• Journal of the Korean Geotechnical Society
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• v.28 no.6
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• pp.31-38
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• 2012

In this present study, the long-term consolidation tests were performed using the remolded Kwang-Yang port clayey soil to clarify the effect of stress history and over-consolidation ratio (OCR) on the long-term consolidation characteristics of the soft clayey soil. For the over-consolidated state clayey soils, in case OCR exceeds 1.5, there are no great differences of secondary consolidation settlement and final settlement even if OCR increases from 2.0 to 3.0. Therefore, it has been understood that the value of OCR applied on the field site to reduce the secondary consolidation settlement and the final settlement is about 1.5. In addition, in order to investigate the relationship between the pre-loading period and the characteristics of long-term consolidation behavior obtained from the test results using the remolded Kwang-Yang port clayey soils, the influence on long-term consolidation behavior was not large though the pre-load was unloaded with the consolidation degree 70~80% exceeded.

• Journal of Industrial Technology
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• v.28 no.A
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• pp.11-17
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• 2008

Applicability of hyperbolic settlement prediction method to consolidation settlement in the dredged and reclaimed ground was assessed by analyzing results of centrifuge tests modelling self-weight consolidation of soft marine clay. From literature review about self-weight consolidation of soft marine clays located in southern coast in Korea, constitutive relationships of void ratio - effective stress - permeability and typical self-weight consolidation curves with time were obtained by analyzing centrifuge model experiments. For the condition of surcharge loading, exact solution of consolidation settlement curve obtained by using Terzaghi's consolidation theory was compared with results predicted by the hyperbolic method. It was found to have its own inherent error to predict final consolidation settlement. From results of analyzing thc self-weight consolidation with time by using this method, it predicted relatively well in error range of 0.04~18% for the case of showing the linearity in the relationship between T vs T/S in the stage of consolidation degree of 60~90 %. However, it overestimated the final settlement with large errors if those relation curves were nonlinear.

• Journal of the Korean Geotechnical Society
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• v.20 no.6
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• pp.109-118
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• 2004

The consolidation of clay occurs with time lag, and this kind of lag can be separated into plastic lag and hydraulic lag. In this study, CRS tests were performed to research the effect of original secondary consolidation of the clay with respect to the characteristics of consolidation. Test results showed that plastic time lag was one of the key factors to get the preconsolidation pressure, and suggested the formula of the Quasi-preconsolidation pressure obtained from the relationship between consolidation time lag and consolidation pressures. In addition though the characteristics of coefficient of consolidation show a wide range of values, after passing the double preconsolidation point, it showed the tendency to converge into the constant value. The coefficient of permeability in normally consolidated state is related to its void ratio, and the permeability variables, n and $C_1$ were determined by the test results using the equation suggested by Samarasinghe. et. al. And then the equation was compared with the Kozeny-Carman's equation. Because of delayed compression caused by consolidation time lag, aging effect could be also found in the relationship between coefficient of permeability and void ratio.

• Proceedings of the Korean Geotechical Society Conference
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• 2007.09a
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• pp.396-398
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• 2007

• Proceedings of the Korean Geotechical Society Conference
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• 1999.11b
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• pp.35-48
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• 1999

The Nakdong River in Korea has formed a delta area .called the Kimhae Plain near the river mouth. Its clay deposit is unusually thick (up to 60m) compared with the clays deposited in other parts of the world. Some parts of the area has been reclaimed with the height of approximately 5 to 7m after installing vertical drains for the development of important new industrial complexes. Settlement measurements were taken during the reclamation works on the soft ground, and it was revealed that the measured settlements were extremely higher than predicted. This paper discusses possible reasons on unusual large settlements from depositional environments of Kimhae clay.

• 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.

• Korean Journal of Agricultural Science
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• v.4 no.1
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• pp.88-93
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• 1977

The following is the result of experiment on consolidation test under various load increment ratios by alternation of standard load increment ratio. The more load increment ratio was, the more settlement was resulted. But expansions were not associated with load increment ratios. Primary consolidation took longer period to complete as load increment ratio was decreased. And under the condition of over-consolidated range, the completion of primary consolidation took longer period as the load was incremented. Under the condition of normal consolidated range, there was no change in time of completing primary consolidation. The coefficient of consolidation was decreased with increment of consolidation load, and the coefficient of consolidation had high values as the load increment ratio was increased. The values of ratio of secondary consolidation was highest near the transition point of consolidation curve.

• Journal of the Korean Geotechnical Society
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• v.25 no.4
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• pp.31-38
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• 2009

A continuous, fast, and convenient experimental method, replacing recent tests such as standard oedometer or self weight consolidation test, is needed for the determination of the consolidation behavior of unformed soft soils. This study introduced the seepage induced fast consolidation test using the flow pump technique. It can obtain the consolidation characteristics of unformed soft soils conveniently and fast. The seepage induced consolidation test apparatus consists of a modified triaxial cell, differential pressure transducer, flow pump, and displacement transducer. The test continuously proceeds with starting seepage forces induced consolidation, loading consolidation, and permeability test on the same sample. In addition, this test result was compared with the standard oedometer test result to make this method valid. From this study it was found that this method is a convenient and time saving effective method for obtaining data required for calculation of consolidation settlement of unformed soft soils.

• Journal of the Korean GEO-environmental Society
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• v.10 no.6
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• pp.69-77
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• 2009

The shortage of bearing capacity and settlement, shear deformation may occur when constructing a structure such as harbor, airport and bridge on soft ground such as marine clay, silty clay, sandy soil because it is very soft. The various ground improvement methods were applied to obtain preceding settlement of soft ground and strength increase. The vertical drain method has been used to reduce the required time for consolidation of the soft ground. Especially, the PBD (Plastic Board Drain) has been widely used among in the vertical drain method. In this study, a behavior of characteristic was evaluated by operating a compound drainage capacity test about the PBD (Plastic Board Drain) method applied in soft clay in deep depth. As a result, the settlement gradually occurred with increase of surface load. The consolidation settlement was processed with dissipation of pore pressure after surface load of $500kN/m^2$. Accordingly, it was found that change of settlement through load steps was resulted from dissipation of pore pressure. It was also found that the drainage capacity of vertical drains was considerably reduced with pressure increase and time elapse.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6C
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• pp.287-294
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• 2009

Suction Drain Method is a relatively new technique to improve soft ground using vacuum pressure which can be directly applied to the soft ground through drains that the pore water pressure around them are decreased without changing total stress. This can accelerate volume changes and increase strength of the ground. This paper shows the results of field test of the suction drain method applied at dredged and reclaimed clay. To evaluate the improvement effects of soft ground by the suction drain method, this paper analyzed real-time field measurements to the results of the laboratory tests and numerical analysis. The comparisons of the settlement and shear strength between suction drain method and surcharge preloading method show possibilities for replacement of the preloading methods. The settlements by suction drain method were 2.3 times larger and undrained shear strength were 300%~400% higher than surcharge method. Moreover, the water content is decreased about 30% and the preconsolidation pressure is increased about $0.52kgf/cm^2$.