• Journal of the Korean GEO-environmental Society
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• v.13 no.6
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• pp.83-90
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• 2012

Generally, the effect of the cement deep mixing method on the improvement of clay ground is far greater than the effect of physical improvement. Although it leads to great improvement strength in the initial stage, there are not many constructional precedents in Korea and it is hard to manage quality according to the cement-clay mixing method. In order to figure out the strength characteristics according to the mixing ratio of cement, sand, and clay and the improvement characteristics of weak ground according to the forms of the specimens to be improved, marine clay was used in this study to conduct the uniaxial compression test and soil bin model test. The test piece specimens for the uniaxial compression test were mixed with sand in a fixed ratio with the criterion of the water cement ratio. The cement was mixed with clay in the ratios of 10%, 20%, 30%, and 40% to the clay weight. The moisture content of the soil ground was made in the ratios of 40%, 60%, and 80%. The test piece specimens went through curing by moistening for 7, 14, and 28 days and underwent the uniaxial compression test according to the curing period. For the bearing test, the soil bin models were made and the ground improved in the Mat type was formed. After that, the bearing strength was compared in this study according to the improvement ratio and analyzed the intervening effect between the walls of the improved specimens.

• The Journal of Engineering Geology
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• v.32 no.4
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• pp.559-569
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• 2022

This study investigated the acidification and mixing with seawater of groundwater, stream water, and reservoir water in the Hunghae area of Pohang City, as well as the source of water expelled to the stream by liquefaction induced by the Pohang earthquake on 15 November 2017. Geologically, the area consists of Tertiary sedimentary rocks. We collected six samples of groundwater, five of reservoir water, four of stream water, two of liquefaction water, and one of seawater to analyze the chemical composition and stable isotopes (𝛿D and 𝛿¹⁸O). Gogkang Stream flows eastward through the central part of the study area into the East Sea. The groundwater and reservoir water in the lower part of the stream are acidic (pH < 4), have a Ca(Mg)-SO₄ composition, and high concentrations of Al, Fe, and Mn, likely due to the oxidation of pyrite in Tertiary rocks. The groundwater in the upper part of the stream have a Ca(Na)-HCO₃(Cl) composition, indicating the mixing of seawater with the stream water. The 𝛿D and 𝛿¹⁸O isotope data indicate the isotopic enrichment of reservoir water by evaporation. Based on the chemical and isotopic data, it is inferred that the two samples of liquefaction water originated from alluvium water in a transition zone with stream water, and from deep and shallow groundwaters that has been infiltrated by seawater, respectively.

• Journal of Bio-Environment Control
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• v.30 no.4
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• pp.287-294
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• 2021

In order to expand facility agriculture and reduce greenhouse construction costs in reclaimed land, a greenhouse foundation method that satisfies economic feasibility and structural safety at the same time is required. As an alternative, the allowable bearing capacity and settlement were reviewed when the DCM(Deep cement mixing) method was applied among the soft ground reinforcement methods. To examine the applicability of the greenhouse foundation, the allowable bearing capacity and settlement were calculated by applying the theory of Terzaghi, Meyerhof, Hansen, and Schmertmann. In case of the diameter of 800mm and the width and length of the foundation of 4m, the allowable bearing capacity was 179kN/m² and the settlement was 7.25mm, which satisfies the required bearing capacity and settlement standards. The calculation results were verified through FEM(Finite element method) analysis using the Mohr-Coulomb material model. The allowable bearing capacity was 169kN/m² and the settlement was 2.52mm. The bearing capacity showed an error of 5.6% compared to calculated value, and the settlement showed and error of 65.4%. Through theoretical calculations and FEM analysis, it was confirmed that the allowable bearing capacity and settlement satisfies the design criteria as a greenhouse foundation when the width and length of the foundation were 4m. Based on the verified design values, it is expected to be able to present the foundation design criteria for greenhouses through empirical tests such as bearing capacity tests and long-term settlement monitoring.

• Journal of the Korean GEO-environmental Society
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• v.13 no.1
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• pp.5-13
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• 2012

For the last decade the amount of waste has rapidly been increased in South Korea and many waste landfills have been built according to government guidelines specifying required systems such as landfill liner, leachate collecting facilities, final cover system, etc. This effort has led the recently constructed landfills to be under well managed sanitary condition. In a meanwhile closed waste-landfill sites in the past before the adoption of the government guidelines exits under unsanitary condition. In these cases untreated leachate flew out to the surroundings due to the absence of liner and leachate collecting facilities and caused groundwater and soils to be contaminated. Waste generated odor and gas also brought civil complaints. Because environmental influences bring serious problems nearby sites, it is required to have unsanitary waste-landfills to be appropriately treated and managed. A study to evaluate environmental influence and contamination level of surroundings nearby and on the unsanitary landfills is necessary before the establishment of "Management guide of closed landfill site." This paper presents an environmental evaluation for the closed site, Doil-dong landfill, according to "Closed landfill management regulation" by Ministry of Environment. "D" landfill, located in Pyeongtaek city, has possobility to contaminate surrounding surfacewater and groundwater by leakage of leachate. The in-situ stabilization carried out to build the DMW(deep soil mixing cutoff wall) wall and drainage systems.

• Journal of Soil and Groundwater Environment
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• v.10 no.6
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• pp.45-55
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• 2005

The geothermal research has been carried out on the Heunghae, Pohang geothermal area know as having geo-heat-flow area in the Korean peninsula. This study results so far indicate that geothermal water in the area is in peripheral waters of hydrothermal area and is not in equilibrium with the reservoir rock. The average oxygen and hydrogen stable isotope values are as follows: deep groundwater $(average:\;{\delta}^{18}O=-10.1\%_{\circ},\;{\delta}D=-65.8\%_{\circ})$, intermediate groundwater (average: $(average:\;{\delta}^{18}O=-8.9\%_{\circ},\;{\delta}D=-59.6\%_{\circ})$, shallow groundwater $(average:\;{\delta}^{18}O=-8.0\%_{\circ},\;{\delta}D=-53.6\%_{\circ})$, surface water $(average:\;{\delta}^{18}O=-7.9\%_{\circ},\;{\delta}D=-53.3\%_{\circ})$ respectively. Deep groundwaters was originated from a local meteoric water recharged from distant, topographically high mountain region and not affected by the sea water. High temperature zone inferred from water geothermometers is around D-1, D-5, D-6, 1-04 well zones. The estimated enthalpy from Silica-enthalpy mixing model is near 410 kJ/kg, which corresponds to the temperature of $98^{\circ}C$, and in consistent with the result of Na-K and K-Mg geothermometer.

• The Journal of Engineering Geology
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• v.26 no.4
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• pp.551-559
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• 2016

The chemical composition and noble gas isotopes of 10 deep groundwater samples were analyzed to know the circulation of groundwaters in the Yangsan fault and the Gampo fault. The chemical types of groundwaters show the $Ca-HCO_3$ type and $Ca-SO_4(Cl)$ type, and show indistinct relationship with geology. Noble gas isotopic data of most groundwaters were plotted along the air-crust mixing line on $^3He/^4He$ vs. $4^He/^{20}Ne$ diagram, and show dominant $^3He$ of air origin except one sample that shows helium mixing of crust origin. This indicates that groundwater actively circulates along fault, and fault could not play an role of upward pathway of a deep-seated helium gas. A comparatively high $^4He$ indicates that groundwater flows in an aquifer assuring relatively enough water-rock interaction.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.4 no.4
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• pp.365-372
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• 2006

A dynamic compartment model is presented to predict the contamination level of agricultural plant by $^{137}C_s$ as a result of a soil deposition. The model considered the processes of a percolation, soil mixing by a plowing before transplanting, plant uptake, leaching to a deep soil, and fixation to a clay mineral. The effects of the soil properties (pH, clay mineral, organic matter content, and exchangeable K), which are spatially varied, on a plant uptake and the leaching rates of $^{137}C_s$ in a root zone soil were modeled by the Absalom model. To test the validity of the model, the $^{137}C_s$ aggregated transfer factors(TFa) for rice plants were compared with those observed from some simulated $^{137}C_s$ soil deposition experiments, which were carried out with respect to rice plants cultivated in seventeen paddy soils of different properties for two consecutive years. Observed $^{137}C_s$ TFa values of the rice plants did not show an evident trend for the pH and clay content of the soil properties, while they increased with an increasing organic matter content or a decreasing exchangeable K concentration. Predicted $^{137}C_s$ TFa values of the rice plants were found to be comparable with those observed.

• Journal of the Korean Geosynthetics Society
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• v.17 no.4
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• pp.53-64
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• 2018

In this study, the evaluation to probability of failure for risk assessment of port structures on DCM reinforced soils, where stability and risk assessment are increasing in importance, was performed. As a random variables affecting the risk of DCM improved ground, the design strength, superposition (overlap) of construction, strength of the natural ground, internal friction angle and unit weight of the modified ground were selected and applied to the risk assessment. In addition, the failure probability for the entire system under ordinary conditions and under earthquake conditions were analyzed. As a result, it was found that the highest coefficient of variation in the random variable for the risk assessment of the DCM improved ground is the design strength, but this does not have a great influence on the safety factor, ie, the risk of the system. The main risk factor for the failure probability of the system for the DCM reinforced soils was evaluated as horizontal sliding in case of external stability and compression failure in case of internal stability both at ordinary condition and earthquake condition. In addition, the failure probability for ordinary horizontal sliding is higher than that for earthquake failure, and the failure probability for ordinary compression failure is lower than that for earthquake failure. The ordinary failure probability of the entire system is similar to the failure probability on earthquake condition, but in this case, the risk of earthquake is somewhat higher.

• Korean Journal of Soil Science and Fertilizer
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• v.14 no.3
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• pp.130-136
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• 1981

Rice hull was reduced to ash by carbonization grades to illcuidate alkalinity increase and extract of inorganic nutrients in the rice hull charcoal. Alkaline reaction of water extraction was neutral at less carbonized charcoal, but much carbonized ash from 65% weight loss reached over 10 of pH value, also origin shape of rice hull was maintained until near 65% carbonized grade. Therefore, physical properties sustained good condition for seedling bed. The more charcoal carbonized to ash, the pH value and concentration of inorganic nutrient in their extracts were increased gradually. Nitric acid concentrations for neutralizing extract from charcoal were stronger in proportion to the carbonized grade but 0.1 N nitric acid solution was very reasonable to neutralize the 65% carbonized charcoal for mixing with heavy texture acidy soil(pH 5.3) of uncultivated deep horizon to transplant the tobacco seedlings. Volume ratio mixing for seedling bed is adequate at five of ash to one of acid solution. Neutralization with nitric acid solution also accelerated extraction of the inorganic nutrient in rice hull ash. Tobacco seedlings grown on bed mixed with neutralized rice hull charcoal and soil had shown better results on the agronomic measurement than alkaline ash bed, and phosphorus and cations were uptaken more amounts.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.1
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• pp.29-33
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• 1999

Transition metallic $Cr^{3+}$ ion was diffused in white sapphire {0001}, ${10\bar{1}0}$ crystal plane which were grown by the Verneuil, it enhanced and changed the physical, electrical and optical properties of sapphires. After mixing the metallic oxide and metal powder, it were used for diffusion powder. When it was used the mixing powder of metal and metallic oxide, the dopping was slowly progressed and it needed the longer duration time and higher temperature, relatively. Metallic powder was vapoured under $1{\times}10^{-4}$ torr of vacuum pressure at $2050^{\circ}C$, first step, it were kept by the diffusion condition of 6 atm of $N_{2}$ accelerating pressure at $2050~2150^{\circ}C$. Each surface density of sapphire crystal are 0.2254(c) and $0.1199\;atom/{\AA}^2(a)$. The color of the Cr-doped sapphires was changed to red. Dopping reaction was come out more deep in the plane of ${10\bar{1}0}$ than {0001}. It was speculated that the planar density was one of the factors to determine diffusion effect.