• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.1
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• pp.183-194
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• 2004

It's essential process to study non-linear material function related to characteristics of compressibility and permeability when we predict the consolidation behavior of soft clay ground. In this study, laboratory tests were conducted to find out the material function using marine clay. Standard oedometer test and Rowe cell test were performed with conditions, which were classified into vertical drainage only, radial drainage only and vertical-radial drainage case. Modified oedometer test equipment was developed to find out the material function and special extrusion device was originated to minimize the sample disturbance effect. Reliability of the results in modified oedometer test could be confirmed by comparing with the Rowe cell's one. Effective stress - void ratio - permeability relations were analyzed using all testing results. As a result, void ratio with effective stress level could be expressed by the power function and permeability with void ratio could be expressed by exponential function. In soft clay with high initial water content and low shear strength, non-linear characteristics related to compressibility and permeability varied with wide range by the effective stress levels. It's important to note that non-linearity of the material function should be considered at prediction of the consolidation behavior.

• Journal of the Korean GEO-environmental Society
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• v.25 no.6
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• pp.19-24
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• 2024

Urban densification has necessitated the development of subterranean spaces such as subway networks and underground tunnels to facilitate the dispersal and movement of populations. Development of these underground spaces requires excavation from the ground surface, which can induce groundwater flow and potentially lead to ground subsidence and sinkholes, damaging structures. To mitigate these risks, it is essential to model groundwater flow prior to construction, analyze its characteristics, and predict potential groundwater discharge during excavation. In this study, we collected meteorological, topographical, and soil conditions data for the city of ○○, where tunnel construction was planned. Using the Visual MODFLOW program, we modeled the groundwater flow. Excavation sections were set as drainage points to monitor groundwater discharge during the excavation process, and the effectiveness of seepage control measures was assessed. The model was validated by comparing measured groundwater levels with those predicted by the model, yielding a coefficient of determination of 0.87. Our findings indicate that groundwater discharge is most significant at the beginning of the excavation. Additionally, the presence of seepage barriers was found to reduce groundwater discharge by approximately 59%.

• Journal of Korean Society of Forest Science
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• v.81 no.1
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• pp.30-39
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• 1992

Artificial acid rain(pH2.0, 3.0, 4.0 and 5.0) was treated on the seeded pots of 4 species to examine its effects on germination, leaf injury and seedling growth. Aluminum ammonium sulfate solution (0.5, 1.0 and 2.5mM) and artificial acid rain (pH3.0, 4.0 and 5.0) were treated on the seeded germinators of 3 species to examine its effects on germination and radicle growth. Artificial acid rain was prepared by diluting sulfuric acid with ground water and ground water(pH6.5) was used as control. Artificial acid rain was sprayed to seeded pots three times per week. About 5mm of artificial acid rain was treated each time from early April to early October, 1991. Germination, seedling establishment, radicle growth, leaf injury and seedling growth were measured and compared among the treatments. The results were summarized as follows 1. Germination, seedling establishment rate of Pinus densiflora were highest on the pH5.0 pot whereas those of Ailanthus altissima was highest on the control pot, and those of Magnolia sieboldii showed the highest value on the pH3.0 pot. 2. The differences in seedling height of Pinus densiflora and Pinus rigida were significant among the treatment levels of acid rain, whereas those of Magnolia sieboldii and Ailanthus altissima were not significant. Seedling heights of Pinus densiflora and Pinus rigida were highest on the pH3.0 pot, and that of Magnolia sieboldii was highest on the pH4.0 pot, and that of Ailanthus altissima was highest on the control pot. 3. Seedling dry weights of Pinus densiflora. Pinus rigida, and Ailanthus altissima differed significantly among the treatments, but that of Magnolia sieboldii did not differ. Highest seedling dry weights of Magnolia sieboldii and Ailanthus altissima were observed on the pH4.0 pot, and that of Pinus densiflora was observed on the pH3.0 pot, and that of Pinus rigida was observed on the pH5.0 pot. 4. With decrease of pH value of artificial acid rain, the number of injured needle and injured individual tended to be increased. 5. The differences in effects of soil acidity were highly significant among the treatments for all species. 6. Radicle growth of Pinus densiflora differed significantly among pH levels and aluminum concentrations.

• Journal of Wetlands Research
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• v.17 no.2
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• pp.184-192
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• 2015

This study is a basic research for low maintenance constructed wetlands which can prevent water quality deterioration due to wetland soils. The purpose of this study is to analyze water quality control mechanisms of constructed wetland on the artificial ground which installed the modular revetment structure(MRS), a device that separates water and soil. This study was then conducted with two different wetland mesocosms (a treatment plot and a control). These mesocosms were monitored to analyze effects of water quality control of the MRS. A treatment plot was built, and separated into soil and water, by filling the MRS with the decomposed granite soil in the mesocosm made of rubber material. A control plot was built where the decomposed granite soils were exposed to water by leaving the soil on the bottom of the mesocosm made of rubber material. Water quality was then analyzed by using Kolmogorov-Smirnov Z examination which then showed that pH, BOD, SS, Chl-a, T-P, T-N had statistically valid difference between a container with the MRS and one without it. According to the analysis of the water quality, the temperature and the EC level came out similarly and both mesocosm showed same level on pH and DO. A treatment plot had higher levels of BOD, SS Chl-a, and T-P. A control plot's T-N value was little lower than that of the treatment plot. This study suggests method of constructed wetlands using the MRS prevents problems occurring in wetland soils: aridity of wetlands by soil erosion, eutrophication, and algal blooms due to nutrients released from wetland soil. These functions of constructed wetland with the MRS increase aesthetic, ecologic, social, and economic value of the wetland. Outcomes of this research will later enable more proficient way of stabilizing water quality and provide data for planning low maintenance constructed wetlands.

• Journal of the Korea Concrete Institute
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• v.29 no.3
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• pp.307-314
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• 2017

Concrete is a durable and cost-benefit construction material, however performance degradation occurs due to steel corrosion exposed to chloride attack. Penetration of chloride ion usually decreases due to hydrates formation and reduction of pores, and the reduced chloride behavior is considered through decreasing diffusion coefficient with time. In the work, HPC (High Performance Concrete) samples are prepared with 3 levels of W/B (water to binder) ratios of 0.37, 0.42, and 0.27 and 3 levels of replacement ratios of 0%, 30% and 50%. Several tests containing chloride diffusion coefficient, passed charge, and compressive strength are performed considering age effect of 28 days and 180 days. Chloride diffusion is more reduced in OPC concrete with lower W/B ratio and GGBFS concrete with 50% replacement ratio shows significant reduction of chloride diffusion in higher W/B ratio. At the age of 28 days, GGBFS concrete with 50% replacement ratio shows more rapid reduction of chloride diffusion than strength development, which reveals that abundant GGBFS replacement has effective resistance to chloride penetration even in the early-aged condition.

• Journal of the Korean Society of Food Culture
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• v.13 no.5
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• pp.509-518
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• 1998

The purpose of this study was to develop korean traditional gruel 'Hodojook' as a easy-to cook product by modifying cooking method and its concentrations. Physical and sensory properties of 'Hodojook' with various levels of concentration were investigated using viskograph and sensory evaluation panel. The result showed that hydrated rice flour has higher maximum viscosity than instantly ground rice. Addition of walnut lowered maximum viscosity and gelatinization beginning temperature. But gelatinization pattern was not affected by the level of walnut and modified cooking method. Sensory characteristics on the roasted odor, roasted taste, oily odor, oily taste and viscosity were significantly increased as the walnut levels are increased. 'Hodojook' of' with the 1:1:6 ratio (rice flour walnut : water) was recommended.

• Korean Journal of Soil Science and Fertilizer
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• v.50 no.5
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• pp.357-368
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• 2017

To establish new metal groundwater standard, 5 metals such as aluminum, chromium, iron, manganese, and selenium were evaluated by Chemical Ranking Of groundWater pollutaNts (CROWN) including possibility of exposure, toxicity, interest factor, connection standard for other media, and data reliability. 430 groundwater samples in 2013 and 2014 were collected semiannually from 110 groundwater wells and they were analyzed for selenium, manganese, iron, chromium, and aluminum. For this study, 430 groundwater samples were categorized into 3 geological distribution features, such as igneous, metamorphic, and sedimentary rock region and geological background levels were divided by pre-selection methods. For the results, the average concentrations of aluminum, chromium, iron, manganese, and selenium in 430 groundwater samples were $0.0008mg\;L^{-1}$, $0.0001mg\;L^{-1}$, $0.174mg\;L^{-1}$, $0.083mg\;L^{-1}$, and $0.0004mg\;L^{-1}$, respectively. In addition, among various geologies, average concentration of selenium was the highest in igneous rock region, average concentrations of chromium, manganese and aluminum were the greatest in sedimentary rock region, and average concentration of iron was the most high in metamorphic rock region. As a result of the geological background concentration with pre-selection method, background concentrations of selenium and aluminum in groundwater samples were the highest from sedimentary rock as $0.0010mg\;L^{-1}$ and $0.0029mg\;L^{-1}$ and background concentrations of manganese and iron in groundwater samples were the greatest from metamorphic rock as $0.460mg\;L^{-1}$ and $1.574mg\;L^{-1}$, and no chromium background concentration in groundwater samples was found from all geology.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.67 no.4
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• pp.296-304
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• 2022

To maximize the medicinal properties of bellflower root (Platycodi radix), its growth and development according to soil texture were investigated using four types of soil: masato (decomposed granite), soil mix, loamy sand, and sandy loam. Saponin content was measured. With regard to bellflower root growth depending on soil texture, its growth was better in the order of loamy sand > sandy loam > soil mix > masato in the above-ground part, and loamy sand > soil mix > sandy loam > masato in the underground part in the order. The average content of general ingredients were 77.3% water, 2.6% crude fat, 3.2% crude flour, 6.0% crude protein, and 10.9% carbohydrates. With respect to saponin analysis of bellflower roots, the saponin content regarding platycodin D, platycodin D3, polygalacin D, and deapioplatycodin D were higher in the order of 282.4, 104.7, 29.1, 19.1 mg/100 g, respectively. The content of organic matter and phosphoric acid was high in soil mix and sandy loam, and platycodin D3 showed similar levels in all soil types. As a result, the soil mix is considered most suitable in terms of yield and component levels, however, it is the most expensive type. As a replacement, sandy loam was adequate in terms of fresh weight related to yield and highest saponin content.

• Journal of the Korean Geotechnical Society
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• v.23 no.3
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• pp.5-13
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• 2007

The performance of innovative prestressed support (IPS) earth retention system applied in soft clay was investigated and presented. The IPS wale system provides a high flexural stiffness to resist the bending by lateral earth pressure, and transfers lateral earth pressure to strut supports. The IPS wale system provides a larger spacing of support than conventional braced and anchored systems. The IPS earth retention system was selected for temporary earth support in a building construction in North Busan area. The excavation was made 28.8 m wide, 52.0 m long, and 16.1 m deep through loose fill to soft clay. The IPS system consists of 650 mm thick slurry walls, and five levels of IPS wales and struts. Field monitoring data were collected including wall deflections at six locations, ground water levels at four locations, IPS wale deflections at thirty locations, and axial loads on struts at twenty locations, during construction. The IPS earth retention system applied in soft clay performed successfully within a designed criterion. Field measurements were compared with design assumptions of the IPS earth retention system. The applicability and stability of the IPS earth retention system in soft clay were investigated and evaluated.

• Journal of the Korean Geosynthetics Society
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• v.14 no.4
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• pp.59-77
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• 2015

In order to meet the new requirements for landfill materials, this study planned a study to apply mixed soil of mixing bottom ash and coastal dredged soil to the dredged ground. Coal ash generated from thermal power plant is divided into fly ash and bottom ash. In the case of fly ash, many studies have been conducted because small particles causes permeability coefficient to be small during recycling so no problem has been raised in the environmental area but the utilization of bottom ash has been limited because environmental problems have been raised during recycling due to its larger particle size and greater permeability coefficient. According to recently published studies, however, the results of the study that conducted the water analysis of leachate generated in the ground improvement section using bottom ash showed that heavy metal contamination levels were found to be within the reference value and no significant environmental problems were found so utilization of bottom ash is evaluated to increase significantly in the future. This bottom ash has the particle size of sand and only transportation costs need to be considered when providing materials because the majority has been disposed and it is judged as the most suitable material in dredging landfill in the economic aspect because most thermal power plants are located in the coast and transportation costs can be reduced by ship. Also, research on mixed soil that can maximize the effect of the construction period and construction cost savings than dredged soil is determined as needed because the demand for coastal dredging reclamation is increasing such as Saemangeum project etc. Therefore, we studied self-weight consolidation characteristics depending on sample processing and mixing method of mixed soil by carrying out interior self-weight consolidation experiments on mixed soil of mixing bottom ash and Kaolinite according to the new development needs of recent coastal reclaimed ground and these result findings are expected to be used as basic data when applying the large coastal dredged ground in the future.