• Magazine of RCR
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• v.8 no.2
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• pp.22-25
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• 2013

• Magazine of RCR
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• v.10 no.2
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• pp.46-52
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• 2015

• Asian Journal of Turfgrass Science
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• v.26 no.2
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• pp.129-134
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• 2012

Research was focused on the improvement of poor drainage problems on golf course fairway which had not been performed soil test or properly amended during the course construction. The analysis of the drainage problem basically was caused by a deterioration of soil physical properties by the top layer compaction. The soil hardness reached about 3,000 Kpa around 5~6 cm of soil profile. The slow infiltration speed to subsoil by the compaction was caused directly a poor drainage capacity. However, the properly amended sand soil showed an apparent value of 1,500 Kpa through the subsoil. The water content test showed a similar result that higher rate of 20~30% and ideal rate of 8~12% at poor drainage area and successfully amended area, respectively. However, an imported topsoil media which had higher content of silt and clay from a trans-planted sod had made a heterogeneous soil profile and that caused a poor drain capacity by a low infiltration rate. Those drainage problems triggered to buildup a reduced soil layer by poor soil gas exchange. The soil environment of deoxidation enhanced anaerobic microbial population and induced methane gas build-up to 55 ppm, and that resulted an adverse effect on turf growth by root growth retardation, consequently.

• Geomechanics and Engineering
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• v.24 no.2
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• pp.129-141
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• 2021

The vacuum preloading method has been used in many countries for soil improvement and land reclamation. However, the treatment time is long and the improvement effect is poor for the straight-line vacuum preloading method. To alleviate such problems, a novel combined air booster and straight-line vacuum preloading method for shallow ground treatment is proposed in this study. Two types of traditional vacuum preloading and combined air booster and straight-line vacuum preloading tests were conducted and monitored in the field. In both tests, the depth of prefabricated vertical drains (PVDs) is 4.5m, the distance between PVDs is 0.8m, and the vacuum preloading time is 60 days. The prominent difference between the two methods is when the preloading time is 45 days, the injection pressure of 250 kPa is adopted for combined air booster and straight-line vacuum preloading test to inject air into the ground. Based on the monitoring data, this paper systematically studied the mechanical parameters, hydraulic conductivity, pore water pressure, settlement and subsoil bearing capacity, as determined by the vane shear strength, to demonstrate that the air-pressurizing system can improve the consolidation. The consolidation time decreased by 15 days, the pore water pressure decreased to 60.49%, and the settlement and vane shear strengths increased by 45.31% and 6.29%, respectively, at the surface. These results demonstrate the validity of the combined air booster and straight-line vacuum preloading method. Compared with the traditional vacuum preloading, the combined air booster and straight-line vacuum preloading method has better reinforcement effect. In addition, an estimation method for evaluating the average degree of consolidation and an empirical formula for evaluating the subsoil bearing capacity are proposed to assist in engineering decision making.

• Korean Journal of Medicinal Crop Science
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• v.20 no.3
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• pp.177-183
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• 2012

To develop the practical cultivation for paddy field, we investigated the properties of paddy soil, growth characteristics and ginsenoside content of 6-year-old ginseng, Cheonpung variety between poor drainage class (PDC) and imperfect drainage class (IDC). Groundwater level in PDC showed monthly small changes of 20~30 cm, while IDC showed monthly great changes of 28~71 cm depending on rainfall. Soil moisture content in PDC and IDC was 17.2%, 22.5%, respectively. Air temperature in IDC was lower than $0.3^{\circ}C$, while soil temperature was higher than $0.8^{\circ}C$ compare to PDC, respectively. Main soil color of PDC was grayish olive, while IDC was brownish olive. PDC showed yellowish mottles only at underground of 20~40 cm, while IDC showed that at underground of 30~90 cm. IDC showed lower pH, EC, potassium, calcium and magnesium content, but higher organic matter, phosphate, and iron content than that of PDC, respectively. All of EC, organic matter, potassium, calcium, and magnesium content were decreased, but iron content was increased at the subsoil layers of PDC. All of EC, organic matter, phosphorus, and potassium content were decreased, but calcium and magnesium content were increased at the subsoil layers of IDC. Root yield in IDC was more increased by 33% than that of PDC. The moisture content and rusty ratio of ginseng root in IDC were lower than that of PDC. Ginsenoside content in IDC was higher than that of PDC because the ratio of lateral and fine root showing relatively high content of ginsenoside was higher in IDC than that of PDC.

• Korean Journal of Soil Science and Fertilizer
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• v.23 no.2
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• pp.128-134
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• 1990

Croping pattern, fertilizer application, Soil chemical characteristics, plant nutritional condition and growth status were investigated in three major vinyl house farms near Yesan. Croping pattern changed from tomato to pumpkin due to tomato diseases such as wilting and blossom-end rot. Wilting seemed to be closely related with high EC, nitrogen and root cyst nematodes. Calcium deficiency seemed to be due to high potassium, EC in soil and high uptake of iron. Chinese cabbages in summer showed poor growth (80% inhibition) due to high EC(1.8mmho/cm) and easily got wenny root disease that might due to high phosphorus (1055ppm) in soil. Summer radish showed poor growth (50% inhibition) due to high EC(1.6mmho/cm), K and Mg resulting in base imbalance. Farmers used 5 kinds of compound fertilizer as basal application and one without P for top dressing. Urea and KCL were used for top dressing. Heavy application of livestock manure and chemical fertilizer for every crop made eutrophic even in subsoil.

• Geomechanics and Engineering
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• v.19 no.5
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• pp.447-462
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• 2019

The vacuum preloading method has been used in many countries for ground improvement and land reclamation works. A sand cushion is required as a horizontal drainage channel for conventional vacuum preloading. In terms of the dredged-fill foundation soil, the treatment effect of the conventional vacuum preloading method is poor, particularly in Tianjin, China, where a shortage of sand exists. To solve this problem, straight-line vacuum preloading without sand is widely adopted in engineering practice to improve the foundation soil. Based on the engineering properties of dredged fill in Lingang City, Tianjin, this paper presents field instrumentation in five sections and analyzes the effect of a prefabricated vertical drain (PVD) layout and a vacuum pumping method on the soft soil ground treatment. Through the arrangement of pore water pressure gauges, settlement marks and vane shear tests, the settlement, pore water pressure and subsoil bearing capacity are analyzed to evaluate the effect of the ground treatment. This study demonstrates that straight-line vacuum preloading without sand can be suitable for areas with a high water content. Furthermore, the consolidation settlement and consolidation degree system is developed based on the grey model to predict the consolidation settlement and consolidation degree under vacuum preloading; the validity of the system is also verified.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.285-289
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• 2006

Recently the target area for the installation of structures have been changed from shallow water into deep one by reservation and use of the wider coastal region, and development of deep water. Additionally, great emphasis in the improved human life quality has been placed on the necessities for the preservation of the agreeable natural and coastal environments and development waterfront, recreation, and resort in the sea. However, the existing gravity-type breakwater did not appropriately cope with the recent changes of circumstances, but required the enormous construction coat for coping with them. Until now, floating breakwuater, which was adequate for the environment and construction cost, has been actively studied in the other countries including Japan. This floating breakwater has been already constructed in many places and satisfactory in poor subsoil and deep water in Japan. Also it showed the same function as a gravity-type breakwater. But floating breakwater was not control long period waves by reason of constructive characteristic. The aim of this study is to discuss field application of Floating Breakwater with Compound Plate Type(FBCPT) in coastal region by using numerical analyses and hydraulic model test.

• Journal of the Korean Institute of Landscape Architecture
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• v.31 no.6
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• pp.95-103
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• 2004

A turfgrass rootzone foundation is one of the important iufluences on the growth of cool-season turfgrass such as Kentucky bluegrass, which is usually grown on korean golf courses and athletic fields in Korea. This study was carried out to evaluate the growth of Kentucky bluegrass on 4 types of turfgrass root-zone foundations: a 2cm thickness of Sand 90%+Peat humus 8%+Zeolite 2% mixture on a subsoil base (C), a 20cm thickness of Sand 90%+Peat humus 8%+Zeolite 2% mixture (S), a 20cm thickness of Sand 45%+fine sand(a sort of Bomyungsa) 45%+Peat humus 8%+Zeolite 2% mixture (S+F), and a 20cm thickness of Sand 45%+fine sand(a sort of Bomyungsa) 45%+Peat humus 8%+Zeolite 2% mixture on a 20cm thick drainage layer (S+F(G)). Visual ratings of Kentucky bluegrass on the C foundation were low throughout the experiment when compared to S, S+F, and S+F(G) foundations, which contained high contents of sand with a high water infiltration rate. However, poor growth of Kentucky bluegrass in the summer of 1991 on the S foundation was likely to be caused by a too high water infiltration rate (185.8cm/hr). The growth of Kentucky bluegrass on the S+F(G) was good while the growth was a little weak at the developing stage on the S +F foundation. If the cost had to be considered when constructing golf courses and athletic fields, The S+F foundation without the drainage layer would be the best choice in terms of low cost and good quality of Kentucky bluegrass compared to the S+F(G). In this result, the infiltration rate was regarded as the most influential factor to the growth of Kentucky bluegrass on rootzone foundations.

• Journal of the Korean Geotechnical Society
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• v.36 no.12
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• pp.35-43
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• 2020

Currently, cofferdams of circular cross section are widely applied as temporary facilities for the installation of bridge foundations in river/sea bridge construction in Korea. Existing caisson, sheet pile, and cell type cofferdam are widely used, but these methods take a lot of time and cost for installation and dismantling. In the case of the existing sheet pile construction method, attention is needed to secure internal and external stability because of the damage to the sheet pile due to ground penetration and difficulty in connecting element members. In this study, penetration design of circular steel pipes using suction pressure was performed on the soft ground of the west coast, and it was confirmed that penetration construction using suction pressure was possible through field tests. It was confirmed that applying the ground analysis results using the cone penetration test (CPT) to the design rather than the standard penetration test (N value) results more similar to the field test results. In addition, it was confirmed that local failure of the inside of the cofferdam was induced when a suction pressure higher than the upper limit suction pressure was applied in the silty sand.