• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.253-261
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• 2003

Mechanical behavior of composition pound improved by sand compaction pile (SCP) with low replacement area ratio could be more significantly affected by mechanical interaction between sand piles and clays than that of clay ground improved by SD or SCP with high replacement area ratio. It is essential to elucidate the mechanical interaction in the improved clay ground, in order to accurately estimate behavior in reducing settlement of the improved ground and increasing strength of clays. In this paper, through a series of model tests of composition ground improved by SCP with low replacement area ratio, each mechanical behaviors of sand piles and clays in the composition ground during consolidation was elucidated, together with stress sharing behavior between sand piles and clays.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.397-404
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• 2001

Sand pile is one of the widely used ground improvement methods. Sand pile improved ground will have composite ground effects, even though the primary purpose is the accelerated consolidation. However, the consolidation of sand pile improved ground as a composite ground is substantially under developed. This study investigate the effect of composite ground for relatively low volume displacement sand piles. Plate bearing tests and earth pressure cell measurements are performed. It turned out that the contribution of sand pile as a load bearing mechanism is not substantial. However the bearing capacity of the surrounding clayey soil is increased by sixty percent, and it cause the stiffness change during consolidation. Therefore it is expected that, the effect of increased stiffness of sand pile improved ground is influenced by change of ground stiffness.

• Geomechanics and Engineering
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• v.7 no.5
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• pp.539-552
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• 2014

A simplified probability-based design charts for stone column-improved ground have been presented based on the unit cell approach. The undrained cohesion ($c_u$) and coefficient of radial consolidation ($c_r$) of the soft soil are taken as the most predominant random variables. The design charts are developed to estimate the diameter of the stone column or the spacing between the stone columns by employing a factored design value of $c_r$ and $c_u$ so as to satisfy a specific probability level of the target degree of consolidation and/or a target safe load that needs to be achieved in a specified timeframe. The design charts can be used by the practicing engineers to design the stone column-improved ground by considering consolidation and /or bearing capacity of the improved ground.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1094-1101
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• 2005

The stability of embankment on the soft ground has included problems on stabilities of embanked body and soft soil, which related with vertical displacement and lateral movement of the soft ground especially. The judge methods for the potentialities of lateral movement have been used in order to stabilization assessment during and after construction of the embankment. In this study, the judge methods on the improved soft ground suggested, which compared with exist judge methods on lateral movement. It is due to recent trend using embanked structures on the soft ground most of improved.

• Journal of the Korean Geotechnical Society
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• v.26 no.12
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• pp.61-70
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• 2010

A series of shaking table tests were conducted to estimate the seismic performance of soft ground deposits improved by stone column. The amplification of acceleration, shear strain, and shear wave velocity were evaluated to compare the seismic response of unimproved ground deposits with that of improved ground deposits. From the test results, it was shown that the stone column can prevent large shear deformation in ground deposits. However, it was also found that the acceleration of improved ground deposits may be amplified more than that of unimproved ground deposits when it was subjected to short periodic seismic wave. The results suggest that it is necessary to perform the ground response analysis with model experiments for both unimproved and improved ground deposits to evaluate the effect of stone column on the seismic performance of improved ground deposits.

• Journal of the Korean GEO-environmental Society
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• v.4 no.4
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• pp.17-23
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• 2003

Accurate prediction of consolidation behaviors of the soft ground improved by plastic board drains is not easy because the consolidation characteristics of the improved ground has not been fully elucidated yet. The shape of drains is one of the most important factors which affect the consolidation characteristics of the improved ground. In this paper, a series of model consolidation tests of soft clay ground improved by plastic board drain were carried out, in order to investigate the effect of both plastic board width and stress level on consolidation characteristics of the improved ground. As the results, behaviors of both settlement and excess pore pressure dissipation were elucidated. Also, the non-uniform distribution of water content in the model ground was obtained. Then, in order to investigate the effect of vertical drainage on the consolidation behavior in the model tests, the comparison between experimental consolidation behaviors and Barron's theoretical ones were carried out. As the results, it was elucidated that the consolidation behavior in the model tests was affected not only by radial drainage but also by vertical drainage.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.16 no.1
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• pp.23-26
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• 1980

The pure polypropylen rope has been used for the head rope, and the lead cored polypropylen rope for the ground rope in the anchovy boat seine. These ropes revealed the disadvantage that deforms the net shape due to their elongation. Te improve the disadvantage, authors developed the rope of new construction which is cored by wires and wrapped by polypropylene fibers, 20mm in diameter for the head rope and 40tnm for the ground rope. To compare the physical properties of the improved rope with the conventional ones, some factors are valued and the following results are found. 1. The improved ropes rev~al some disadvantages, such as the head rope is heavier, the ground rope lighter, and both of them are stiffer than the conventional ones, contrary to the required condition of ropes) However no special difficulties are found in practical use. 2. The improved ropes display much advantages, such as elongation is 30 percent less, breaking strength is 35 precent greater, and elastic recovery is 10 percent greater than the conventional ones. Thus, it is considered that the improved ropes are more suitable for the head rope and the ground rope of the anchouy boat seine net than the conventional ones.

• Journal of the Korean Institute of Landscape Architecture
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• v.31 no.6
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• pp.85-94
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• 2004

This study was carried out to analyze physicochemical properties according to the soil height and to the six types of sites that were used as planting ground in the reclaimed land from the sea, Gwangyang Bay. The physicochemical properties of the soil types were tested by t-test(p<0.01, 0.05), at each of the 6 planting ground sites(p<0.01, 0.05), and at each height(p<0.01) of the planting grounds. These areas were tested by ANOVA and were significantly different. Improved soil was better than reclaimed soil from the sea for Zelkova growth because the improved soil contained lower amounts of pH, ECe, N $a^{+}$, $Ca^{++}$, $Mg^{++}$ SAR. Due to freedom from variables such as salt content in the underground as well as the physical and chemical disturbance of the soil, favorable planting ground for tree growth was recorded at the higher grounds than at the lower ones. Soil detriment to the tree growth in the studied sites included elements such as soil hardness, and the distribution of sodium in the tree root systems. The planting grounds for the favorable growth of landscape trees were determined in the following order: the grounds of mounding> the coved ground of improved soil, and the filled ground of improved soil.l.l.l.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.809-814
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• 2009

Deep mixing method has been used for ground improvement and foundation system for embankment, port and harbor foundations, retaining wall, and liquefaction mitigations. It has attractive benefits because it is not only improved strength of soft ground but superior for prevention of settlement. However, the quality controls of improved mass affect to the efficiency of the deep mixing method is not properly established. These effects vary depending upon the construction environments and conditions of agitation in consideration of an agitator. The strength and shape of the improved column are not unique and these are affected by mechanical properties of agitators. In this study, in order to investigate the efficiency of deep mixing method for ground improvement on a soft clay ground, experimental studies are performed considering mechanical properties of agitator; the location of exit-hole of admixtures, an angle of mixing wing and a speed of revolution. The experiments are conducted with the simulated apparatus for deep mixing plant that reduced the scale in 1:8 of the real plant. According to the results, the diameter and shape of improved column mass vary depending on the mechanical properties and operating conditions of agitator. Its quality is better when the exit-hole of admixtures is located in the mixing wing, when an angle of mixing wing is large, and when the speed of revolution is rapid.

• Journal of Industrial Technology
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• v.25 no.A
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• pp.67-73
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• 2005

In this research, centrifuge model experiments and numerical approach of finite element method to analyze experimental results were performed to investigate the behavior of improved ground with sand compaction piles. One of typical clay minerals, kaolinite powder, were prepared for soft ground in model tests. Jumunjin standard sand was used to sand compaction pile installed in the soft soil. In order to investigate the characteristics of mechanical behavior of sand compaction piles with low replacement ratios, centrifuge model experiments with the replacement ratio of 40%, changing the width of improved area with respect to testing results the width of surcharge loads, were carried out to obtain of bearing capacity, characteristics of load-settlement, vertical stresses acting on the sand pile and the soft soil failure mechanism in improved ground.