• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 지반공학 공동 학술발표회
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• pp.443-452
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• 2005

The compaction pile methods with low replacement area ratio used sand(SCP) or gravel(GCP) has been usually applied to improvement of soft clay deposits. In order to design accurately compaction pile method with low replacement area ratio, it is important to understand the mechanical interaction between sand piles and clays and its mechanism during consolidation process of the composition ground. In this paper, a series of numerical analyses on composition ground improved by SCP and GCP with low replacement area ratio were carried out, in order to investigate the mechanical interaction between sand piles and clays. The applicability of numerical analyses, in which and elasto-viscoplastic consolidation finite element method was applied, could be confirmed comparing with results of a series of model tests on consolidation behaviors of composition ground improved by SCP. And,through the results of the numerical analyses, each mechanical behaviors of compaction piles and clays in the composition ground during consolidation was elucidated, together with stress sharing mechanism between compaction piles and clays.

• 한국지반공학회논문집
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• 제19권5호
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• pp.253-261
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• 2003

샌드드레인공법(SD공법)이나 고치환율의 샌드콤팩션파일공법(SCP공법)과 비교하여 저치환율SCP공법에 의해 개량된 복합지반의 역학거동은 모래말뚝과 점토지반 양방의 역학적 상호작용의 영향을 보다 현저하게 받는다. 따라서 본 공법의 적용에 있어서 침하저감효과나 모래말뚝 사이의 점토의 강도증가 등을 정확히 평가하기 위해서는 복합지반 내부에서의 모래말뚝과 점토와의 역학적 상호작용을 해명하여야 할 필요성이 있다. 본 연구에서는 저치환율의 모래말뚝이 타설된 복합지반에 대한 일련의 모형실험을 통하여 압밀중에 발생되는 모래말뚝과 점토 각각의 역학거동과 복합지반 내부에 대한 응력분담거동에 대하여 고찰하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.197-202
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• 2004

In order to design accurately sand compaction pile (SCP) method with low replacement area ratio, it is important to understand the mechanical interaction between sand piles and clays and its mechanism during consolidation process of the composition ground. In this paper, a series of numerical analyses on composition ground improved by SCP with low replacement area ratio were carried out, in order to investigate the mechanical interaction between sand piles and clays. The applicability of numerical analyses, in which an elasto-viscoplastic consolidation finite element method was applied, could be confirmed comparing with results of a series of model tests on consolidation behaviors of composition ground improved by SCP. And, through the results of the numerical analyses, each mechanical behaviors of sand piles and clays in the composition ground during consolidation was elucidated, together with stress sharing mechanism between sand piles and clays.

• Geomechanics and Engineering
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• 제9권5호
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• pp.669-685
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• 2015

A three-dimensional elastoplastic constitutive model, also known as a UH model (Yao et al. 2009), was developed to describe the stress-strain relationship for normally consolidated and over-consolidated soils. In this paper, an acoustic tensor and discriminator of bifurcation for the UH model are derived for the strain localization of saturated clays under undrained and fully and partially drained conditions. Analytical analysis is performed to illustrate the points of bifurcation for the UH model with different three-dimensional stress paths. Numerical analyses of cubic specimens for the bifurcation of saturated clays under undrained and fully and partially drained conditions are conducted using ABAQUS with the UH model. Analytical and numerical analyses show the similar bifurcation behaviour of overconsolidated clays in three-dimensional stress states and various drainage conditions. The results of analytical and numerical analyses show that (1) the occurrence of bifurcation is dependent on the stress path and drainage condition; and (2) bifurcation can appear in either a strain-hardening or strain-softening regime.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회 3차
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• pp.37-46
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• 2010

Marine clays are soft soil deposits having complicated mineralogy and formation characteristics. Thus, characterization of its geotechnical behavior has been a main issue for geotechnical engineers. Nowadays, the importance and applications of geophysical exploration on marine clays are increasing significantly according to the accuracy, efficiency, and reliability of geophysical survey technology. For marine clays, seismic survey is effective for density and elasticity characterization, while electro-magnetic wave provides the information about the fluid conductivity phenomena inside soil. For practical applications, elastic wave technology can evaluate the consolidation state of natural marine clay layers and estimate important geotechnical engineering parameters of artificially reclaimed marine deposits. Electrical resistivity can provide geophysical characteristics such as particle cementation, pore geometry shape, and pore material phase condition. Furthermore, nondestructive geophysical monitoring is applicable for risk management and efficiency enhancement during natural methane gas extraction from gas hydrate-bearing sediments.

• Geomechanics and Engineering
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• 제29권6호
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• pp.615-626
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• 2022

The soft clays are widely distributed, and one of the prominent engineering problems is the creep behavior. In order to predict the creep deformation of soft clays in an easier and more acceptable way, a simple creep constitutive model has been proposed in this paper. Firstly, the triaxial creep test data indicated that, the strain-time (𝜀-t) curve showing in the 𝜀-lgt space can be divided into two lines with different slopes, and the time referring to the demarcation point is named as t_EOP. Thereafter, the strain increments occurred after the time t_EOP are totally assumed to be the creep components, and the elastic and plastic strains had occurred before t_EOP. A hyperbolic equation expressing the relationship between creep volumetric strain, stress and time is proposed, with several triaxial creep test data of soft clays verifying the applicability. Additionally, the creep flow law is suggested to be similar with the plastic flow law of the modified Cam-Clay model, and the proposed volumetric strain equation is used to deduced the scaling factor for creep strains. Therefore, a creep constitutive model is thereby established, and verified by successfully predicting the creep principal strains of triaxial specimens.

• Geomechanics and Engineering
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• 제31권6호
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• pp.623-635
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• 2022

This paper presents the re-evaluation of existing piezocone penetration test (CPTu)-based shear wave velocity (V_s) equations through their application into well-documented data obtained at nine sites in six countries. The re-evaluation indicates that the existing equations are appropriate to use for any specific soil, but not for various types of clays. Existing equations were adjusted to suit all nine clays and show that the correlations between the measured and predicted V_s values tend to improve with an increasing number of parameters in the equations. An adjusted equation, which comprises a CPTu parameter and two soil properties (i.e., effective overburden stress and void ratio) with the best correlation, can be converted into a CPTu-based equation that has two CPTu parameters and depth by considering the effect of soil cementation. Then, the developed equation was verified by application to each of the nine soils and nine other worldwide clays, in which the predicted V_s values are comparable with the measured and the stochastically simulated values. Accordingly, the newly developed CPTu-based equation, which is a time-saving and economical method and can estimate V_s indirectly for any type of naturally deposited clay, is recommended for practical applications.

• Korean Chemical Engineering Research
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• 제46권1호
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• pp.23-36
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• 2008

고분자-점토 나노복합체는 소량의 점토를 사용하여 큰 기계적 물성향상을 나타내 많은 관심을 끌고 있는 분야이다. 층상 구조를 갖고 있는 점토를 고분자 matrix에 분산하는 과정으로 요약할 수 있는 고분자-점토 나노복합체 제조는 친수성 점토 표면을 조절하는 기술, 점토의 물리적 성질을 이용하는 무기재료에 관한 지식, 고분자 합성, 고분자 유변학, 고분자 용액 거동, 기계적 물성이 복합적으로 작용하는 계이다. 이러한 복잡성을 설명하기 위해, 이 총설에서 점토 종류와 그 특성을 설명하였다. 또한 점토 특성과 고분자-점토 나노복합체 제조 방법의 연관성에 대해 설명하고, 제조된 복합체의 구조 분석과 방법에 대해 설명하였다. 그리고 복합체의 특징적인 물성을 분류한 후 그 물성과 복합체의 구조를 연관하여 살펴보았다. 마지막으로 최근의 연구 경향과 향후 연구 경향을 제시하였다.

• 한국지반공학회논문집
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• 제19권2호
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• pp.7-14
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• 2003

본 연구는 광양만 지역과 목포 남악지역의 점토를 이용하여 양생온도를 20$\times$, 50$\times$ , 80$\times$로 달리하고 각각의 온도에서 양생기간을 1일, 7일 14일, 40일로 하여 재성형.재압밀 시료를 제작하여 양생온도.양생기간이 연대효과 재현에 어떤 영향이 있는지를 밝히고, 불교란시료와 재압밀된 점토의 역학적 특성과 연대효과의 특성을 알아보기 위하여 1축압축시험, 3축압축시험 그리고 표준압밀시험을 실시하였다. 그 결과 압축지수비는 원지반점토의 연대효과를 나타내는데 유용한 지수임을 확인할 수 있었으며 또한 고온으로 양생한 점토가 연대효과를 잘 표현하고 연대효과의 재현에 필요한 최적의 양생온도는 80$\times$ 정도 부근이고 양생기간은 27일정도 임을 알 수 있었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.486-493
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• 2008

Consolidation settlements on marine dredged clays are often greatly and potentially damaging to structures. Currently, large-scale projects are in planning or progressing in Korea. These projects has been performed on thick and soft clay layers. So, the evaluation of long-term consolidation settlement is very important in design and construction. Therefore, In this study, a long-term consolidation characteristics of marine dredged clays are investigated. First, the relationship of $C_{\alpha}/C_c$ on marine dredged clays near Gwang-yang Port was evaluated. Second, long-term consolidation characteristics of the pseudo-preconsolidated ground were evaluated.