• Journal of the Korean GEO-environmental Society
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• v.3 no.3
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• pp.15-25
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• 2002

The permeability coefficient is one of the fundamental engineering properties of soft clays. Consolidation process as well as migration of pollutants in soil are affected the permeability coefficient, which generally decreases with the reduction in void ratio during consolidation. After Kozeny(1927) and Carman(1956), many researchers have proposed the relationships between void ratio and permeability in such forms as; (1) log e - log k(1+e), (2) e - log k, or (3) log e - log k. Constant rate of strain (CRS) tests was performed with undisturbed samples obtained at Kunsan and Kimhae deposits, which are representative Korean marine clay. From the results of the tests, the relationships were found valid for Kunsan and Kimhae clays. The experimental correlation $C_k=0.5e_o$ was satisfied with Kimhae clay but not with Kunsan clay.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.127-135
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• 2002

The accurate evaluation of settlement is important to every steps in the constructions involving soft soils. Relating with those constructions, especially, it has been emphasized recently that the influnce of secondary settlement is important. The ratio of $C_a/C_c$ and the surcharging tests can be applied collaboratively to predicting and reducing secondary consolidation. A series of incremental loading consolidation test and surcharging tests for undisturbed samples of Kunsan clay were performed in this study. As a result of the tests, the ratio of $C_a/C_c$ for the clay was found to be 0.0329. Also, the relationship between void ratio and $t/t_p$ was shown to be linear. Accordingly, the secondary compression index, $C_a for a long term loading had a constant value regardless of time. When the total surcharge ratio was 0.4 and the dissipation ratio of excessive porewater pressure was in the range from 80% to 100%, secondary settlement was effectively reduced for Kunsan clay.

• Journal of the Korean Geotechnical Society
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• v.20 no.9
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• pp.155-166
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• 2004

The characteristics of soft clays are very important for the land development plan. This study is to investigate correlations between the engineering properties and the characteristics of clay minerals of the undisturbed clay samples obtained from Sihwa area. This study included X-Ray diffraction analysis, X-Ray fluorescence spectrometer analysis, scanning electron microscopy analysis and energy dispersive X-Ray spectrometer analysis. The correlations between the clay mineral properties and the laboratory and field testing results were investigated. The characteristics of soft clay in Sihwa area were compared with those in Yangsan and Kunsan area.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.20 no.4
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• pp.169-179
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• 2015

To understand the transport pathways of muddy sediment of the Kunsan basin in Yellow Sea, grain sizes and clay mineral of 32 surface sediments and a sediment core were analyzed. In the study area, illite is predominant (63.4~71.9%), followed by chlorite (15.1~20.2%), kaolinite (10.3~17.2%) and smectite (2~6.9%), According to the spatial distribution of the clay minerals, illite, kaolinite+chlorite and smectite show relatively higher contents in the center of the north, northeast, and the south of the study area, respectively. Considering the spatial distribution of clay mineral contents the sand ridge alignments and tidal current pathways, the smectite particles were probably derived from the south of the study area, but kaolinite and/or chlorite particles were mainly transported from the Korean coastal zone. Meanwhile, down-core variation in the contents of clay minerals of the core revealed a distinct change in fine-grained muddy sediment provenance: muddy sediment input from the Korean coastal areas has increased while the input from China has decreased since the last 5,000 year ago, by showing the amount decrease of smectite and the increase of kaolinite+chlorite at the top layer of the late Holocene muddy sediment unit of the core.

• Journal of the Korean Geotechnical Society
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• v.20 no.8
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• pp.113-121
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• 2004

The present study is suggested to estimate the degree of secondary consolidation caused by various changes of stress such as loading, unloading and reloading in improving poor subsoil through pre-compression loading construction method and, for this purpose, examined the characteristics of the consolidation of Kunsan clay through incremental loading test (IL) using standard consolidation tester and constant loading rate test (CLR), which were adapted from the constant rate of strain test (CRS). In addition, after CRS test, this study determined the characteristics of secondary consolidation and relationships among void ratio, effective stress and time according to the ratio of effective over-consolidation on reloading at the point of time of random expansion. Kunsan clay had larger expansion and smaller secondary consolidation settlement when the ratio of effective over-consolidation was high. In addition, when loading was applied after the load was removed at once, the secondary consolidation coefficient $C'_{\alpha}$ was smaller than that when the load was removed gradually, and when the ratio of effective over-consolidation was over 1.4 a similar value was produced. Based on the entire settlement resulting from reloading, the secondary consolidation coefficient $C"_{\alpha}$ increased non-linearly with the lapse of time but the final value was similar to that in the case of rapid removal. The strain velocity of void ratio was in a regular linear relationship with the increase of loading time regardless of the ratio of effective over-consolidation in both tests and it grew smaller with the increase of the ratio of effective over-consolidation.tion.

• Journal of the Korean Geotechnical Society
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• v.22 no.8
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• pp.55-62
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• 2006

The design of sand mat should be reviewed by the behaviour of excess pore pressure which is obtained by combining characteristics of soft ground with the permeability of sand mat. In this paper, in order to investigate the distribution of hydraulic gradient of sand mat, a banking model test was performed using dredged sand as materials of sand mat, and these results were compared by the numerical analysis results utilizing Terzaghi's consolidation equation. The results show that the pore pressure was influenced by the settlement increasing in the central area of sand mat as the height of embankment increases, and uprising speed of excess pore pressure due to residing water pressure is delayed compared with the results of numerical analysis. Finally, the construction of sand mat should be spreaded to reduce the increased hydraulic gradient at the central area of embankment.

• Journal of the Korean GEO-environmental Society
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• v.22 no.9
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• pp.5-16
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• 2021

In this study, piezocone coefficients of clays (Hwasung, Gunsan, Changwon, Busan) were analyzed from piezocone penetration tests those accompanied with vane shear and UU tests. Piezocone coefficients of west sea clays (Hwasung, Gunsan), i.e, N_kt is 12.6 and N_qu is 8.8, while those of south sea clays are 16.5 and 9.2 respectively. The difference of liquid limit between south and west clays causes main roles those which west sea clay is generally lower than 50%, i.e, CL, and liquid limit of south sea clay is mostly higher than 50%, i.e CH. Piezocone coefficients obtained from several tests show similar trends even though they still have some differences depending on each test. However, they show clear differences depending on liquid limit. Therefore, piezocone coefficients need to be used with caution depending on LL.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2003.08a
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• pp.222-226
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• 2003

대부분의 경우에 하구의 미세-점착성 퇴적물은 보통 무기성 광물과 유기물 및 생화학물의 혼합체이며, 광물 입자들은 주로 점토와 실트로 구성되어 있다. 이러한 혼합체의 침식특성은 사질성 퇴적물과는 달리 입자간의 응집현상에 의한 의해 크게 영향을 받으며, 응집강도는 광물질 구성, 입경분포, 유기물 함량 등으로 묘사되는 퇴적물 자체의 물리ㆍ화학적 기본특성에 따라 크게 변화하고 (Mea, 1986), 특히 저면 퇴적물의 침식 여부는 흐름 전단응력에 의한 저면퇴적물의 저항력 즉, 저면전단강도의 상대적 크기의 차이에 좌우되므로, 그 침식 특성은 저면전단강도 흑은 저면밀도로 묘사되는 저면특성에 따라 크게 변화한다(황규남 등, 2003). 또한 각 해역마다 저면 퇴적물은 퇴적물 공급원, 수동학적 조건, 생태학적 조건 등이 모두 다른 상태에서 형성된 퇴적층이므로, 저면 퇴적물의 기본특성 및 저면특성은 "site- specific" 한 성격을 갖는다. (중략)

• 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.15 no.2
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• pp.129-138
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• 1999

This study is performed for the development of a field monitoring and test technique both of self-weight and hydraulic consolidation by which the soil parameters of dredge-reclaimed clay can be obtained effectively. The field monitoring development and tests mentioned above make it possible to reproduce the process of the self-weight consolidation from settling to reclaimed soft ground. The experimental research is mainly focussed on the characteristics of self-weight consolidation of dredged clayey soil. And theoretical study has pointed out the limits in the application of Terzaghi's one dimensional consolidation theory in interpreting reclaimed clayey ground. Furthermore, a finite difference analysis has been made on the basis of Mikasa s self-weight consolidation theory which takes the problems of Terzaghi's theory into consideration. The relationships between specific volume, effective stress, and the coefficient of permeability of Kunsan reclaimed clayey soil have been obtained by laboratory tests. On the other hand, through the field monitoring, pore pressure, total pressure, and water levels have been measured after pouring. The results of these experiments have been analyzed, and compared with those from Terzaghi's method and the finite difference analysis of Mikasa's self-weight consolidation theory. In conclusion, the measured settlements is comparatively consistent with Mikasa's self-weight consolidation theory rather than Terzaghi's consolidation theory.