• Journal of the Korean Geotechnical Society
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• v.24 no.8
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• pp.149-160
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• 2008

Offshore pile foundations are prone to lateral soil pressures resulting from embankment construction for the reclamation on deepwater soft clay. Since the 1990s, offshore reclamation has actively progressed in Korea, connecting with the development of Songdo newtown, Incheon newport, and Busan newport representatively. Special attention has been given to lateral soil-structure interaction problems related to passively-loaded offshore pile foundations. Based on a plane strain large deformation finite element (LDFE) approach, this paper presents the results of investigation into undrained (short-term) and drained (long-term) behavior of passively-loaded offshore pile foundations. This study examines the effects of major factors, such as soil profile, pile head boundary condition, magnitude of embankment load, and average degree of consolidation. The results allowed quantification of differences in the magnitude of lateral soil pressure acting on the piles between undrained and drained phases.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.4
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• pp.411-420
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• 2005

Maintaining a good quality of drinking water produced through appropriate water treatment processes to the tap is as important as improving water quality in a water treatment plant (WTP). The quality of most tap water, however, does not have the same quality as that of the water produced in a WTP due to the contamination in the distribution system while they are delivered through pipes and water tanks. It is very important to maintain water quality in distribution system to water suppliers for consumer's health and safety. Furthermore, it is not possible to investigate the water quality of all points in the distribution system because the system has a wide area and very complex hydraulic characteristics. One economic solution to prevent water quality in distribution system from being deteriorated is monitoring several points that might have the least water quality in the distribution system. If the quality of water of the monitoring points selected by proper ways is better than the quality index of Drinking Water Quality Guidelines suggested by Korean Ministry of Environment, all other points in the distribution system would be safe to drink.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.756-760
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• 2007

삽교천 홍수예보시스템은 1999년에 개발되어 현재까지 운영되고 있으나, 개발 이후 유역특성의 변화를 반영한 모형 개선이 이루어지지 않았고, 삽교천 하구둑의 영향을 고려한 모형은 개발되어 있지 않은 실정이다. 이 지역 중에서 특히 천안/아산지역은 급격한 인구증가와 산업화 및 도시화에 의해 면적당 자산의 고도화가 증가하며, 이에 따라 홍수시 피해잠재능은 점점 증가하고 있는 상황이다. 또한, 하구둑의 영향을 고려한 모형을 개발하여 정확한 홍수예보를 위한 전산시스템의 개선자료를 제공할 필요가 있다. 따라서 삽교천 하구둑에 의한 배수영향을 고려하기 위해 FLDWAV모형을 이용하고, 삽교천 하구둑 수문조작에 따른 내수위(하류경계 조건)를 예측하는 모형을 개발하여 하구둑 운영을 고려한 연계모형을 개발하였다. 향후 설치될 우강지점에 대한 수위자료가 구축되면 예측의 정확도를 검증할 수 있으며, 홍수예보시 정확성을 높일 수 있을 것이다.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.6
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• pp.619-625
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• 2008

Urban sewer systems are designed to operate in open-channel flow regime and energy loss at square manholes is usually not significant. However, the energy loss at surcharged manholes is considered as one of the major causes of inundation in urban area. Therefore, it is necessary to analyze the head loss associated with manholes, especially in surcharged flow. Hydraulic experimental apparatus which can change the manhole inner profile(CASE I, II, III, and IV) and the invert types(CASE A, B, C) were installed for this study. The experimental discharge was $16{\ell}/sec$. As the ratio of b/D(manhole width/inflow pipe diameter) increases, head loss coefficient increases due to strong horizontal swirl motion. The head loss coefficients for CASE I, II, III, and IV were 0.46, 0.38, 0.28 and 0.37, respectively. Side covers increase considerably drainage capacity at surcharged square manhole when the ratio of d/D(side cover diameter/inflow pipe diameter) was 1.0. The head loss coefficients for CASE A, B, and C were 0.45, 0.37, and 0.30, respectively. Accordingly, U-invert is the most effective for energy loss reduction at surcharged square manhole. This head loss coefficients could be available to evaluate the urban sewer system with surcharged flow.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.157-157
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• 2015

최근 들어, 송 배수 시스템의 펌프운영을 최적화하여 운영비용을 절감하기 위한 연구가 활발히 진행되고 있다. 펌프운영을 모의하기 위해서는 수 일간의 시간모의가 필수적이며, 최적화 알고리즘 등과의 연계를 통한 시뮬레이션이 필요한 경우가 많다. 하지만, 대규모 네트워크의 경우 관로 및 절점의 수가 수천, 혹은 수 만개에 달해 수리해석 및 최적화에 소요되는 시간이 길어지는 문제가 발생한다. 이에 본 연구에서는 효율적인 수리해석을 위해 상수관망 네트워크를 골격화(skeletonization)하는 방법을 제안한다. 상수관망시스템의 골격화는 본래의 상수관망 수리 거동을 변화시키지 않는 범위에서 관로와 절점의 삭제, 통합을 통해 복잡한 상수관망을 단순화하는 과정이다. 이러한 골격화 방법은 단순골격화 방법과 등가길이관 방법(Equivalent Length Pipe Method)으로 구분할 수 있다. 단순 골격화 방법은 해당 상수관망 수리해석에 큰 영향을 미치지 않는 소구경관을 삭제하거나, 특정 구역의 여러 수요절점을 하나의 수요절점으로 통합하는 방법이다. 등가길이관 방법은 관경과 연장이 상이한 복수의 관에 동일한 유량이 흐르는 경우, 관경, 연장, 조도계수 등을 조절하여 동일한 수두 손실이 발생하는 하나의 관으로 통합하는 방법이다. 국내에 실제 운영되고 있는 지방상수도를 대상으로 골격화를 진행하였으며, 수리해석 프로그램은 미국 환경청에서 개발한 EPANET을 사용하였다. 본 연구에서 개발한 골격화 기법을 통해 대규모 상수관망의 해석에 소요되는 시간을 단축할 수 있으며, 실제 상수관망의 운영에 도움이 될 것으로 기대한다.

• Journal of Korea Water Resources Association
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• v.41 no.3
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• pp.305-314
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• 2008

Urban sewer systems are designed to operate in open-channel flow regime and energy loss at circular manholes are usually not significant. However, the energy loss at manholes, often exceeding the friction loss of pipes under surcharge flow, is considered as one of the major causes of inundation in urban area. Therefore, it is necessary to analyze the head loss associated with manholes, especially in surcharge flow. Hydraulic experimental apparatus which can be changed the invert type(CASE A, B, C) and step height(CASE I, II, III) was installed for this study. The range of the experimental discharges were from $1.0{\ell}/sec$ to $5.6\;{\ell}/sec$. As the manhole diameter ratio($D_m/D_{in}$) increases, head loss coefficient increases due to strong horizontal swirl motion. Head loss coefficient was maximum because of strong oscillation of water surface when the range of manhole depth ratios($h_m/D_{in}$) were from 1.0 to 1.5. The average head loss coefficients for CASE A, B, and C were 0.45, 0.37, and 0.30, respectively. Accordingly, U-invert is most effective for energy loss reduction at circular manhole. This head loss coefficients could be available to design the urban sewer system with surcharge flow.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.4
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• pp.447-458
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• 2009

Energy loss at manholes, often exceeding friction loss of pipes under surcharged flow, is considered as one of the major causes of inundation in urban areas. Therefore, it is necessary to analyze head loss at manholes, especially in case of surcharged flow. Hydraulic experiments were conducted with three cases. Case A is to test whether the shapes of the manholes influence head loss coefficients. Case B and C were proposed to further reduce head losses by improving the manhole hydraulic efficiency. In case B, the joining part of the pipe at both shapes of manholes is shifted from central part to side part. The test in case C is to check the average head loss coefficient by installing the side benching in square manhole, based on shifted joining part model. The average head loss coefficient for circular and square manhole on case A was 1.6. This did not show much difference of the head loss coefficients in spite of the discharge variation in this case. However, case B and C show large difference between head loss coefficients due to the strong oscillation of water surface and the horizontal swirl motion. The circular and square manholes in case B reduced the head loss by 30% and 6% than ones in case A, respectively. The average head loss coefficient for circular manhole in case B was 1.1. Case C reduced average loss coefficients of the square manhole in case A from 1.6 to 1.1. Accordingly, the circular manhole in case B and the square manhole in case C showed the effective way to reduce the head loss. These head loss coefficients could be available to apply to the urban sewer system with surcharged flow.

• Water for future
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• v.29 no.3
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• pp.197-205
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• 1996

Flow carrying capacity of water distribution systems is getting reduced by deterioration of pipes in the systems. The objective of this study is to develop a managerial decision-making model for the rehabilitation of water distribution systems with a minimum cost. The decisions made by the model also satisfy the requirements for the discharge and pressure at demanding nodes in the system. The replacement cost, pipe break repair cost, and pumping cost are considered in the economic evaluation of the decision along with the break ratio and interest ratio to determine the optimal replacement time for each pipe. Then, the hydraulic integrity of the water distribution system is checked for the decision by a pipe network simulator, KYPIPE, if the discharge and pressure requirements, the decision made for the optimal replacement time is revised until the requirements are satisfied. The model is applied to an existing water distribution system, the Metropolita Water Supply Project (1st Phase). The result shows that the decisions for the replacement time determined by the economix analysis are accepted as optimal and the hydraulic integrity of the system is in good condition.

• Journal of Korea Water Resources Association
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• v.48 no.10
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• pp.845-855
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• 2015

Studies of optimizing pump operation in water distribution networks (WDN) are receiving spotlight in recent days. However, the water networks are quite complex including thousands of or even tens of thousands of nodes and pipes, thus simulation time is an issue. In some cases, implementing a computer model for pump operation decisions is restrictive due to intensive computation time. To that end, it is necessary to reduce the simulation time of water networks by simplifying the network layout. In this study, WDN skeletonization approaches were suggested and applied to a real water transmission network in South Korea. In skeletonizing the original network, it was constrained to match the water pressure and water age in the same junction locations to maintain the hydraulic and water quality characteristics in the skeletonized network. Using the skeletonization approaches suggested in this study, it is expected to reduce the simulation time of WDN and apply for developing a computer module of WDN real-time optimal operation.

• Journal of Korea Water Resources Association
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• v.44 no.12
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• pp.1001-1013
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• 2011

Development of an optimal water supply system considering water quantity, quality, and economical efficiency is needed to decide optimal available area by combine water supply systems in overlapped area where are more than 2 water sources. The EPAnet and the KModSim were coupled to develop optimal network model. The developed network model was calibrated by measured data from water supply system in Geoje City, Korea in 2007 which have three water sources such as Sadeong booster pumping station, Guchun dam reservoir and Yoncho dam reservoir. The optimum network model was validated by operating results of 2011 to assess the economically optimized service area and optimal pump combination under the given hydraulic operating rules developed in this study. The developed model can be applied into designing water supply systems and operating rules for the conjunctive operation since the model can give the optimal solution satisfied with water quantity, economical efficiency and quality.