• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1520-1524
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• 2004

This paper describes the development of a robotic maintenance system for use in a maintenance operation of the nozzle dam in a water chamber of a steam generator at the Kori nuclear power plant in Korea. The robotic maintenance system was designed to minimize the personnel exposure to a hazardous radioactive environment. This robotic maintenance system is operated by a teleoperated control which was designed to perform the nozzle dam maintenance tasks in a remote manner without endangering the human workers. Specific maintenance tasks involve the transportation, insertion, and removal of nozzle dams in a water chamber inside a steam generator via a narrow man-way entrance port. The developed robotic maintenance system has two major subsystems: a two degrees of freedom guiding device acting as the main guiding arm and a master-slave manipulator with a kinematic dissimilarity. The mechanical design considerations, control system, and capabilities of the robotic maintenance system are presented. Finally, a graphical representation of the nozzle dam maintenance processes in a simulated work environment are also demonstrated.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.3
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• pp.230-236
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• 2014

Wafer level package technology is added to the surface of wafer circuit packages to create a semiconductor technology that can minimize the size of the package. However, in conventional packaging, warpage and fracture are major concerns for semiconductor manufacturing. We optimized the wafer dam design using a finite element method according to the dam height and heat distribution thermal properties. The dam design influences the uniform deposition of the image sensor and prevents the filling material from overflowing. In this study, finite element analysis was employed to determine the key factors that may affect the reliability performance of the dam package. Three-dimensional finite element models were constructed using the simulation software ANSYS to perform the dam thermo-mechanical simulation and analysis.

• Geophysics and Geophysical Exploration
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• v.22 no.3
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• pp.99-106
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• 2019

Resistivity method has been used for the dam safety inspection and, for the convenience of fieldwork, two-dimensional (2D) resistivity data has been usually measured along the dam crest. However, since the dam has three-dimensional (3D) structure, 2D resistivity survey along the dam crest violates 2D assumption and 3D effects caused by 3D topography and material properties in the dam distort the inversion result of 2D resistivity data acquired along the dam crest. Furthermore, it is really hard to evaluate the 3D structure of the dam and 3D leakage pathway using 2D resistivity survey because 2D resistivity survey can provide only 2D resistivity section beneath the survey line. In this study, 3D resistivity survey was conducted at a dam in Korea. By comparing the results from 3D and 2D resistivity surveys, merit and demerits of 3D survey were investigated. Finally, it was confirmed that 3D survey can provide more accurate information about the dam status and 3D leakage pathway compared to the 2D survey. Therefore the 3D resistivity survey should be actively expanded for more accurate dam safety inspection even though more time and expense are required.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.124-143
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• 2010

Cofferdam is a temporary levee or dam structure built by using sheet pile or earth materials to prevent water infiltration during construction work of bridge, dam, harbour dock, or hydraulic structures in the river. In this regard, it is required to secure cutoff ability for dry work and workability for rapid installation and removal of the temporary dam or levee structures. In this paper, case studies for design and construction of cofferdam were performed, and water diversion method was briefed with some examples of cofferdam type as well. For the case study details of design and construction were reviewed based on cofferdams under construction related to 16 submerged weirs of "The 4-river restoration project" and dam type cofferdam respectively. From the review, it was known that the method for changing the water flow is selected based on the data from geological and geo-hydraulic site investigation in order to mitigate environmental effects by making sure if the design cross-sectional area of flow and maximum working days are sufficiently guaranteed. Finally, the primary findings and main conclusion derived are summarized that determination of applicable type of cofferdam should be checked by case study and meet design requirements such as water inflow control, constructability.

• Geomechanics and Engineering
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• v.11 no.4
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• pp.571-585
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• 2016

The crest of the Pubugou central core rockfill dam (CCRD) cracked in the first and second impounding periods. To evaluate the safety of the Pubugou CCRD, an inversion analysis of the constitutive model parameters for rockfill materials is performed based on the in situ deformation monitoring data. The aim of this work is to truly reflect the deformation state of the Pubugou CCRD and determine the causes of the dam crest cracks. A novel real-coded genetic algorithm based upon the differences in gene fragments (DGFX) is proposed. It is used in combination with the radial based function neural network (RBFNN) to perform the parameters back analysis. The simulated settlements show good agreements with the monitoring data, illustrating that the back analysis is reasonable and accurate. Furthermore, the deformation gradient of the dam crest has been analysed. The dam crest has a great possibility of cracking due to the uncoordinated deformation, which agrees well with the field investigation. The deformation gradient decreases to the value lower than the critical one and reaches a stable state after the second full reservoir.

• Journal of the Korean Geotechnical Society
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• v.21 no.7
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• pp.91-105
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• 2005

In this study, the deformation behavior of Daegok dam during the construction was analyzed based on the measurement data and a comparative analysis with foreign CFRD measurements was performed. From measuring settlements of Daegok dam with depth, overall behavior was evaluated to be consistent with measured data of other CFRD dams. In addition, construction modulus, void ratio and shape factor were also evaluated to be major factors in predicting the settlement behavior during construction of CFRD-typed dam from measured data of 38 CFRD-typed dams, and the maximum internal settlement is proportional to the void ratio. From the relationship between the maximum internal settlement and the height of a dam, 26 dams were assessed to have its relative modulus ranging between 0.001 and 0.01. In case of general CFRD, the average modulus of maximum internal settlement to the height of a dam is estimated to be 0.005. In case of a low void ratio, the construction modulus was high with its shape factor below 4. On the other hand, in case of a high void ratio, the relative settlement rate was high with its shape factor more than 4.

• Smart Structures and Systems
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• v.26 no.3
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• pp.319-329
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• 2020

Structural damage to an arch dam is often of major concern and must be evaluated for probable rehabilitation to ensure safe, regular, normal operation. This evaluation is crucial to prevent any catastrophic or failure consequences for the life time of the dam. If specific major damage such as a large crack occurs to the dam body, the assessments will be necessary to determine the current level of safety and predict the resistance of the structure to various future loading such as earthquakes, etc. This study investigates the behavior of an arch dam cracked due to water pressure. Safety factors (SFs), of shear and compressive tractions were calculated at the surfaces of the contraction joints and the cracks. The results indicated that for cracking with an extension depth of half the thickness of the dam body, for both cases of penetration and non-penetration of water load into the cracks, SFs only slightly reduces. However, in case of increasing the depth of crack extension into the entire thickness of the dam body, the friction angle of the cracked surface is crucial; however, if it reduces, the normal loading SFs of stresses and joints tractions reduce significantly.

• Korean Journal of Hydrosciences
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• v.7
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• pp.37-49
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• 1996

This study aims at suggesting an alternative to improve flood controling capacity according to the cument design criteria for the existing Soyanggang Multi-purpose Dam which was constructed 20 years ago as the largest dam in Korea. The peak inflow of the adopted probable maximum flood (PMF) at the time of construction was 13,500 $m^3$/s. However, the newly estimated peak inflow of the PMF is 18,000 $m^3$/s which is 1.34 times bigger than the original one. This is considered to be due to the accumulation of the reliable flood and storm event records after construction, and due to the increasing tendency of the local flood peaks according to the influence of world-wide weather change. The new estimation of the probable maximum precipitation (PMP) was based on the hydro-meteorological method suggested by the guideline of the World Meteorological Organization (WMO). The unit hydrograph which was applied for the estimation of PMF was derived through linear programming algorithm by minimizing the sum of absolute deviations of the calculated and recorded flood hydrographs. In order to adopt the newly estimated PMF as a design flood, following four alternatives were compared : (1) allocation of more flood control space by lowering the normal high water level, (2) construction of a new spillway in addition to the existing spillway, (3) construction of a new dam which has relevant flood control storage at the upstream of the Soyanggang dam, (4) raising the existing dam crest. The preliminary evaluation of these alternatives resulted in that the second alternative is most economic and feasible. So as to stably cope with the newly estimated PMF by meeting all the current functions of the multipurpose dam, a detailed study of an additional spillway tunnel has to be followed.

• Journal of Korea Water Resources Association
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• v.35 no.6
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• pp.807-816
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• 2002

The purpose of the present study was to evaluate the changes of flow duration characteristics of a large river basin due to construction of a dam. The changes of water surface are quantified from remote sensing film taken before and after dam construction. Gongiu gauging station was selected to analyze the changes of flow duration, and annual exceedance series of Gongju and Kyuam gauging station were selected to estimate the changes of flood quantile before and after dam construction. From the analysing results, it was found that the construction of dam contributes to make new duration stable and to decrease flood flow. In conclusion, it was confirmed that the construction of the dam is useful for water supply and flood prevention.

• Journal of the Korean Association of Geographic Information Studies
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• v.10 no.3
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• pp.31-39
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• 2007

In this study, the hydrosphere change of the Daecheong dam basin was detected qualitatively and quantitatively using Landsat satellite images until recentness since the construction of Daecheong dam. The hydrosphere change of the basin was analyzed by applying supervised classification about Landsat satellite images which were classified according to the hydrosphere, vegetation, road and etc. for four distinct years which are 1981, 1987, 1993, and 2002 year. Landsat satellite images of each year were achieved overlay analysis with extracting only the hydrosphere, and though these results, the hydrosphere change of the Daecheong dam basin was monitored efficiently.