• Journal of Industrial Technology
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• v.16
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• pp.175-179
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• 1996

This research is the experimental and numerical study of investigating the characteristics of consolidation due to selfweight of soft marine clay. Column tests and centrifuge tests were carried out to selfweight of soft marine clay. Column tests and centrifuge tests were carried out to simulate the selfweight consolidations in field. Tests were conducted with changing drain boundary conditions and initial void ratios corresponding to four and five times of liquid limits. The RI meter was used to measure void ratio during consolidation of sample in column tests. Test results were analyzed by using the Terzaghi's infinitesimal strain theory and the finite strain theory.

• Geomechanics and Engineering
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• v.10 no.5
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• pp.617-633
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• 2016

A numerical study has been conducted to examine the improvement achieved in the ultimate pullout capacity of horizontal circular anchor plates embedded in undrained clay, by constructing granular columns of varying diameter over the anchor plates. The analysis has been carried out by using lower bound theorem of limit analysis and finite elements in combination with linear programming. The improvement in uplifting capacity of anchor plate is expressed in terms of an efficiency factor (${\xi}$). The efficiency factor (${\xi}$) has been defined as the ratio of ultimate vertical pullout capacity of anchor plate having diameter D embedded in soft clay reinforced by granular column to the vertical pullout capacity of the anchor plate with same diameter D embedded in soft clay only. The variation of efficiency factor (${\xi}$) for different embedment ratios and different diameter of granular column has been studied considering a wide range of softness of clay and different value of soil internal friction angle (${\phi}$) of the granular material. It is observed that ${\xi}$ increases with an increase in diameter of the granular column ($D_t$) and increase in friction angle of granular material. Also, the effectiveness of the usage of granular column increases with decrease in cohesion of the clay.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.03a
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• pp.127-134
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• 1998

• Geotechnical Engineering
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• v.3 no.1
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• pp.7-24
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• 1987

Preloading surcharge method along with vertical drains was adopted to improve the performance of a very soft marine clay deposit. The onshore deposit, located in the Ulsan Bay area, consists of a 2 to 10m thick, very soft, highly compressible marine clay layer developed just below. the sea water level. The initial undrained shear strength of the clay layer was about 0.6 ton/m2. But, the deposit was designed after treatment to support some auxiliary facilities for a new ilo refinery plant, requiring bearing capacities of 3.6 to 5.4 ton/m2 and maximum allowablee settlement of less than 7.5cm. A total of 35, 000 wick drains Ivas installed to expedite drainage during preloading, and surcharge loads of up to 5m above the original ground level were applied in a step-by-step loading sequence to prevent ground failure by excess surcharge loads. An extensive program of field instrumentation was implemented to monitor the behavior of the clay deposit. Measurers!ends included settlements, excess pore pressure and its dissipation, ground farmer level fluctuation, and lateral movement of the so(t clay layer under the preloads. This paper describes the design concepts, construction methods and control procedures used for improvement of the clay layer. It also presents the ground behavior measured during construction, rind comparisons with theoretical predictions.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.02a
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• pp.78-83
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• 1999

The ultimate settlement of soft clay consists of three parts: $\circled1$ immediate settlement, S$\sub$d/; $\circled2$ Primary consolidation settlement, S$\sub$c/; $\circled3$ Secondary consolidation settlement, S$\sub$s/. In general, S$\sub$c/ can be accurately calculated by one-dimensional consolidation and S$\sub$s/ or S$\sub$d/ may be ignored. This paper focuses on a calculation method to estimate the immediate settlement induced by lateral deformation of subgrade, to which shear stress is applied by embankment on soft ground. Immediate settlement and consolidation settlement are discussed by comparing the field measurement of the Yangsan test embankment on treated soft foundation by vertical paper drains.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.417-424
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• 2005

Observed field behaviors are frequently different from the behaviors predicted in the design state due to several uncertainties involved in soil properties, numerical modelling, and error of measuring system even though a sophisticated numerical analysis technique is applied to solve the consolidation behavior of drainage-installed soft deposits. In this study, genetic algorithms are applied to back-analyze the soil properties using the observed behavior of soft clay deposit composed of multi layers that shows complex consolidation characteristics. Utilizing the program, one might be able to appropriately predict the subsequent consolidation behavior from the measured data in an early stage of consolidation of multi layered soft deposits. Example analyses for drainage-installed multi-layered soft deposits are performed to examine the applicability of proposed back-analysis method.

• Geomechanics and Engineering
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• v.4 no.4
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• pp.243-249
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• 2012

In the companion paper, the nonlinear consolidation of soft clays subjected to cyclic loading was analytically investigated. This paper reports the results of an experimental program conducted to verify some critical assumptions made in the analytical study. It, also, includes a numerical study carried out to examine the capability of the proposed theory to determine the consolidation characteristics of soft clays subjected to cyclic loading. Results show that the permeability of the soft clays does not significantly change during the cyclic loading. It is also shown that, compared to the Terzaghi's solution for a linear clay, the inherit nonlinearity of the clay tends to decrease the degree of consolidation due to the smaller rate of dissipation in the excess pore water pressure.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.227-234
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• 2004

Sand compaction pile (SCP) method is composed of compacted sand pile inserted into the soft clay deposit by displacement method. SCP-reinforced ground is composite soil which consists of the SCP and the surrounding soft soil. When a surcharge load is applied on composite ground, time-dependent behavior occurs in the soft soil due to consolidation according to radial flow toward SCP and stress transfer also takes place between the SCP and the soft soil. This paper presents the numerical results of cylindrical composite ground that was conducted to investigate consolidation characteristics and the stress transfer mechanism of SCP-reinforced composite ground. The results show that the consolidation of soft clay has a significant effect on the stress transfer mechanism and stress concentration ratio of composite ground

• Geomechanics and Engineering
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• v.13 no.6
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• pp.963-975
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• 2017

Improvement of soft clay deposit by preloading with vertical drains is one of the most popular techniques followed worldwide. These drains accelerate the rate of consolidation by shortening the drainage path. Although the analytical and numerical solutions available are mostly based on equal strain hypothesis, the adoption of free strain analysis is more realistic because of the flexible nature of the imposed surcharge loading, especially for the embankment loading used for transport infrastructure. In this paper, a numerical model has been developed based on free strain hypothesis for understanding the behaviour of soft ground improvement by vertical drain with preloading. The unit cell analogy is used and the effect of smear has been incorporated. The model has been validated by comparing with available field test results and thereafter, a hypothetical case study is done using the available field data for soft clay deposit existing in the eastern part of Australia and important conclusions are drawn therefrom.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.33-43
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• 2002

Recently, as large constructions on the coast increase, an application of a surface layer stabilization method which is one of the improvement methods for dredged soft clay has increased. However, there are few studies about this. The purpose of this study is clarifying characteristics of ultra-soft marine clay and hardening agent. Also, it is verifying an optimal mixture ratio of hardening agent through the laboratory tests according to designed experiments and proving by statistical analysis and pilot tests. Laboratory tests were performed with proper hardening agent and test soil in accordance with the design of experiments. Regression equations between hardening agents materials and unconfined compressive strength were derived from the tests. The applicability of regression equations were also verified by pilot tests. From the test results, it was found that hardening agent materials(cement, slag, fly-ash, inorganic salts, arwin, gypsum etc.) have some effect upon compressive strength. The optimal mixture ratio which satisfies the required compressive strength was derived from the statistical analysis. The effect of ground improvement by cements and hardening agents was confirmed through the pilot tests. This study will suggest data for design or construction criteria of stabilization of surface layer on ultra-soft marine clay.