• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.66-66
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• 2017

Hydraulic jump is typically designed to occur over low-haed dam spillways and weirs in the river. An important engineering application of the hydraulic jump is to dissipate the intense kinetic energy of the flows over such hydraulic structures. Turbulent flow and roller-like vortex riding up the free sureface of the jump cause most of the energy dissipation. We carry out a high resolution three-dimensional numerical simulations of a submerged hydraulic jump in a spillway and compare numerical results with a laboratory measurement obtained by the PIV. The numerical results further show the dynamic behavoirs of the inner and outer layers of the submerged wall-jet and the recirculating roller of the hydraulic jump.

• Earthquakes and Structures
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• v.18 no.3
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• pp.285-296
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• 2020

Dams are important structures for management of water supply for irrigation or drinking, flood control, and electricity generation. In seismic regions, the structural safety of concrete gravity dams is important due to the high potential of life and economic loss if they fail. Therefore, the seismic analysis of existing dams in seismically active regions is crucial for predicting responses of dams to ground motions. In this paper, earthquake response of concrete gravity dams is investigated using the finite element (FE) method. The FE model accounts for dam-water-foundation rock interaction by considering compressible water, flexible foundation effects, and absorptive reservoir bottom materials. Several uncertainties regarding structural attributes of the dam and external actions are considered to obtain the fragility curves of the dam-water-foundation rock system. The structural uncertainties are sampled using the Latin Hypercube Sampling method. The Pine Flat Dam in the Central Valley of Fresno County, California, is selected to demonstrate the methodology for several limit states. The fragility curves for base sliding, and excessive deformation limit states are obtained by performing non-linear time history analyses. Tensile cracking including the complex state of stress that occurs in dams was also considered. Normal, Log-Normal and Weibull distribution types are considered as possible fits for fragility curves. It was found that the effect of the minimum principal stress on tensile strength is insignificant. It is also found that the probability of failure of tensile cracking is higher than that for base sliding of the dam. Furthermore, the loss of reservoir control is unlikely for a moderate earthquake.

• Water Engineering Research
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• v.6 no.4
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• pp.149-159
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• 2005

With increasing recognition on conservation of endangered species in Taiwan, one of the major conservation projects is the habitat restoration of Formosan Landlocked Salmon which is major threatened by check dams in the channel for their blockading pathway to upstream and causing the problems of population isolation and close-blood mating. By creating an opening in the central dam body appropriately, partial removal dams can provide pathway for the fish for the better upstream channel habitat. Four check dams at Gau-Shan Creek were remodeled between April of 1999 and September of 2002 with information supported from model experiments under certain hydraulic condition of field environment. Based on the follow-up investigation, the channel morphology of observation sections is in stable condition and the total number of Formosan Landlocked Salmon in this creek increased promptly at the reach containing partial-removed dams.

• Journal of the Korean Society of Safety
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• v.19 no.2
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• pp.88-92
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• 2004

The paper decribes a procedure for the evaluation of the effect of seepage force on stability of slopes. The stability of an embankment impounding a water reservoir is highly depend upon the location of seepage line with the embankment. To evaluate the accurate safety factor of an embankment, it is important to illustrate the seepage phenomenon. Of particular interest is the stability following a rapid change of reservoir level. Seepage forces in embankments are easily determined interest is the stability following a rapid change of resrvoir level. Seepage forces in embankments are easily detemined if frictional forces are expressed in relation to hydraulic gradient I. If a piezometer is inserted into a body of embankment, the level to which fee water rises is a measure of the energy at that point.

• Journal of Korea Water Resources Association
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• v.55 no.11
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• pp.923-929
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• 2022

The Chuncheon Mullori area is an underprivileged area of water welfare where local water supply is not supplied, and it is supplying water to the villages with small water supply facilities using lateral flow and groundwater as water sources. This is an area with poor water supply conditions, such as relying on water trucks due to water shortages during the recent severe drought. Therefore, in order to solve the problem of water shortage during drought and to prepare for the increasing water demand, a sand dam was installed along the valley, and this facility has been operating since May 2022. In this study, repeated simulations were performed according to the hydraulic conductivity of the filler material and the storage coefficient value for the inflow condition for about two years from mid-March 2020 to mid-March 2022. For each case, the amount of discharge through the perforated drain pipe was calculated. Overall, as the hydraulic conductivity increased, the amount of discharge and its ratio increased. However, when the hydraulic conductivity of the second floor was relatively low, the amount of discharge increased and then decreased as the hydraulic conductivity of the third floor increased. This is considered to be due to the fact that the water level was kept low due to the rapid drainage compared to the net inflow into the third floor because the water permeability of the third floor and the drainage coefficient of the drain pipe were large. As a result of simulating the flow of the open channel in the upper part of the sand dam as a hypothetical groundwater layer with very high hydraulic conductivity, the decrease in discharge rate was slower than the increase in the hydraulic conductivity of the hypothetical layer, but it was clearly shown that the discharge volume decreased relatively as the hydraulic conductivity of the virtual layer increased.

• Geotechnical Engineering
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• v.12 no.6
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• pp.65-78
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• 1996

The Chungpyung Dam is a 16 yearn old rock-fill dam for a Pumped storage hydro-Power plant, located in the middle of the Korean Peninsula. Since the dam is subjected to the daily water level fluctuation, such as rapid drawdown and refill, thus inducing a structural impact on the behavior of dam body, it draws attention of many engineering concerns. Traditionally, steady-state analysis was employed to investigate the seepage in the dam body, but in this study the seepage analysis was numerically performed by 2-D FEM thansient analysis. As a boundary condition for an analysis, the water level fluctuation was incorporated to simulate the daily change. As a res41t, the various seepage phenomena such as hydraulic gradient, seepage vector, and pore water pressure distribution were quantified at the corresponding time of interest as the water level rises and recedes. The seepage flux was also estimated and compared with the measured data which were both acceptable considering design criteria. The result proves that there is no sign of hazardous sources contributing to the possibility of piping, internal erosion and excess leakage through the dam body.

• Journal of Korea Water Resources Association
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• v.42 no.7
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• pp.579-589
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• 2009

Hwang River in South Korea, has experienced channel adjustments due to dam construction. Hapcheon main dam and re-regulation dam. The reach below the re-regulation dam (45 km long) changed in flow regime, channel width, bed material distribution, vegetation expansion, and island formation after dam construction. The re-regulation dam dramatically reduced annual peak flow from 654.7 $m^3$/s to 126.3 $m^3$/s and trapped the annual 591 thousand $m^3$ of sediment load formerly delivered from the upper watershed since the completion of the dam in 1989. An analysis of a time series of aerial photographs taken in 1982, 1993, and 2004 showed that non-vegetated active channel width narrowed an average of 152 m (47% of 1982) and non-vegetated active channel area decreased an average of 6.6 km2 (44% of 1982) between 1982 and 2004, with most narrowing and decreasing occurring after dam construction. The effects of daily pulses of water from peak hydropower generation and sudden sluice gate operations are investigated downstream of Hapcheon Dam in South Korea. The study reach is 45 km long from the Hapcheon re-regulation Dam to the confluence with the Nakdong River. An analysis of a time series of aerial photographs taken in 1982, 1993, and 2004 showed that the non-vegetated active channel width narrowed an average of 152 m (47% reduction since 1982). The non-vegetated active channel area also decreased an average of 6.6 $km^2$ (44% reduction since 1982) between 1982 and 2004, with most changes occurring after dam construction. The average median bed material size increased from 1.07 mm in 1983 to 5.72 mm in 2003, and the bed slope of the reach decreased from 0.000943 in 1983 to 0.000847 in 2003. The riverbed vertical degradation is approximately 2.6 m for a distance of 20 km below the re-regulation dam. It is expected from the result of the unsteady sediment transport numerical model (GSTAR-1D) steady simulations that the thalweg elevation will reach a stable condition around 2020. The model also confirms the theoretical prediction that sediment transport rates from daily pulses and flood peaks are 21 % and 15 % higher than their respective averages.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1602-1610
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• 2005

In this study was investigated and analyzed of damage characteristics for infrastructures by typhoon that have been many occur. The objective Structures were the road and hydraulic structure. The road structure was included the cut-slopes, retaining walls and bridges. The hydraulic structure is divided with the dike, small-scale dam, reservoir and floodgate. The analysis result of the bridge damage cause is river bottom height increase and passage ability decrease. The principal damage reasons of the cut-slope structure are weakening the ground due to the localized torrential downpour and drainage defective. Also, the principal damage reasons of the small-scale dam, reservoir, dike and the floodgate are continuous collapse of dike beside the floodgate.And we divided a typhoon damage occurrence cause with artificial and natural. As the result of analysis, the many damage occurrence cause will be removed by system improvement and technical development.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.6
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• pp.679-687
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• 2013

Although stable and safe drinking water supply to the customers is a basic function of multi-regional water supply systems in Korea, most systems have their vulnerabilities in emergency time due to the branch-type. Application of connections from the other water supply system can provide a solutions for these tentative problems. This paper describes reduction planning of water supply accidents that can minimize a service interruption to customers in multi-regional water supply system by connecting pipe lines between local water supply systems in Mokpo city areas. The result of this study shows that Juam dam multi-regional water supply systems can cover all of the water shortage in southern parts of Jeonnam multi-regional water supply systems by transmitting water through connected pipes between local networks. This can be effective to supply water interactively in various contingencies, when a pipe line accident occurs in southern area of Jeonnam multi-regional water supply systems. On the contrary, southern area of Jeonnam multi-regional water supply systems can cover 99.5 %($62,500m^3/day$) of the water shortage of Juam dam multi-regional water supply systems when service interruptions caused by various pipe accidents occur in the system.

• Journal of the Korean GEO-environmental Society
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• v.8 no.6
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• pp.77-83
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• 2007

In this study, deformation behavior of existing concrete face rockfill dam, which is raised to a certain height to enhance storage capacity or to improve hydraulic and hydrologic stability, is examined using numerical analysis method. The results obtained from FEM analysis show a possibility that additional fill at downstram slope of existing CFRD dam body may lead undesirable deformations and stresses in existing dam body, especially in face concrete, such as settlements in upper part and bulging in lower part, excessive bending moments, and eventualy tensile cracks. Therefore, in designing multi-staged raising construction of CFRD, it is essential to consider deformations and stresses to be developed within and between exisiting dam body and added parts due to additional fill, and to prepare a proper measure to prevent abnormal deformations and stresses in the dam body including added parts.