• Journal of the Korean Geotechnical Society
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• v.39 no.10
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• pp.27-39
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• 2023

To effectively manage flood risk, it is crucial to assess the stability of flood defense structures like levees under extreme flood conditions. This study focuses on the time-dependent probabilistic assessment of embankment slope stability when subjected to rapid water level drops. We integrate seepage analysis results from finite element analysis with slope stability analysis and employ Monte Carlo simulations to investigate the time-dependent behavior of the slope during rapid drawdown. The resulting probability of failure is used to develop fragility curves for the levee slope. Notably, the probability of slope failure remains low up to a specific water level, sharply increasing beyond that threshold. Furthermore, the fragility curves are strongly influenced by the rate of drawdown, which is determined through hydraulic analysis based on flood scenarios. Climate change has a significant impact on the stability of the water-side slope of the embankment due to water level fluctuations.

• Journal of the Korean Geotechnical Society
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• v.38 no.11
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• pp.19-30
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• 2022

Developing a fragility curve for the levee requires calculating the probability of failure according to the water level for each failure mode. Since probabilistic analysis requires iterative analysis to account for variability in geotechnical parameters, the fragility curve development inevitably requires many iterative calculations. Therefore, approximate probabilistic analysis techniques are usually applied to reduce the amount of calculation in developing the levee fragility curve. However, their accuracy has not been determined clearly. This study calculated the failure probability of slope and piping failure mode for an actual levee through probabilistic methods, such as FOSM, PEM, and MCS. Then, the fragility curve of the levee according to the water level was developed. The results of the approximate methods: FOSM and PEM, were compared with those of MCS to evaluate the applicability to the fragility curve for slope and piping failure mode.

• Journal of the Korean Geotechnical Society
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• v.25 no.9
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• pp.101-106
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• 2009

In this study we analyzed the seepage characteristics of meandering section of rivers commonly seen in domestic terrain. The seepage analysis is designed to be more realistic by considering a tangent and meandering section of levee. The levee was idealized to reflect the relevant characteristics by considering the curved angle of 90 degrees and 130 degrees in the spatial frequencies, water elevation conditions, and hydraulic conductivities. Seepage analysis becomes more detailed and precise with the seepage curve shape which is interpreted to indicate the flow of three-dimensional numerical analysis program using VisualFEA. As a result of the analysis, it is shown that the water level in the straight levee was constant, regardless of hydraulic conductivities, and the total head in the meandering section was increased by the overlapping of seepage. Consequently, it is found that the total head was increased more significantly in the case of 90 degrees curved levees than 130 degrees, and the total head showed similar characteristics In the straight levee.