• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.301-310
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• 2003

In order to design accurately sand compaction pile (SCP) method with low replacement area ratio, it is important to understand the mechanical interaction between sand piles and clays and its mechanism during consolidation process of the composition ground. In this paper, a series of numerical analyses on composition ground improved by SCP with low replacement area ratio were carried out, in order to investigate the mechanical interaction between sand piles and clays. The applicability of numerical analyses, in which an elasto-viscoplastic consolidation finite element method was applied, could be confirmed comparing with results of a series of model tests on consolidation behaviors of composition ground improved by SCP. And, through the results of the numerical analyses, each mechanical behavior of sand piles and clays in the composition ground during consolidation was elucidated, together with stress sharing mechanism between sand piles and clays.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.936-942
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• 2013

This paper presents the results of laboratory tests conducted to investigate the effectiveness of applying methodology of a sand compaction(SCP) and a gravel compaction pile(GCP) on soft ground. The test conditions involved relatively low replacement ratios (=10, 20, and 30%) of a pile to unit cell at 1g (gravity acceleration) level. Results revealed that GCP significantly enhanced bearing capacity, settlement reduction, and consolidation rate compared with SCP.

• 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.

• The Journal of Engineering Geology
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• v.26 no.4
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• pp.485-495
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• 2016

To reinforce and improve the soft ground under a breakwater while using materials efficiently, the replacement ratio and leaving periods of surcharge load are optimized probabilistically. The results of Bayesian updating of the random variables using prior information decrease uncertainty by up to 39.8%, and using prior information with more samples results in a sharp decrease in uncertainty. Replacement ratios of 15%-40% are analyzed using First Order Reliability Method and Monte Carlo simulation to optimize the replacement ratio. The results show that replacement ratios of 20% and 25% are acceptable at the column jet grouting area and the granular compaction pile area, respectively. Life cycle costs are also compared to optimize the replacement ratios within allowable ranges. The results show that a range of 20%-30% is the most economical during the total life cycle. This means that initial construction cost, maintenance cost and failure loss cost are minimized during total life cycle. Probabilistic analysis for leaving periods of shows that three months acceptable. Design optimization with respect to life cycle cost is important to minimize maintenance costs and retain the performance of the structures for the required period. Therefore, more case studies that consider the maintenance costs of soil structures are necessary to establish relevant design codes.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1C
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• pp.19-24
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• 2006

In this study, centrifugal model tests were performed to evaluate the stress sharing between SCP and surrounding clayey soil at composite ground improved by sand compaction pile with the low area replacement ratio. The SCPs were formed by the "frozen pile" method and pressure cells were installed on pile and surrounding clayey soil to observe stress sharing characteristics. As a result of centrifugal tests, it is shown that the value of stress concentration ratio is mainly affected by area replacement ratio, loading condition and elapsed time.

• Journal of the Korean GEO-environmental Society
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• v.15 no.1
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• pp.25-34
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• 2014

The aim of this study is to analyze the mechanical characteristics and settlement feature of the composite ground with structural form changes. The laboratory model test is a soil tanker to be contained with clay and grid form improved soil, which is conducted in total 9 case with the uniaxial compressive strength of improved soil and replacement ratio of improved soil. The numerical analysis for variation of stress distribution ratio with depth was performed in the same conditions which are the laboratory model test. As a result, stress distribution ratios in mid and high replacement ratio are increasing and settlement is decreasing, except low replacement ratio. This study is presented for form effect ratio and settlement reduction factor with change of structure form, which is able to be helpful in further research and reference for change of structural forms at composite ground.

• Journal of the Korean GEO-environmental Society
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• v.12 no.8
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• pp.33-38
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• 2011

Presently, domestic SCP method with low replacement ratio is required as alternative in order to overcome the profitability of the sand resource because of the deficiency phenomenon of the sand resource by the actual condition design and construction is made by SCP method with low replacement ratio more than 70% for the port construction in the safe side. Sand compaction pile(SCP) method has been mainly used to improve the properties of soft clay or loose sandy ground. In design of SCP at soft clay ground, it is very important to determine the stress concentration ratio of composite ground relevant to the area replacement ratio. In this study, 2-dimensional FEM analyses were carried out to evaluate the stress concentration ratio of composite ground depending upon the area replacement ratio. When the interpretation result replacement ratio was 30%, the stress assigned rate showed and as the replacement ratio was high, the stress assigned rate according to the sinkage showed the low stress assigned rate.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.443-452
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• 2005

The compaction pile methods with low replacement area ratio used sand(SCP) or gravel(GCP) has been usually applied to improvement of soft clay deposits. In order to design accurately compaction pile method with low replacement area ratio, it is important to understand the mechanical interaction between sand piles and clays and its mechanism during consolidation process of the composition ground. In this paper, a series of numerical analyses on composition ground improved by SCP and GCP with low replacement area ratio were carried out, in order to investigate the mechanical interaction between sand piles and clays. The applicability of numerical analyses, in which and elasto-viscoplastic consolidation finite element method was applied, could be confirmed comparing with results of a series of model tests on consolidation behaviors of composition ground improved by SCP. And,through the results of the numerical analyses, each mechanical behaviors of compaction piles and clays in the composition ground during consolidation was elucidated, together with stress sharing mechanism between compaction piles and clays.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.472-485
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• 2008

In this study, sand compaction pile method was adopted to improve the soft ground under the permanent dyke, namely west sea dyke of Incheon New Port. The row replacement ratio 30% was applied to consider the ground condition, environmental side and the construction cost of the site. The stability and displacement analysis was carried out by respectively SLOPE/W and PLAXIS 2D program. Based on this analysis, it is found that the safety factor and displacement is within an allowable criteria. The model experiment was carried out using the acryl soil box with $400(H){\times}1200(L){\times}250(W)mm$ to show the displacement of the dyke and behavior of soft ground. Based on this experiment results, it is found that the settlement does not occur from 1 and 2 loading phases and horizontal displacement of 0.0075% occurs from 2 phases. It is also found that the differential settlement occurs 0.05mm corresponding respectively 0.02% and 0.03% of the dyke height(15cm).

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.394-401
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• 2006

This study developed two dimensional finite element program(FE-SCP) for the analysis of a composite ground reinforced by sand compaction piles with a low area replacement ratio based on the Mohr-Coulomb elastic perfectly plastic constitutive model. Program FE-SCP give some conveniences to users such as automatic mesh generation according to the replacement ratio and the effective sand pile diameter in the post processor. Also, it contains optimum processor in calculation of In-situ stress equilibrium considering different coefficient of earth pressure between sand pile and surrounding clay. Estimated stress-strain behavior using FE-SCP and the measured one from a centrifuge test showed good agreement comparing to the result from a general finite element program.