• Journal of the Korean GEO-environmental Society
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• v.14 no.1
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• pp.69-75
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• 2013

Suction stress is evaluated from soil water retention curves in order to deduce effective stress in unsaturated soils. $K_0$ consolidated triaxial tests were performed for silty sand to interpret effective stress in consolidation and shearing of unsaturated soils. Suction stresses from both consolidation stress and shear strength in triaxial tests were compared with those from soil water retention curves. The effective stresses on consolidation and shear strength are on each unique line, which are the same as that of the saturated case. It was found that the effective stress from soil water retention curves agrees with those from consolidation and shear strength in triaxial tests.

• The Journal of Engineering Geology
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• v.22 no.2
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• pp.145-155
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• 2012

The matric suction and volumetric water content of Jumunin standard sand with a relative density of 60% were measured using an Automated Soil-Water Characteristic Curve (SWCC) apparatus during both drying and wetting processes. The test time for the drying process was longer than that for the wetting process, because the flow of water is likely to be protected by air trapped in voids within the soils during the drying process. Based on the matric suction and volumetric water content, the SWCC was estimated using the model proposed by van Genuchten (1980). For the drying process, the unsaturated fitting parameters ${\alpha}$, n, and m were 0.399, 8.586, and 0.884, respectively; for the wetting process, the values were 0.548, 5.625, and 8.220, respectively. The hysteresis phenomenon occurred in the SWCCs, which means the SWCC of the drying process is not matched with the SWCC of the wetting process. Using these unsaturated parameters, we estimated the Suction Stress Characteristic Curve (SSCC), based on the relationship between suction stress and the effective degree of saturation. The suction stress showed a rapid decrease when the matric suction exceeds the Air Entry Value (AEV). Therefore, the effective stress of unsaturated soils is different from that of saturated soils when the matric suction exceeds the AEV. The suction stress of the drying process exceeds that of the wetting process for a given effective degree of saturation. The hysteresis phenomenon was also recognized in SSCCs. The hysteresis phenomenon of SSCCs arises from that of SWCCs, which is induced by the ink bottle effect and the contact angle effect. In the case of a sandy slope, the suction stress is positive and acts to enhance the slope stability as the water infiltrates the ground, but is negative when the suction stress exceeds the AEV. The results obtained for the wetting process should be applied in analyses of slope stability, because the process of water infiltration into ground is similar to the wetting process.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.3
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• pp.96-103
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• 1997

This paper presents a mathematical method that represents efficiently high-speed coastal fishing vessel. That is, it represents the numerical hull by using irrational function and hull form characteristic curves, which define a hull form under design conditions. Then it suggests a process that hull form characteristic curves are represented with NURBS and hull form is varied.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.11a
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• pp.345-348
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• 2005

소프트웨어 개발 후 인도 전 테스트 단계중에 발생되는 테스트 노력 소요량을 고려한 소프트웨어 신뢰도 성장 모델을 제시하여 테스트 노력소요량 동태를 시간함수인 로지스틱 곡선으로 설명한다. 테스트 단계중에 소요되는 테스트노력의 양에 대한 결함 검출비를 현재의 결함 내용에 비례하는 것으로 가정하여 소프트웨어 신뢰도 성장 모델을 비동차 포아송 프로세스(NHPP)로 공식화하여, 이 모델을 이용하여 소프트웨어 신뢰도 척도에 대한 데이터 분석기법을 개발한다. 그간 여러 문헌에서 소프트웨어 신뢰도 향상 모델을 연구할 때 소프트웨어 테스트 중에 소요되는 테스트노력의 양으로서 지수함수 곡선, 레일레이 곡선, 웨이불 곡선을 사용해 왔다. 그러나, 모든 소프트웨어 개발 환경에서 지금까지 제시된 그러한 곡선중 하나에 의해서 테스트노력 소요 곡선을 표현하는 것은 적절하지 못하다는 것이 밝혀지고 있다. 본 논문에서는 로지스틱 테스트노력 곡선이 소프트웨어의 개발/테스트 노력곡선으로 적절하게 표현될 수 있다는 것과 실제 데이터를 근거로 하여 적용하여서 예측성이 매우 좋은 능력을 가지고 있다는 것을 보이고자 한다.

• Journal of the Korean Geotechnical Society
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• v.33 no.6
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• pp.37-48
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• 2017

Soil-water characteristic curve (SWCC) has been widely used to estimate the shear strength and coefficient of permeability for unsaturated soils. In general, it is divided into the drying path in which the water is discharged and the wetting path in which the water is permeated, and it has a hysteresis indicating different suctions at the same volumetric water content. In reality the field behavior of unsaturated soils is much closer to the wetting path during the infiltration. The drying path has been practically used for various analyses because obtaining the wetting path takes longer than the drying path. Although many approaches for estimating wetting path have been studied till now, these are complex and do not fit well. Therefore, a simple method for estimating wetting path based on empirical approach in this study is proposed in unsaturated soils, and a feasibility study is conducted as well.

• Journal of the Korean Geotechnical Society
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• v.29 no.2
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• pp.57-64
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• 2013

In this paper, in order to solve high water content of water sludge and promote its recycle, sludge mixtures with various mixing ratios were produced. Sludge mixture consisted of water sludge and weathered granite soil. Their physical properties and unsaturated characteristics (soil-water characteristic curve, and unsaturated permeability function) were investigated by laboratory tests. Experimental test results indicated that at a given matric suction volumetric water content of sludge mixture increased as water sludge content increased. Air entry values of sludge mixture increased from 0.9 kPa to 2.4 kPa with an increase in water sludge content or fine content. In addition, unsaturated permeability function, which is an important factor for performing infiltration analysis, was predicted using saturated permeability and soil-water characteristic curve of sludge mixture.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.313-313
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• 2020

여름철 발생하는 집중호우는 해안지역 및 하천유역의 저지대에 상습적인 침수를 유발하며, 도시지역은 높은 불투수율로 인해 추가적인 침수 피해가 발생하는 경우가 많다. 본 연구에서는 폭함수를 통해 하천망의 공간적인 특성을 함수형태로 나타내어 유역의 수문분석에 이용하는 폭함수 단위도법(WFIUH, Width Function Instantaneous Unit Hydrograph)을 소개하고, 적용성을 검토하기 위하여 실제 유역 및 강우 사상에 적용해보았다. WFIUH는 기존의 집중형 수문모형과 다르게 매개변수를 물리적으로 결정할 수 있으며, 유역특성과 시공간적 변동성을 수문곡선 산정에 반영할 수 있는 장점이 있다. WFIUH의 적용성을 검토하기 위하여 2003년 한반도에 심각한 침수피해를 입힌 태풍 매미로 인해 발생한 강우사상과 그로인해 큰 피해가 있었던 마산 지역의 남천, 삼호천 일부 유역을 대상으로 강우-유출 분석을 실시하였다. 분석결과 범용 수문모형인 HEC-HMS와 비교 시 유사한 결과를 보이며, 실제 관측치와도 유사한 결과를 보이는 것으로 나타났다. 또한 강우의 이동을 반영하여 강우의 이동이 수문곡선과 첨두유량에 미치는 영향을 비교분석 하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1D
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• pp.83-90
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• 2011

A need still exists that the unsaturated condition is to be considered when evaluating the infiltration and drainage capacity for compacted geomaterials in road foundation or embankments. For this reason, numerical analysis were used to analyze the time-dependent unsaturated infiltration and drainage condition depending on various geomaterial types. Therefore, laboratory data from the soil-water characteristic curve tests on geomaterials were adopted from previous studies. In addition, the unsaturated permeability was estimated using SWCC. Then the infiltration and drainage performance of unsaturated compacted soils were evaluated under various conditions based on the proposed method. The results demonstrated that the effect of initial suction and SWCC path on each material could be substantial and the proper application on analysis is very important to enhance the prediction on each capacity.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.17 no.1
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• pp.29-36
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• 2019

High-level radioactive waste (HLW) such as spent fuel is inevitably produced when nuclear power plants are operated. A geological repository has been considered as one of the most adequate options for the disposal of HLW, and it will be constructed in host rock at a depth of 500~1,000 meters below ground level with the concept of an engineered barrier system (EBS) and a natural barrier system. The compacted bentonite buffer is one of the most important components of the EBS. As the compacted bentonite buffer is located between disposal canisters with spent fuel and the host rock, it can restrain the release of radionuclides and protect canisters from the inflow of groundwater. Because of inflow of groundwater into the compacted bentonite buffer, it is essential to investigate soil-water characteristic curves (SWCC) of the compacted bentonite buffer in order to evaluate the entire safety performance of the EBS. Therefore, this paper conducted laboratory experiments to analyze the SWCC for a Korean Ca-type compacted bentonite buffer considering dry density, confined or unconfined condition, and drying or wetting path. There was no significant difference of SWCC considering dry density under unconfined condition. Furthermore, it was found that there was higher water suction in unconfined condition that in confined condition, and higher water suction during drying path than during wetting path.

• 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).