• Geotechnical Engineering
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• 제13권4호
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• pp.67-74
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• 1997

This paper presents the deterministic model to evaluate the two dimensional stability of geotextile-reinforced embankments on soft foundations. The potential failure surfaces in this study are assumed as the logarithmic spiral curves refracted at the boundary of layers. To facilitate the iterative calculations, we developed a program that determines the geotextile tensile force for an geoteztile-reinforced embankments. This program can be used for situations with a varying number of soil layers and soil types. A series of calculations have been made for a schematised situation. The results of these series are collected in stability charts, which are compared with those by circular potential failure surfaces. Using these charts in an early stage of the design provides a reasonable estimate of the stability of geotextile-reinforced embankments. In a later stage a more detailed calculation can be made by the developed programs.

• Geomechanics and Engineering
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• 제14권4호
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• pp.355-366
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• 2018

One of the significant problems in the design of onshore pipelines in seismic areas is their stability in case of liquefaction. Several model tests and numerical analyses allow investigating the behavior of pipelines when the phenomenon of liquefaction occurs. While experimental tests contribute significantly toward understanding the liquefaction mechanism, they are costly to perform compared to numerical analyses; on the other hand, numerical analyses are difficult to execute, because of the complexity of the soil behavior in case of liquefaction. This paper reports an overview of the existing computational methods to evaluate the stability of onshore pipelines in liquefied soils, with particular attention to the development of excess pore water pressures and the floatation of buried structures. The review includes the illustration of the mechanism of floating and the description of the available calculation methods that are classified in static and dynamic approaches. We also highlighted recent trends in numerical analyses. Moreover, for the static condition, referring to the American Petroleum Institute (API) Specification, we computed and compared the uplift safety factors in different cases that might have a relevant practical use.

• Geotechnical Engineering
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• 제2권1호
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• pp.45-54
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• 1986

An experimental study was carried out in the laboratory on a model of a reinforced earth retaining wall to provide the empirical data for the rational design and the construction methods on a reinforced earth retaining wall. Observed measurements included the variation of tension in the aluminium foil reinforcing strips was monitored by electrical resistance strain gauges pasted on its at different stages of construction. In addition, the lateral movement of the wall was measured by dial gauges and the mode of collapse of the wall was investigated. The measured values are discussed in comparison with the results of the existing studies of the reinforced earth retaining wall. A significant result of the experiments is that the variation of tension in reinforcing strips is non-linear with the maximum tension occuring close to wall face. Attachment of reinforcement to wall increases the stability against overturning.

• Geotechnical Engineering
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• 제3권4호
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• pp.55-70
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• 1987

The use of reinforced earth is not new. But available information on basic proper.ties like strength and deformation behavior of reinforced earth materials is not adequate. Therefore, tile purpose of this present investigation is first to research the frictional characteristics of the reinforcement and standard rand using a shear testing appratus. The second purpose of this articles are to report the results of comparison test on the strength and stress-strain behavior of a dry sand einforced with aluminium fcils and geotextiles under different confining pressures. Finally, the paper explores the possibility of geotextile reinforced earth masonry walls. It was observed that the stress-strain response of sand ai.e considerably improved by the introduction of geotextiles. The results of tests are used in developing the geotextile reinforced earth masonry walls. It is hoped that this paper will be helpful in providing the basic data for the rational design and construction methods of reinforced earth structures.

• Journal of the Korean Geotechnical Society
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• 제21권5호
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• pp.15-24
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• 2005

Modeling techniques of piled pier were reviewed and the influences of pile cap's boundary conditions were analyzed in this study. The method using flexible springs seems to be useful fur the practical design since its simplified model can represent the complex behaviors of pile groups efficiently. Parameter studies were performed far various pile group arrangements, pile spacings, end bearing conditions, and loading stages to analyze their effects on the lateral displacements, maximum pile bending stresses, and lateral stiffness of pile groups. Through the parameter studies, it was found that when lateral stiffness of pile groups was estimated by using three-dimensional analysis method (YSGroup), its complex behavior could be predicted better than other methods based on single pile analysis.

• Proceedings of the Korean Geotechical Society Conference
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.700-707
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• 2008

As plan connecting island to island or island to land is needed, a lot of long-span bridge is being designed lately in Southern part of Korea. With development of pile equipment, overhanging large-scaled concrete pile are adopted to foundation type of main tower or pylon. About the number of 15~30 group piles per tower foundation is designed to resist long-spaning super-structure load, but by restricted condition of site investigation cost, a few boring-hole tests are performed to identify sub-ground layers. Up to now, direct-curved method connecting two or three known boring logs and representative interval method are usually used to evaluate unknown depth and rock properties at locations where piles are constructed. Because this approach is not logical and so rough, much difference occurs between designed length of piles and real length of it. In this paper, using a lot of various prediction method(reciprocal distance method, inverse square distance method and kriging method etc.), we suggest optimum length of group piles.

• Proceedings of the Korean Geotechical Society Conference
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1296-1305
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• 2008

In this study, the spatial distribution of depth between alluvial soil and weathered soil of Song-do new city is analyzed using geostatistics. From analysis results, the boundary depth of north-east region is deeper than that of south-west region, and average depth of north-east region is 27.14m and average depth of south-west region is 23.25m. The boundary depth is estimated by ordinary kriging and inverse distance method, and estimated results are almost similarity. So, in Song-do new city, these two method can be used to estimate the boundary depth. The ordinary kriging method is a very useful tool because the more exact analysis of spatial continuity and distribution characteristic is possible.

• Proceedings of the Korean Geotechical Society Conference
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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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.

• Geotechnical Engineering
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• 제8권3호
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• pp.61-74
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• 1992

In order to provide fundamental data for the design of geotextile drains, the in-plane permeability coefficients were determined by tests and permeable cllaracteristics were investigated, mainly on domestic nonwoven and composite getextile products used for drainage purpose. The results obtained are as follows, The thickness, the in-plane permeability coefficient and the transmissivity with the in- crease of compressive stress are found to be remarkably decreased when the compressive stress is lass than about 10KN/m2. The inflane permeability of filament nonwovens are found to be lower than that of composites or staple-fiher nonwovens, and the compressibility of the geotextile shown to be larger for the polyester nonwovens than for the polypropylene nonwovens. The relation of compressive stress, q and compressibility, Cr is expressed as Cr=13.37 In q+23.28 and that of compressibility on the basis of 2KN /m2, Cr' and decrease ratio of in-plane permeability coefficient is followed Pr: 1.25Cr'

• Geotechnical Engineering
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• 제11권4호
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• pp.99-110
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• 1995

In this study, friction angles on the surface of vertical rigid ground anchor in normally consolidated dry sand were measured by model pullout tests in laboratory. Friction angles were obtained from the normal and shear stresses measured along depth of the anchor stir face by attaching several 2-dimensional load cells. Model tests were conducted under the plane strain state and axial symmetric state. From the results of tests, it was concluded that the maximum friction angle on the anchor surface coincides nearly with the maximum angle of stress obliquity on the plane of zero-extension direction obtained by plane strain compression test. This result was made with regard to the strength anisotropy and stress dependency of sand. It showed that when angle of shear resistance of the sand is applied to the friction angle of the anchor surface, the design capacity could be less than the applied force, thus making the anchor unsafe.