• Earthquakes and Structures
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• v.17 no.5
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• pp.511-519
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• 2019

The concrete gravity dam is one of the most important parts of the nation's infrastructure. Besides the benefits, the dam also has some potentially catastrophic disasters related to the life of citizens directly. During the lifetime of service, some degradations in a dam may occur as consequences of operating conditions, environmental aspects and deterioration in materials from natural causes, especially from dynamic loads. Cumulative Absolute Velocity (CAV) plays a key role to assess the operational condition of a structure under seismic hazard. In previous researches, CAV is normally used in Nuclear Power Plant (NPP) fields, but there are no particular criteria or studies that have been made on dam structure. This paper presents a method to calculate the limitation of CAV for the Bohyeonsan Dam in Korea, where the critical Peak Ground Acceleration (PGA) is estimated from twelve sets of selected earthquakes based on High Confidence of Low Probability of Failure (HCLPF). HCLPF point denotes 5% damage probability with 95% confidence level in the fragility curve, and the corresponding PGA expresses the crucial acceleration of this dam. For determining the status of the dam, a 2D finite element model is simulated by ABAQUS. At first, the dam's parameters are optimized by the Minitab tool using the method of Central Composite Design (CCD) for increasing model reliability. Then the Response Surface Methodology (RSM) is used for updating the model and the optimization is implemented from the selected model parameters. Finally, the recorded response of the concrete gravity dam is compared against the results obtained from solving the numerical model for identifying the physical condition of the structure.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.2
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• pp.13-23
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• 2019

In this study, an overtopping model experiments and three dimensional seepage characteristics at the deteriorated homogeneous reservoirs were performed to investigate the behavior of failure for embankment and spillway transitional zone due to overtopping. The failure pattern, pore water pressure, earth pressure and settlement by overtopping were compared and analyzed. The pattern of the failure by overtopping was gradually enlarged towards reservoirs crest from the spillway transition zone at initial stage. In the rapid stage and peak stage, the width and depth of failure gradually increased, and the pattern of the failure appeared irregular and several direction of the erosion. In the early stage, the pore water pressure at spillway transitional zone was more affected as its variation and failure width increased. In the peak stage, the pore water pressure was significantly increased in all locations due to the influence of seepage. The earth pressure increased gradually according to overtopping stage. The pore pressure by the numerical analysis was larger than the experimental value, and the analysis was more likely to increase steadily without any apparent variation. The horizontal and vertical displacements were the largest at the toe of slope and at the top of the dam crest, respectively. The results of this displacement distribution can be applied as a basis for determining the position of reinforcement at the downstream slope and the crest. The collapse in the overtopping stage began with erosion of the most vulnerable parts of the dam crest, and the embankment was completely collapsed as the overtopping stage increased.

• Tunnel and Underground Space
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• v.5 no.4
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• pp.308-317
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• 1995

The stability study on the rock slope where have produced failures in Boryung dam site was evaluated using the streonet analysis techniques. SMR(Slope Mass Rating) approach which is suitable for preliminary assessment of slope stability in rock was also carried out for rating rock mass. The 3-4 major discontinuity sets are distributed and all type of failure(plane, wedge and toppling failure) are presented in this slope face. The dip of slope must be lowered to friction angle(26degree), otherwise the possibility of plane and toppling faiue will always exist in this slope.

• Journal of the Korean GEO-environmental Society
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• v.8 no.6
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• pp.45-52
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• 2007

Maintenance of structural and hydrological safety of the superannuated fill dam is very important subject on the viewpoint of disaster prevention. Mainly, the core of the superannuated fill dams have been damaged continuously by the various harmful external forces such as the typhoons, flash floods and earthquake, and these can be connected to the large scaled general dam failure. Therefore, the research on the repair, remediation and reinforcement of dam is necessary. In this study, the permeable grouting method for the remediation of fill dam was examined by the electrical resistivity survey and the change of permeability of core front. As a result, the permeable grouting method can be useful remediation method for the superannuated fill dam, the leakage from the core front decreased greatly before and after the construction of grouting. Furthermore, it can be said that the turbidity of fill dam may not be greatly increased by grouting.

• Proceedings of the Korea Water Resources Association Conference
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• 2001.05b
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• pp.691-696
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• 2001

• 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.

• Journal of the Korean Geotechnical Society
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• v.26 no.4
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• pp.59-68
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• 2010

Piping, a common form of internal embankment erosion, is caused by progressive movement of soil particles through an embankment. The phenomenon commonly occurs with precursory signs of development of fractures in dam structures, but also occurs without any noticeable signs in dams that showed satisfactory dam performance for several years, due to dissolution of soluble material in an embankment. While piping accounts for nearly 50% of the causes for dam failure, few studies have been made for systematic evaluation of the phenomenon. In this study, we attempted to monitor the changes in electrical resistivities of fill-dam material while a saddle dam is dismantled for the construction of emergency spillways of Daechung dam. Two artificial subhorizontal boreholes were drilled into the embankment structure to simulate piping along the two artificial flow channels. Monitoring of changes in electrical resistivity showed an increase in resistivity values during piping. Thus, the investigation of resistivity over time could be an effective method for piping prediction.

• The Journal of Engineering Geology
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• v.25 no.4
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• pp.449-458
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• 2015

The compilation of a flood hazard map is an efficient technique in managing areas at risk of flooding in the case of a dam-break. A scenario-based numerical modeling approach is commonly used to compile a flood hazard map related to dam-break and to determine the model parameters that capture peak discharge, including breach formation and progress, which are important in the modeling method. This approach might be considered less reliable if an existing model is used without local validation. In this study, a dam-break model is linked to a routing model to identify flood-risk areas in the case of failure of the Sandae Reservoir Gyeongju, Gyeongbuk. Model parameters are extracted from a DEM, and maps of land use and soil texture. The simulation results are compared with on-site investigations in terms of inundation and depth. The model reproduces the inundation zone with reasonable accuracy.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.4
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• pp.433-447
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• 2023

There is a growing demand for the stability of existing dams due to abnormal climate and the aging of dams. Emergency Action Plans (EAPs) for reservoir or dam failure only consider a single rainfall event. Therefore, this study simulates dam failure caused by continuous rainfall events, and proposes the establishment of EAP by selecting the optimal shelters. We define a mega rainfall event scenario caused by continuous rainfall events with 500-year frequency in the Chungju Dam watershed and estimate the mega flood. The mega flood event scenario is divided into two cases: scenario A represents the flooding case caused by discharge release from a dam, while scenario B is the case of a dam break. As a result of flood inundation analysis, the flooded damage area by the scenario A is 50.06 km² and the area by the scenario B is 6.1 times of scenario A (307.45 km²). We select optimal shelters for each administrative region in the city of Chungju, which has the highest inundation rate in the urban area. Seven shelter evaluation indicators from domestic and foreign shelter selection criteria are chosen, and Analytical Hierarchy Process (AHP) method is used to evaluate the alternatives. As a result of the optimal shelter selection, the six shelters are selected and five are schools. This study considers continuous rainfall events for inundation analysis and selection of optimal shelters. Also, the results of this study could be used as a reference for establishment of the EAP.

• Advances in Computational Design
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• v.1 no.2
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• pp.195-206
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• 2016

Dams play a vital role in the development and sustainment in a country. Failure of dams leads to the catastrophic event with sudden release of water and is of great concern. Hence earthquake-resistant design of dams is of prime importance. The present study involves static, modal and transient analyses of dam-reservoir-foundation system using finite element software ANSYS 15. The dam and the foundation are modeled with 2D plane strain element "PLANE 42" and the reservoir by fluid acoustic element "FLUID 29" with proper consideration of fluid-structure interaction. An expression for the fundamental period of concrete dams is developed based on modal analysis. Seismic response of gravity dams subjected to earthquake acceleration is evaluated in terms of peak displacement and stress.