• Korean Journal of Soil Science and Fertilizer
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• v.40 no.1
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• pp.57-63
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• 2007

Soil aggregation has been considered as an important factor not only for increasing soil productivity and soil quality but also improving nutrient use availability and water use efficiency. However, the relationship between soil aggregation and soil properties hasn't well reported for Korean soils. Objective of this research was to identify the relationship among soil water-stable aggregate (WSA), soil properties and soil dispersion ratio. Soil samples were analyzed for water-stable aggregate, Middleton's dispersion ratio, and soil physical and chemical properties. Water-stable aggregate was significantly correlated to soil textural properties, soil organic matter, and exchangeable cations. Middleton's dispersion ratio was significantly correlated with water-stable aggregate ($r=-0.76^{***}$). Regression equation for water-stable aggregate was estimated by Middleton's dispersion ratio (Y=-0.79X + 96.49; $r^2=0.58^{**}$). In this research, we conclude that water-stable aggregate was significantly correlated with some soil properties and was able to be estimated by rapid and easily measurable Middleton's dispersion ratio.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.536-539
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• 2003

This study area has been contaminated by oils. To identify contaminated ranges and to assess the possibility of contamination dispersion, monitoring wells were installed and slug test, field soil permeability test, automatic or manual measurement of groundwater table, and groundwater quality analyses in field and laboratory were performed. In addition, a groundwater modeling program was used to assess the possibility of oil contamination dispersion, based on field data and groundwater quality data. The results showed that concentration of oil contaminants in groundwater have been decreased by dispersion and adsorption.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2014.06a
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• pp.258-259
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• 2014

It is needed the introduction of a new wave dispersion relationship considering the condition of seabed to examine closely the interaction between wave and seabed. In this study, a wave dispersion relationship is newly developed considering the condition of seabed such as permeability and displacement. Wave damping rates are compared and analysed according to the various soil parameters such as seabed soil thickness, elastic modulus, saturation, permeability, and porosity.

• Geomechanics and Engineering
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• v.36 no.6
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• pp.589-599
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• 2024

Dispersion occurs when clay soil disperses under specific conditions and is rapidly washed away. While there are numerous methods for rectifying it, they are neither cost nor time-effective. The current study used metakaolin and zeolite to improve heavily dispersive clay soil either separately or in combination at 0%, 2%, 4%, 6%, and 8% of the soil weight. After 7 days of curing, the samples were tested to determine the extent of change in the dispersion potential, as well as the improvement of the geotechnical properties of the soil. The results indicated that the addition of 2% zeolite with 6% to 8% metakaolin decreased the dispersion potential considerably. Double hydrometry test findings revealed that the dispersion potential decreased by almost 70% and entered the non-dispersive group; the crumb test also revealed this. Atterberg limits testing indicated a decrease in the plasticity index which reduced the flexibility of the samples. The greatest decrease in PI (67.5%) was achieved with the addition of 8% zeolite plus 8% metakaolin to the soil. The results of density tests revealed that a decrease in the optimal moisture content increased the maximum dry density of soil. This increase in density was a response to the high reactivity of metakaolin with calcium hydroxide and the formation of calcium hydroxide hydrate gel. This eventually caused an increase in the unconfined compressive strength, the greatest increase in strength of about 1.8-fold was observed with a combination of 2% zeolite and 6% metakaolin compared to the unmodified sample.

• Journal of Soil and Groundwater Environment
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• v.8 no.3
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• pp.8-12
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• 2003

The centrifuge test result on capped sediment was compared to the advection- dispersion equation proposed for one layered to predict contaminant transport parameters. The fitted contaminant transport parameters for the centrifuge test results were one to three orders of magnitude greater than the estimated parameters from the advection-dispersion equation. This indicates that the centrifuge model over estimated the contaminant transport phenomena. Thus, the centrifuge provides a non-conservative approach to modeling contaminant transport. It should be also noted that the advection-dispersion equation used in this study is a one layered model. Two layered modeling approaches are more appropriate for modeling this data since there are two layers with different partitioning coefficients. Further research is required to model the centrifuge test using two-layered advection-dispersion models.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1997.05a
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• pp.79-82
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• 1997

토양내에서 오염유기물질이 불포화토양내에 유입될 때의 dispersion coefficient를 adsorption과 desorption과정에 대해 알아보았다. apparent dispersion coefficient를 측정하기 위해 일상적인 상대습도(46%)조건에서 parametric analysis를 행하였다. 실험에 사용된 토양은 fine sand와 silt-clay혼합시료였고, 흐름방향은 상향과 하향으로 하였다. 그리고, Freon gas를adsorbing solute로 사용하였다. 오염물질로는 DCM, TCE, DCB를 사용하였다. 분석을 위해서 linear와 probability scale의 breakthrough curve를 사용하였다. 공기에서의 diffusion coefficient의 예측을 위하여 Graham's law를 계산에 사용하였고, DCM diffusion coefficient는 0.098$\textrm{cm}^2$/s로 계산되었다. 연구결과, adsorption과 desorption의 속도는 차이가 있는 것으로 나타났으며, diffusion이 flow regime을 좌우하는 것으로 나타났다. 그리고, desorption에서의 D$^{a}$ D$^{o}$ 는 1보다 클수도 있다. 또한, dispersion은 silt-clay혼합시료에서의 속도와 함께 증가한다. dispersion은 Freon의 sorption방향에 크게 의존한다.

• Proceedings of the Korean Geotechical Society Conference
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• 1994.09a
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• pp.182-190
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• 1994

Mattress foundations using geogrids are often used on soil foundations to increase the supporting capability of a mattress-soil foundation system, in which the mattress foundation trasmits a point load applied above to a wider area of the soil foundation underneath. To examine this load dispersion capability of the mattress foundation, model experiments were carried out on lab-floor. Expecially, the effect of the thickness of the mattress and the subgrade modulus of the soil foundation on load dispersion are considered. The load distribution and the tensile force generated on geogrid of the upper part of the mattress are examined in the paper.

• Korean Journal of Soil Science and Fertilizer
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• v.13 no.2
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• pp.65-70
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• 1980

This experiment was aimed at selecting the most suitable dispersing agent to the Korean soils. The particle size distribution of 18 soil samples representing the great soil groups in Korea was analysed with 5 different dispersing agents by pipette-method. Passing percent of 0.05, 0.02 and 0.002mm in diameter was used for the comparision of the dispersion capacity of chemical agents. The results obtained are as follows; 1. The influence of chemical agents on dispersion seemed to be greater to finer soil particles. The passing percents of 0.002mm showed a great differences according to the chemical agents used, while little differences was observed in those of 0.05mm. 2. It was showed that sodium pyrophosphate had the highest dispersion capacity for the most of Korean soils, the dispersion capacity of sodium hexametaphosphate was also high enough except for volcanic ash soils. 3. It was recommendable that sodium hexametaphosphate could widely be used as a dispersing agent in the routine analysis of soil particle size distribution except for the Volcanic ash soils. 4. The dispersion of Volcanic ash soils was rather poor when chemical agents used. Therefore, special care should be taken for the dispersion of allophane soils.

• Journal of Soil and Groundwater Environment
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• v.11 no.6
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• pp.28-34
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• 2006

Laboratory column tests using $Cl^-$ tracer were conducted to study the correlation of soil particle distribution and hydrodynamic dispersion mechanism with three kinds of ununiformed soil samples, in which the ratio of gravel and sand versus silt and clay is 24.5 for S-1 soil, 4.48 for S-2 soil, and 0.4 for S-3 soil. Chloride breakthrough curves with time were fitted with gaussian functions. The relative concentrations of chloride were converged to 1.0 after 0.7 hours for S-1, 6.3 hours for S-2, and 389 hours for S-3. Average linear velocity, longitudinal dispersion coefficient, and longitudinal dispersivity were calculated by chloride breakthrough curves. Longitudinal dispersion coefficients were $1.20{\times}10^{-4}\;m^2/sec$ for S-1, $8.87{\times}10^{-7}\;m^2/sec$ for S-2, and $1.94{\times}10^{-9}\;m^2/sec$ for S-3. Peclet numbers calculated by the molecular diffusion coefficient of chloride and the mean grain diameters of soils were $2.59{\times}10^2$ for S-1, $6.27{\times}10^0$ for S-2, and $1.35{\times}10^{-4}$ for S-3. Mechanical dispersion was dominant for the hydrodynamic dispersion mechanism of S-1. Both mechanical dispersion and molecular diffusion were dominant for the hydrodynamic dispersion mechanism of S-2, but mechanical dispersion was ascendant over molecular diffusion. Hydrodynamic dispersion in S-3 was occurred mainly by molecular diffusion. When plotting three soils on the graph of $D_L/D_m$ versus Peclet number produced by Bijeljic and Blunt (2006), the values of $D_L/D_m$ for S-1 and S-2 were more than 2.0 order compared to their graph. S-3 was not plotted on their graph because the Peclet number was as small as $1.35{\times}10^{-4}$.

• Journal of the Korean Society of Clothing and Textiles
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• v.25 no.8
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• pp.1465-1474
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• 2001

The dispersion stability of particles and the adsorption of surfactant were examined as a fundamental environment to adhesion of particulate soil to fabric. The adsorption of surfactant on the PEF fabrics decreased with the addition of electrolytes and decreased with increasing the ionic strengths showed similar tendency to PET fabric. And the dispersion force of $\alpha$-Fe$_2$O$_3$particles decreased with the addition of electrolyte. The adhesion of particulate soil to fabric, increased with decreasing the adsorption of surfactant the correlation between the two was high at low ionic strength. The correlation between the adsorption of surfactants on $\alpha$-Fe$_2$O$_3$ particles and the adhesion of particles to fabric was smaller as shown in the correlation between the adsorption of surfactants on fiber substrate and the adhesion of particles on fabric. However, the correlation between the adhesion of particles to fabric and the stability of particle dispersion was relatively more significant.