• The Journal of Engineering Geology
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• v.23 no.4
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• pp.503-510
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• 2013

Shear wave velocity is widely used as an parameter for investigating subsurface characteristics and for obtaining the design parameters based on theoretical equations. This study seeks to estimate the coefficient of shear wave velocity in Busan clay via laboratory tests. Eight specimens were extracted at depths of 10, 12, 15, 20, 22, 25, 30, and 31 m. The specimens were subjected to the consolidation test to determine the relationship between effective stress and shear wave velocity. The relationship shows a non-linear trend and is similar to the results of a previous study. The coefficient shows constant coverage and a relationship between ${\alpha}$ and ${\beta}$ is suggested. The results demonstrate that this coefficient could be used as a reference value to determine engineering parameters based on the shear wave velocity.

• Journal of the Korean Geotechnical Society
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• v.21 no.2
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• pp.5-16
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• 2005

Tn this study, model soil deposits are prepared in large test chambers to minimize the scale effects. Also, slurry of mixture containing 50 percent kaolin clay and 50 percent silica has been consolidated to simulate the process of natural soil deposit formation and to reduce the consolidation time. To provide a more detailed description of varying soil properties along the soil profile of model clay deposits and to compare the in-situ test results with those from prototype tests, miniature in-situ tests, including vane shear, piezoprobe, and cone penetration tests were conducted in each of the clay deposits. The current results indicate that consistent soil deposits were prepared for the current and previous test programs. Also, reasonable predicting methods of prototype behavior based on model in-situ test results were suggested in this study by examining differences between the test results from both the model and prototype tests.

• Journal of the Korean GEO-environmental Society
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• v.15 no.3
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• pp.49-55
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• 2014

Characteristics of sedimentation of dredged soil is depended on the field condition and characteristics of dredged soil because dredged fill ground was formed by various field condition, sedimentation and self-weight consolidation process of dredged soil. Dredged fill ground is formed as separated sedimentary layer by characteristics of dredged soil. Therefore, it requires some special test method to consider a various field condition, characteristics of sedimentation and self-weight consolidation of dredged soil. In this study, in order to identify the characteristics of sedimentation of dredged soil with disposing velocity geo-centrifuge test and laser particle size analyzer were performed. As a results, river and mixed dredged soil show the separation sedimentation by soil particle size. And sedimentation of clayey dredged soil is parallel to the bottom surface of dredged fill space.

• Journal of the Korean Geotechnical Society
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• v.25 no.11
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• pp.117-130
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• 2009

In this paper, a series of laboratory chamber tests were carried out to evaluate the applicability of a porous concrete pile fabricated with recycled aggregates (RAPP) for the soft ground improvement. While performing the laboratory chamber tests for the RAPP, the surface settlement, excess pore pressure and vertical stress distribution with time were compared with those of SCP provided by You (2003) under the same experimental condition. In addition, the experimental results were compared with the numerical simulation using ABAQUS in this study. The results show that the settlement reduction is significantly enhanced due to the stress-sharing mechanism between the RAPP and soil formation by stress concentration on the RAPP. Furthermore, the comparison of consolidation rate shows that the RAPP can accelerate consolidation as well, which behaves as a vertical drain.

• Journal of the Korean Geotechnical Society
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• v.25 no.8
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• pp.33-45
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• 2009

The conventional single-core PBDs have been widely used in order to accelerate consolidation settlement of soft grounds. When using the single-core PBD in a thick clay deposit, a delay of consolidation may occur due to high confining pressure in the thick deposit and necking of drains. This study is to compare the performances of soil improvement by the single-core and double-core PBD installed at a site in Busan New Port which exhibits approximately a 40m-thick clay layer. An in-situ test program was performed at the test site where a set of the double-core PBDs and single-core PBDs were installed to compare the efficiency of each drain. In addition, the discharge capacity of each PBD has been measured using the modified Delft Test. A series of laboratory tests for estimating in-situ soil properties have also been performed in order to obtain input parameters for a numerical program ILLICON. The discharge capacity of the double-core PBD is higher than that of the single-core PBD in the modified Delft Test. However it is observed from the comparative in-situ test and numerical analysis that there is no difference in the performance of ground improvement between the two drain systems. This discrepancy comes from the fact that the amount of water released during consolidation in most common field conditions is much smaller than the capacity of even the single core PBD. And thus, considering actual field conditions, it can be concluded that the single-core PBD has enough discharge capacity even in the thick clay deposit such as this test site.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.3
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• pp.75-84
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• 1991

When we construct the earth structures such as embankments, on soft ground which are consisted of thick marine silty clay, the foundations deform due to consolidation and creep. For the stabilization of the earth structures constructed on soft foundations, we usually uses the mattress and they play an important role in increasing an ultimate bearing capacity by the dispersion of load of embankment. The purpose of this paper was to predict rationally a long term deformation of earth structures and to contribute to embankment design and maintenance. We determined a rheological model of marine clay from experimental data, and developed a computer program using the chosen model and found out the long term behavior of embankment. The results of this paper are as follows: 1. The developed program can analyze simultaneously consolidation and creep. 2. From the results of creep test, the rheological model of marine silty clay can be represented by the Vyalov model. 3. The displacement of embankment on reinforced foundation were smaller than those of the unreinforced foundation in showing the effects of geotextiles on foundation deformations.

• Journal of the Korean Geotechnical Society
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• v.24 no.1
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• pp.111-118
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• 2008

In the study a 2 dimensional model test was executed to grasp the effect of the taking load of equipments on the ground when improving a soft ground like dredging reclaimed ground. The static load and the dynamic load in the consolidated model ground was $0.02kg/cm^2,\;0.03kg/cm^2\;and\;0.04kg/cm^2$ respectively. After consolidating far two months by consolidation load of $0.02kg/cm^2,\;0.03kg/cm^2\;and\;0.04kg/cm^2$ respectively, the ultimate bearing capacity was $0.16kg/cm^2,\;0.19kg/cm^2,\;0.24kg/cm^2$ respectively. And the energy price of dynamic load test at the same point as the settlement of static load test indicated $E=336{\sim}945kg{\cdot}cm,\;E=252{\sim}780kg{\cdot}cm\;and\;E=323{\sim}727kg{\cdot}cm$ for each consolidation load. When the static load and the dynamic load operated at the same ground condition, the heaving quantity was bigger in the case of the dynamic load than in the case of the static load, and the horizontal displacement quantity the in the case of dynamic load was exhibited very deficiently compared to the quantity in the case of static load test.

• Journal of the Korean Geotechnical Society
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• v.24 no.5
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• pp.107-115
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• 2008

This paper is performed to examine the effect of creep during the primary consolidation and the applicability of the Yin's EVP (Elasto-Visco-Plastic) model. In ordinary consolidation theories using the elastic model, the primary consolidation process can be expressed but the secondary consolidation process cannot. It is due to the viscosity, which can express the secondary consolidation, and is sometimes related to the scale effect (difference of the thickness of clay layer between laboratory sample and field condition) such as hypotheses Type A and Type B shown by Ladd et al. (1977). Usually, the existence of the creep during the primary consolidation has been conformed and the Type B is well acceped. On the other hand, from the large-scaled consolidation tests the intermediate characteristic between Type A and Type B was proposed as Type C by Aboshi (1973). In this study, to clarify the effect of creep on the settlement-time relation during the primary consolidation in detail, Type B consolidation tests were performed using the separate-type consolidation test apparatus for a peat and clay. Then the test results were analyzed by using Yin's EVP Model (Yin and Graham, 1994). In conclusion, followings were obtained. At the end of primary consolidation, the compression for the subspecimens should not be the same because of the difference of the excess pore water pressure dissipation rate. And the average settlement measured by the separate-type consolidometer coincides with the analyzed one using the Yin's EVP model. As for the dissipation of the excess pore water pressure, however, the measured excess pore water pressure dissipates faster compared with the Yin's model.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.909-914
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• 2008

미세-점착성 퇴적물로 구성되는 퇴적저면의 침식특성을 해석하기 위해, 고령토 퇴적저면에 대한 침식실험이 환형수조를 이용하여 수행되었다. 현재, 퇴적저면의 침식특성 연구에 대한 국내사례는 전무한 실정으로, 본 연구는 퇴적저면에 대한 침식실험 방법 및 결과의 타당성 검증을 목적으로 한다. 이를 위하여, 본 연구에서는 압밀시간 조건에 따라 4가지의 서로 다른 퇴적저면이 조성되었고, 각 저면별로 저면깊이에 따른 저면밀도의 변화가 우선적으로 정밀 측정되었다. 각 퇴적저면별 침식실험으로부터는, 바닥전단응력(${\tau}_b$)의 변화에 따른 저면 침식깊이(즉, 수층 부유사 농도)의 변화 측정을 통하여, 저면깊이에 따른 저면전단강도(즉, 침식한계전단응력, ${\tau}_S$)의 변화 값들이 정량적으로 분석되었으며, 최종적으로 잉여전단응력(${\tau}_b-{\tau}_S$)과 침식률 간의 관계식이 산정되었다. 퇴적저면 침식특성에 관한 과거 해외 연구 결과와의 비교 검토를 통하여, 본 연구에서 사용 혹은 적용된 실험장치, 실험 방법 및 실험결과가 타당성이 있음이 확인되었다.

• Journal of the Korean GEO-environmental Society
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• v.10 no.4
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• pp.59-63
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• 2009

In this study, Nano-geosynthetics with electroosmosis method was used and tried to verify the possibility of usage for soft ground improvement. Electroosmosis tests were performed with increasing the voltage level and changing distance between electrodes. The electrokinetic cell was assembled and a Nano-geosynthetics was inserted into the plastic drain board. And electroosmosis was applied to the disturbed kaolin clay. In order to study the effects of ground improvement, ground settlement, water content, collected pore water and shear strength were compared and analyzed with non-applied kaolin clay. Also, the electroosmosis tests were performed with changing the distance between electrodes and the voltage size. As a results of changing the distance and voltage between electrodes, the more voltage size was increased, the more the settlement of ground, shear strength and collected pore water were increased. As the distance between electrodes were increased, the settlement of ground, shear strength, water content and collected pore water were decreased. Finally, Nano-geosynthetics as a material of electrode have the sufficient potential to improve soft ground.