• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.105-117
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• 2002

In the design of foundations for the super-structures such as transmission towers and oil-platforms, the foundations must be considered as a medium to resist cyclic tensile forces. In this study, the uplift capacity of the drilled shaft used as the medium resisting to this pattern of forces is investigated by performing cyclic uplift test of a small model-drilled shaft constructed in compacted granite soil in a steel chamber. In this test, the behavioral difference between a pile loaded on the top of the pile and a pile loaded at the bottom of the pile was investigated intensively. The load transfer curves obtained from the test were investigated by changing the confining pressure in the chamber. The load tests also included creep test and cyclic test. It is found from the tests that uplift capacity of the shaft loaded at the bottom is greater than that of the shaft loaded on the top of the pile. It is found also from the creep test that the pile loaded at the bottom was more stable than the shaft loaded on the top. If a pile loaded at the bottom is pre-tensioned, the pile will be most effective to the creep displacement. It is found also from the cyclic tests that apparent secant modulus obtained in a cycle of the load increases with the number of cycles.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.100-101
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• 2004

Many researches in Korea have been performed to understand the pollution of stream waters by acid mine drainage. However, few studies have been conducted regarding the effect of particulate and colloidal fractions on the transport of trace metals. To estimate harmful effects of trace metals, it is important to evaluate the particulate and colloidal metals as well as dissolved metals, because particulate and colloidal fractions of trace metals play an important role in transport of trace metals and may adversely affect habitats and organisms in riverine system. Colloids are solids with effective diameters in size range from 0.001 $\mu$m to 1 $\mu$m. According to Jone et al. (1974), metals in surface water, like Al, Fe, and Mn, require filtration with pore-size membranes smaller than 0.45 $\mu$m to define dissolved concentrations. The main objective of this study is to understand the effects of particulate, colloidal, and truly dissolved fractions on the transport and fate of trace metals in acid mine drainage. This study was conducted for the Onjeong creek in the Uljin mine area. Sampling was carried out in 13 sites, spatially covering the area from mine dumps to the downstream Onjeong reservoir. To examine the metal partitioning between particulate, colloidal, and truly dissolved fraction, we used successive filtration techniques consisting of conventional method (using 0.45 $\mu$m membranes) and tangential-flow ultrafiltration (using 0.001 $\mu$mm membranes). Ultrafiltration may seperate much smaller particles from aqueous phase (Josephson, 1984; Hernandez and Stallard, 1988). The analysis of metals were performed by inductively coupled plasma - atomic emission spectrometer (ICP-AES: model Perkin Elmer OPTIMA3000XL). Anions such as SO$_4$, Cl and NO$_3$ were measured with ion chromatograph (IC: model Dionex 120). Sample analysis is still in progress. The preliminary data show that the studied creek is severely polluted by Al, Fe, Mn, Pb and Zn. Toward upstream sites with relatively lower pH, less than 50% of Al and Fe occur in the sorbed form on particles or colloids, whereas more than 80% of Al and Fe occur in the sorbed form in downstream sites or tributaries with relatively higher pH. Less than 30% of Zn is present in particle or colloidal forms in the whole range of creek. Truly dissolved fraction of trace metals is negatively correlated with pH. The Kd values for Al, Fe and Zn consistently increase with increasing pH and decrease with increasing particle concentration.

• Journal of Soil and Groundwater Environment
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• v.13 no.6
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• pp.23-30
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• 2008

Air sparging technique has been used for remediation of VOC(volatile organic compound)-contaminated aquifer. The aim of this study was to develop an innovative air sparging technique that enhances the efficiency of air intrusion into a specific horizontal layer of aquifer where the contaminants exist with the help of water-soluble surfactant. A twodimensional physical box model, packed with homogeneous sand, was used for simulating the aquifer in this study. Aqueous solution of anionic surfactant (100 mg/L, sodium dodecylbenzene sulfonate) was used to suppress the surface tension of groundwater. Three sets of experiments were conducted: air sparging experiment without surfactant application, air sparging experiments for box model where the surfactant solution was applied right above the air injection point, and air sparging experiments with surfactant solution layer formed in the middle of the box. It was found that the sparging influence zone was expanded up to five times of that formed by sparging without surfactant application. The size of sparging influence zone was more sensitive to the air flow (injection) rate with surfactant application than that without surfactant. More importantly, injection of air into the target aquifer layer was successful with surfactant application. Findings in this study are expected to provide more options for designing remediation processes using air sparging.

• Korean Journal of Soil Science and Fertilizer
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• v.36 no.4
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• pp.210-217
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• 2003

An alternative method to the empirical approach such as Langmuir and Freundlich model, surface complexation model using thermodynamic database is used to simulate adsorption behavior of cadmium for oxide minerals. Sorption of cadmium onto amorphous silica ($SiO_2$) and synthetic goethite (${\alpha}$-FeOOH) at various conditions of pH, initial cadmium loading, oxide concentration, and ionic strength, were investigated. For both oxide minerals, increasing cadmium concentration resulted in right shifting of the sorption curve of cadmium as the function of pH. The $pH_{50}$, where 50% of cadmium sorbed, of goethite (pH 5.25) was much smaller than that of the silica (pH 7.83). The sorption of cadmium onto both minerals were not affected by the background ion strength from $10^{-1}$ to $10^{-2}$ M of $KNO_3$. It indicated that the binding affinity of goethite surface for cadmium is much stronger than that of silica. The strong affinity of oxide mineral for cadmium can be explained by the existence of coordination or covalent bond between cadmium and surface of it.

• Journal of Environmental Impact Assessment
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• v.25 no.6
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• pp.369-383
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• 2016

A distributed watershed model CAMEL(Chemicals, Agricultural Management and Erosion Losses) was applied to a part of grazing grassland and vegetation buffer strip(VBS) located in Daegwanryeong, Korea. A set of scenario analyses was carried out for grassland and VBS with various combinations of VBS widths, soil textures and ground surface slopes. The simulation results indicate that annual direct runoff decreases with wider VBS and the removal efficiency of pollutants generally decrease with steeper slopes. The removal efficiency of sediment is not significantly different with VBS widths. For gentle and medium slopes($10^{\circ}$, $20^{\circ}$), the removal efficiency of TOC and TN is not significantly different with VBS widths. As for a steep slope($30^{\circ}$), however, the removal efficiency of TOC and TN increases with narrower VBS. The removal efficiency of TP is generally high except for medium and steep slope of sandy loam where the removal efficiency of TP increases with wider VBS. This result of TP is contrary to the results of TOC and TN due to the adsorption characteristics of phosphorus associated with fine sediment particles. It is expected that CAMEL can be used for evaluating the effectiveness of VBS to reduce non-point source pollution discharges.

• Journal of the Korean Geographical Society
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• v.39 no.4
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• pp.495-513
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• 2004

The shape of land surface work as a cradle for various environmental processes and human activities. As spatially distributed process modelings become increasing important in current research communities, a classification system that delineates land surface into characteristic geomorphological units is a pre-requisite for sustainable land use planning and management. Existing classification systems are either morphometric or generic, which have limitations to characterize continuous ecological processes over the landscape. A new classification system was developed to delineate the land surface into different geomorphological units from Digital Elevation Models(DEMs). This model assumes that there are pedo-geomorphological units in which distinct sets of hydrological, pedological, and consequent ecological processes occur. The classification system first divides the whole landsurface into eight soil-landscape units. Possible energy and material nows over the land surface were interpreted using a continuity equation of mass flow along the hillslope, and subsequently implemented in terrain analysis procedures. The developed models were tested at a 12$\textrm{km}^2$ area in Yangpyeong-gun, Kyeongi-do, Korea. The method proposed effectively delineates land surface into distinct pedo-geomorphological units, which identify the geomorphological characteristics over a large area at a low cost. The delineated landscape units mal provide a basic information for natural resource survey and environmental modeling practices.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.4
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• pp.476-482
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• 2014

In this study, we analyzed the effect of corn growth on the radar backscattering coefficient. At first, we measured the backscattering coefficients of various corn fields using a polarimetric scatterometer system. The backscattering coefficients of the corn fields were also computed using the 1st-order VRT(Vector Radiative Transfer) model with field-measured input parameters. Then, we analyzed the experimental and numerical backscattering coefficients of corn fields. As a result, we found that the backscatter from an underlying soil layer is dominant for early growing stage. On the other hand, for vegetative stage with a higher LAI(Leaf-Area-Index), the backscatter from vegetation canopy becomes dominant, and its backscattering coefficients increase as incidence angle increases because of the effect of leaf angle distribution. It was also found that the estimated backscattering coefficients agree quite well with the field-measured radar backscattering coefficients with an RMSE(Root Mean Square Error) of 1.32 dB for VV-polarization and 0.99 dB for HH-polarization. Finally, we compared the backscattering characteristics of vegetation and soil layers with various LAI values.

• Geotechnical Engineering
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• v.14 no.5
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• pp.129-142
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• 1998

This research is focused on the inducement of the constitutive equation considering the creep strain component and on the development of a finite element method program. The purpose of this research was to contribute to the design of construction structures or to the construction management in soft clay ground through predicting the long-term strain of construction structures reasonably bused on the above program. Modified Cam Clay model was adopted to describe the elastic-plastic behavior of clayey soil. And in the calculation of the creep sprain, the secondary coefficient of consolidation C. was applied for considering the volumetric creep element and the constants m, $\alpha$, A were rosed by the empirical creep equation proposed by Singh 8E Mitchell for considering the deviatoric creep element. To examine the reliability of the program which is developed in this study, the estimated values by this program were compared with the theoretical solution and the experimental results. And the applicability of the developed program was found to be reliable from the sensitive analysis of each parameters used in this study. According to the results obtained from the application of the program on the field measurement data, the estimated values by the program were found with be consistent with the actual values. And from the analysis of the displacement of embankments, the case of considering the creep behavior induced much fower errors than the case of neglecting it. But the results obtained from considering the volumetric creep behavior only were slightly underestimated the results from considering the deviator creep behavior showed the slightly overestimated values. Therefore, it remains the task of further studios to develop the laboratory test devices to obtain the reliable creep parameters, and to select the appropriate soil parameters, etc.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.5
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• pp.543-561
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• 2020

This paper is the result of the study on the effect of the support structure of the tunnel steel rib. In tunnel excavation, the top and bottom half excavation methods result in subsidence of steel rib reinforcement due to insufficient support of steel rib reinforcement when the ground is poor after excavation. The foundation of the steel rib installed in the upper half excavates the bottom part of the base, causing the subsidence to occur due to various effects such as internal load and lateral pressure. As a result, the tunnel is difficult to maintain and its safety is problematic. To solve these problems, steel rib support structures have been developed. For the purpose of verification, the behavior of the supporting structure is verified by model experiments reduced to shotcrete and steel rib material similarity, the numerical analysis of ΔP and ΔP generated by bottom excavation by Terzaghi theoretical equation. As a result, it was found that the support structure of 20.100~198.423 kN is required for the 10~40 m section of the depth for each soil of weathered soil~soft rock. In addition, as a result of the reduced model experiment, a fixed level of 50% steel rib deposit of steel rib support structure was installed. The study shows that the installation of steel rib support structures will compensate for uncertainties and various problems during construction. It is also thought that the installation of steel rib support structure will have many effects such as stability, economy, and air reduction.

• Journal of Wetlands Research
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• v.13 no.1
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• pp.95-104
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• 2011

This study was implemented to select the suitable site for Palustrine Wetland at habitat restoration for Oriental stork, red species and top-level predator in ecosystem. The evaluation items was fitted by review the antecedent studies on the suitable site selection model and evaluation items of wetland. The study sites were setted in $5,884,800m^2$ area including Yesan-gun Dae-ree, in which Oriental stork' park will be located, through DEM(Digital Elevation Model) watershed analysis. The thematic map by valuation items with secure of water resource, soil, topography, distance between roads, houses, etc., land using, wildlife corridor, and type of water resource was prepared using GIS program. The sites with high evaluation score were selected as suitable creation sites for wetland through overlapping those maps. Total 8 sites with over 18 point were selected. The characteristics of selected sites show that the soil are consisted of clay, the connectivity is valued high with surface water, the slope are gentle, and the connectivity is good with surroundings ecosystem. The result of water quality analysis, which was implement to survey available water resources and develop the solution of problem of water environment, showed that water quality at Salmok reservoir and Bogang reservoir is generally good, but the water quality at stagnant water body rising out from groundwater is not good. This study has limit to select the suitable sites of wetland only by analyzing physiotherapy environment in study area. Hereafter, the study is need to examine closely enhancement effects of biological diversity through investigation of biotic environment.