• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.155-162
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• 2003

The soil-water characteristic curve (SWCC) represents the essential constitutive relationship for solving various problems in unsaturated soil mechanics. A reliable and convenient experimental method is needed for the determination of the SWCC in engineering applications. This study introduces and proves that the suction-saturation experimental measurement based on the flow pump technique is a convenient and accurate method for obtaining the SWCC. The flow pump technique provides complete control over the test conditions and is capable of detecting all the important elements of the SWCC. In particular, it is capable of defining continuous drying and wetting curves, the moment of air occlusion, and the hysteretic behavior of unsaturated soils. Not only the optimal testing procedure but also the analysis technique for the flow pump technique has been established in this study. Especially, the method of the suction drop measurement was developed to measure the SWCC. This method is a convenient and time saving method without losing accuracy.

• Journal of the Korean Geotechnical Society
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• v.22 no.4
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• pp.73-83
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• 2006

Seepage analysis through unsaturated zone based on the theory of unsaturated flow is commonly performed to evaluate dam safety. However, the concepts of unsaturated soil behavior have not been transferred into the hands of practicing geotechnical engineers since the problems involving unsaturated soils often have the appearances of being extremely complex. There is variability and uncertainty associated with the unsaturated hydraulic properties that in turn will lead to variability in predicting unsaturated soil behavior such as seepage rate and the pore water pressure distribution. In this paper, measurements of the soil-water characteristic curve and saturated hydraulic conductivity for the core material of dam were conducted. Then, finite element stochastic analysis was used to capture the effect of unsaturated hydraulic properties on the seepage behavior of dam. It is observed that the amount of seepage increases, as the values of unsaturated soil parameters a and n increase. The values of m and p showed opposite trend.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.764-771
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• 2010

The stability analysis method of an unsaturated slope considering the suction stress was performed on the infinite sand slope. During drying and wetting processes, the Soil-Water Characteristics Curve (SWCC) of the sand with the relative density of 75% was measured using the automated SWCC apparatus. Also, the Suction Stress Characteristics Curve (SSCC) was estimated. Based on these results, the stability analysis of an unsaturated infinite slope was carried out considering the slope angle, the weathering zone and the relative change in friction angle as a soil depth. According to the result of slope stability analysis, the safety factors of slope were less than 1 when the slope angles were more than $50^{\circ}$. The safety factors of slope tend to increase with increasing the depth from the ground surface. Especially, the safety factors have a tendency to increase and decrease above near the ground water level due to the suction stress. The maximum safety factor of slope in this analysis was occurred at the Air Entry Value (AEV) of drying process. The influence range of suction stress above the ground water level can be found out and can be defined as the funicular zone which means the metric suction range from the air entry point to the point of residual volumetric water content.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.265-272
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• 2000

This study introduces the current theory of the SWCC and tries to verify the theory by performing laboratory tests for the local soils of Korea. First, the SWCCs of Poi-dong soil and Shinnae-dong soil, the most typical weathered residual soils in Korea, were experimentally obtained and the results were compared among others. Second, a SWCC model for deformable soils was proposed. For deformable soils, which show huge volume change during desaturation, the volume change behavior should be considered, and the SWCC should be expressed as a function of void ratio as well as suction.

• Journal of Industrial Technology
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• v.29 no.A
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• pp.145-153
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• 2009

In this study, to determine characteristics of compaction and the soil water characteristic curve(SWCC) in decomposed granitic soils, compaction tests and SWCC tests were carried out for samples having various contents of coefficient of uniform($c_u$), By compacting their samples with standard Proctor density test, the effects of binder contents on maximum dry density and optimum moisture content were investigated and compared. Samples compacted with the maximum dry density and the optimum moisture content were tested by means of the SWCC, to determine their SWCC parameters, such as Brooks & Corey(${\lambda}$, ${\Psi}_b$), Van Genuchten (${\alpha}$, n, m), Fredlund & Xing(a, n, m).

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4C
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• pp.185-191
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• 2010

Volumetric pressure plate extractor (VPPE) can be used for measurement of the soil-water characteristic curve in the laboratory using the axis-translation technique. The volume of extracted water from the soil specimen in VPPE can be measured continuously during the test without stoppage of air pressure for the measurements. However, the water volume measurement in VPPE using an air trap, a ballast tube, a burette, and a vacuum device so as to maintain a constant pore-water pressure in the soil specimen, is quite complicated and tedious. In order to improve the measuring problems of VPPE, a modified volumetric pressure plate extractor (MVPPE) was developed and tested on residual soil specimens. In addition, the modified apparatus can measure the volume of the extracted water using both Method A and Method B of ASTM D 6836-02 depending on the range of matric suction. Measuring principles and the improvements of MVPPE and typical results obtained from the tests are discussed in the paper.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.03a
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• pp.101-110
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• 1998

• 한국도로학회:학술대회논문집
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• 2011.03a
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• pp.9-14
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• 2011

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.2
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• pp.515-524
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• 2015

The number of occurrence of differential settlement and track irregularity at track transition zone recently comes to increase, which leads to frequent maintenance activities that have an impact on train operation. Such track transition zone damages are attributed to the change of mechanical properties of fill materials due to environmental factors such as rainfall and freeze, and thaw. Consequently, this study attempts to establish the soil water characteristic curve (SWCC) of fill materials, and conduct seepage analysis to assess the distribution of degree of saturation (DOS) for track transition zone in case of rainfall. The SWCC of fill materials was successfully obtained using filter paper test method. The results of seepage analysis revealed that rainfall intensity, the slope of backfill, backfill condition (fill or cut), and SWCC are significantly influential in controlling the distribution of DOS.

• Journal of the Korean Geotechnical Society
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• v.21 no.3
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• pp.119-131
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• 2005

Seepage analysis through unsaturated zone based on the theory of unsaturated flow is commonly performed to evaluate dam safety. However, the concepts of unsaturated soil behavior have not been transferred into the hands of practicing geotechnical engineers since the problems involving unsaturated soils often have the appearances of being extremely complex. The behavior of dam such as seepage rate and the pore water pressure distribution is different according to the unsaturated hydraulic properties, but nevertheless simply assumed properties have been used due to insufficient data from domestic soils. In this paper, the effect of unsaturated hydraulic properties on the behavior of dam was studied through a series of numerical analyses, and then the results were discussed. It is observed that water table moves at a (aster rate, as the values of unsaturated soil parameter a and n increase. The value of m showed opposite trend. The sensitivity calculated using the approximation form showed maximum values near the water table. And the value of n that is related to the slope of soil water characteristic curve gives greatest influence on the change of sensitivity with time.