• Journal of the Korean Geosynthetics Society
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• 제10권3호
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• pp.25-32
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• 2011

The matric suction and volumetric water content of dredging soils obtained from Saemangeum area were measured by the automated Soil-Water Characteristic Curve (SWCC) apparatus under both drying and wetting conditions. Based on the test result, SWCCs of the dredging soils were estimated by the van Genuchten(1980) model. The matric suction of drying process is larger than that of wetting process at a same effective degree of saturation. The suction stresses for various matirc suctions were estimated using Lu and Likos(2006) model and the Suction Stress Characteristic Curves (SSCC) were predicted using the independent parameter of SWCC. The suction stress of drying path was increased and decreased, while the suction stress of wetting path was continuously decreased with increasing the effective degree. Also, the suction stress of drying path is larger than that of wetting path at a same effective degree of saturation. The Hydraulic Conductivity Function(HCF) was also predicted by the van Genuchten(1980) model. The hydraulic conductivity was increased with increasing the volumetric water content. The hydraulic conductivity of drying path is larger than that of wetting path at a same matric suction. According to the results of SWCCs and SSCCs, the hysteresis phenomenon of suction stress or matric suction during both drying and wetting paths was occurred. The main reason of hysteresis phenomenon is a ink bottle effect of water among soil particles.

• Journal of the Korean Geotechnical Society
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• 제30권3호
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• pp.47-58
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• 2014

To investigate the unsaturated characteristics of the tailings obtained from the waste dump at Imgi mine, matric suction and volumetric water content were measured in both drying and wetting processes using Automated Soil-Water Characteristics Curve Apparatus. Based on the measured result, Soil Water Characteristic Curves (SWCC) were estimated by van Genuchten model. According to the unsaturated soil classification method, the tailings of the waste dump correspond to clayey sand. As a result of Suction Stress Characteristic Curve (SSCC) by Lu and Likos model, SSCC has a shape of S which is similar to SWCC. The hysteresis phenomenon occurred in SSCCs, which means the suction stress of drying path is larger than that of wetting path in the same effective degree of saturation. The effective stress of unsaturated soil is equal to that of saturated soil when matric suction is less than Air Entry Value (AEV). However, the effective stress of unsaturated soil is larger than that of saturated soil when matic suction is more than AEV. Meanwhile, unsaturated hydraulic conductivity by van Genuchten model decreased with increasing matric suction, and the hydraulic conductivity of drying path is larger than that of wetting path.

• Transactions of the Korean Society of Mechanical Engineers B
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• 제24권8호
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• pp.1119-1127
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• 2000

Convective heat transfer in a channel filled with porous media has been analyzed in this paper. The two-equation model is applied for the heat transfer analysis with the velocity profile, considering both the inertia and viscous effects. Based on a theoretical solution, the effect of the velocity profile on the convective heat transfer is investigated in detail. The Nusselt number is obtained in terms of the relevant physical parameters, such as the Biot number for the internal heat exchange, the ratio of effective conductivities between the fluid and solid phases, and hydraulic boundary layer thickness. The results indicate that the influence of the velocity profile is characterized within two regimes according to the two parameters, the Biot number and the conductivity ratio between the phases. The decrease in the heat transfer due to the hydraulic boundary layer thickness is 15% at most within a practical range of the pertinent parameters.

• Proceedings of the Korean Geotechical Society Conference
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1693-1706
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• 2008

It is of importance to determine the zero effective stress void ratio($e_{00}$), which is the void ratio at effective stress equal to zero, and the relationships of void ratio-effective stress and of void ratio-hydraulic conductivity for characterizing non-liner finite strain consolidation behavior for ultra-soft dredged materials. The zero effective stress void ratio means a transitional status from sedimentation to self-weight consolidation of very soft soil deposits, and acts as a starting point for self-weight consolidation in the non-linear finite strain numerical analysis such as PSDDF. In this paper, a new method for determining the zero effective stress void ratio has been introduced with the aid of measuring electrical resistivity of the specimen. A correlation between the zero effective stress void ratio and the initial slurry void ratio has been proposed, which can be used in PSDDF analysis as an input parameter. Combining all of the accessible experimental data, the consolidation characteristics of a dredged soil from the Incheon area has been studied in detail.

• Journal of the Korean Geotechnical Society
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• 제17권4호
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• pp.49-55
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• 2001

본 논문에서는 서해안 폐기물 매립지 하부의 점성토와 고화차수재를 재료로 수행된 확산시험 결과와 현장 조건을 적용하여 오염물이동성에 대한 수치해석을 수행하였다. 무기화합물이 하부 차수재와 원지반퇴적층으로 이동되는 일차원 이동 특성을 대상으로 하였으며 일차원 용질이동해석 프로그램 CDFD(convection-dispersion finite difference)를 현장의 비균질한 지층에 이용할 수 있도록 수정하여 적용하였다. 그 결과 원지반점성토를 통한 용질이동 메카니즘에 확산이 기여하는 정도가 50%로 매우 큰 영향을 갖고 있음을 보여주며 원지반 투수계수가 클수록 인공차수층의 필요성이 증대됨을 알 수 있었다.

• Geomechanics and Engineering
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• 제14권3호
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• pp.283-291
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• 2018

Cracks in soil provide significant preferential pathways for contaminant transport and rainfall infiltration. Water exchange between the soil matrix and crack is crucial to characterize the preferential flow, which is often quantitatively described by a water exchange ratio. The water exchange ratio is defined as the amount of water flowing from the crack into the clay matrix per unit time. Most of the previous studies on the water exchange ratio mainly focused on cracked sandy soils. The water exchange between cracks and clay matrix were rarely studied mainly due to two reasons: (1) Cracks open upon drying and close upon wetting. The deformable cracks lead to a dynamic change in the water exchange ratio. (2) The aperture of desiccation crack in clay is narrow (generally 0.5 mm to 5 mm) which is difficult to model in experiments. This study will investigate the water exchange between a deformable crack and the clay matrix using a newly developed experimental apparatus. An artificial crack with small aperture was first fabricated in clay without disturbing the clay matrix. Water content sensors and suction sensors were instrumented at different places of the cracked clay to monitor the water content and suction changes. Results showed that the water exchange ratio was relatively large at the initial stage and decreased with the increasing water content in clay matrix. The water exchange ratio increased with increasing crack apertures and approached the largest value when the clay was compacted at the water content to the optimal water content. The effective hydraulic conductivity of the crack-clay matrix interface was about one order of magnitude larger than that of saturated soil matrix.

• Nuclear Engineering and Technology
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• 제26권1호
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• pp.54-62
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• 1994

The hydraulic properties of domestic natural clay/crushed rock mixture suggested as a candidate backfill material for the low and intermediate level waste repository were investigated. The dry density-water content relationship was studied to define an optimum water content that gives a maximum attainable dry density at constant compaction pressure. The hydraulic conductivities of clay/crushed rock mixture as a function of clay content were also measured. As the clay content decreased, the maximum attainable dry density increased and the optimum water content became more distinct. However the attainable density is not significantly sensitive to water content. The hydraulic conductivities of the mixture increased from 5 $\times$ 10$^{-12}$ m/s to 7 $\times$ 10$^{-10}$ m/s with clay content decreasing from 100 wt.% to 25 wt.% at dry density of 1.2 Mg/㎥. In case of dry density of 1.5 Mg/㎥, they maintain the lower values of 5 $\times$ 10$^{-12}$ m/s even at 25 wt.% clay content. The concept of effective clay dry density was suggested to estimate the hydraulic conductivity of the mixture. It was shown that the effective clay dry density concept can explain welt the hydraulic conductivities of the mixtures with various dry density and crushed rock content.

• Geomechanics and Engineering
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• 제12권5호
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• pp.803-813
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• 2017

This study discussed the possible optimization of enzyme-mediated calcite precipitation (EMCP) as a soil-improvement technique. Magnesium chloride was added to the injection solution to delay the reaction rate and to improve the homogenous distribution of precipitated minerals within soil sample. Soil specimens were prepared in 1-m PVC cylinders and treated with the obtained solutions composed of urease, urea, calcium, and magnesium chloride, and the mineral distribution within the sand specimens was examined. The effects of the precipitated minerals on the mechanical and hydraulic properties were evaluated by unconfined compressive strength (UCS) and permeability tests, respectively. The addition of magnesium was found to be effective in delaying the reaction rate by more than one hour. The uniform distribution of the precipitated minerals within a 1-m sand column was obtained when 0.1 mol/L and 0.4 mol/L of magnesium and calcium, respectively, were injected. The strength increased gradually as the mineral content was further increased. The permeability test results showed that the hydraulic conductivity was approximately constant in the presence of a 6% mineral mass. Thus, it was revealed that it is possible to control the strength of treated sand by adjusting the amount of precipitated minerals.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 한국지하수토양환경학회 2003년도 추계학술발표회
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• pp.426-430
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• 2003

Subsurface biobarrier technology has potential applications to contain contaminated groundwater and/or to degrade toxic pollutants in groundwater. Effective biobarrier formation is need to assess of hydrogeologic characteristics and to conduct practical operation strategies and design based on this prior to design biobarrier. Thus, in this study, we examined hydrogeologic characteristics in biobarrier construction site. Hydraulic conductivities which calculated from slug test data have shown difference with each well as 1.20$\times$10$^{-3}$ -6.00$\times$10$^{-5}$ cm/sec. Tracer test is a method in which concentration of tracer solution during withdrawal in each well by vacuum extraction system is measured with time. Tracer solution was continuously injected by constant head tank. Measured tracer concentration versus time data were fitted to analytical solution of convection dispersion equation (CDE). The fitting data of CDE to the measured data at each extraction well yielded were 0.61cm/min(pore velocity), 5.38$\textrm{cm}^2$/min(dispersion coefficient) for discharge rate of 0.47 1/min and 1.75cm/min(pore velocity), 36.34$\textrm{cm}^2$/min(dispersion coefficient) for discharge rate of 0.93 1/min. As a result, we acquired fundamental parameters which need to design biobarrier and operation strategies.

• Journal of Soil and Groundwater Environment
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• 제15권2호
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• pp.1-9
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• 2010

Estimations of porosity and bulk density, particle size analysis of soli samples, tracer test and slug test were performed in a petroleum contaminated area of Kangwon for understanding characteristics of the aquifer. Porosities of the samples were estimated 0.158~0.257, and bulk densities were estimated as $1.73\sim2.10\;g/cm^3$. Majority proportion of the soil samples was 0.5~1.0 mm size. In the soil texture triangle, all samples were distributed at sand area. Uniformity coefficients were estimated as 7.71~10.39, and thus all samples were poorly-sorted. In the tracer test, Darcy velocity was estimated to $4.8\times10^{-6}$ cm/day, effective porosity was 0.175, and longitudinal dispersivity was 0.1 m. According to the slug test, hydraulic conductivities of the test wells were estimated as $2.243\times10^{-2}\sim1.634\times10^{-2}$ cm/sec. These hydrogeologic parameters can be used for efficient remediation design of the petroleum contaminated area.