• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.7-14
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• 2003

This study has investigated the feasibility of caissons for accelerating consolidation (C.A.C.) constructed in clays with anisotropic permeability by improving the former study on C.A.C. in isotropic clays. Analytical solutions for excessive pore water pressures of two-dimensional consolidation equation and average degrees of consolidation with varying time factors have been provided by considering anisotropic permeability. With varying anisotropic permeability ratios of 5, 10, and 50, consolidation times required for reaching the average degree of consolidation of 90% for C.A.C. at the section of $\xi$=0.1 are shorter than those for conventional caissons by 8, 13, and 47 times, respectively. C.A.C. is more effective in reducing consolidation time as anisotropic permeability ratio increases. This study provides also plots for average degrees of consolidation versus the width to depth ratios of analyzed sections and permeability ratios, which will enable engineers to determine easily average consolidation settlements.

• Geomechanics and Engineering
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• v.6 no.2
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• pp.173-194
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• 2014

Laboratory and field data showed that deep mixed (DM) columns accelerated the rate of consolidation of the soft foundations. Most analyses of consolidation of DM column-improved foundations so far have been based on the elastic theory. In reality, the DM columns may yield due to the stress concentration from the soft soil and its limited strength. The influence of column yielding on the degree of consolidation of the soft foundation improved by DM columns has not been well investigated. A three-dimensional mechanically and hydraulically-coupled numerical method was adopted in this study to investigate the degree of consolidation of the DM column foundation considering column yielding. A unit cell model was used, in which the soil was modeled as a linearly elastic material. For a comparison purpose, the DM column was modeled as an elastic or elastic-plastic material. This study examined the aspects of stress transfer, settlement, and degree of consolidation of the foundations without or with the consideration of the yielding of the DM column. A parametric study was conducted to investigate the influence of the column yielding on the stress concentration ratio, settlement, and average degree of consolidation of the DM column foundation. The stress concentration ratio increased and then decreased to reach a constant value with the increase of the column modulus and time. A simplified method was proposed to calculate the maximum stress concentration ratios under undrained and drained conditions considering the column yielding. The simplified method based on a composite foundation concept could conservatively estimate the consolidation settlement. An increase of the column modulus, area replacement ratio, and/or column permeability increased the rate of consolidation.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.1
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• pp.101-107
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• 2014

It has been known that Terzaghi's consolidation theory is not well consistent with the consolidation phenomenon on the soft clay ground, but this theory has still been adopted normally in practice because there is no method for estimating the consolidation settlement and rate easier than Terzaghi's theory. It is impossible to map whole part of consolidation settlement vs time curve to the curve of Terzaghi'z average degree of consolidation. If the primary consolidation and the secondary compression are happened same time, it would be useless of trying to find the end of primary consolidation, but it is needed for using Terzaghi's theory that the end of consolidation is determined to the time of beginning consistency between the final settlement analyzed with curve fitting and the experimented consolidation settlement.

• Journal of The Korean Society of Agricultural Engineers
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• v.65 no.6
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• pp.51-63
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• 2023

To improve the problem that the settlement curve of the consolidation theory of Terzaghi does not match well with the actual settlement curve, we included a secondary compression settlement and analyzed it by varying the beginning point and then obtained the following results. The current methods of calculating the compression index from the  log𝜎 curve and the coefficient of consolidation from the time-dependent settlement curve for each consolidation pressure proved that the final settlement amount will be consistent after a long time, but the actual settlement amount will always be smaller than the predicted settlement amount during the settlement progress stage. The consolidation factors estimated by the curve fitting with the condition that the secondary compression begins in the second half of the primary compression showed similar values to the consolidation factors estimated by the curve fitting for the primary compression only, and the settlement curves were in better agreement throughout the compression. It showed different values, showing low validity. It can be inferred that secondary compression acts from the point when a significant portion of the excess pore water pressure is dissipated, and the loading stress begins to have more influence on the skeletal structure of the soil. Analysis results show that secondary compression begins at the range of 91 % to 98 % on the average degree of primary consolidation.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.685-692
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• 2000

Vertical drain used improvement soft clay is made of not only decreasing construction time but also increasing the ground strength during some decades. As, it is applied to improvement soft clay with vertical drain, it is designed by the result that is caused by oedemeter test ignored anisotropic of the ground related to consolidation conditions. When we are expected consolidation conditions, the most important factors is soil of compaction and water permeability. Above all, anisotropic of the ground permeability show the results which differ between vertical and radial drainage. Recently, We study for radial consolidation coefficient and permeability coefficient that utilized Rowe Cell Consolidation and permeability tester but, it dont use well because of not only a supply lack also difficulty of test. The paper experimented with searching anisotropic of the ground so there are Rowe Cell test, standard consolidation tester and modified standard consolidation test that have pohang's soft clay ground. Therefore, we find anisotropic of the ground and a tester of easy use more than before. We made a comparison test result between the devised tester and Rowe Cell tester, Also, we learned average degree of consolidation for partial penetrating vertical drains. We were found relations as effective stress-void and effective stress-permeability coefficient through those tests.

• 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.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.49-54
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• 2000

Several soil parameters can be calculated for results of Piezocone test; sensitivity, soil classification, OCR, undrained shear strength, coefficient of consolidation etc., and used to analysis geotechnical problems. Particularly, the coefficient of consolidation which is related to degree of consolidation varies according to rigidity index(I/sub r/). In this study, rigidity index(I/sub r/) was analyzed by Roy's formula. Trixial tests and unconfined compression tests data in the ten sites was analyzed. In conclusion, rigidity index(I/sub r/) was suggested such as rigidity index(I/sub r/) = 15∼60, average rigidity index value(I/sub r/) of approximately 33 within a country.

• Geotechnical Engineering
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• v.14 no.2
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• pp.41-54
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• 1998

Predictions of consolidation settlement and time must be always erroneous because of heterogeneity of soil media. errors associated with the measurement of soil parameters, drawback of consolidation theories and so on. When filling is done on compressible soils, the observational procedure is a useful means in practice of evaluating the final consolidation settlement and time. However, the existing observational procedures including some disadvantages such as the difficulty of ending the linearity in the settlement curves, the unavoidable personal error, and so on. A new observational procedure($\sqrt{s}$ method) is suggested here for the consolidation analysis in field. As the results of applying the $\sqrt{s}$ method with other methods to two field data. the fecal settlements predicted by the s method as well as by the Asaoka'$\sqrt{s}$ method agreed well with the measured values. However, results obtained from the hyperbolic method(Tan, 1991) were always overestimated. and there happened many cases not to be predicted by the Hoshino's method. In the settlement curve from the $\sqrt{s}$method, the linearity between 60 and 90 eye of the average degree of consolidation is shown. and then the possibility of a personal error seems to be unusual. The final consolidation times(at $U_{95}$) predicted by the $\sqrt{s}$ method agreed well with the measured ones. but the ones by Asaoka and Tan(1996) methods were very much underestimated or overestimated. where $U_{95}$, is the average degree of consolidation of 95%. The big errors of these two methods seem to result from unconsidering the effect of stage construction.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.495-508
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• 2010

Vertical drains are commonly used to accelerate the consolidation process of soft soils, such as dredged materials. The installation of vertical drain provides a radial drainage path to water in the deposit soil in addition to the vertical direction. An estimation of time rate of settlement is considerably complicated when vertical drains are installed to enhance consolidation process of dredged material because the vertical drains are commonly installed before self-weight consolidation is ceased. In this paper, the vertical drain theory developed by Barron(1948) is applied to analyze the non-linear consolidation behavior considering radial drainage. The overall average degree of self-weight consolidation of the dredged soil under the condition that the water is drained in both radial and vertical directions is estimated using the Carillo(1942) formula. In addition, the Morris(2002) theory and the one-dimensional non-linear finite strain numerical model, PSDDF, are applied to analyze the self-weight consolidation in case of only the vertical drainage is considered. The new analysis approach proposed herein can simulate properly the time rate of the self-weight consolidation of dredged materials that is facilitated with vertical drains.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.445-454
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• 2006

Myungji Housing Complex is located in the Nakdong River plain in which the Busan soft clays are developed. It has thick soft soil laver of about GL(-)50m including loose sandy layers, upper and lower clayey layers. The clayey layers have been being consolidated since the land reclamation was completed to build the place for Housing Complex(Apartment) in 1997. Therefore, as one of a series of advance preparations of this project, study was carried on the geotechnical characteristics under the foundation The first part of this paper represents a brief geological history. Then, geotechnical characteristics of clay was analyzed in the classical developments in soft clay. They were based on the geotechnical data obtained by site investigations performed from 1992 to 2005. Finally, we evaluated the average degree of consolidation at this point in time and the residual settlements of upper clayey layer using dissipation and oedometer tests for this project