• Journal of Korea Water Resources Association
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• v.41 no.1
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• pp.65-74
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• 2008

The small and medium sized dams have the fill dam type of a lot of occasions, which are often weak in cases of major floods. For this reason, although a countermeasure is in great need, due to the importance of the facilities and financial situations, no direct safety measures have been taken. In this study, in order to minimize construction expenditure for practical safety measures in cases of major floods, the overflow section of spillway has been analyzed focusing on how the overflow capacity will increase in the case of partially rebuilding a part of the overflow section of spillway favorable for hydraulic conditions. The Labyrinth weir and movable weir was chosen for reconstruction models of the overflow section. Moreover, for analyzing the after-effects of the reconstruction, a small scale dam was temporarily chosen for various experiments such as the hydraulic model testing and the three dimension numerical evaluation through the use of Flow-3D.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1B
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• pp.11-20
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• 2008

The spillway type of small and midsize dams in Korea is almost overflow weir. To examine flood control capacity of overflow spillway, FLOW-3D was applied to Daesuho dam and analysis was focused on the discharge of dam spillway by changing weir shape. Overflow phases and discharges of linear labyrinth weir and curved labyrinth weir were compared with those of existing linear ogee weir. Hydraulic model experiment was performed to verify numerical result. Verification results showed that overflow behaviors and flow characteristics in the side channel by hydraulic model experiment and numerical simulation are well matched, and water surface elevation at side wall coincides with each other. When the reservoir elevation was increased up to design flood level, in case of the linear ogee weir the flow over the crest ran through smoothly in the side channel, whereas in cases of linear labyrinth weir and curved labyrinth weirs, the flow discharge was increased by 40 cms, and the flow over the weir crest, rotating counter-clockwise, was submerged in the side channel. The results of the water level-discharge curve revealed that labyrinth weir can increase discharge by 71% compared to the discharge of linear ogee weir at low reservoir elevation since it can have longer effective length. But as water surface elevation rises, the slope of water level-discharge curve of labyrinth weir becomes milder by submergence and nappe interference in the side channel.

• Journal of Urban Science
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• v.10 no.1
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• pp.39-48
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• 2021

In this study, to evaluate the characteristics of the pollution in the major inflow tributaries and major environmental facilities in the watershed of Ara waterway, An inflow flow rate measurement and water quality analysis were conducted during dry and rainy seasons. In addition, the flow rate measurement, water quality analysis, and pollutant load at each monitoring point were compared and evaluated. Influx of BOD5, T-P and T-N into the tributaries of the ARA waterway watershed, excluding the Gulpo river watershed, during dry season were only 0.007%, 0.005% and 0.004% respectively of the incoming loads in the entire ARA waterway basin. In addition, it was confirmed that the discharge pollutant loads during rainfall event was about 440 times more for BOD5, about 545 times on T-P, and about 23 times on T-N in comparison to the pollutant loads during the dry days. When the Gulhyeon rubber dam was deflated, the discharged pollutant load during a rainfall was higher than the estimated load at the G7 monitoring point because the deposited pollutants from the upstream riverbed flowed down. Therefore, during a rainy season, it is necessary to manage the influx of high-load water pollutants from the overflow and deflation of the Gulhyun rubber dam as well as to find a strategy to reduce the pollutant loads in the Gulpo river watershed.

• Journal of the Korean Institute of Landscape Architecture
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• v.34 no.4 s.117
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• pp.116-128
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• 2006

This study focuses on hydrological changes caused by developments in the 13th, 14th (Motjarigol) district in Eun Pyoung New Town, Seoul on the basis of the Land Use Planning of development plan. Through analyses from the hydrological experiments about rainfall outflow using universal equation and amounts of infiltration through soils, the changes in amounts of overflows were estimated and the results were discussed from a urban ecological point of view. As a result, it has been predicted that the amount of rainfall outflow at post-development was dramatically increased, compared to pre-development. Installing of Derbris Dams and infiltration facilities were suggested as alternative plan to meditigate these changes. If we apply these alternatives, the rainfall outflow would be reduced up to 30% compared to the development plan without BMPs (Best Management Practice). In conclusion, it is proposed that once the ecological principles were considered during development planning process, we can minimize the adverse effects of developments to our environments.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.117-128
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• 2005

Korea is affected by typhoon 2-3 times a year, and 50${\sim}$60 % of annual rainfall is concentrated during summer with heavy daily precipitation. Recently such natural conditions cause many of failures or damages of reservoirs and embankments. Overflow by heavy flood is the main cause that results 54.2 % of total embankment failures with damages of spillway, outlet channel and stilling basin. Since damages by overflow are triggered by scour of soils nearby the structures, use of proper backfill materials with great resistance against erosion should be considered and application of suitable construction method to protect erosion may be adopted. Most failures of levee are caused by piping along the surface of cross-structure underneath levee. Such failures may be protected by deep consideration of piping at the stage of design and good quality control during construction. Sufficient magnitude of spillway and outlet channel is the ideal way to prevent failures by the flood. For existing structures, remodeling with reinforcement to protect against flood with review of required storage of dam should be considered.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.17 no.2
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• pp.61-71
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• 2014

A river fishway is a hydraulic structure enabling fish to overcome stream obstructions such as dams and weirs. The main aim of this paper is to investigate the collectibility of upstream-migrating fishes and hydraulic problems in pool-and-weir type fishway which has been established for upstream-migration at Namgang weir in the downstream of Namgang dam, and to grope for improvement measures which pool-and-weir type fishway can be switched to pool-and-partial weir type fishway through hydraulic field experiment. Exsisting fishway had problems which upstream-migrating fishes can not take a rest due to the seiche and vortex phenomena in pools and migrate to upstream because of height difference in entrance pool. In order to prevent hydraulically the seiche and vortex phenomena and establish rest area for fishes in each pool, we carried out hydraulic field experiments. In the fishway, it was to improve pool-and-weir into pool-and-partil weir, to decrease the height difference in entrance pool, and to reduce oriffice velocity of each pool. Also, we investigated fishes collectibility of after improving fishway for 6 days in September 2013. To resolve chronic problems(seiche-vortex phenomena and rest area for fishes), as weirs were remodeled into partial weir only which central part of weirs was part of non-overflow weir, we confirmed results that pool-and-weir type fishway could be switched to efficient pool-and-partial weir type fishway with relatively simple construction and low cost. Type-B which has the closed oriffices and the parts of non-overflow has the ideal conditions, but this conditions are limited to fishway of Namgang weir used in this study. Representative Ice-habor type fishway is pool-and-partial weir type fishway which has together parts of overflow and oriffices, and has excellent ability of upstream-migration. To switch from pool-and-weir type fishway to pool-and-partial weir type fishway, the size of oriffice has to be regulated by the discharge of fishway and the dimension on parts of non-overflow and overflow in weirs. Entrance pool is important facility which upstream-migrating fishes have to not only be collect but also charge with energy. In this study, entrance-pool is temporary and roughly-built, but fishes gather together more than the case of no entrance-pool. In the case of fishway which was protruded to downstream, as entrance of fishway turns toward or parallels to weir, the collectibility of fishway was excellent by attraction water.

• Computers and Concrete
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• v.13 no.2
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• pp.209-220
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• 2014

Vibration based damage detection is very popular in the civil engineering area. Especially, special structures like dams, long-span bridges and high-rise buildings, need continues monitoring in terms of mechanical properties of material, static and dynamic behavior. It has been stated in the International Commission on Large Dams that more than half of the large concrete dams were constructed more than 50 years ago and the old dams have subjected to repeating loads such as earthquake, overflow, blast, etc.,. So, some unexpected failures may occur and catastrophic damages may be taken place because of theloss of strength, stiffness and other physical properties of concrete. Therefore, these dams need repairs provided with global damage evaluation in order to preserve structural integrity. The paper aims to show the effectiveness of the model updating method for global damage detection on a laboratory arch dam model. Ambient vibration test is used in order to determine the experimental dynamic characteristics. The initial finite element model is updated according to the experimentally determined natural frequencies and mode shapes. The web thickness is selected as updating parameter in the damage evaluation. It is observed from the study that the damage case is revealed with high accuracy and a good match is attained between the estimated and the real damage cases by model updating method.

• Korean Journal of Agricultural Science
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• v.50 no.3
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• pp.469-484
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• 2023

In this study, three types of structures-stepped gabion retaining walls, vertical gabion retaining walls, and parapets-were installed on the dam floor crest to prevent the overflow of deteriorative homogeneous reservoirs. The acceleration response, displacement behavior, and pore water pressure ratio behavior were compared and evaluated using shaking-table model tests. The experimental conditions were set to 0.154 g in consideration of the domestic standard and the seismic acceleration range according to the magnitude of the earthquake, and the input waveform was applied with Pohang, Gongen, and artificial earthquake waves. The acceleration response according to the design ground acceleration increased as the height of the embankment increased, and the observed value were larger in the range of 1.1 to 2.1 times the input acceleration for all structures. The horizontal and vertical displacements exhibited maximum values on the upstream slope, and the embankment was evaluated as stable and included within the allowable range for all waveforms. The settlement ratio considering the similarity law exhibited the least change in the case of the parapet structure. The amplification ratio was 1.1 to 1.5 times in all structures, with the largest observed in the dam crest. The maximum excess pore water pressure ratio was in the range of 0.010 - 0.021, and the liquefaction evaluation standard was within 1.0, which was considered very stable.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.17-25
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• 2017

Owing to recent climate change, the scale of rainfall tends to increase gradually and the risk of flooding has increased. Therefore, the importance of improving the levee management and disaster response is increasing. Levee management in Korea is carried out at the level of damage recovery after the occurrence of damage. Therefore, it is necessary to develop a technology for predicting and managing the levee safety with proactive river management. In this study, a method to estimate the safety against erosion and overflow was suggested. A map of levee safety that can be used as basic data is presented by displaying the levee safety on the map. The levee erosion safety was calculated as the ratio of the internal and external force for each shore type. The levee overflow safety was calculated as the ratio of the maximum conveyance and design flood. The maximum conveyance was a discharge when the level of the river was equal to the level of the levee crown. The levee safety was classified into 5 grades: very safe, safe, normal, dangerous, and very dangerous. As a research area from downstream of Nam River Dam to Nakdong River Junction, the levee safety against erosion and overflow was estimated for all levees and all cross-sections of the river. The levee safety was displayed on a map using GIS. Through the levee safety map as a result of this study, the levee safety can be observed intuitively. Using the levee safety map, a maintenance plan for a river can be easy to build. This levee safety map can be used to help determine the priority of investment for efficient budget used.

• Journal of Korea Water Resources Association
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• v.38 no.3 s.152
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• pp.179-188
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• 2005

This study on the HwaBuk Multipurpose Dam showed that two- and three- dimensional numerical model experiments, as well as hydraulic model experiments, can be useful analysis tools for engineers. A commercially available RMA2, which solves the shallow water equations, and FLOW-3D, which solves the Reynolds averaged Navier-Stokes equations, were used to simulate the hydraulic model setup. Numerical simulation results on the following were compared with the hydraulic model results: the flow in the reservoir basin and the approaching channel; the discharge in the overflow weir; the water surface profiles in the rollway, chute, and stilling basin; and the pressure distributions in the rollway. It was shown that there is a reasonably good agreement between the numerical model and the hydraulic model for the most of computations. There were, however, some differences between the numerical simulation results and hydraulic model results for the hydraulic jump in the stilling basin because of air entrainment effect.