• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1712-1716
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• 2008

Performance of ground improvement project using prefabricated vertical drains of condition, in which approximately 10m dredged fill overlies original soft foundation layer in the coastal area has been conducted. From field monitoring results, excessive ground settlement compared to predicted settlement in design stage developed during the following one year. In order to predict the final consolidation behavior, recalculation of consolidation settlements and back analysis using observed settlements were conducted. Field monitoring results of surface settlements were evaluated, and then corrected because large shear deformation was occurred by construction events in the early stages of consolidation. To predict the consolidation behavior, material functions and in-situ conditions from laboratory consolidation test were re-analyzed. Using these results, height of additional embankment is estimated to satisfy residual settlement limit and maintain an adequate ground elevation. The recalculated time-settlement curve has been compared to field monitoring results after additional surcharge was applied.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.349-356
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• 2003

Almost every material of PVD (Prefabricated Vertical Drain) has the fatal problem on the condition - the length must shorten with the settlement of the surrounding grounds - which all PVDs must satisfy. Kinking deformation by buckling of PVD due to consolidation settlement Is discussed in this paper. A new testing device to clarify the deformation of PVD under consolidation of surrounding clay was developed and the fiber drain and a PVD made of plastics were compared under the same condition of consolidation using natural clay specimens. The results are also shown in this paper.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.475-479
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• 2010

For a rational evaluation of the spatial distribution of consolidation settlement, it is necessary to adopt probabilistic method. In this study, mean and standard deviation of consolidation settlement of whole analysis region are evaluated by using the spatial distribution of consolidation layer which is estimated from kriging and statistics of soil properties. Using these results and probabilistic method, the area need to be raised the ground level for balancing the final design ground level are determined.

• Geomechanics and Engineering
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• v.10 no.2
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• pp.225-245
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• 2016

Settlement of foundations in permafrost regions primarily results from three physical and mechanical processes such as thaw consolidation of permafrost layer, creep of warm frozen soils and the additional deformation of seasonal active layer induced by freeze-thaw cycling. This paper firstly establishes theoretical models for the three sources of settlement including a statistical damage model for soils which experience cyclic freeze-thaw, a large strain thaw consolidation theory incorporating a modified Richards' equation and a Drucker-Prager yield criterion, as well as a simple rheological element based creep model for frozen soils. A novel numerical method was proposed for live computation of thaw consolidation, creep and freeze-thaw cycling in corresponding domains which vary with heat budget in frozen ground. It was then numerically implemented in the FISH language on the FLAC platform and verified by freeze-thaw tests on sandy clay. Results indicate that the calculated results agree well with the measured data. Finally a model test carried out on a half embankment in laboratory was modeled.

• Journal of the Korean Geotechnical Society
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• v.19 no.3
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• pp.33-38
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• 2003

Marine sediment capping is a technique where clean sand is placed over contaminated sediment to reduce the migration of contaminants to the environment. The design of in-situ caps placed over marine sediment must take into consideration the self-weight consolidation of the cap and the consolidation of the sediment as a result of adding the cap layer. Centrifuge tests were adopted to simulate the effects of consolidation settlement of capped marine sediment caused by the placement of a clean sand layer. The modeling of models technique was utilized to verify the correct modeling procedures used in this study. Two centrifuge tests were conducted with the same boundary conditions at different gravitational accelerations of 100 g and 50 g. There was good agreement between these tests. It can be concluded that the centrifuge experiment is able to model consolidation settlement of capped marine sediment.

• Journal of the Korean GEO-environmental Society
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• v.9 no.2
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• pp.5-13
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• 2008

To identify the reclamation history formed by top dredged soil reclamation layer over the original ground, various field tests and laboratory tests were conducted. Especially when the original ground was not completely consolidated, CPTu test was carried out to calculate rational settlement due to the banking load. CPTu test results showed that the degree of consolidation of weak clay ground by dredged reclamation was on average 80%. As the research area was not completely consolidated by dredged reclamation in the past, the consolidation settlement should account for the residual settlement (20%) in the case of additional banking load. When the degree of consolidation of the original ground was not taken into account, the residual consolidation was expected in excessive settlement (up to 20%) and in such case PBD (Plastic Board Drain) was not effective in obtaining desired degree of consolidation.

• Journal of the Society of Disaster Information
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• v.15 no.1
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• pp.84-97
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• 2019

Purpose: The consolidation settlement of soft ground is dependent on the distribution of pore water pressure which is also affected by hydraulic conductivities (boundary condition) of layers, thickness of clayey soil layer and surcharge. Results: However, the current consolidation analyses are mostly based on Terzaghi's consolidation theory that assumes the initial pore water pressure ratio with depth to be constant. In this study, numerical analysis are carried out to investigate the variation of pore water pressure dissipation with depth and thickness of clayey soil layer, time, surcharge as well as drainage conditions. Conclusion: Comparative study with Terzaghi's consolidation theory is also conducted. The result shows that Terzaghi's consolidation theory should be used with caution unless it is ideally corresponded to the isochrone.

• Journal of the Korean Geosynthetics Society
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• v.21 no.2
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• pp.1-9
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• 2022

Recently, the reclamation of public waters has been on a downward trend due to environmental problems, but there is a limitation to evaluating environmental characteristics index uniformly. In this study, the stability of settlement behavior on public waters reclaimed land was analyzed using the experimental test. From the primary consolidation influence factors, the characteristics of the waste lime was similar that of clay in process of consolidation. Assuming that the waste lime landfill is the layer reinforced with thin geosynthetic reinforcement, the settlement was predicted by calculating the amount of increase using the Westergaard method. As a result of predicting settlement with degree of consolidation, it was found that the increase in stress was reduced by 40% when the surface layer of the soft ground was reinforce with geotextiles compared to the case where it was not reinforced. In addition, the consolidation behavior characteristics of clay and waste lime were compared using the correlation between the plasticity index and internal friction angle of waste lime. Since the waste lime in the public process of consolidation, it was predicted that long-term settlement will increase further.

• Journal of the Korean GEO-environmental Society
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• v.10 no.7
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• pp.143-150
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• 2009

Material functions about effective stress, permeability, coefficient of consolidation and coefficient of volume change has important role to predict consolidation velocity and settlement of soft ground. Modified oedometer for radial drainage is adapted to find out material functions on laboratory tests. Undisturbed sample for laboratory tests were taken from construction sites of industrial complexes on southern coastal area which consists of upper dredged fill and lower original clay layer. For different drainage condition in consolidation process void ratio, effective stress, permeability, coefficient of consolidation and coefficient of volume change has been assessed with results of existing standard oedometer tests. It is worthwhile to note that consolidation material functions could be expressed as regression equation by Stark (2005), heterogeneity for permeability could be assessed from these relationships.

• Journal of Industrial Technology
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• v.23 no.A
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• pp.109-118
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• 2003

This paper is results of numerical works of investigating effects of horizontal drain arrangements on vacuum consolidation. Extensive numerical analyses were carried out to find the appropriate arrangements of horizontal drain of vacuum consolidation. Commercially available program of CRISP, well known to be good to modelling the behavior of clay material, was used Cam-clay model, based on the Critical State of Soil Mechanics(CSSM), was used to simulate the geotechnical engineering behavior of clay. Model test results carried out previously in the laboratory were compared with numerically estimated results and it was found that results about consolidational settlement with times were in good agreements. Based on this confirmation, parametric numerical study was performed to investigate effects of horizontal drain arrangements on vacuum consolidation with changing the vertical and horizontal spacings between drains for the given soil properties and vacuum. The effect of distance of drain located in top layer from the surface of the ground on the settlement due to vacuum was also investigated. As a results of numerical analyses, appropriate arrangements of horizontal drain to maximize the consolidation settlement due to vacuum were found. The mechanism of vacuum consolidation about the vacuum pressures being transferred to the effective stresses around drains was also evaluated.