• Geotechnical Engineering
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• v.12 no.5
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• pp.89-102
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• 1996

In order to investigate the characteristics of pressure drainage for geotextile, small-scale model tests were carried out for the horizontal and vertical geotextile drain to accelerate consolidation of foundation under embankment for the purpose of foundation reinforcement. According to the result of this study, the accumulative drainage discharge is found to increase as compressive stress of geotextile increases with logarithmic function. The drainage discharge under each step of compressive stress linearly increases with the increase of hydraulic head and its increasing rate is smaller when the compressive stress is higher. The drainage discharge shows to be greater when the number of geoteztile layers is more and the foundation material is finer. The relationship between transmissivity of geogextile and drainage discharge has positive correlation and the rate of increase is appeared to be the same regardless of foundation material and hydraulic head. And it proves that the drainage capacity of geotextile drain is determined by the transmissivity of geoteztile.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6C
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• pp.287-294
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• 2009

Suction Drain Method is a relatively new technique to improve soft ground using vacuum pressure which can be directly applied to the soft ground through drains that the pore water pressure around them are decreased without changing total stress. This can accelerate volume changes and increase strength of the ground. This paper shows the results of field test of the suction drain method applied at dredged and reclaimed clay. To evaluate the improvement effects of soft ground by the suction drain method, this paper analyzed real-time field measurements to the results of the laboratory tests and numerical analysis. The comparisons of the settlement and shear strength between suction drain method and surcharge preloading method show possibilities for replacement of the preloading methods. The settlements by suction drain method were 2.3 times larger and undrained shear strength were 300%~400% higher than surcharge method. Moreover, the water content is decreased about 30% and the preconsolidation pressure is increased about $0.52kgf/cm^2$.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.169-176
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• 1999

본 논문은 지하수 흐름하에서의 풍화 잔류토의 세립자 유동특성을 파악하기 위한 수치모델을 개발하고, 실내에서 실시한 수리 모형실험을 통하여 수치모델의 적합성을 규명하였다. 한국의 풍화 잔류토는 점토와 모래의 중간 상태의 특성을 보이는 관계로 기존의 토립자 유동모델중 점토 또는 모래에 적합한 모델에 의해서는 정확한 유동특성의 파악에 한계가 있었다. 따라서, 본 연구에서는 한국의 풍화 잔류토에 적합한 세립자 유동모델을 제시함으로써 풍화 잔류토를 대상으로 시공되는 굴토공사, 댐 축조공사, 그리고 터널공사시 지하수 유입에 따른 세립토사의 유실특성을 이론적으로 규명하였고, 현장에서 배수재로 광범위하게 쓰이고 있는 토목섬유인 부직포의 투수 및 배수특성을 검토하였다

• Journal of the Korean GEO-environmental Society
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• v.11 no.9
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• pp.55-60
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• 2010

This study are carried out to an lab model tests to develop a construction method that solidifies high-water content cohesive soil by using filter type drain and vacuum pressure, and that stabilizes the ground by accelerating horizontal drain at incline or in tunnel. The calibration chamber was designed within length of 1.5m and height of 50cm, and a drainage hole for preconsolidation, a switchgear and a piezometer were installed at the bottom part of the chamber. Also, a settlement gage was installed at the top part so that it can measure the settlement by time. The calibration ground basis was made in a form of thin layer from kaolinite and bentonite in 9:1 ratio stirred at 130% water content condition. A filter type drain was installed at chamber center and a vacuum pressure of 0.8MPa was applied through a hose linked to the cap at the top part, then, the settlement was measured in every 1 hour interval. After experiment, the moisture contents were measured by position, then, verified the increase of solidity of the ground through a triaxial compression test on undisturbed profile. After 11 days from the effective date, it was observed that the settlement decreased by maximum 35mm and the water content ratio was reduced by 38% at most while the solidity of the ground increased by 5~8 times greater than before preconsolidation.

• Journal of the Korean Geosynthetics Society
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• v.4 no.3
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• pp.3-10
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• 2005

This paper aims at investigating the characteristics of discharge capacity according to lateral pressure, hydraulic gradient and deformation of drain materials. A series of experiments were conducted to achieve this objective. In experiments, fiver drain boards as well as harmonica and castle types of drain boards were installed in a rubber membrane, and clay in sully was filled around them. The test results showed that the harmonica type of drain boards have the greatest discharge capacity comparing to castle and fiber drain boards. The results also indicated that the hydraulic gradient has more effect on reduction of discharge capacity than the lateral pressure.

• Journal of the Korean Geotechnical Society
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• v.19 no.2
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• pp.15-25
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• 2003

To evaluate the effect of trapped air bubbles in horizontal drains on discharge capacity, unsaturated discharge capacity tests are carried out for four types of drains selected according to the size of section as well as the shape of core. Unsaturated discharge capacities with the elapse of time, the increase of confining pressures, and hydraulic gradients are examined and are compared with saturated discharge capacities. It is found that the unsaturated discharge capacities at a hydraulic gradient of 0.01 decreased by 17%~80% due to the remained air bubbles in the drains compared with the saturated discharge capacities. It is caused by the fact that the horizontal direction of water flow is not consistent with the direction of movement of floating air bubbles in case of horizontal drains. Especially, far the drain with filament shaped core, discharge capacities decreased significantly due to the difficulty in removing air bubbles.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1581-1584
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• 2008

In this study, performance Assesment of the existing tunnel drain and higher permeable for the In-plane Test. Two separate simulation tests from geotexitile and Lightweight Foamed Mortar compare. perfomed:the one is the in-plane test and the other is the clogging phenomenon test. As a result, NATM Composite used to Ligheweight Foamed Mortar pemability 80%, more than existing tunnel drain. Also, clogging phenomenon test do low assesment more than existing tunnel drain geotextile.

• Journal of the Korean Geosynthetics Society
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• v.5 no.4
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• pp.19-25
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• 2006

To examine the general features of a sand-clay composite triaxial test by making specimen varying ratios of diameters (dw) of sand columns that are installed on the soft ground as drains to diameters (de) of drain zone so called drainage space ratio (n=de/dw), densities of the granular columns, and strength of soft soils round around. I also conducted a test to research the reinforcement ability and effects of the ground when the granular columns are wrapped with supplementary materials such as geotextile. The results of the triaxial compression test showed that the shear strength increase is much big when the granular columns are wrapped with supplementary materials, while the shear strength increases as the diameter and density of the granular column increase in general. Also the drainage space ratio shows a distinct increase just below 3 and a similar shear behavior to sand is appeared. The pore water pressure coefficient decreases as the drainage space ratio decreases, however, when the drainage space ratio is less than 3~4, it declines significantly as shown in the results of shear behavior.

• Proceedings of the KAIS Fall Conference
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• 2010.11a
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• pp.451-453
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• 2010

PVDF(polyvinylidene fluoride) 필름은 압전특성을 가지며 음파에너지를 발생시키는 유연성 고분자필름이다. 이 연구에서는 기존 원통형 연직 배수재에 PVDF 필름의 음파에너지를 적용하여 점토의 미세입자가 배수재의 성능을 저하시키는 막힘현상(clogging)을 방지함으로써 배수재의 성능을 향상시키고, 압밀을 촉진시키고자 하였다.

• Geotechnical Engineering
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• v.14 no.1
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• pp.81-92
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• 1998

Coal ash from thermal power plants has been produced in large quantity and discarded uselessly, However, it is possible to supply construction material properly by utilizing the coal ash as construction material. In this study, the applicable model and its applicability for deformation analysis of coal ash fill and reclamation ground are studied. Camflay model gives complete constitutive law which illustrates deformation and pore water pressure while soil is loaded under the various stresses at drained and undrained conditions. The merit of proposed model which is acquired from laboratory tests is that only a few soil parameters are available. The whole parameters of Camflay model are obtained by typical mechanical test and CV triaxial test on the sample with optimum mixing ratio( i.e. fly ash : bottom ash=5:5) Then the results from proposed numerical analysis are compared with laboratory results. The differences between laboratory test and numerical analysis are negligible. Parameters deter mined from laboratory tests are useful as a basic data for deformation analysis of coal ash reclamation ground using Camflay model.