• Journal of the Korean GEO-environmental Society
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• v.24 no.7
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• pp.5-14
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• 2023

Recently, earthquakes have occurred frequently in worldwide. These earthquakes cause various forms of natural and physical damage. In particular, liquefaction in which the ground shows liquid-like behavior causes great damage to the structure. Accordingly, various liquefaction damage reduction methods are being studied and developed. Therefore, in this study, a method of reducing liquefaction damage in the event of an earthquake applicable to existing structures was studied using the sheet pile method. The 1-G Shaking table test was performed and the ground was constructed with Jumunjin standard sand. A two-story model structure was produced by applying the similitude law, and the input wave applied a sine wave with an acceleration level of 0.6 g and a frequency of 10 Hz. The effect of reducing structure damage according to various embedded depth ratio was analyzed. As a result of the study, the structure settlement when the ground is reinforced by applying the sheet pile method is decreased by about 71% compared to when the ground is not reinforced, and the EDR with minimum settlement is "1". In addition, as the embedded depth ratio is increased, the calculation of the pore water pressure in the ground tends to be delayed due to the sheet pile. Based on these results, the relationship with structural settlement according to the embedded depth ratio is proposed as a relational equation with the graph. The results of this study are expected to be used as basic data in developing sheet pile methods applicable to existing structures in the future.

• Journal of the Korean Geotechnical Society
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• v.28 no.6
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• pp.71-79
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• 2012

Sand compaction pile and stone column replacement methods have been commonly used for improving soft ground in the nearshore. Recently, DCM (Deep cement mixing) method, which can harden soft clays by mixing with cement, is more popularly used in such soft ground improvement. Sandy soils also exist in the seashore. Therefore, in this study, the effect of salinity in sea water and curing methods on the strength of cemented sand was evaluated in terms of unconfined compressive strength (UCS). The sand was mixed with five different cement ratios and distilled water or sea water, and then compacted into a cylindrical specimen. They were cured for 3 days under sea water for DCM construction condition and air cured for onshore curing condition. When a specimen was cured under sea water without confinement, it was easily collapsed due to initiation of cracks. When the cement ratio and curing method were the same, the UCS of the specimen without sea water was at maximum 3.5 times higher than those with sea water. The sea water used for mixing sand had more influence on strength reduction than the sea water used for curing. When the cement ratio was the same, the UCS of air-cured specimen was at average 2 times higher than those of water-cured specimen, regardless of water used.

• Journal of the Society of Disaster Information
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• v.13 no.4
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• pp.483-490
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• 2017

Recently, the demand for industrial and residental land are increasing with economic growth, but it is difficult to obtain the area for development with good ground condition. Various kinds of vertical drain technologies such as sand drain, sand compaction pile, packed drain, PVD are commercially available to improve the soft ground. Discharge capacity is the important factor of vertical drains. However, under field conditions, discharge capacity is changed with various reasons, such as soil condition, overburden pressure, and so on. In this paper, the experimental study was carried out to estimate the discharge capacity of four different types of PBD, PBD for double core PBD, deep type PBD, X type PBD, general type PBD. Characteristics of the discharge capacity for the surcharge load and hydraulic gradient were analysed. The double core PBD was excellent for discharge capacity in this study.

• Journal of the Korean Geotechnical Society
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• v.15 no.4
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• pp.207-220
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• 1999

Model tests were performed to investigate the failure modes in embankments on soft ground supported by piles with cap beams. In the model tests, Jumunjin standard sand was placed on simulated cap beams and soft ground. The cap beams are placed perpendicular to the longitudinal axis of the embankment. The colored sand and the Jmniin standard sand were placed one after the other above cap beams and soft ground to make lateral stripes with 3mm thickness in the embarkment. The colored sand was prepared by coating the Jumunjin sand with black lead powder. The photographs illustrate the two characteristic modes of failure in embarkments. One is the soil arching failure and the other is the punching shear failure. The failure mode depends on the height of embankment and the space between cap beams. That is, if the embankment is high enough compared with the space between cap beams, it will fail in arching failure. On the other hand if the embarkment is relatively low or the space between piles is too wide, it will fail in punching shear failure. The soil arching develops in embarkment as a semicylindrical arch with a thickness equal to the width of the cap beam. And the soil wedge developed above the cap beams remains intact during both arching and punching failures. The boundary of punching shear failure of the displaced soil mass can be defined on the basis of observation of the photographs.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.9-10
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• 2015

Waste Concrete Powder will be generated during the manufacture of construction waste as recycled aggregate Waste concrete. The main component of the waste concrete Powder is a silica-based composition 51% SiO₂, waste concrete cement-based composition Al₂O₃ 10%, CaO 26% component are contained. The material is silica sand of PHC piles should experiment by replacing the Waste Concrete Powder. The compressive strength results are as follows. 25% when the Silica was replaced 32.5Mpa, when 50% have replaced 43.4Mpa, when 75% have replaced 45.3Mpa was measured. Compared with the non-replaced test sample it appears that the strength increases. Therefore, it is determined that the practical use of the PHC piles by replacing silica via this experiment is possible.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.1210-1217
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• 2006

실내시험 및 모형시험에 의하면 굴패각은 모래의 대체재료로써 활용가능한 것으로 나타났다. 본 연구에서는 굴패각 모래 혼합시료에 대한 대형전단시험 결과와 굴패각 모래 다짐말뚝에 대한 현장재하시험 결과를 제시하였다. 굴패각 모래 혼합시료는 혼합율 30%까지는 혼합율이 증가할수록 전단강도가 증가하였으며 그 이상의 혼합율에서는 수렴하는 경향을 나타내었다. 순수모래다짐말뚝과 굴패각-모래 다짐말뚝에 대한 재하시험 결과로부터 두 말뚝간의 허용지지력에는 거의 차이가 없음을 알 수 있었다.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.990-997
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• 2005

In this paper, the measured results obtained from the ground improved by SCP method at quay-wall caisson foundation in Pusan New Port 1-1 phase are analyzed and then compared with the values predicted by a consolidation theory. The measured settlement is generally smaller than the predicted settlement. For consolidation velocity, the measured velocity is later than the predicted value. According to the execution of caisson placing phases, the predicted value shows higher settlement than the measured one with time being.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.966-973
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• 2005

The stress concentration ratio in accordance with area replacement ratios were considered as core elements of design. However, the stress concentration ratio will be vary depends on progress of consolidation in clay ground. And, since it is not sure to know the affecting factors accurately, the value is decided based on field experiences. To use SCP method more effective and correspond to soil improvement, the decision on proper area replacement ratio through the exact stress concentration ratio is very important. Accordingly, a numerical analysis on influence of various factors that needed to make rational designing guide for decision of proper area replacement ratio to stress concentration ratio was executed in this study.

• Proceedings of the Korean Geotechical Society Conference
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• 1992.10a
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• pp.121-130
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• 1992

Assessement of comsolidation characteristics of soft soil is very important in the project of soft soil improvement. In the design step, the consolidation characteristics of soil is determined by the laboratory tests (typically oedometer test), generally. But there is big differences between the condition of laboratory test and the condition of field(in situ). the differences results in the considerable difference between the predicted and measured consolidation behavior. This article analyzed the consolidation data of the "SOFT SOIL IMPROVEMENT PROJECT of the 2nd Namdong Industrial Complex at Inchon". The project was improving the road way net work in the 2nd Namdong Industrial Complex by preloading and sand pile method. Field instrumentation was performed at 10 points which consist of pneumatic piezometers, magnetic probe extensometers, inclinometers and electronic dipmeter. The results showed that there is big difference in the laboratory predicted consolidation behavior and field consolidadion behavior. Also there was big difference in the settlement behavior and pore pressure behavior. This article investigated the above factors by comparing the settlement, pore pressure and strength at different conditions.onditions.

• Proceedings of the Korean Geotechical Society Conference
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• 1992.10a
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• pp.149-155
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• 1992

In case of construction of the final refuse disposal site on the ground where 20m soft clay layer is deposited, Sand Compaction Pile(SCP) was driven with a view to increase the strength and reduce the settlement when the reclaimed revetment intend to be constructed first in a short time. Field monitoring method is carried out in order to overcome the problems of settlement and stability in the construction of the reclaimed revetment and the assumed problems in the design of composite ground. In this paper the observed data from monitoring sections are analysed, fedback to the desigh and field, and compared with FEM analysis. Conclusions are as follow: in case of 70% replacement the use of modified soilparameters makes the FEM analysis of SCP possible. In case of 27% replacement, n(stress concentration ratio)=0.2-0.3, B(measured settleme reduction coefficient)=0.43 are evalated. Also, horizontal displacement is remarkably happened around the ground.