• Journal of the Korean Geotechnical Society
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• v.15 no.1
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• pp.141-149
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• 1999

In order to investigate the anisotropy in the coefficient of consolidation of the clay deposit, a series of consolidation tests were carried out on the artificially deposited clay sample by both Rowe-type and conventional consolidometers. The results of the tests showed that the coefficient of consolidation for radially inward drainage by Rowe-type consolidometer was about two times larger than that for vertical drainage by the conventional consolidometer. The smear effect caused by vertical sand drain installation was found to be significant, especially in the overconsolidated region, but smaller with the increase in consolidation pressure.

• Geotechnical Engineering
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• v.12 no.5
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• pp.79-88
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• 1996

In this study, prediction of soil behavior under vacuum preloading with vertical drain is explored on the basis of numerical models and toe results were compared with field measurements. Reasonable prediction of the time rate of settlements and pore pressure dissipation under vacuum preloading is the maj or concern. The conventional method for vatsuum preloading is based on modeling vacuum preloading as surcharge loading for the consolidation analysis. However, this modeling may violate the real behavior of soils under vacuum loading since the total stress in the analysis varies due to the modeled surcharge loading whereas in'.situ total stress of soils under vacuum loading is constant. In this study a new method is suggested. Instead of modeling vacuum loading as surcharge loading, negative hydraulic head is applied at the surface drain boundary to simulate the vacuum preloading. Comparisons of predictions and field measurements of soil behavior under vatsuum preloading are presented and the usefulness of the new modeling technique is demonstrated.

• 기술발표회
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• s.2006
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• pp.248-260
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• 2006

광양항 3단계 1차 컨테이너터미널 부지 연약지반개량의 경우 광양지역의 특성상 재하용 토사확보 곤란, 시공기간 단축 및 환경훼손 최소화를 위해 진공압밀공법이 적용되었다. 본 사례연구에서는 진공압밀공법의 시공에 따른 문제점 및 개선사항을 제시하였고, 현장계측 및 진공 압밀완료 후에 실시된 지반조사 결과 등을 분석하여 준설매립지반에서의 진공압밀공법의 적용성을 평가하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5C
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• pp.283-292
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• 2008

In this research, finite difference (FD) scheme for the interface of the layer between different soil characteristics was suggested. Based on the suggested scheme, FD analysis program for the consolidation analysis of the multi-layered and smeared soil was developed. And the applicability of the program was investigated by the FD analysis conducted for the various soil conditions. Analysis results showed that the permeability near the drainage boundary had a dominant effect on the consolidation rate. And the consolidation rate of the soil with the constant permeability in smeared area was retarded more than the soil with the linear variation of permeability in smeared area. Simple assumption of the constant variation of permeability in smeared area could be used when the decreasing rate of permeability in smeared area was relatively low. But exact assumption of the permeability variation in smeared area should be considered when the decreasing rate of permeability in smeared area was relatively high. Finally, based on the analysis result on Busan area, the analysis considering multi-layered soil should be needed to exactly evaluate time for the completion of consolidation.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.17 no.1
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• pp.16-20
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• 2005

Consolidation of dredged fill has become important task for site treatment. The variation of stratum thickness during consolidation processing needs to be taken into consideration since hydraulic fill would go through a much larger scale strain than land soil when it is subject to a load. In this study, the consolidation period considering the variation of stratum thickness was analyzed and compared the results with those of existing consolidation studies which did not consider the variation of stratum thickness. According to the results of the study, the consolidation period of the ground with a larger strain was calculated more close to observed value in case of Mikasa theory which takes the variation of stratum thickness into consideration.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.299-306
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• 2003

Dredged soil experiences large settlement during consolidation because of its high water contents. Large settlement alters the thickness of the consolidation layer greatly with time. However, the consolidation theory proposed by Terzaghi assumes the thickness of the consolidation layer to stay constant. Mikasa has developed a more rational theory considering the change of thickness of consolidation layer but it is not well applied at the site. In this study consolidation tests have been performed using Rowe cell for the four dredged clay samples with a water content of 100%, 120%, 133% and 150%. From the test results compression index characteristics and coefficient of consolidation characteristics have been investigated. Coefficients of consolidation obtained by Terzaghi's and Mikasa's theories, have been evaluated and compared with each other. When Mikasa theory is applied in the field design, the period to reach the required degree of consolidation has been reduced compared with the result by Terzaghi theory because the time factor $T_{v}$ by Mikasa theory decreases with increasing of final strain of consolidation layer, Calculation method consolidation time by Mikasa theory was concisely explained for its practical use.e.

• Journal of the Korean Geotechnical Society
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• v.26 no.1
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• pp.21-33
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• 2010

In this paper, the consolidation and the permeability characteristics of Songdo were evaluated based on the laboratory and field tests. The test results indicate that silty clay layer above approximately E.L-15 m are consolidation layer, and sand layers embedded in consolidation layers are drainage layers. Consolidation layer was overconsolidated state before the reclamation work; however, it transferred to normalized state after the reclamation work. In addition, the average and the range of consolidation properties and magnitude of anisotropy of coefficient of consolidation were evaluated according to the soil types such as clay, silty, and clayey silt since these properties are sensitive to soil types. These analysis results can be used as preliminary design parameters of consolidation and permeability m Songdo area.

• Journal of the Korean Geotechnical Society
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• v.23 no.4
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• pp.69-77
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• 2007

In this study, the consolidation behavior of clayey ground improved by vertical drain method was analyzed by the finite difference method based on the three-dimensional elasto-viscous consolidation theory, which can express the behavior of the secondary consolidation without considering the distinction of the normally consolidated and overconsolidated states. And the applicability of the elasto-viscous consolidation theory was discussed by comparing with the test results obtained from the model test of ground improved by vertical drain system. From these results, it is found that the amount of the settlement when the excess pore water pressure almost dissipated in the clay ground with vertical drains became smaller than that of the one-dimensional condition, and then the amount and rate of the residual settlement at secondary consolidation process became larger than those of the one-dimensional condition. finally, the effect of soil parameter on behavior of consolidation process was investigated by the results of a series of numerical analysis for the normalized and overconsoldiated states.

• Geotechnical Engineering
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• v.12 no.6
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• pp.153-162
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• 1996

The undrained creep tests with isotropically and anisotropically overconsolidated clays were performed to investigate the effects of anisotropic consolidation on the undrained creep rupture behavior. Results of tests showed that the undrained creep rupture behaviors were iuluenced significantly by stress history including overconsolidation ratio and consolidation pressure ratio$(\sigma_{3c}/\sigma_{le})$. That is. the creep strength of clay increases with the increase of both overconsolidation ratio and consolidation pressure ratio. It, therefore, is dangerous to decide the possibility of creep rupture of clay by the isotropically consolidated creep rupture test in the case of the coefficient of earth pressure lower than 1.0. And the creep strength of clay could be obtained by the equation of the upper yield strength suggested by Finn and Shead(1973) irrespective of both overconsolidation ratio and consolidation pressure ratio.

• Journal of the Korean GEO-environmental Society
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• v.9 no.6
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• pp.31-41
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• 2008

Consolidation characteristics of reclamated ground with dredged soil and methods of evaluating them are investigated in this paper. For a dredged and reclamated ground with a very high water content, self-weight consolidation being progressed, its consolidation characteristics are difficult to find since it is almost impossible to have a undisturbed sample. In order to overcome such a problem, methods of laboratory tests with disturbed sample were studied to obtain consolidation parameters required to analyze consolidation settlement in practices, using the conventional infinitesimal consolidation theory, were evaluated by carrying out various laboratory tests with disturbed soils such as oedometer test, constant rate of deformation test, Rowe-cell tests with ring diameters of 60 mm, 100 mm and 150 mm and the centrifuge model tests with 40 g-levels. Constitutive relations of void ratio - effective vertical stress - permeability were evaluated by using the inverse technique implemented with the finite strain consolidation theory and results of centrifuge model tests. Design soil parameters related to consolidation such as compression index, swelling index, coefficient of volume change and vertical and horizontal consolidation coefficients were proposed properly by analyzing the various test results comprehensively.