• Journal of the Korean Society of Environmental Restoration Technology
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• v.6 no.4
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• pp.62-73
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• 2003

The study was to apply a mat style reed planting method at confluence to improve plants growth conditions by relaxing disturbed topographical base due to water flow and was intended to review the effect to build up a vegetation strip by monitoring process after the construction. First off, We've attempted to construct reed mats on selected sites as confluences of Tan and Gaehwa stream and then examined and analyzed characteristics of soil and vegetation community. As the results of the examination, the soil texture was proven to be a mix of sand and loamy sand and be 6.3 ~ 7.0 soil pH. In addition, it contained 1.0 ~ 4.6% of organic matter, 0.04 ~ 0.22% of T-N and 27.8 ~ 41.2% of water content. For its vegetation structure, the Tan stream confluence was first actually a point bar without plants prior to the construction but 8 kinds of hygrophytes including Persicaria hydropiper and 9 kinds of terrestrial plants such as Potentilla supina, Artemisia annua, and Alopecurus aequalis var. amurensis. On the other hand, the Gaehwa stream confluence contained 6 kinds of hygrophytes such as Bidens frondosa and other 11 kinds of terrestrial plants prior to the construction while it produced 7 kinds of hygrophytes including Ranunculus ternatus as well as Phragmites australis and 9 kinds of terrestrial plants such as Potentilla supina after the construction. For the Phragmites australis, almost of them was weathered away in early days just after planting because of development period passed, but on May, six months later from planting, it was investigated that its length was approximated as 65 ~ 85cm with 75% coverage and that the number of it was 437 ~ 633/$m^2$. The study was shown that reed mats can improve environmental conditions of disturbed topographical base, enabling natural growth of various riparian vegetation including the introduced plant, reed. In the meantime, it was supposedly judged that to recover or build up a vegetarian strip, supplementary materials should be prepared to help produce and grow plants because it is not probable to expect river drift by water flow at confluence and that corrosion, burying or inundation owing to changes of water lever should be considered.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6C
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• pp.339-347
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• 2008

The penetration of the probe produces the excess pore pressure due to the disturbance. The objective of this study is to evaluate the disturbance zone by using the dissipation of the excess pore water pressure, which was generated due to the penetration of the penetrometer with different size. The CPT, DMT and FVP (Field Velocity Probe) are adopted for in-situ tests. The tests are carried out in the construction site of north container pier of Busan new port, Korea where is accelerating the consolidation settlement using plastic board drains (PBD) and surcharges by crushed gravels. The coefficient of consolidation $(C_h)$ and soil properties are deduced by the laboratory test. The in-site tests are performed after the predrilling the surcharge zone at the point of 90% degree of consolidation. To minimize the penetration effect, the horizontal distance between penetration tests is 3m, the change of the pore pressure is monitored at the fixed depth of 24m. The coefficient of consolidation $(C_h)$ and the $t_{50}s$ are calculated based on the laboratory test and the in-situ data, respectively. The equvalent radi based on the $t_{50}$ shows that the FVP and the DMT produce the smallest and the greatest equivalent radi, respectively.

• Journal of agriculture & life science
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• v.46 no.2
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• pp.35-42
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• 2012

This study was conducted to investigate growth responses at 45 days after cutting in six Sedum cultivars (S. reflexum 'Blue Spruce', S. rupestre 'Angelina', S. sexangulare, S. sexangulare var. elatum, S. spurium 'Atropurpureus', S. takesimense) using vegetation mats (individual coir tape and jute treated with different thicknesses and soil compositions) to broaden usefulness of evergreen Sedum cultivars. All the treatments including both single and interaction between treatments showed significant effects (p<0.001) on the number of branches, plant height, and shoot fresh weight except the number of branches treated with different mat types. No. of branches was showed two times in compost than in sand regardless of cultivars and mat types with the exception of S. takesimense showing no added branches in all treatments. Each plant height of all the cultivars except 'Angelina' showed the highest value under the conditions treated with 5 mm thick coir tape using compost. The fresh weight of 'Blue Spruce' treated with 5 mm thick coir tape using compost was 13.19 g of which value was the highest in all treatments. The better growth response in all Sedum cultivars was shown in the treatment of 5 mm thick coir tape than with jute net treatment.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.02a
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• pp.93-112
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• 2000

The permeability of converter slag, replacing material of sand mat on improving soft clay foundation, was evaluated in the laboratory. The effects of grain size, flow water time and aging were investigated using sea and fresh water. Converter slag being submerged with fresh water, the coefficients of permeability in A and B samples less than 10mm grain sizes were measured as 6.52${\times}$10$\^$-2/cm/sec and 5.99${\times}$10$\^$-1/cm/sec, while changed as 1.88${\times}$10$\^$-2/cm/sec, 3.86${\times}$10$\^$-1/cm/sec under sea water condition. Also, the condition of turbulent flow may exit and was experimentally identified from the relationship between hydraulic gradient and seepage velocity. After 180 days on using sea water, the coefficients of permeability of sample A and B samples decreased ten times smaller than those initial values. And after that time continually decreased as for till 360 days. The reduction of permeability coefficient was considered to influence filled with voids in high-calcium quicklime(CaO). However, in-situ coefficient of permeability was practically satisfactory.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.02a
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• pp.12-31
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• 2000

The permeability of converter slag, replacing material of sand mat on improving soft clay foundation, was evaluated in the laboratory. The effects of grain size, flow water time and aging were investigated using sea and fresh water. Converter slag being submerged with fresh water, the coefficients of permeability in A and B samples less than 10mm grain sizes were measured as 6.52${\times}$10$\^$-2/cm/sec and 5,99${\times}$10$\^$-1/cm/sec, while changed as 1,88${\times}$10$\^$-2/cm/sec, 3.86${\times}$10$\^$-1/cm/sec under sea water condition. Also, the condition of turbulent flow may exit and was experimentally identified from the relationship between hydraulic gradient and seepage velocity. After 180 days on using sea water, the coefficients of permeability of sample A and B samples decreased ten times smaller than those initial values. And after that time continually decreased as for till 360 days. The reduction of permeability coefficient was considered to influence filled with voids in high-calcium quicklime(CaO). However, in-situ coefficient of permeability was practically satisfactory.

• Journal of the Korean GEO-environmental Society
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• v.8 no.3
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• pp.19-25
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• 2007

Stone columns is the ground improvement method which composed of compacted gravel or crushed stone inserted into the soft ground consisting of loose sand and clay. There are many difficulties in quantitative analysis of soil-pile interaction because settlement behavior of stone columns is affected by various parameters. In this study, various parameters of behavior of end-bearing group piles are investigated by load tests. Finally, the improved characteristics of soft ground and the influence of design parameters are investigated in this study using PR (performance ratio) value. From the PR value calculation and test results, we know that settlement behavior of stone columns is affected by area replacement ratio of composite ground, diameter of column rather than embedment ratio and mat.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.232-239
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• 2005

Recently geosynthetics that can be constructed on soft ground have been used for reinforcement and separation in various ways. Through laboratory model tests and numerical analysis, in this study, estimated the suitability of cable elements and appropriate input factors considering loading effect in modeling of geosynthetics. First, in laboratory model tests, geosynthetics were constructed on the clay, and covered with the thickness, 7.5cm of sand mat. And then static and dynamic model tests were performed measuring loading, settlement, ground lateral displacement, and displacements of geosynthetics, but, for cyclic loading, bearing capacity increased linearly with stiff slop because cyclic loading with constant cyclic pressure compacted the ground. Numerical analysis were performed with FLAC 4.0 2D using Mohr-Coulomb and Modified Cam-Clay models, and they compared with the results of model tests. Cable elements of FLAC in modeling geosynthetics couldn't consider the characteristics of geosynthetics that increase shear strength between geosynthetics and clay according to the loading increase. Therefore, in this study, appropriate equation that can consider loading effects in Cable elements was proposed by Case Study.

• Journal of Ocean Engineering and Technology
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• v.23 no.1
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• pp.114-121
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• 2009

In this study, acceleration responses of caisson structures under various environmental conditions are experimentally examined as a basic study to develop the health assessment technique for harbor structures. To achieve the objective, three approaches are implemented. Firstly, a target caisson structure is selected and its small-scaled caisson is constructed in the laboratory. Secondly, a finite element model of the caisson is generated to identify dynamic responses of the baseline structure. Thirdly, experimental tests are performed on the caisson model to examine dynamic responses under various boundary conditions and impact locations. Four different boundary conditions, 'standing on concrete floor', 'standing on styrofoam block', 'standing on sand-mat' and 'hanging by crane', are considered and correlation coefficients of frequency response functions between four states are analyzed.

• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.5
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• pp.93-105
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• 2001

The permeability of converter slag, replacing material of sand mat on improving soft clay foundation, was evaluated in the laboratory as well as in situ test. Effects of grain size, flow water time and aging were investigated using sea and fresh water Converter slag which has a grain size less than 10mm were submerged with fresh water and sea water. In fresh water, the coefficients of permeability in samples A and B were measured as 4.50${\times}$10$^{-2}$ cm per second and 1.20${\times}$10$^{-1}$ cm per second, respectively while as 1.88$\times$10$^{-2}$ cm per second and 3.86$\times$10$^{-1}$ cm per second in sea water. The condition of turbulent flow may exit and was experimentally certified based on the relationship of hydraulic gradient and seepage velocity. After 180 days in using sea water, the coefficients of permeability of samples A and B decreased ten times smaller than those initial values, and after that time continually decreased as for till 360 days. Finally, filling with voids in high-calcium quicklime(CaO) may result in the reduction of coefficient of permeability. In-situ coefficient of permeability however was Practically satisfactory.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.482-491
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• 2009

In this study, the mechanical behavior of very soft ground that is reinforced on the surface has been investigated with the aid of a series of numerical analyses. Key material properties of each dredged soft ground, reinforcement and backfill sand mat have been parametrically estimated in the numerical analysis. Along with the result of the study previously performed, a series of in-situ loading conditions and settlement exerted by surface reinforcing operation by construction vehicles has been numerically simulated. These result have been used to evaluate the limit bearing capacity for the unreinforced and reinforced soft ground. Also, the results of the numerical analysis obtained in this research were compared with Yamanouchi's empirical correlation for the limit bearing capacity. Engineering charts listed in this paper for estimating the limit bearing capacity provide field engineers with preliminary design tool for surface reinforcement of very soft ground.