• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.99-107
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• 2003

Moisture flow and heat flow within pavement systems have been recognized as coupled processes with complex interactions between them. The distribution of moisture and temperature within pavement due to the moisture flow and heat flow varies not only seasonally but also vertically and horizontally. This paper presents an analysis model by the finite element method for the two-dimensional coupled moisture and heat flow in unsaturated soils. To test the model the analysis result by the model is compared with the analysis result by the software, GEO-SLOPE developed by GEO-SLOPE International Ltd. in Alberta, Canada. And a sensitivity analysis using ASTM method is performed to identify how model inputs affect the modeling analysis.

• Economic and Environmental Geology
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• v.42 no.6
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• pp.561-574
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• 2009

Unsaturated/saturated groundwater flow and solute transport model, VSFRT2D(Variable Saturated Flow and Reactive Transport model) was developed considering effects of pumping, irrigation, and denitrification. VSFRT2D employed Richards equation as governing equation for groundwater flow and previously existing unsaturated models modified by including computational procedure of evapotranspiration at surface using Thornthwaite method when precipitation doesn't occur. Bioremediation processes based on monod kinetics are described using four nonlinear contaminant transport equations and three nonlinear microbes transport equations. The developed model was applied to field data in Hongsung area contaminated with nitrate. In order to identify the effect of precipitation, pumping, evapotranspiration, irrigation, fertilizer application, and various bioremediations on groundwater flow and contaminant transport, individual processes were separated and simulated. Then all results obtained from the individual processes are compared with each other. The simulation results show that bioremediation had a negligible effect on nitrate concentration change. However, pumping for irrigation, precipitation, and nitrogen fertilizer application showed profound influences on nitrate concentration change.

• 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 Society of Hazard Mitigation
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• v.9 no.3
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• pp.9-17
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• 2009

Most of the current drainage criteria have been developed on the basis of experimental field results and theoretical analyses of infiltration under saturated conditions. The objective of this study is to extend the understanding of pavement drainage systems by considering unsaturated condition in the sublayers. Analyses of unsaturated flows through pavements was performed by running finite element program(SEEP/W) with a range of pavement materials and drainage parameters. Meanwhile, the widely used DRIP program developed by FHWA is based on assumption of saturated condition of pavements. Differences between saturated and unsaturated condition in the sublayers of the pavements are verified. It is verified that for unsaturated conditions time to drain would take longer time compared to saturated condition.

• Journal of the Korean Geotechnical Society
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• v.23 no.10
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• pp.57-64
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• 2007

Since matric suction of unsaturated soil was related to soil and ground water contaminations, it is very important to analyze its mechanism that was represented by shear characteristics. In three phases of soil, a little air makes the condition of unsaturated soil on contract or shrinkage surface between water and air. Capillarity and suction in pore of unsaturated soil cause surface tension and surface force so it makes negative pore water pressure and increases effective stress as a result. Therefore, negative pore water pressure in partially saturated soil affects the soil structure and degree of saturation and it is important to evaluate accurately unsaturate flow and behavior. In this study, the shear strength characteristics of the seven sandy soils were investigated using consolidated drained triaxial tests with special emphasis on the effects of the negative pore pressure and the matric suction. These tests involved shearing under either a constant net confining pressure and varying matric suction or under a constant matric suction and varying net normal stress.

• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.4
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• pp.35-41
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• 2005

In order to analyse the flow problems for an unsaturated soil, it is required to examine closely the characteristics of the coefficient of permeability which is changing with the matric suction. To this ends, a permeability test was conducted on the three samples;granular soil, cohesive soil and silty soil. The specimen was made by pressing the static pressure on the mold filled with soil and the void ratio was controled with the different compaction ratio. And the test was performed by using the modified apparatus of the steady state method which was proposed by flute (1972). The range of matric suction was 0-90 kPa. The measured results for the coefficients of permeability were analysed with the void ratio and the compaction ratio, and it was examined closely the characteristics of the permeability for an unsaturated soil.

• Geotechnical Engineering
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• v.9 no.2
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• pp.65-69
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• 1993

강우에 의해 발생되는 토양(soil)에서의 Recharge를 구하기 위해 두가지 모델 즉, ((i) Simple Mass Balance Model (ii) Numerical Model : UNSAT 1)을 사용했는데, 이 두 모델들은 불포화상태의 흙(unsaturated zone : above groundwater table)에서 그의 가정과 개념에 약간 차이가 있다. Unsaturated Zone에서의이 두 모델의 적용에 있어서 몇가지 중요한 사항이 지적되고 있는데, 균질의 불포화 영역(unsaturated zone)의 토양에서 Mass Balance Model을 사용함으로써 얻은 Recharge는 UNSAT 1(numerical model)을 통해 얻은 결과와 비교할 때 서로 상이한 결과를 보였다. 또한, Recharge의 계산에 있어서 지하수위의 변화에 따른 영향을 알아보기 위해 Sensitivity Analysis를 수행하였다. 즉, 고정수위(fixed groundwater table)로 가정했을 때 발생되는 오차를 한개의 수리학적 계수(hydraulic parameter)의 함수로 보고 계산을 했으며 이 결과를 그림으로 나타내어 보았다. 이 연구의 결과는 Model Simulation에 있어서 수리학적 경계조건을 결정하는데 큰 도움이 될 것이며, 또한 이 연구에서는 Unsaturated-Saturated Flow Model이나 Drainage Model을 함께 병행시켜 Simulation을 수행하는데 촛점을 두고 있다.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.836-841
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• 2008

CFRD (Concrete Faced Rockfill Dam) has been world-widely constructed due to a lot of advantages compared with rockfill dam and recently, sand/gravel materials, instead of crushed rock materials, are also utilized as a main rockfill material to overcome geological and environmental problems. In this paper, the process of water infiltration into the originally unsaturated sand/gravel-fill dam is studied using two-dimensional saturated-unsaturated seepage theory. According to the results of seepage analysis, if the effective drainage zone is installed in the dam, the reservoir water infiltrate into the dam along a downward flow path towards the lower drainage area. The main body constructed with sand/gravel materials, therefore, remains unsaturated.

• Journal of Soil and Groundwater Environment
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• v.21 no.1
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• pp.1-5
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• 2016

Capillary barriers, consisting of relatively fine-over-coarse materials, have been suggested as an alternative to traditional compacted soil covers. So, We were analysed to capillary barrier effect according to five cases of multi-layer cover systems. Water balance simulation was conducted with unsaturated flow model HELP to assess unsaturated hydraulic parameters such as hydraulic conductivity, climate affecting the performance of capillary barriers. Simulation were conducted for 5 Cases in the Ulsan area. Result of simulation indicated that three cases was formed unsaturated condition and capillary barrier effect.

• Journal of Korean Society on Water Environment
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• v.23 no.5
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• pp.683-688
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• 2007

Water flow into unsaturated soils is most often modeled by Richards equation consisting of the mass conservation law and Darcy's law. Three standard forms of Richards equation are presented as the head (${\Psi}$)-based form, the moisture content (${\theta}$) based form, and the mixed form. Numerical solutions of these partial differential equations with highly nonlinear terms can cause poor results along with significant mass balance errors. The numerical solution based on the mixed form of Richards equation is known that the mass is perfectly conserved without any additional computational efforts. The aim of this study is to develop fully implicit numerical scheme of Richards equation for one-dimensional vertical unsaturated flow in homogeneous soils using the finite difference approximation, and then to perform sensitivity analysis of infiltration to the variations in the unsaturated soil properties and to different soil types.