• Geotechnical Engineering
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• v.13 no.1
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• pp.137-146
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• 1997

In this study, a large consolidation test was carried out to estimate the consolidation behaviour of dredged clay ground improved by horizontal drain using plastic board drain with a vacuum pressure. The test results were analyzed by a numerical simulation using potential consolidation theory applied to a hollow cylinder. The rapid decreases in pore pressure and the drain speed in the plastic board indicate that the consolidation occurred quickly after the vacuum state was applied to the test soil. According to the numerical analysis obtained by applying the linear potential consolidation theory to a clay hollow cylinder with external radial drainage, the pore pressure is affected by the strain and the permeability of the soil rather than by the diffusion types. Therefore, measured surface settlement agreed with the numerical solution at the point where consolidation pressure increasing rate u: -0.5. Also the behaviour of the clay layer settlement in the place where the drain was installed was similar to that shown in Barron's consolidation theory. Finally, the design and construction procedure including the selection of the appropriate arrangement of horizontal drains were discussed based on the results of the laboratory tutsts. It is also shown that the potential consolidation theory make it possible to predict consolidation behaviour in the field using horizontal drains exactly.

• 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.

• Geotechnical Engineering
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• v.13 no.3
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• pp.5-20
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• 1997

A governing equation of uncoupled three dimensional finite strain theory of consolidation is presented. This equation is suitable for relatively thick layers, possessing large strain, non-linear material property, and variable permeability. A special numerical solution procedure has to be adopted for the finite difference scheme because the solution is not stable in using Forward-Time Centered-Space (FTCS) method and the governing equation is highly non-linear. The solution is capable of predicting settlement with respect to time. The results predicted by the developed method of analysis have been compared with those of experimental tests on different types of highly compressible soils with vertical wick drain. The uncoupled three dimensional finite strain theory of consolidation appears to predict settlement behavior well. A detailed comparison shows good agreement in terms of total settlement, and reasonable agreement with respect to time.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.1015-1023
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• 2010

While various PCPT-based methods for the analysis of consolidation were developed, additional laboratory test is needed to estimate the coefficient of consolidation. In this paper, hyperbolic method using PCPT dissipation curve for the estimation of coefficient of consolidation was proposed. To verify proposed method, field settlement test data and PCPT dissipation test data at same site were collected and analyzed. It is observed that proposed method shows good agreement with measured field settlement data.

• Magazine of the Korean Society of Agricultural Engineers
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• v.33 no.4
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• pp.96-104
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• 1991

The research effort has been focused on better calculation methods for the coefficient of consolidation under the theory of one dimensional consolidation. This research has been made available to engineers in the form of the computer program COMCv. The following conclusions can be drawn from the result of the engineering analysis, programming, and field observations. 1.Performing comparative study on six mehods(Taylor, Casagrande, Sivaram & Swamee,Su, Cour, and Scott) which can find out the coefficient of consolidation, the computer program COMCv is developed for each method. 2.Comparing the observed settlement and computed one in use of the coefficient of consolidation computed with COMCv, the result by the method of Sivaram & Swamee, Taylor, and Su is closer to the observed settlement.

• Proceedings of the Korean Geotechical Society Conference
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• 2007.09a
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• pp.383-395
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• 2007

As a state-of-the-art paper related to consolidation settlement, the 31th Terzaghi lecture was briefly described. Case histories that are compared between predicted and measured settlements in the Nakdong River deltaic plane were introduced to show the true picture of our technology. Structures and other features of clays in this country were needed to understand, which are closely related to sample disturbance and also consolidation properties. In order to improve the settlement-related technology, some problems that we have faced and their alternatives were considered.

• Journal of the Korean Geotechnical Society
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• v.25 no.9
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• pp.5-17
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• 2009

The microcomputer program PileNSF (Pile Negative Skin Friction) is developed by the authors in a graphical user interface (GUI) environment using $MATLAB^{(R)}$ for predicting the bearing capacity of a pile embedded in a consolidating ground by surcharge loading. The proposed method extends the one-dimensional soil-pile model based on the nonlinear load transfer method in OpenSees to perform an advanced one-dimensional consolidation settlement analysis based on finite strain. The developed program has significant features of incorporating Mikasa's finite strain consolidation theory that accounts for reduction in the thickness of the clay layer as well as the change of the soil-pile interface length during the progress of consolidation. In addition, the consolidating situation of the ground by surcharge filling after the time of pile installation can also be considered in the analysis. The program analysis by the presented method has been verified and validated with several case studies of long-term test on single piles subjected to negative skin friction. Predicted results of negative skin friction (downdrag and dragload) as a result of long from consolidation settlement are shown to be in good agreement with measured and observed case data.

• Journal of the Korean Geotechnical Society
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• v.29 no.4
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• pp.13-22
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• 2013

To simulate the soft ground improved by vertical drain method and to investigate the effect of overlapping smear on subsequent consolidation behavior, a series of consolidation tests with a large consolidation chamber and mandrel insertion device were conducted. Based on the test result, numerical analysis was also performed to analyze the efficiency of the vertical drain method. Laboratory test and numerical analysis results showed that the effect of smear zone increased consolidation settlement but the overlapping smear zone decreased the consolidation settlement. In addition, vertical drain accelerated consolidation rate but narrowing the drain spacing did not affect the consolidation rate because of the effect of smear. The efficiency of consolidation rather decreased substantially when the smear zone was overlapped.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.6
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• pp.183-193
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• 2003

Most construction works on the soft ground adopt instrumentation to manage settlement and stability of the embankment. The rapid progress of the information technologies and the digital data acquisition on the soft ground instrumentation has led to the fast-growing amount of data. Although valuable information about the behaviour of the soft ground may be hiding behind the data, most of the data are used restrictedly only for the management of settlement and stability. One of the critical issues on soft ground instrumentation is the long-term settlement prediction. Some observational settlement analysis methods are used for this purpose. But the reliability of the analysis results is remained in vague. The knowledge could be discovered from a large volume of experiences on the observational settlement analysis. In this article, we present a database to store settlement records and data mining procedure. A large volume of knowledge about observational settlement prediction were collected from the database by applying the filtering algorithm and knowledge discovery algorithm. Statistical analysis revealed that the reliability of observational settlement analysis depends on stay duration and estimated degree of consolidation.

• Geomechanics and Engineering
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• v.20 no.2
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• pp.87-101
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• 2020

The construction of combined pile-raft foundations is considered as the main option in designing foundations in high-rise buildings, especially in soils close to the ground surface which do not have sufficient bearing capacity to withstand building loads. This paper deals with the geotechnical report of the Northern Fereshteh area of Tabriz, Iran, and compares the characteristics of the single pile foundation with the two foundations of pile group and geogrid. Besides, we investigate the effects of five principal parameters including pile diameter and length, the number of geogrid layers, the depth of groundwater level, and pore water pressure on vertical consolidation settlement and pore water pressure changes over a year. This study assessed the mechanism of the failure of the soil under the foundation using numerical analysis as well. Numerical analysis was performed using the two-dimensional finite element PLAXIS software. The results of fifty-four models indicate that the diameter of the pile tip, either as a pile group or as a single pile, did not have a significant effect on the reduction of the consolidation settlement in the soil in the Northern Fereshteh Street region. The optimum length for the pile in the Northern Fereshteh area is 12 meters, which is economically feasible. In addition, the construction of four-layered ten-meter-long geogrids at intervals of 1 meter beneath the deep foundation had a significant preventive impact on the consolidation settlement in clayey soils.