• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.2
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• pp.129-138
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• 2008

In case of judging the stability of dike or dam structures which need hydraulic interception, the first thing to do is to examine whether a piping phenomenon occurred or not. Generally, dike or dam structures are constructed while layer compacting is executed, so permeability is likely to be anisotropic- different from each other in hydraulic conductivity in the horizontal direction [$k_x$] and hydraulic conductivity in the vertical direction[$k_y$]. This study looked into exit hydraulic gradient and Seepage velocity by conducting an Seepage analysis subsequent to various hydraulic conductivity ratios[k-ratio = ky / kx] and examined the influence on piping by comparing & examining critical Seepage Velocity based on critical hydraulic gradient in theoretical equation and critical Seepage Velocity in empirical equation. As the research result, it was found that hydraulic conductivity ratio operates as a very important factor in case the stability against piping occurrence is considered with the concept of critical hydraulic gradient, but relatively the hydraulic conductivity ratio is very low in its importance in relation to the concept of critical Seepage Velocity.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.800-807
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• 2006

Sea dyke construction is simply defined that the cutting procedure of sea water flow. Sea dyke construction is more difficult than in-land construction because it’s placed on deep seabed and exposed sea wave attack. Especially, the final closure of sea dyke is most dangerous due to the fast velocity of tidal flow. The final closure section is consisted with vast rubble and heavy stone gabion, therefore the discharge velocity at land side of final close section is irregularly and sometime occur the fast discharge velocity. In this study, the seepage model test performed to evaluate seepage behavior with tidal variation of final closure and continuous sea dyke section such as discharge velocity, hydraulic gradient, and phreatic line. Based on the seepage model test results, the maximum discharge velocity of final closure section is 1.7m/sec. Also the local discharge velocity increment and vortex is occurred.

• Journal of the Korean GEO-environmental Society
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• v.16 no.6
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• pp.39-43
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• 2015

This study extends the Distributed Temperature Sensing (DTS) application to delineate the saturated zones in shallow sediment and evaluate the groundwater flow in both downward and upward directions. Dry, partially and fully saturated zones and water level in the subsurface can be recognized from this study. High resolution seepage velocity in vertical direction was estimated from the temperature data in the fully saturated zone. By a single profile, water level can be detected and seepage velocity in saturated zone can be estimated. Furthermore, thermal gradient analysis serves as a new technique to verify unsaturated and saturated zones in the subsurface. The vertical seepage velocity distribution in the recognized saturated zone is then analyzed with improvement of Bredehoeft and Papaopulos' model. This new approach provides promising potential in real-time monitoring of groundwater movement.

• Journal of the Korean Society of Safety
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• v.14 no.4
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• pp.158-167
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• 1999

In parallel flow condition, to estimate the stability of the extended embankment constructed on a permeable foundation ground, a laboratory model test was performed due to extended materials and water level increasing velocity of a flood period. A laboratory model test was peformed for different permeability coefficients ($K_1=2.0{\times}10^{-5}cm/sec,\;K_2=1.5{\times}10^{-4}cm/sec,\;K_3=2.3{\times}10^{-3}cm/sec$) using seepage. The fluctuation of water level occurring to an extended embankment was analyzed by laboratory model tests as vary the increasing velocity of water level with 0.6cm/min, 1.2cm/min, 2.4cm/min respectively. In analysis results, the increase of water level into embankment occurs rapidly because seepage water moving along with a permeable soil flow into embankment. The larger the permeability coefficient of an extended part is the longer initial seepage distance, and the exit point of downstream slope is gradually increased and then shows unstable seepage behavior as occurring partial collapse. As the increasing velocity of water level increase, the initial seepage line is formed low, and the discharge increases. Therefore, the embankment extended by a lower permeable soil than existing embankment shows stable seepage behavior because an existing embankment plays a role as filter for an extended part.

• Journal of the Korean Society of Safety
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• v.11 no.2
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• pp.109-115
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• 1996

The movement of water through a river embankment and its influenced upon the stability of the slope of the embankment are described. The stability of the embankment is depended upon the location of seepage line. As the seepage flow occurs in the embankment, the slope of the embankment loses its stability. Of particular interest is the stability following a rapid change of water level. The variation of seepage line in the embankment model by a fluctuation of water level is discussed. The experimental models were construction with slopes of 1 : 1.5, 1 : 2.0, 1 : 2.5 and the flow velocity was turned from 60cm/sec~90cm/sec. Based on the experimental study, the following conclusions are drawn. 1) When water level is raised, the seepage line of downstream slope Is raised rapidly as flow velocity increases. 2) For the case of permeable layer, the seepage line raised rapidly as compare with impermeable layer when water lever is raised.

• Journal of the Korean Geosynthetics Society
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• v.5 no.1
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• pp.25-32
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• 2006

Sea dyke construction is simply defined as a cutting procedure of sea water flow. Sea dyke construction is more difficult than in-land construction because it is placed on deep seabed and exposed sea wave attack. Especially, the final closure of sea dyke is most dangerous due to the fast velocity of tidal flow. The final closure is consisted with vast rubble and heavy stone gabion, therefore the discharge velocity at land side of final close section is irregularly and sometime occur the fast discharge velocity. In this paper, the seepage model test performed to evaluate seepage behavior of final closure and continuous sea dyke section such as discharge velocity, hydraulic gradient, and phreatic line with installation of bottom protection filter mat. Based on the seepage model test results, the maximum discharge velocity of final closure section is 1.7m/sec and the discharge velocity is decreased maximum 23.7% with installation of bottom protection filter mat.

• Journal of the Korean Society of Safety
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• v.15 no.1
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• pp.146-152
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• 2000

To estimate the behavior of reinforced and unreinforced embankment constructed on a impermeable foundation ground, a laboratory model test was performed for two types of soils and water level increasing velocity of a flood period. The experiment models were constructed with slopes of water level is 1.25cm/min, 2.5cm/min each. From model test results, as the slope of reinforced and unreinforced embankment was the slower, the more seepage line rised. In the unreinforced embankment, the rising velocity of water level was the faster, the larger the embankment failure was. And the reinforced embankment with geotextile was the more safe than the unreinforced embankment for seepage force.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.5
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• pp.1253-1263
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• 1994

The stability of the embankment is depended upon the location of seepage line. As the seepage flow occurs in the embankment, the slope of the embankment loses its stability. Of particular interest is the stability following a rapid change of embankment level. The variation of seepage line in the embankment model according to flow velocity was investigated. In addition to this non-steady state flow in embankment by a fluctuation of water level is discussed. The experimental model was construction with slopes of 1 : 2.5 and flow velocity is turned from 60 cm/sec~90 cm/sec. Analysis of the experimental results, the seepage line is influenced by flow velocity and coefficient of permeability.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1727-1734
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• 2008

After the final closure of sea dyke, seepage behaviour of embankment is highly changed by variation of water head different between tide wave and controlled water level at fresh lake. Especially, the seepage behaviour of bottom protection layer of final closure section is more important factor for structural and functional stability of sea dyke, because of the bottom protection layer of final closure section is penetrated sea side to fresh lake. Even though bottom protection layer was filled with dredged fine sand, it has a high permeability. In this paper, mainly described about the seepage velocity and borehole image of bottom protection layer filled with dredged sand after final closure. Various in-situ tests such as BIPS (Borehole Image Processing System) and ABI (Acoustic Borehole Imager) survey, wave velocity measuring, and color tracer survey were conducted to evaluate the seepage behavior of bottom protection layer. Based on the in-situ tests, the bottom protection layer of final closure section was almost filled with dredged sand which is slightly coarse grain sand and there have sea water flow by water head different between tide wave and controlled water level at fresh lake. Also, comply with tracer survey results, the sea water flow path was not exist or generated in the bottom protection layer. However, because of this result not only short term survey but also just one test borehole survey results, additional long term and other borehole tests are needed.

• Journal of the Korean GEO-environmental Society
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• v.2 no.2
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• pp.51-58
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• 2001

The primary objective of this paper was to study the seepage and the failure behavior of unreinforced and reinforced embankment, respectively. Experimental study was conducted to examine the infiltration characteristics. The embankment infiltration tests were conducted with water level condition(h=15cm, 25cm, 35cm), slope inclination(1:1.5, 1:2.0), and the rising velocity(1.25cm/min, 2.5cm/min), respectively. From the model test results, as the slope inclination is decreased, the rising velocity of seepage line increased with both reinforced and unreinforced embankment. With the unreinforced embankment, the rising velocity of water level was faster and the failure circle is lager than those of reinforced ones. And the reinforced embankment with geotextile was safer against seepage force than that of the unreinforced embankment.