• Title/Summary/Keyword: soft clays

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Long-term consolidation characteristics of dredged and reclaimed ground (준설매립지반의 장기압밀 특성)

  • Lee, Choong-Ho;Kim, Ju-Hyun;Baek, Won-Jin;Chae, Young-Su
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.03a
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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.

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The Study of Secondary Compression Index on Soft Clays (점성토의 2차압축지수에 관한 연구)

  • 윤일형;서정석;도헌영
    • Proceedings of the Korean Geotechical Society Conference
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    • 2002.10a
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    • pp.537-544
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    • 2002
  • Deformations of clays continue beyond the end of primary consolidation: this is secondary consolidation. Mesri(1973) have shown that C $\_$a/' is related to the natural water content W$\_$n/. For clays, C $\_$a/' is approximately equal to 0.01 W $\_$n/. And the ratio C $\_$ae// C $\_$c/ is approximately equal to 0.04. In this study, coefficient of secondary compression was analyzed by the consolidation tests datas in the 3 sites. In conclusion, coefficient of secondary compression was similar to Mesri's suggestions.

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GEOPHYSICAL CHARACTERIZATION OF MARINE CLAYS - FROM GEOTECHNICAL PARAMETER ESTIMATION TO PROCESS MONITORING -

  • Choi, Gye-Chun;Chang, Il-Han;Oh, Tae-Min;Kim, Hak-Sung
    • Proceedings of the Korean Geotechical Society Conference
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    • 2010.09c
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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.

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Estimation of Degree of Consolidation in Soft Ground Using Field Measurements and Rheology Model (현장 계측치와 유변학적 모형을 이용한 연약지반의 압밀도 추정)

  • Lee, Dal-Won;Yoon, Hyun-Jung
    • Journal of The Korean Society of Agricultural Engineers
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    • v.47 no.2
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    • pp.87-96
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    • 2005
  • In this research, an attempt is made to derive the practical estimation of the degree of consolidation in soft clay from field measurements under embankments. For the practical estimation of pore water pressure in soft clay, the elasto-viscous rheological model was proposed, with a transform of parameters and a field geotechnical measurements in southern Korea. By using the rheological properties of soft clays and the dissipation of excess pore water pressure behaviour during step loading, a degree of consolidation or pore water pressure estimation in the future can be performed, and are shown to be generally close to the field measurements of pore water pressure. Finally, a pore water pressure behaviour in soft clay can be explained through measured data in field and the excess pore water pressure data can also be used to estimate settlement.

A Consideration on Deformation Characteristics of Normally-Consolidated Clays by Various Stress Paths (다양한 응력경로에 따른 정규압밀 점성토의 변형특성 고찰)

  • 김창엽;정충기
    • Journal of the Korean Geotechnical Society
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    • v.15 no.1
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    • pp.161-173
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    • 1999
  • Settlement analysis based on oedometer test results with or without Skempton-Bjerrum's modification method ( widely used for practical purposes when estimating consolidation settlements of soft clay deposits) has shortcomings that it cannot simulate real stress states and deformation behaviors of soils in case that in-situ loading and deformation conditions are not 1-dimensional. In this study, the stress path method, reflecting various probable stress paths, was employed to normally - consolidated kaolinite samples by using automated triaxial testing device which can control stress paths automatically. From this experimental study, elastic, consolidation, secondary compression and pore pressure development - dissipation behaviors under various stress paths were analyzed and deformation characteristics of soft clays, which can be the basis of rational estimation of settlements, were studied. Also by comparing results of stress path tests with those of 1-dimensional consolidation tests, limitations and problems of conventional methods were clarified.

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A Study on Undrained Shear Strength Characteristic of Pusan Clay (부산 점토의 비배수전단강도 특성에 관한 연구)

  • Ryu, Woongryul;Byun, Yoseph;Chun, Byungsik
    • Journal of the Korean GEO-environmental Society
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    • v.11 no.3
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    • pp.43-51
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    • 2010
  • In the downstream areas of the Nakdong river, Pusan clays are commonly found and thickness may reach to maximum of 100m. From geological point of view, Pusan clay are characterized as holocene clays, deposited for approximately 20,000 years ago. Recently, there have been many construction projects based on these soft ground areas. It is needed to know clearly soil properties of the areas for design and safety analysis, especially undrained shear strength of soft clays. However, Pusan clay have not been studied systematically because the clay layers are usually very deep, having high sensitivity characteristic. In this study, undisturbed UD samples obtained from the downstream areas of the Nakdong river were researched using laboratory tests (CthUE, CKcUC, CIUC, UU and UC) and in-situ tests (Field Vane, CPTu). The undrained shear strength characteristics of the samples were depicted using stress-strain relationship.

Consideration of Physical and Compression Characteristics among Western and Southern Coastal Marine Clays - Incheon·Mokpo·Gwangyang·Busan - (서·남해안 해성점토의 물리·압축특성 고찰 - 인천·목포·광양·부산 -)

  • Kim, Sangkwi;Yea, Geuguwen;Kim, Kilsu;Kim, Hongyeon
    • Journal of the Korean GEO-environmental Society
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    • v.12 no.6
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    • pp.43-51
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    • 2011
  • Marine clays are widely distributed in Korean eastern, western and southern coastal areas. Understanding engineering characteristics of the soft ground is very important, whenever civil structures are constructed in those coastal areas. It is because the ground is composed of highly compressible marine clay. In this paper, the physical and compression characteristics of Incheon, Mokpo, Gwangyang and Busan marine clay were analyzed and the characteristics between western and southern coastal marine clays were compared. For this, test results of 1,471 samples from 114 sites were used. As a result, Incheon clay showed the lowest plasticity and the highest unit weight due to influx of silt from the Yellow River and the turn of the tide of Incheon area. However, Gwangyang clay showed highly compressible characteristic due to extensive reclamation. On the other hand, Mokpo and Busan clay showed partially similar levels of characteristics. The compression index of Mokpo and Busan clay was high more than twice in comparison with Incheon clay and that of Gwangyang clay was higher than seventy percents in comparison with Mokpo and Busan clay.

Numerical Analysis on Consolidation of Soft Clay by Sand Drain with Heat Injection (수치해석을 통한 샌드드레인과 열주입에 의한 연약지반의 압밀 해석)

  • Koy, Channarith;Yune, Chan-Young
    • Journal of the Korean Geotechnical Society
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    • v.33 no.11
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    • pp.45-57
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    • 2017
  • Temperature change affects consolidation behavior of soft clays. The increase of temperature in soft clays induces the increase of pore water pressure. The dissipation of the excess pore water pressure decreases volume and void ratio. Also, the consolidation rate is accelerated by high temperature which induces the decrease of viscosity of pore fluid. The effects of temperature on the consolidation behavior such as consolidation settlement, consolidation time, and pore water pressure were investigated in this study. A numerical analysis of hydro-mechanical (HM) and thermo-hydro-mechanical (THM) behavior was performed. The combination of heat injection and sand drain for consolidating the soft ground, with varying temperature (40 and $60^{\circ}C$) and sand drain diameter (40, 60, and 80 mm), was considered. The results show that the temperature inside soil specimen increases with the increase of the temperature of heating source and the diameter of sand drain. Moreover, the heat injection increases the excess pore water pressure and, accordingly, induces additional settlement in overconsolidated (OC) state and reduces the consolidation time in normally consolidated (NC) state.

Application of a modified structural clay model considering anisotropy to embankment behavior

  • Zhang, Hao;Chen, Qiushi;Chen, Jinjian;Wang, Jianhua
    • Geomechanics and Engineering
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    • v.13 no.1
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    • pp.79-97
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    • 2017
  • Natural clays exhibit features such as structural and anisotropy. In this work, a constitutive model that is able to replicate these two salient features of natural clays is presented. The proposed model is based on the classical S-CLAY1 model, where the anisotropy of the soil is captured through the initial inclination and rotation of the yield surface. To account for the structural of the soil, the compression curve of the reconstituted soil is taken as the reference. All parameters of the proposed constitutive model have clear physical meanings and can be conveniently determined from conventional triaxial tests. This proposed model has been used to simulate the behavior of soft soil in the undrained triaxial tests and the performance of Murro embankment in terms of settlement and horizontal displacements during embankment construction and consolidation stage. Results of numerical simulations using proposed model have been compared with the field measurement data. The comparisons show that the two features significantly influence the prediction results.