• Tunnel and Underground Space
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• v.10 no.3
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• pp.355-365
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• 2000

As large underground projects such as radioactive waste disposal, hot water and heat storage, and geothermal energy become influential, the study, which consider all aspects of thermics, hydraulics and mechanics would be needed. Thermo-Hydro-Mechanical coupling analysis is one of the most complex numerical technique because it should be implemented with the combined three governing equations to analyze the behavior of rock mass. In this study, finite element code, which is based on Biot's consolidation theory, was developed to analyze the thermo-hydro-mechanical coupling in continuum rock mass. To verify the implemented program, one-dimensional consolidation model under the isothermal and non-isothermal conditions was analyzed and was compared with the analytic solution. The parametric study on two-dimensional consolidation was also performed and the effects of several factors such as poisson's ratio and hydraulic anisotropy on rock mass behavior were investigated. In the future, this program would be revised to be used for analysis of general discontinuous media with incorporating discrete joint model.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.4
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• pp.138-146
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• 2007

Geotechnical performance at the soft ground is strongly dependent on the properties of the soil beneath and adjacent to the structure of interest. These soil properties can be described using deterministic and/or probabilistic models. Deterministic models typically use a single discrete descriptor for the parameter of interest. Probabilistic models describe parameters by using discrete statistical descriptors or probability distribution density functions. The consolidation process depends on several uncertain parameters including the coefficients of consolidation and coefficients of permeability in vertical and horizontal directions. The implication of this uncertain parameter in the design of prefabricated vertical drains for soil improvement is discussed. A sensitivity analysis of the degree of consolidation and calculation of settlements to these uncertain parameters is presented for clayey deposits.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4C
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• pp.137-144
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• 2009

In this research, the ground with smeared zone was reconstructed using the large consolidation test apparatus. And the reconstituted kaolinite samples at different locations were retrieved for the oedometer test. From the oedometer test results the permeability- void ratio-effective stress behavior was investigated. Based on the experimental analysis, spatial differences of permeability according to the drainage distance by both smear and radial drainage consolidation reduced as the consolidation proceeds and eventually disappeared in normally consolidated region. And the spatial variation of permeability by radial drainage consolidation showed larger differences in smaller extent than the spatial variation of permeability by smear.

• Geotechnical Engineering
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• v.10 no.4
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• pp.167-180
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• 1994

A series of long term consolidation tests were conducted under loading -unloading and loading(pc) -unloading(p.) -reloading(p,) conditions using reconstituted clay in order to investigate the effect of stress history on secondary consolidation characteristics and the applicability of the secondary consolidation model suggested by Bjerrum to overconsolidated clays. According to the test results, the secondary compression settlement affected by the stress history in the first half of experimental period and the coefficient of secondary compression, C‥‥ is dependent on overconsolidation ratio, OCR(p,1 p.), maBium OCR (p./p.), and unloading duration time. Moreover the coefficient of secondary consolidation in the latter half of experimental period Cn is mainly affected by OCR and it gradually reduces with OCR increment. Finally the comparison of the experimental results with the Bjerrum model indicates that the Bjerrum model can be applied beyond certain range of stress history in the overconsolidated clay.

• Journal of the Korean Geotechnical Society
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• v.15 no.5
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• pp.281-290
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• 1999

The coastal area, particularly along the West and South coasts in Korea, is often reclaimed with dredged marine-clay to meet the demand of land capacity. A large number of ground improvement techniques are developed for such a newly formed soft clay deposit. However, the quick lime column method, which is effectively used for the purpose of ground improvement in the other countries, is seldom applied in Korea. This study, therefore, focuses on the development of appropriate soft soil improvement technique by using quick lime column. A model test as well as finite element analysis was conducted to identify the consolidation characteristics around the lime column. Although actual pore water pressure measured from model tests does not coincide with the predictions made by finite element method and Chen ＆ Law's theoretical formula, their trends are quite similar. It is revealed from this study that the pressure caused by the expansion of lime column affects considerably the consolidation characteristics of the surrounding ground.

• Journal of the Korean Geotechnical Society
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• v.16 no.1
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• pp.43-50
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• 2000

In this paper, the consolidation efficiency and the equivalent diameter of the cross shaped drain are examined by using the laboratory test and the numerical model, and the results are compared with those of the band shaped drain. The equivalent diameter of the tested drains is back-calculated from the laboratory experiment and compared with those calculated from the formula suggested in the literature. The efficiency of the cross shaped drain is evaluated by using the 3-D flow program which was validated by the settlement-time test fill data. The results of laboratory test show that the equivalent diameter of the band shaped drain was close to the Rixner's formula and that of the cross shaped drain was fit to the following formula: $d_w\;=\; \\tarc{3}{4}.(b+t)$The results of the numerical analysis show that the cross shaped drain can reduce the consolidation time by 9-10% from that for the band shaped drain. The equivalent diameter obtained from the numerical flow model by using the field data is 3.5 times smaller than that obtained from the laboratory consolidation test.

• Composites Research
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• v.16 no.3
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• pp.1-8
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• 2003

Densification occurs by the inelastic flow of the matrix materials during the consolidation processes at high temperature for MMCs, and the results depend on many process conditions such as applied pressure, temperature and volume fraction of fiber and matrix materials. This is particularly important in titanium matrix composites since material failure may occur by either the applied conditions or microstructural parameters through the processes, and thus a generic model based on micro-mechanical approaches enabling the evolution of density over time to be predicted has been developed. The mode developed is then implemented into FEM so that practical process simulation has been carried out. Further the experimental investigation of the consolidation behavior of SiC/Ti-6Al-4V composites using vacuum hot pressing has been performed, and the results obtained are compared with the model predictions.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.923-932
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• 2009

Generally most of pile foundations are constructed with group pile rather than single pile. The study on efficiency and bearing capacity which are major elements for rational design of this group pile has been actively progressed, whereas there are truly only a few studies of negative skin friction working on group pile due to the consolidation of ground. The purpose of this study is to determine, among the elements of negative skin friction applied to pile, the occurrence modality of negative skin friction at center, side, and corner of $3{\times}3$ group pile using model test and, based on those observations, to propose the effective design direction of group pile.

• Geomechanics and Engineering
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• v.8 no.4
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• pp.559-594
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• 2015

A nonlinear creep function incorporated into the elastic visco-plastic model may describe the long-term soil deformation more accurately. However, by applying the conventional procedure, there are challenges to determine the model parameters due to limitation of suitable data points. This paper presents a numerical solution to obtain several parameters simultaneously for a nonlinear elastic visco-plastic (EVP) model using the available consolidation data. The finite difference scheme using the Crank-Nicolson procedure is applied to solve a set of coupled partial differential equations of the time dependent strain and pore water pressure dissipation. The model parameters are determined by applying the algorithm of trust-region reflective optimisation in conjunction with the finite difference solution. The proposed method utilises all available consolidation data during dissipation of the excess pore water pressure to determine the required model parameters. Moreover, the reference time in the elastic visco-plastic model can readily be adopted as a unit of time; denoting creep is included in the numerical predictions explicitly from the very first time steps. In this paper, the settlement predictions of thick soft clay layers are presented and discussed to evaluate and compare the accuracy and reliability of the proposed method against the graphical procedure to obtain the model parameters. In addition, comparison of the available experimental results to the numerical predictions confirms the accuracy of the numerical procedure.

• 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.