined. IDFIS system would have possibility with compact design, because of the increase of floc size favours the floc settling speed and reduces the settling time.

• Journal of Korea Water Resources Association
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• v.41 no.10
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• pp.983-993
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• 2008

In recent times, sea level increasing caused by abnormal weather and global warming, sea-sand dredging and complex development causes various kind of erosion damages onto the coastal area in the world. The various types of erosion control and protection methods are applied but there are no signs of fruitful effectiveness. The PC concrete protection block for shore protection structure is practically installed in globally but most of structures in the present day became villainous because of bad accessability. In this study, hydrophilic revetments for control and protection of coastline erosion will be developed in order to make up for a faculty of the shore erosion protection block with better accessibility and excellent protection ability. Experimental measurements were researched to insure for the capacity and facility on reflection coefficient, overtopping volume, and overtopping height characteristics of newly developed shore erosion protection block in model tests. As the result, hydraulic model tests show much excellent than the general step block. Field tests were carried out also to verify through vegetative test on an affinity and construction work test of control-protection on coastline erosion with actual utilization. In the latter case, deposition of sand accumulation occurred in fairly short time at the established reaches and then we can be confirmed to utilize for newly developed block as the revetments for control and protection of coastline erosion.

• 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.