• Journal of the Korean Geosynthetics Society
• /
• v.7 no.4
• /
• pp.1-8
• /
• 2008

Soil vapor extraction (SVE) is an effective and cost efficient method of removing volatile organic compounds (VOCs) and petroleum hydrocarbons from unsaturated soils. However, soil vapor extraction becomes ineffective in soils with low gas permeability, for example soils with air permeabilities less than 1 Darcy. The aim of this study is to investigate numerically the performance of a prefabricated vertical drain (PVD) as a SVE well, and the pattern of the induced air flow. A validated numerical model for a single PVD extraction well is developed based on the result of a well-designed laboratory model test. The validity of the simple analytical approach to determine air permeability based on the results of model tests is also discussed.

• The Korean Journal of Ecology
• /
• v.27 no.4
• /
• pp.245-256
• /
• 2004

The simple biosphere model 2 (SiB2), which is one of the land surface models, simulates the exchange of momentum, energy and mass such as water vapor and carbon dioxide between atmosphere and biosphere, and includes the biochemical sub-model for representation of stomatal conductance and photosynthetical activities. Throughout the SiB2 simulation, the significant information not only to understand of water and carbon budget but also to make an analysis of interaction such as feed-back and-forward between environment and vegetation is given. Using revised SiB2-Paddy, one sample study which is the evaluation of the runoff in Chaophraya river basin according to land use/cover change is presented in this review. Hence, SiB2 is available in order to ecological studied, if revised SiB2 for realistic simulation about soil respiration, computing leaf area index, vegetation competition and soil moisture is improved.

• Journal of Soil and Groundwater Environment
• /
• v.6 no.2
• /
• pp.69-81
• /
• 2001

The constitutive relation among capillary pressure, saturation and relative permeability should be predetermined in order to simulate immiscible water-gas flow in porous media. The relation between saturation and relative permeability becomes more important when the capillary force can be disregarded and viscous friction force governs the flow. In this study, a 2-dimensional finite difference numerical model was developed, in which the variation of viscosity with pressure and that of relative permeability with water saturation can be treated. Seven cases of parallel plate tests were performed in order to obtain the characteristic equation of relative permeability which would be used in. the developed numerical model. It was not possible, however, to match the curves of relative permeability from the plate tests with the existing emperical models. Consequently a logistic equation was proposed as a new emperical model. As this model was composed of the parameter involving aperture size, any aperture size of fracture can be applied to the model. For the purpose of verification, the characteristic equation of relative permeability was applied to the developed numerical model and the computed results were compared with those of plate test. As a result of application of numerical model, in order to check the field applicability, to single fracture surrounding an underground storage cavern, the simultaneous flow of water and propane gas was able to be simulated properly by the model.

• Journal of Soil and Groundwater Environment
• /
• v.7 no.4
• /
• pp.59-67
• /
• 2002

As a parameter for hydrodynamic modeling to define the range of seawater intrusion, dispersivities are frequently determined from pre-experiments or theoretical studies because field experiments need a lot of time and expenses. If the dispersivities are inadequate for an aquifer, the numerical results may have some errors. We examined the validity of longitudinal dispersivities by comparing the ranges of seawater intrusion with numerical modeling, field data and apparent resistivity sections. In the numerical modeling the TDS distributions simulated by the Xu's longitudinal dispersivity are more similar to the values of TDS measured at monitoring wet]s and boreholes than those by the Neuman's longitudinal dispersivity. The ranges of seawater intrusion by numerical simulations using Xu's longitudinal dispersivity show that the contour line of 1000 ㎎/L. as TDS is located at 480 m from the coast in May, while at 390 m in July. The difference is originated from the shift of the interface between seawater and fresh water. It moved toward the coast in July because of the seasonal increase of hydraulic gradient according to rainfall. A contour line of 15 ohm-m was used to define the range of seawater intrusion in apparent resistivity sections. From this criterion on the interface between seawater and fresh water, the range of seawater intrusion is located at 450 m from the coast. This result is similar to the range of seawater intrusion simulated by the numerical modeling using Xu's dispersivity. Therefore the range of seawater intrusion shows the difference due to the dispersivities used for the hydrodynamic modeling and the dispersivity generated by the Xu's equation is considered more effective to decide the range of seawater intrusion in this study area.

• Journal of the Korean Geographical Society
• /
• v.46 no.6
• /
• pp.673-692
• /
• 2011

Advances in computer technology have enabled us to develop and use numerical landscape evolution models (NLEMs) for exploring the dynamics of geomorphic system from a variety of viewpoints which previously could have not been taken. However, as of yet there have been no trials using or developing NLEMs in Korea. The purpose of this research is to develop a 2 dimensional NLEM on a geological time scale and evaluate its usefulness. The newly developed NLEM (ND-NLEM) treats bedrock weathering as one of the major geomorphic processes and attempts to simulate the thickness of soil. As such it is possible to model the weathering-limited as well as the transport-limited environment on hillslopes. Moreover the ND-NLEM includes not only slow and continuous mass transport like soil creep, but also rapid and discrete mass transport like landslides. Bedrock incision is simulated in the ND-NLEM where fluvial transport capacity is large enough to move all channel bed loads, such that ND-NLEM can model the detachment-limited environment. Furthermore the ND-NLEM adopts the D-infinity algorithm when routing flows in the model domain, so it reduces distortion due to the use of the steepest descent slope flow direction algorithm. In the experiments to evaluate the usefulness of the ND-NLEM, characteristics of the channel network observed from the model results were similar to those of the case study area for comparison, and the hypsometry curve log during the experiment showed rational evidence of landscape evolution. Therefore, the ND-NLEM is shown to be useful for simulating landscape evolution on a geological time scale.

• Journal of Soil and Groundwater Environment
• /
• v.14 no.5
• /
• pp.29-40
• /
• 2009

In general, understanding groundwater flow in fractured bedrock is critical during tunnel and underground cavern construction. In that case, borehole data may be useful to examine groundwater flow properties of the fractured bedrock from pre-excavation until completion stages, yet sufficient borehole data is not often available to acquire. This study evaluated groundwater discharge rate into Jikri tunnel in Gyeonggi province using hydraulic parameters, groundwater level data in the later stage of tunneling, national groundwater monitoring network data, and electrical resistivity survey data. Groundwater flow rate into the tunnel by means of analytical method was estimated $7.12-74.4\;m^3/day/m$ while the groundwater flow rate was determined as $64.8\;m^3/day/m$ by means of numerical modeling. The estimated values provided by the numerical modeling may be more logical than those of the analytical method because the numerical modeling could take into account spatial variation of hydraulic parameters that was not possible by using the analytical method. Transient modeling for a period of one year from the tunnel completion resulted in the recovery of pre-excavation groundwater level.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2009.05a
• /
• pp.1068-1071
• /
• 2009

현재 한강수계의 화천댐 상류, 임진강 상류지역의 상당부분이 북한에 속해있다. 따라서, 장기유출모의 수행을 위한 기본입력자료인 수문기상자료 및 수치주제도(토지이용, 토양)의 활용에 있어 미계측 유역으로 간주되어 왔다. 그러나, 전세계 기상통신망(GTS: Global Telecommunication System)을 통해 수문기상자료(강수량, 기온, 습도, 풍속 등)는 기상청에서 제공되고 있으며, 국제연합대학(United Nations University)에서 추진하고 있는 WaterBase 프로젝트를 통해 토지이용도(24종류, 1km 해상도) 및 토양도(5,000종류, 10km 해상도)를 활용할 수 있는 상황이다. 하지만, 언급한 자료에 대한 국내검토는 충분히 이루어지지 못하고 있다. 따라서, 본 연구에서는 화천댐 상류유역을 대상으로 전세계 기상통신망 수문기상자료와 전지구 토지이용과 토양자료에 대한 검토를 수행하였다. 또한 물리적 기반의 장기유출모형인 SWAT-K의 입력자료로 활용하여 유역물수지 및 유출분석을 실시한 후, 그 적용성을 평가하였다. 이러한 연구는 기후변화 및 북한지역의 댐건설과 같은 한강수계의 수문학적 조건 변화로 인한 수자원 관리 및 계획를 위해 보다 활발히 이루어져야 할 것으로 판단된다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.12 no.2
• /
• pp.181-186
• /
• 1994

This paper applicate the digital elevation model(DEM) method in geographic information systems(GIS) on the earthwork volumes, intending to present an efficient geographic information-obtain method and an optimum earthwork volumes method after analyzing the obtain method of geographic informations which are made up of as spatial data(X, Y) and attribute data(Z), analyzing area determination method by geographic information-obtain method each other and the accuracy of earthwork volumes computation. The results of this paper showed that the method of earthwork volumes computation, which was based on the earthwork volumes-calculation grid applied by the DEM method of based grid to randomly get the geographic information of geographic transformation point and translated geography into nonlinear and unequal interval, was very efficient.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.23 no.12
• /
• pp.1412-1415
• /
• 2012

Return signals of a ground penetrating radar(GPR) for mine detection at various frequencies and soil moisture contents are analyzed in this paper. We first compute the dielectric constant, conductivity and attenuation loss based on clay loam which is Korea standard soil. The mine-detection images of GPR at various frequencies are also obtained using the finite-difference time-domain(FDTD) technique. Then, the signal-to-clutter ratio(SCR) and received power of the radar are studied. It is shown that the variable frequency channels are suitable for a GPR to detect landmines at various soil conditions.

• Korean Journal of Environmental Agriculture
• /
• v.9 no.2
• /
• pp.105-111
• /
• 1990

The soil adsorption coefficient of butachlor was measured mainly following the guidelines of U. S. EPA and OECD. The soil adsorption coefficient, Koc, of butachlor agreed well with the values in the literature. It was observed that soil adsorption differed about 5% with an increase or decrease by $15^{\circ}C$, implying that temperature does affect soil adsorption. The estimated value of the soil adsorption coefficient using water solubility and molecular structure deviated by factors of 2 and 20, respectively. The soil adsorption coefficient, Koc, of butachlor was 543 so this value means that butachlor is tightly bound to organic matter in soil and is considered immobile. A novel trial estimating the soil adsorption coefficient by molecular structure might be utilized to design efficient and/or non-polluting agrochemicals by organic chemists.