• Korean Journal of Soil Science and Fertilizer
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• v.49 no.6
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• pp.807-812
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• 2016

Soil amendment, especially addition of clay minerals, has been widely conducted to improve the physical and chemical properties of cultivated soils. However, there are no systematic studies on the effects of the structural type of clay minerals added. This study was conducted to investigate the effects of structural type of clay minerals on physical properties of soils. Two experimental soils, layer-dominant and granule-dominant ones, were mixed with either a layer-type smectite or a granule-type zeolite at a level of 2.0 wt%. It was observed that water permeability of soils was decreased by smectite whereas not significantly changed by zeolite. This effect was much greater in layered clay-dominant soil than in granular clay-dominant soil. Our results clearly indicated that the relationship of structural type between a soil and an amendment plays a decisive role in the soil properties. Therefore, it is highly recommended that the structural types of both soil and amendment be taken into consideration for soil amendment by clay minerals.

• Magazine of the Korean Society of Agricultural Engineers
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• v.27 no.2
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• pp.57-71
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• 1985

The characteristics of compaction and unconfined compressive strength were investigated by mixing with lime to all soils adjusted by given percentages of two kinds of clays to sand to obtain the most effective distribution of grain size and the optimum lime content for soil stabilization. In addition, unconfined compressive strength and durability tested by adding of sodium metasilicate, sodium sulfate, sodium carbonate, sodium gydroxide and magnesium oxide to lime-soil mixture mixed with 8 percent lime to adjusted soil having the mixing percentage of 60 percent of cohesive black clay and 40 percent of sand by weight to get the effect and the optimum content of chemicals. The results obtained were as follows; 1.With the addition of more lime, the optimum moisture content was increased, and the maximum dry density was decreased, whereas the more the amount of clay and the less was the maximum drt density. 2. In the soil having more fine grain size the unconfined compressive strength was larger in the earlier stage of curing period, in accordance with the longer period, the mixing percentages of sand to clay showing the maximum unconfined compressive strength, on the basis of 28-day strength, were 60% : 40% (black clay) and 40% : 60% (brown clay) respectively. 3. The reason why the soil adjusted with black clay was remarkably bigger in the unconfined compressive strength than ones adjusted with brown clay for all specimen of lime-soil mixture was the difference in the kind of clay, the amount of chemical compositions the value of pH. Black clay was mainly composed of halloysite that reacted with lime satisfactorily, whereas the main composition of brown clay was kaolinite that was less effect in the enhance of unconfined compressive strength. Also the difference of unconfined compressive strength was because black clay was larger in the amount of composition of calcium oxide and magnesium oxide in the value of pH affecting directly on the unconfined compressive strength of lime-soil mixture than brown clay. 4. In the lime-soil mixture mixed with 8 percent of lime to soil that mixing percentage of sand to black clay was 60% : 40%, on the standard of 7-day strength, the effect of chemical was arranged in the order of magnesium oxide, sodium carbonate, sodium sulfate, sodium hydroxide and sodium metasilicate. 5. The optimum amount of chemical being applicable to the maximum unconfined compressive strength of lime-chemical-soil mixture was 1 percent by weight for air dry soil in the case of adding sodium carbonated and 0.75 percent on sodium hydroxide, the unconfined compressive strength was increased continuously with increase of the amount of chemical up to 2 percent of chemical content is the lime-chemical-soil mixture added sodium metasilicate, sodium sulfate and magnesium oxide. 6. It was considered that the chemical played and accelerant role of early revelation of strength because the rate of increase of unconfined compressive strength of all of lime-chemical-soil mixtures was largest on the 7-day cured specimen. 7. The effect of test on freezing and thawing after adding suitable amount of chemical on the lime-soil mixture mixed with 8 percent of lime to soil that mixing percentage of sand to black clay was 60% : 40% was arranged in the order of magnesium oxide, sodium carbonate, sodium sulfate, sodium metasilicate and sodium hydroxide.

• Korean Journal of Agricultural Science
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• v.43 no.3
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• pp.353-359
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• 2016

Soil organic carbon (SOC) retention has gradually gotten attention due to the need for mitigation of increased atmospheric carbon dioxide and the simultaneous increase in crop productivity. We estimated the statistical maximum value of soil organic carbon (SOC) fixed by clay content using the Korean detailed soil map database. Clay content is a major factor determining SOC of subsoil because it influences the vertical mobility and adsorption capacity of dissolved organic matter. We selected 1,912 soil data of B and C horizons from 13 soil series, Sangju, Jigog, Jungdong, Bonryang, Anryong, Banho, Baegsan, Daegog, Yeongog, Bugog, Weongog, Gopyeong, and Bancheon, mainly distributed in Korean upland. The ranges of SOC and clay content were $0-40g\;kg^{-1}$ and 0 - 60%, respectively. Soils having more than 25% clay content had much lower SOC in subsoil than topsoil, probably due to low vertical mobility of dissolved organic carbon. The statistical analysis of SOC storage potential of upland subsoil, performed using 90%, 95%, and 99% maximum values in cumulative SOC frequency distribution in a range of clay content, revealed that these results could be applicable to soils with 1% - 25% of clay content. The 90% SOC maximum values, closest to the inflection point, at 5%, 10%, 15%, and 25% of clay contents were $7g\;kg^{-1}$, $10g\;kg^{-1}$, $12g\;kg^{-1}$, and $13g\;kg^{-1}$, respectively. We expect that the statistical analysis of SOC maximum values for different clay contents could contribute to quantifying the soil carbon sink capacity of Korean upland soils.

• Advances in environmental research
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• v.4 no.3
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• pp.197-210
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• 2015

Hexavalent chromium [Cr (VI)] adsorption on lateritic soil and lateritic soil blended with black cotton (BC) soil, marine clay and bentonite clay were studied in the laboratory using batch adsorption techniques. In the present investigation the natural laterite soil was blended with 10%, 20% and 30% BC soil, marine clay and bentonite clay separately. The interactions on test soils have been studied with respect to the linear, Freundlich and Langmuir isotherms. The linear isotherm parameter, Freundlich and Langmuir isotherm parameters were determined from the batch adsorption tests. The adsorption of Cr (VI) on natural laterite soil and blended laterite soil was determined using double beam spectrophotometer. The distribution coefficients obtained were 1.251, 1.359 and 2.622 L/kg for lateritic soil blended with 10%, 20% and 30% BC soil; 5.396, 12.973 and 48.641 L/kg for lateritic soil blended with marine clay and 5.093, 8.148 and 12.179 L/kg for lateritic soil blended with bentonite clay respectively. The experimental data fitted well to the Langmuir model as observed from the higher value of correlation coefficient. Soil pH and iron content in soil(s) has greater influence on Cr (VI) adsorption. From the study it is concluded that laterite soil can be blended with clayey soils for removing Cr (VI) by adsorption.

• 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.

• Proceedings of the Korean Geotechical Society Conference
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• 1997.10a
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• pp.19-36
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• 1997

This paper discusses the reduction and subsequent recovery and increase of shear strength of clay in the vicinity of soil-cement column. Laboratory and field tests were conducted to investigate the effects on surrounding clay during and after soil-cement column installation in soft Ariake clay. Discussions were made on the mechanism of strength changes of clay by considering the thixotropic recovery, reconsolidation effect, penetration of cement slurry and diffusion of exchangeable cations. On the basis of field and laboratory observations, 10 days after column installation, the decreased shear strength of surrounding clay during mixing was recovered and 30 days later, shear strength of surrounding clay increased 30% by average. Therefore, it is recommended that the increase of shear strength of clay can be taken into consideration in the bearing capacity and stability analysis of the composite ground.

• Korean Journal of Soil Science and Fertilizer
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• v.37 no.5
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• pp.293-303
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• 2004

This experiment was conducted to investigate the direction or orientation of clay particle movement in argillic horizons (Bt) for clarifying the soil classification of soils. Soil samples were collected from 22 soil series containing Bt horizons. Physical and chemical characteristics and mineral and chemical compositions of clay in the soils were analyzed. Micoromorphological characteristics of the Bt horizons were also investigated with thin sections of the natural undisturbed and oriented soil samples. Average clay content in the Bt horizons was 28% and 1.33 times higher comparing to that in the surface layer. Soil pH was higher, but cation exchange capacity (CEC) and organic matter content were lower in Bt horizon than those in the surface layer. There was an evidence of clay accumulation in Bt horizons of all soil series examined except Bangog series. Although there was an increase of clay content in the horizons in Bangog series, the clay was not originated from illuviation process. The translocation of clay was in the order of an 2:1 expandable clay minerals > 2:1 non-expandable clay minerals > 1:1 clay minerals. The illuvial substances in argillic horizon were composed with clay, amorphous iron and opaque mineral. The micoromorphological features of Bt horizon were void coating, channel infilling and grain coating. There was an apparent boundary between clay coating and the groundmass in residuum and colluvium, but Bt horizon of alluvium was composed of a skew plane amputated by the physical operation.

• Journal of Ginseng Research
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• v.9 no.1
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• pp.36-41
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• 1985

The study was conducted to investigate the changes of soil physico-chemical properties between soils of preplanting fields and 2 years old ginseng fields, and compare the missing plant rate among the 2 years 016 ginseng fields. 1, The missing plant rate of 2 years old ginseng was high in sand loam while low in clay loam soil texture, soil porosity and NO3-N were remarkably increased in 2 years old ginseng field than preplanting soil, as the clay content was increased, soil porosity seemed to be increased but exchangeable nitrogen decreased. 2. The preplanting soil management methods did not significantly influenced on the missing plant rate and soil porosity in 2 years old ginseng fields, However NO3-N content and Fusarium density seemed to be decreased as the plow frequency was increased, exchangeable nitrogen content, whereas, seemed to be increased with more organic matter. 3. Differences of clay content (below 15% and above 20% of clay content) was significantly influenced on soil porosity, bulk density, total nitrogen, organic matter and P2O5 content. 4, Missing rate showed negative correlation with clay, soil moisture, and organic matter content but positive corelation with NO3-N in 2 years old ginseng fields.

• Asian Journal of Turfgrass Science
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• v.5 no.2
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• pp.87-94
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• 1991

This study was carried out to determine the optimal seeding rate of Korean lawngrass in three different soil textures. The results obtained are summarized as follows;1.In early development, there were not significant differences in leaf length and width except for leaf width in mean seeding rates. And there was significant difference in tillering number. Tillering number of Korean lawngrass grown in sandy clay loam soil was more abudant than that grown in sandy clay and sandy loam soils.2.The rate of ground cover of Korean lawngrass grown in sandy clay loam soil was faster than that in other soils. The ground cover rate was faster in the following order: 15, 12, 10, 7, 5, 3 kg/10a. But in sandy clay loam soil, it was showed that the plot seeded at 12kg/10a be faster than that at l5kg/10a. Plots seeded from 5 to 15kg/10a in sandy clay loam soil and 15kg/10a in sandy clay soil were showed the 100% ground cover during the period of the year seeded.3.There were not significant differences in dry weight of each part measured at 11 and l4months after seeding. But there were significant differences in dry weight of shoot and total dry weight. Total and shoot dry weight of Korean lawngrass grown in sandy clay loam soil were heavier than that in others. 4.It was revealed that the optimal seeding rate in sandy clay loam soil was 12 kg/10a. But it was suggested that the optimal seeding time and rate in each soil textures be undertaken in future.

• Geomechanics and Engineering
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• v.20 no.6
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• pp.505-516
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• 2020

In recent years, Nano-technology significantly invaded the field of Geotechnical engineering, particularly in soil stabilisation techniques. Stabilisation of weak soil is envisioned to modify various soil characteristics by the addition of natural or synthetic materials into the virgin soil. In the present study, laboratory experiments were executed to investigate the influence of nano-silica particles in the consistency limits, compressive strength of the soft clay blended with cement. The results revealed that the high compressibility behaviour of soft clay modified to medium-stiff condition with fewer dosages of cement and nano-silica. The mechanism behind the strength development is verified with the previous researches as well as from Fourier Transform Infrared spectroscopy (FTIR), X-ray diffraction test (XRD) and Scanning Electron Microscopy (SEM) analysis. Based on the results, the presence of nano-silica in soft clay blended with cement has a positive effect on the behaviour of soil. This technique proves to be very economical and less detrimental to the environment.