• Journal of the Korean GEO-environmental Society
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• v.14 no.5
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• pp.41-47
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• 2013

Well-graded and dense soils have good engineering properties. Unsaturated soil properties such as shear strength, compressibility and permeability are closely related to the soil-water characteristic curve of the soil. Therefore it is important to study the effects of the coefficient of uniformity and the porosity on the soil-water characteristic curve of the sandy soils, which are also related to the grain size distribution and the density of the soil, respectively. In this study soil-water characteristic curves (SWCCs) for six sandy soil specimens were investigated using Tempe pressure cells. The test data were best-fitted to Fredlund and Xing equation. The obtained fitting parameters and the characteristic points of SWCCs were discussed and correlated with the porosity and the coefficient of uniformity of the specimens. The results show that the smaller the porosity of the specimen becomes, the larger the value of the residual matric suction becomes, whereas the larger the coefficient of uniformity of the specimen becomes, the larger the value of the residual matric suction becomes. Regardless of the coefficient of uniformity, the smaller the porosity of the specimen, the flatter the max. slope of SWCC.

• Korean Journal of Soil Science and Fertilizer
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• v.30 no.1
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• pp.51-55
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• 1997

Three soils, sandy loam, loam and silty clay loam, were selected and three inches soil cores with 4 bulk density(BD) levels were made by compressing the soils wetted with 3 levels water. Mechanical and water characteristics were measured and analyzed the mechanical resistance limiting water, available water and least-limiting water range. Mechanical resistance limiting water(MRLW) were appeared at higher bulk density than $1.6Mg/m^3$ in sandy loam, and $1.4Mg/m^3$ in loam and silty clay loam. The least-limiting water ranges were sharply decreased at the bulk density $1.6Mg/m^3$ in sandy loam and loam, $1.4Mg/m^3$ in silty clay loam. There were big deferences between available water contents and least limiting water ranges in finer texture and higher bulk density soils.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.5
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• pp.581-587
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• 2014

Sediment basin that is typical facility installed for development business to prevent soil erosion has low removal efficiency and therefore, it causes complaints from the residents and has a bad effect on ecosystem. Thus there is a limit to control soil erosion using the existing design methods of sediment basin, so the purposes of this study is providing suitable design factors for sediment basin with regarding soil characteristic of development areas and analysing sedimentation characteristic by inflow concentration changes. The results, for analyzing the sedimentation characteristic by soil concentrations within approximately 2,000 ~ 20,000 mg/L of initial SS concentration, indicated similar sedimentation trends for same soil in the supernatant regardless of initial concentrations. However, for different soil characteristic (percent finer), there are different results in sedimentation rate and concentrations of the supernatant. Thus it is recommended that sediment basin to prevent soil erosion during construction should be designed based on retention time derived from soil sedimentation experiments regardless of inlet concentration. In addition, installing the soil erosion prevention facility at the back to satisfy effluent water quality should be considered to minimize soil erosion effectively.

• Environmental Engineering Research
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• v.24 no.4
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• pp.654-661
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• 2019

This study assessed the stabilization of fluorine (F)-contaminated soil using calcium hydroxide (Ca(OH)₂) and the consequent changes in human health risk. The bioavailable F decreased to 3.5%, (i.e., 57.9 ± 1.27 mg/kg in 6% Ca(OH)₂-treated soil sample) from 43.0%, (i.e., 711 ± 23.4 mg/kg in control soil sample). This resulted from the conversion of water-soluble F to stable calcium fluoride, which was confirmed by XRD spectrometry. Soil ingestion, inhalation of fugitive dust from soil, and water ingestion were selected as exposure pathways for human health risk assessment. Non-carcinogenic risks of F in soils reduced to less than 1.0 after stabilization, ranging from 4.2 to 0.34 for child and from 3.0 to 0.25 for adult. Contaminated water ingestion owing to the leaching of F from soil to groundwater was considered as a major exposure pathway. The risks through soil ingestion and inhalation of fugitive dust from soil were insignificant both before and after stabilization, although F concentration exceeded the Korean soil regulatory level before stabilization. Our data suggested that substantial risk to human health owing to various potential exposure pathways could be addressed by managing F present in soil.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.6
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• pp.1314-1319
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• 2011

This study was carried out to investigate the surface soil organic carbon fractions affecting by different land use types, including needle-leaf forest (FN), broad-leaf forest (FB), pasture, annual upland cropping land (upland), and paddy rice land (paddy). We chose seven regions across Korean inland, considering sea level altitude, and measured soil organic carbon content and physico-chemical properties such as bulk density at a depth of 0~15 cm using core samples in April for the each land use type. In addition, labile organic carbon fractions in soil including light fraction and hot water extractable carbon were investigated. From this study, organic carbon storage (Mg C per ha) in the upper 15-cm soils was highest in FB (37.8), and decreased in the order of pasture (29.1), FN (28.8), paddy (21.9), and upland crop (19.9). In forest, more than 20% of soil organic carbon existed as light fraction, the free organic matter. Hot-water extractable carbon contents of soils in five land use types were lower than 7% of their soil organic carbon content.

• Geomechanics and Engineering
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• v.23 no.2
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• pp.139-149
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• 2020

Piles are widely used in structural foundations of engineering projects. However, the deformation of the soil around the pile caused by driving process has an adverse effect on adjacent existing underground buildings. Many previous studies have addressed related problems in sand and saturated clay. Nevertheless, the failure mechanism of pile driving in unsaturated soil remains scarcely reported, and this issue needs to be studied. In this study, a modeling test system based on particle image velocimetry (PIV) was developed for studying deformation characteristics of pile driving in unsaturated silt with different water contents. Meanwhile, a series of direct shear tests and soil-water characteristic curve (SWCC) tests also were conducted. The test results show that the displacement field shows an apparent squeezing effect under the pile end. The installation pressure and displacement field characteristics are sensitive to the water content. The installation pressure is the largest and the total displacement field is the smallest, for specimens compacted at water content of 11.5%. These observations can be reasonably interpreted according to the relevant unsaturated silt theory derived from SWCC tests and direct shear tests. The variation characteristics of the soil displacement field reflect the macroscopic mechanical properties of the soil around the pile.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1998.10a
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• pp.407-413
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• 1998

Considerable progress has been made in the application of time-domain reflectrometry(TDR) to measurement of soil water content. The TDR provides a means of monitoring the water content of soil over a wide range of values, in the field and in the laboratory The TDR measures the volumetric moisture content of the soil via a bureid sensor(probe). Probes can be buried and monitored remotely and an immediate result can be obtained. In addition to, the results are very reliable.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.46 no.3
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• pp.236-240
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• 2001

The lysimeter experiment was conducted to investigate the temporal changes of irrigation requirement, soil water percolation and rice root distribution during rice growing period under different soil texture that were sandy loam, clay loam and clay paddy soil in 1999 and 2000. The irrigation requirement in the first year was 3,306 l/$m^2$ in clay loam, 2,650 l/$m^2$ in sandy loam and 2,002 l/$m^2$ in clay soil. However, the highest irrigation requirement was 5,281 l/$m^2$ in sandy loam and the next was 4,984 l/$m^2$ in clay loam and 3,968 l/$m^2$ in clay soil in the second year, Soil water percolation in the first year was 2,141 l/$m^2$ in clay loam, 1,228 l/$m^2$ in Sandy loam and 862 l/$m^2$ in clay soil. However, in the second year, the highest water percolation of 4,448 l/$m^2$ was measured in sandy loam, and was followed by 3,833 l/$m^2$ in clay loam and 2,925 l/$m^2$ in clay soil. Distribution ratio of rice roots measured in 0-10cm of soil depth was 56.0% in sandy loam, 61.4% in clay loam and 72.1% in clay soil, respectively. It was interpreted that the greater water percolation measured in the second year was caused mainly by the large amount of rice root growth. Therefore, it was concluded that the soil water percolation in rice paddy soil was affected greatly not only by soil texture but also the growth of rice root.

• Korean Journal of Soil Science and Fertilizer
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• v.41 no.6
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• pp.393-398
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• 2008

Several researchers have proposed models or equations to predict soil $CO_2$ flux from more readily available biotic and abiotic measurement. Tree commonly used abiotic variables were N mineral and soil temperature and soil water content. This study was conducted to determine $CO_2$ emission to mineral N, soil water content and soil temperature with clay loam and sandy loam in pepper cultivation in 2004~2005. $CO_2$ flux in the upland with different levels of soil water potential was measured at least once in two weeks during the cropping period in the pepper cultivation plots. Soil water potential in the clay loam and sandy loam soils was established at -30kPa and -50kPa by measuring the soil gravimetric water content with two replications. $CO_2$ emission rate from the differently managed plots was highly correlation coefficient to between the mineral N ($R=0.830^{**}$, $0.876^{**}$) and soil temperature ($r^2=0.793^{**}$, $0.804^{**}$) in the clay loam and sandy loam, respectively. However, the relationships between $CO_2$ emission and soil water content were non-significant. $CO_2$ emissions at sandy loam soils was lower to 21~37% than at clay loam soils for both soil water conditions without differences in yield. At difference levels of soil water conditions, $CO_2$ emission at -50kPa decreased to 37.5% in comparison with that at -30kPa. From the path analysis as to contribution factors of GHGs, it appeared that contribution rate was in the order of soil temperature (54.9%), mineral N (32.7%), and soil moisture content (12.4%).

• Korean Journal of Soil Science and Fertilizer
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• v.23 no.1
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• pp.8-14
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• 1990

Retardation and hydrodynamic dispersion coefficient necessary for model of water and solute movement in a soil were determined for horizontal soil column with different initial soil water conditions. The soil columns were compacted with sandy loam soil. The bulk density was $1,350+50kg/m^3$, and initial water contents were 0.05, 0.08 and 0.14. Advancement of 0.05% $CaSO_4$ solution was used as the standard and advancements of 0.5% KCl, $CaCl_2$ and $KH_2PO_4$ were compared. Retardation of non-reactive $Cl^-$ was related with the initial soil water content, ${\theta}n$, as ${\theta}/({\theta}-{\theta}n)$, and anion exclusion was ignored. Retardations of active $K^+$, $Ca^{{+}{+}}$ and $H_2PO_4{^-}$ were related as 1/(R+1) $^*{\theta}/({\theta}-{\theta}n)$, in which R was retardation coefficient. Measured R was 0.64 for $K^+$, 0.80 for $Ca^{{+}{+}}$ and 2.6 for $H_2PO_4{^-}$, respectively. Calculated R using Langmuir adsorption isotherm showed fair degree of applicability. Soil water diffusivity, $D({\theta}),m^2/sec$, calculated for different initial water content showed unique function as $$log(D({\theta}))=13.448{\theta}-9.288$$ Hydrodynamic dispersion coefficient of $Cl^-$ above soil water content 0.36 was similar to soil water diffusivity and decreased to near self diffusion coefficient at soil water content near 0.2. Those of $K^+$, $Ca^{{+}{+}}$ $H_2PO_4{^-}$ at soil water content of 0.38 were $5.5{\times}10^{-6}$, $2.4{\times}10^{-6}$ and $7.1{\times}10^{-7}m^2/sec$ and decreased rapidly with decreasing soil water content lower than 0.36.