• Korean Journal of Agricultural Science
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• v.38 no.3
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• pp.493-504
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• 2011

This study was carried out to safety evaluation, the practical application and improvement of design method of the agricultural reservoir due to raising embankments. Also, it was to compare and analyze the pore water pressure (PWP), seepage (leakage) quantity and piping phenomenon according to high water table and rapid drawdown. The seepage analysis by finite element analysis was used for steady state and transient condition. The pore water pressure distribution for steady state and transient condition showed positive(+) PWP on the upstream slope, it was gradually changed negative(-) PWP on the downstream slope. The PWP in the core ranged from 100 ~ -33 kPa, the seepage line in the incline-type core suddenly decreased towards the lower levels from the higher levels. The PWP according to rapid drawdown is remained in the vicinity of the upstream slope, therefore, it is investigated to be in an unstable state by the slope stability analysis. The PWP after raising embankments showed smaller than in the before raising embankments. It was likely to be the piping phenomenon because the gradients in the before raising embankments showed largely at downstream slope, and the stability for piping in the after raising embankments increased stable state. The seepage quantity per 1 day and the leakage per 100m for the steady state and transient condition appeared to be safe against the piping. It reduced slightly regardless of the transient condition before the raising embankments and it decreased largely about 2.4 times in the early days after the raising embankments.

• Korean Journal of Agricultural Science
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• v.39 no.1
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• pp.97-110
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• 2012

This study was carried out for safety evaluation, the practical application and improvement of design method of the agricultural reservoir embankment according to backside extension. Seepage analysis, slope stability analysis and finite element analysis were performed for steady state and transient conditions. Also, the pore water pressure, seepage quantity, safety factor and stress-strain behavior according to high water level and rapid drawdown were compared and analyzed. The pore water pressure at contact region between backside extension and old embankment was kept high after rapid drawdown. Therefore, backside extension is recommended that design method is required to be improved and reinforced more than the others raising embankment. The hydraulic gradients before and after backside extension showed high value at the base of the core, but they showed stable state at the upstream slope and downstream slope. The seepage quantity per 1 day and the leakage per 100 m for the steady state and transient conditions appeared to be safe against the piping. The safety factor of slope stability showed high at the steady state, and transient conditions did not show differences depending on the rapid drawdown. The safety factor was appeared high at the upstream slope before backside extension and downstream slope after extension. The excess pore water pressure for steady state and transient conditions showed negative(-) at the upstream slope, it was small at the downstream slope. The mean effective stress (p') showed high at the base of the core and to be wild distribution after the extension. The displacement after extension showed 0.02-0.06 m in the upstream slope, the maximum shear strain after extension was smaller than that before extension.

• Magazine of the Korean Society of Agricultural Engineers
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• v.34 no.1
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• pp.87-99
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• 1992

A mathematical model, UNSATR which predicts the seepage flow through the body of dike especially under the tidal fluctuation has been developed. This model has been revised from UNSAT2 model which was developed on the basis of the saturated-unsaturated theory by Neuman. UNSATR has been verified and applied to the hydraulic model in order to estimated the seepage quantity, the formation of free water surface etc. The results lead to the following conclusions : 1. Seepage rates between the mathematical model and hydraulic model experiment are very similar to each other both in constant and transient water level conditions. 2. The lapsed time to be steady state of the free water surface becomes late as the tidal levels are relatively low mainly due to the seepage flow from the unsaturated zone of the body of dike. 3. Under the transient state of water levels, owing to the flow from the unsaturated domain, streamlines crossing to the free water surface are found and time lag during a falling tide may allow the free water surface inside the body of dike to stand at a high level than the outside water level. 4. The utility and validity of UNSATR model are convinced when the analyses on seepage problems through the porous embankment of the soil structures on the conditions of the steady and unsteady states are carried out.

• Journal of the Korean GEO-environmental Society
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• v.6 no.4
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• pp.47-58
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• 2005

Development of underground space is conducted for various useful facility and underground structures and deep excavation technology for reclaimed area has been researched and developed. The seepage flow and behavior of phreatic line in reclaimed area was predominated by transient flow caused by tidal action. Also the soil-water characteristic relation is most important factor for transient flow analysis, therefore the research about the soil-water characteristic is strongly required. In this paper, laboratory tests (pressure cell, desiccator, and tensiometer test) and theoretical analysis were performed to investigate the soil-water characteristic such as air-entry value, metric suction, and residual water content. And the feasibility of prediction method for soil-water characteristic are presented by transient seepage analysis and comparison between analysis results and in-situ measured seepage flux in LNG TK-00 storage tank. Based on the result of laboratory and theoretical analysis, Fredlund and Xing's method provide to work out well for reclaimed ground soils. Also, the transient analysis result is more reasonable and effective for design of deep excavation work in coastal and reclaimed ground.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.5
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• pp.43-51
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• 1998

In design and management of sea0dikes, engineers need to study various transient seepage conditions through dikes not only for the sea water infiltration into dikes due to cyclic rises of sea water level also for the seepage flow out from dikes toward the sea due to cyclic drawdown of sea water level. Characteristics of seepage flow toward the sea from dikes are more complicated than as known and remained unclearly. The case of such seepage flow may be explained by figuring out seepage characteristics in filter as a part of sea-dikes. Filters in most sea-dikes in Korea are inevitably placed with reversely inclined shape due to field construction conditions. Most computer programs for seepage analysis based on the various numerical methods give practically acceptable results, but for the case of reversely inclined section of filters any verification to apply them might be needed. In this study, large scaled model tests were executed to verify and understand seepage flow through earth-filled sea-dikes. The results from numerical analysis and model tests show some remarkable differences in pore pressure distribution under cyclic changes of see level, and some of the results need to be considered in design and construction practices with further study.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.2
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• pp.13-24
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• 1984

The main part of this thesis deals with a three-dimensional transient seepage flow, discussing its fundamental conception into Which the mathematical analysis was introduced based upon the finite element method, propriety of geometrical analysis and flow movement of seepage water. As is commented in the body of the report, the saturated-unsaturated method with respect to the free water surface method is revealed to have the relative merits and demerits. Generally, the unknown sections in the form of free water surface matters in case that tunnels or pores appear. On the other hand, the applicable range is quite large and variable to the methods accordingly. Also, an example as to the seepage analysis in the rock bed section is described. An unfavorable time-consuming problem is inevitale because the complicated and widely multifarious joints and faults are responsible for the intensity of seepage flow.

• Journal of the Korean Geotechnical Society
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• v.39 no.10
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• pp.19-26
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• 2023

This research aimed to predict the seepage rate in the base rocks of a concrete face rockfill dam (CFRD) by conducting numerical analysis under various conditions. We examined the relationship between basic grouting and seepage, emphasizing the significance of the permeability coefficient of the grouting material and the rock. Moreover, we observed a decrease in seepage with an increase in the cross-sectional area of the dam. The results of this study provide essential input factors and outcomes of numerical analysis, incorporating various parameters, to inform the design phase. Additionally, our findings offer a dependable approach for calculating a reasonable seepage rate during both operational and maintenance phases.

• 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.

• Proceedings of the Korean Geotechical Society Conference
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• 1991.10a
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• pp.235-254
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• 1991

In the analysis of seepage behavior through the porous media, unsaturated domain should be included for obtaining more accurate results. The seepage programs considering its domain have been developed and practically used widely. The programs are reviewed and two case studies are presented in this paper. The case studies are performed using PC-SEEP and obtained good results for the cases of saturated-unsaturated transient flow.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.955-962
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• 2008

This study concerns the effect of drainage in reinforced soil on its stability during rainfall. A series of finite-element analysis based transient seepage analysis were performed on a number of cases with different drainage conditions in terms of layers of geotextiles installed in the reinforced zone. The results were then coupled with the limit-equilibrium slope stability analysis to investigate the variation of global stability factor of safety with rainfall infiltration into the reinforced wall. The results were thoroughly analyzed to get insight into the mechanism of pore water pressure reduction effect of the geotextile and into its effect on overall slope stability. It is shown that layers of geotextile installed in the reinforced zone can prevent decrease in suction in the reinforced zone during rainfall, thereby reducing potential risk of decreasing shear strength of the reinforced zone. Practical implications of the findings were discussed.