• 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.

• Journal of the Korean Geosynthetics Society
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• v.19 no.1
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• pp.25-33
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• 2020

To improvement the swelling characteristics of the existing cutoff wall against the moisture, the permeability of the sand, calcium bentonite and solidifier mixture according to the contact with trichloroethylene (TCE) was evaluated. Characteristics analysis and the permeability test of the research materials were performed. The permeability was decreased as the mixing ratio of the calcium bentonite was increased and it was increased as the mixing ratio of the solidifier was increased. In conclusion, when mixing 15% of calcium bentonite and more than 30% of solidifier, the permeability coefficient in the underground water movement was analyzed as more than α × 10^-4 cm/sec showing that it does not block the underground water movement. In addition, as the permeability coefficient of mixtures after TCE reaction was analyzed as less than α ×10^-7 cm/sec, it satisfied the condition of blocking layer (less than 1.0 × 10^-6 cm/sec). Therefore, the calcium bentonite and solidifier can be utilized as barrier that showing the characteristic of percolation ability conversion in soil and underground water contaminated with TCE.

• Journal of the Korea Concrete Institute
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• v.17 no.4 s.88
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• pp.569-579
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• 2005

An investigation for long-term strength characteristics of crushed sand concrete using crushed sands produced in Yang-san, Kim-hae and Jin-hae that can be assumed to respectively represent eastern, middle and western suburbs of Busan has been carried out. Concrete is composed of 70~80% of aggregates in whole volume so the effect of aggregates quality to the characteristics of concrete is very important. Since 1980s, aggregates used in concrete have already been substituted crushed stone because of the exhaustion of natural gravel and sand. Crushed sand tends to increase in using quantity because of the prohibition of sea sand picking and deterioration of river sand. Crushed sand is blended with river sand in order to investigate the quality changes and characteristics of concrete as variation of blend ratio of crushed sand (n, 50, 70, 80, 90, 100%). Slump and air content were measured to investigate the properties of fresh concrete. Unit weight, compressive strength and modulus of elasticity in age of 7, 28, 60, n, 180 days were measured to investigate properties of hardened concrete. Compressive strength, unit weight and modulus of elasticity were increased with a passage of time and they are expected to keep on increasing in long-term age as well. The experimental results of the qualifies of crushed aggregates in each producing area, were all satisfied with Korea Standard. The results of the measurement of slump exposed that slump preferably decreased as mixing rate increased till 70~80% but it increased to mixing rate 70~80%. The air content was exposed that it decreased by micro filler phenomenon according to that crushed sand b)ended ratio increased. According to the result of measuring unit weight in age of 7, 28, 60, 90, 180days, it increased in accordance with that blended ratio of crushed aggregates increases. As a result of measuring compressive strength and modulus of elasticity in age of 7, 28, 50, 90, 180days, compressive strength was highest when it is 70% of blended ratio.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.731-734
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• 2005

Crushed sand is blended in order to investigate the quality changes and characteristics of concrete with variation of blend ratio of crushed sand (50, 60, 70, 80, 90, $100\%$). Slump and air content were measured to investigate properties of fresh concrete, and unit weight, compressive strength and modulus of elasticity in age of 7, 28, 60, 90, 180 days were measured to investigate properties of hardened concrete. Compressive strength, unit weight and modulus of elasticity were increased as time goes by and they are expected to keep on increasing in long-term age as well. As a result of measuring compressive strength and modulus of elasticity in age of 7, 28, 60, 90, 180days, compressive strength was highest when it is $70\%$ of blended ratio.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1005-1012
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• 2005

Shell-sand mixtures are commonly used for reclamation projects. This study presented the engineering properties of shell-sand mixtures. Shell shows higher specific gravities and less compressibilities than quartz sand. From large shear box tests, it can be seen that the shear strength increased with the increase of shell mixtures. At 30% shell mixtures showed about 6 increase in shear friction angle.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1998.06a
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• pp.12-16
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• 1998

최적 위치별 퇴적토에 대한 토양 특성 및 수목 식재용 유기토양 활용 가능성을 알아보고 각 시료의 수분, 유기물 함량 등에 따른 적절한 혼합을 통하여 식물 발아 성장의 최적화를 온실에서의 식물재배 실험을 통하여 달성하고자 한다. 또한 식재용 토양 활용 가능성을 알아보기 위한 기본 물성 및 유해성 평가를 하여 중금속이 식물 성장에 어떤 영향을 미치는가를 고려하여 재활용 여부를 알아보았다. 퇴적토를 이용한 식물의 발아 및 생장 실험은 원퇴적토와 모래와의 혼합비를 달리하고 다른 불순물이 함유되지 않도록 하여 발아일수와 발아적온, 생육적온 등 최적 조건을 팬지와 금잔화에 대하여 실험하였다.

• Journal of Korea Water Resources Association
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• v.53 no.3
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• pp.167-179
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• 2020

Recently, new levee material has been developed to enhance natural soil strength and vegetation growth using biopolymer. In the study, critical tractive force of vegetated mats mixed with biopolymer mixed soil has been evaluated to apply the mixed soil to levee construction material. The mixed soil has been produced by mixing beta-glucan, clay, and sand. Full scale test bodies have been constructed with 3 cm thick of the mixed soil. Total 4 test bodies have been constructed and experimented. Critical tractive forces have been evaluated by observation and measurement of failure conditions and soil loss. Although performance of the vegetated revetments are affected by vegetation coverage conditions, the critical tractive forces are shown about 40 N/㎡ and the critical velocities are shown about 4 m/sec by full scale experiment. Erosion resistance is also enhanced by combination of root and net with mat materials.

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.567-570
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• 2008

The present study investigated the applicability of the minium fludization velocity measuring method using linear regression analysis between the standard deviation of pressure fluctuation and gas velocity in multi-particle sand on a fluidized bed 0.109 in inner diameter. We measured minium fludization velocity according to the standard deviation of particle distribution in Gaussian distribution. The measured value compared with other researchers' equations. The minium fludization velocity derived from the linear regression analysis of the standard deviation of pressure fluctuation and pressure drop inside the bed. We also found that the minium fludization velocity of a multi-particle system using the standard deviation of pressure fluctuation must be measured at freely bubbling region.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.27 no.1
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• pp.72-77
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• 1982

To develop a new propagation method of Korean ginseng (Panax ginseng C.A. Meyer) by cutting, stem cuttings with leaflets obtained from ginseng seedlings were planted in rooting media treated with three levels of NAA concentration. NAA solution of 1.0 ppm was the most effective for the rooting of ginseng stem cuttings as well as for root growth after initiation of the roots from cuttings. A mixture of sand and leaf compost as a rooting medium for ginseng stem cuttings showed the best results in rooting percentage of cuttings and root growth after rooting. An acril film cap covering was very effective to prevent water loss by transpiration from the leaflets of stem cuttings and for rooting and root growth after rooting. Cuttings of leaf petiole with 5 leaflets from 2 year old ginseng plants showed good rooting as well as root growth after rooting in a mixture of sand and leaf compost treated with 1.0 ppm NAA.

• Korean Journal of Agricultural Science
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• v.3 no.1
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• pp.53-60
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• 1976

The purpose of this study was to evaluate the value of briquet ash as a component of rooting media in Chrysanthemum morifolium. Various rooting media were made in mixture at different ratio and alone using sand, vermiculite and briquet ash as components of soil mixture. In order to investigate the effect of the particle size of briquet ash on rooting of stemouttings, various particle sizes were used as rooting media. Rooting ratio, number of root and root length were examined to evaluate the effect of the various rooting media and the particle sizes of briquet ash. The important conclusions of this study are summerized as follows; 1. Briquet ash was better rooting medium than sand, but it showed more effective result when it was used in mixture with other rooting media. 2. The particle size of briquet ash as a rooting medium to produce a healthy vegetatively propagated plant showed the best result at 2-3mm.