• Journal of the Korean Geosynthetics Society
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• v.13 no.4
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• pp.33-43
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• 2014

Recently, the case to construct the structure on the soft clayey ground has increased and in order to the reduction of the cost of construction and maintenance on the social infrastructure facilities we have been trying to improve the soft clayey ground using the existing methods such as the pre-loading method and the vertical drain method. Like this, when various ground improvement methods are applied on the soft clayey ground, a long-term consolidation settlement will be key issue due to low permeability coefficient of cohesive soil. According to existing research results that relate to the consolidation settlement, the loading periods for existing the standard consolidation test (Oedometer test) to obtain the consolidation parameters are needed for minimum ten days or more. Therefore, in this study, the standard consolidation test (24 hours step-loading) and constant strain rate consolidation test changed by strain rate was performed using the remolded marine clay on Gwangyang bay composed of a soft clayey ground of the south-west coast. From the laboratory test results, the characteristics of compression, strain-effective stress relations by constant strain rate and the variation characteristic of the pore water pressure by different of loading speed and the relation between consolidation parameters and constant strain rate are compared and analyzed.

• Journal of the Korean Geotechnical Society
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• v.17 no.4
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• pp.183-190
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• 2001

굴패각을 혼합한 해성점토를 매립재료로 활용하기 위한 기초 자료를 얻기 위해, 혼합토의 전단.변형특성을 검토했다. 또한 삼축압축실험과 균질화이론을 근거로 한 수치해석에 의해 혼합재(굴패각)의 겉보기 탄성계수를 구하기 위한 방법을 제안했다. 일련의 실험결과로부터, 굴패각의 혼합에 의해 점토의 전단.변형특성이 개선됨을 확인했고, 굴패각의 겉보기 탄성계수를 구하기 위해 미시구조를 검토할 수 있는 균질화법을 도입했다. 굴패각의 겉보기 탄성계수는 굴패각의 골격구조의 변화에 기인해 변화하고 선행압밀응력이 작은 경우에 그 영향이 크게 나타나는 것을 알 수 있었다.

• Journal of the Korean Geotechnical Society
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• v.21 no.3
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• pp.133-140
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• 2005

In order to accelerate the rate of consolidation settlement and gain a required shear strength for a given soft clay deposit, vertical drain method combined with a preloading technique has been widely applied. In this paper, a theory of axisymmetric nonlinear consolidation fer drainage-installed deposit, which considers secondary compression (or creep) during primary consolidation, as well as the variations of compressibility and permeability during the consolidation process, has been developed. A computer program named AXICON based on Hypothesis B fur the analysis of axisymmetric nonlinear consolidation was developed by adopting finite difference method. The results of AS(ICON were compared with Hansbo's solution based on Hypothesis A, as well as in-situ settlements and pore pressures measured in test embankment of Ska-Edeby. The results indicated that Hypothesis A usually underestimated the in-situ settlement and Hypothesis B was considered to be logically correct. It was also shown that one may able to appropriately predict the real in-situ behaviors using the proposed program.

• Journal of the Korean GEO-environmental Society
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• v.10 no.6
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• pp.89-98
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• 2009

In this research, settling tests with marine clays in Korea and extensive literature review were performed to investigate the characteristics of sedimentation and consolidation so that their behaviors during dredging and reclamating could be evaluated. Design parameters related to Yano's method (1985), one of experimental approaches having been used widely in Korea to estimate sedimentation and consolidation, were analyzed and their proprieties were reassessed. For samples from four different sites of south and west coasts in Korea respectively, settling tests with 1m height of columns were carried out, changing initial water content and height of sample in order to evaluate settling and consolidation characteristics of them from analyzing test results. More reliable regression curves than values from literature review were obtained as analyzing test results of estimating coefficient of sedimentation/ consolidation and initial setting velocity with changing initial water content. Relation between height of soil solid and surface height of slurry at the stages of initiation and termination of consolidation was also assessed. Finally, for marine clays of south and west coasts of Korea, ranges and average values of these design parameters were evaluated and typical empirical equations between these design parameters were also proposed. On the other hand, comparisons of characteristics of sedimentation and consolidation between marine clays from south coast and them from west coast were also performed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6C
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• pp.339-347
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• 2008

The penetration of the probe produces the excess pore pressure due to the disturbance. The objective of this study is to evaluate the disturbance zone by using the dissipation of the excess pore water pressure, which was generated due to the penetration of the penetrometer with different size. The CPT, DMT and FVP (Field Velocity Probe) are adopted for in-situ tests. The tests are carried out in the construction site of north container pier of Busan new port, Korea where is accelerating the consolidation settlement using plastic board drains (PBD) and surcharges by crushed gravels. The coefficient of consolidation $(C_h)$ and soil properties are deduced by the laboratory test. The in-site tests are performed after the predrilling the surcharge zone at the point of 90% degree of consolidation. To minimize the penetration effect, the horizontal distance between penetration tests is 3m, the change of the pore pressure is monitored at the fixed depth of 24m. The coefficient of consolidation $(C_h)$ and the $t_{50}s$ are calculated based on the laboratory test and the in-situ data, respectively. The equvalent radi based on the $t_{50}$ shows that the FVP and the DMT produce the smallest and the greatest equivalent radi, respectively.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.823-830
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• 2004

Consolidation tests under various deformation modes were performed to investigate the effect of deformation modes on the coefficient of consolidation in the normally consolidated clay in remolded and undisturbed clay. The degree of soil anisotropy was evaluated using cross-anisotropic elasticity theory suggested by Graham et al.(1983). Experimental results showed that the vertical compressibility was larger than the horizontal compressibility by $12{\sim}21%$ for the remolded clay and by $23{\sim}60%$ for the undisturbed clay, respectively. The results of a series of consolidation tests under the specific deformation modes showed that the coefficient of consolidation under 1 dimensional vertical strain condition was larger than that under 3 dimensional strain condition due to different deformation mode. Furthermore, the coefficient of consolidation under 1 dimensional vertical strain condition was larger than that under 1 dimensional horizontal strain condition by $40{\sim}60%$ in undisturbed clay, which clearly emphasized the significant effect of soil anisotropy on the rate of consolidation. Consequently, it can be concluded that the anisotropic deformation modes of soils, especially naturally deposited clays, should be taken into account for more accurate evaluation of the coefficient of consolidation.

• Journal of the Korean GEO-environmental Society
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• v.16 no.7
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• pp.15-22
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• 2015

This study gives the characteristics of sedimentation-consolidation and surface strength for dredging and landfill areas in each coast. For the analysis of the sedimentation-consolidation characteristics, the column tests were performed and the results were compared with existing various literatures and design reports for dredged soil disposal. The surface strength of landfill soils of west and south coast were investigated by using the portable cone tester. As a results of analysis, the coefficient of sedimentation-consolidation on south coastal dredging soils is more sensitive with variation of initial water contents than on the west coastal dredging soils. And the surface strength of the dredging landfills is a higher in the west coast than in the south coast. Finally, the results of this study will be utilized as a basis data for analysis and design in the field of dredging and landfill.

• Journal of the Korean Geotechnical Society
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• v.24 no.6
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• pp.77-84
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• 2008

The existing equations for radial consolidation cannot account for the changes of well resistance with time and cannot predict the appropriate in-situ consolidation curve. In this study, small cylinder cell tests are performed to evaluate the discharge capacity of PVD. Also, a block sample of 1.2 m in diameter and 2.0 m in height was consolidated to observe the change in the drainage capacity with time for three types of PVD. From the test results on a block sample, the drainage curves normalized with initial drainage of each PVD are similar, regardless of the PVD type and the consolidation curve, which is predicted using solutions of radial consolidation based on the discharge capacity measured in a small cylinder cell tests, significantly overestimates the degree of consolidation. The term of well resistance in the radial consolidation solution was back-calculated to fit the consolidation curve of a large block sample and it is defined as the time dependent well resistance factor, L(t). The L(t) was found to be linearly proportional to the dimensionless time factor, Th. It was also shown that the consolidation curve evaluated by using L(t) provides more accurate prediction than the existing solution.

• Journal of the Korean Geotechnical Society
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• v.27 no.7
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• pp.69-79
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• 2011

Laboratory tests are generally used to determine the input parameters for the selected constitutive models controlling various stress and drainage conditions, but have disadvantages in that the tests are performed on the samples obtained from the bore hole which are prone to be disturbed by various factors such as the tube penetrations, sample preparations and storage. To overcome these disadvantages, it is necessary to understand the effect of disturbance on the stiffness of the sample, especially the normally consolidated clays which are generally considered as soft clays. Therefore, in this study triaxial tests are performed on the normally consolidated kaolinite to evaluate the sample disturbance effects on the stiffness and to determine the field representative input parameters. The stress path results show that the shear and coupling modulus degradation patterns with strain are affected seriously by the disturbance. However, the strengths of the normally consolidated kaolinite are little influenced by the disturbance.

• Journal of the Korean GEO-environmental Society
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• v.19 no.9
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• pp.21-28
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• 2018

In this study, a standard consolidation test (Oedometer) was performed on the relative density of sand in the south coast to evaluate long-term creep settlement characteristics. Experimental results show that the cumulative settlement at the final loading stage decreases as the relative density increases and the variation of the void ratio decreases. As a result of analyzing the settlement rate of long-term creep of sand, creep settlement of 4.7~11.0% occurred depending on relative density with respect to total settlement. The creep parameter, Beta, of Schmertmann et al. (1978) was estimated to be 0.17~0.40 (average 0.21), and it tended to converge to a certain value when the load step becomes more than a certain level. It was found that there is no significant difference in the creep parameter depending on the layer thickness, and it was confirmed that the creep parameter could be applied regardless of the field layer thickness.