• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.641-648
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• 2000

The horizontal drain method by installing drains horizontally in the ground is often used to expedite the dispersion of pore water and to increase the strength of dredged soft clay under the action of gravity or vacuum. In this study a numerical analysis method is developed to predict the consolidation process of soft ground with horizontal drains. One-dimensional self-weight consolidation theory is extended tn three-dimensions] theory with appropriate boundary conditions of horizontal drains. In the condition of pore water drainage by gravity, the behavior of the dredged clay with horizontal drains is compared with that of the clay without drains. The influence of design factors of drains on consolidation process is also analyzed.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.553-560
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• 2002

The improvement effect of soft ground is estimated by unconfined strength mainly. The unconfined strength of solidification agent treated soil is likely to vary with ununiformed mixing ratio and water content change of in-situ ground place by place. So, it is unreasonable to apply a solidification agent mixing ratio obtained from laboratory test results on all over the soft ground. In this study, it was analysed how the unconfined strength would be effected by the water content of soft ground. For this study, a series of unconfined compressive tests are peformed on various water content soil samples. The test results showed that the strength was fallen to 30∼80% by two times increase of water content approximately, This means that strength of solidification agent treated soil is influenced greatly by water content of raw soft ground and mixing ratio of solidification agent. It was suggested that the method how to decide the mixing ratio with soft ground water content.

• Journal of the Korean GEO-environmental Society
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• v.10 no.6
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• pp.69-77
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• 2009

The shortage of bearing capacity and settlement, shear deformation may occur when constructing a structure such as harbor, airport and bridge on soft ground such as marine clay, silty clay, sandy soil because it is very soft. The various ground improvement methods were applied to obtain preceding settlement of soft ground and strength increase. The vertical drain method has been used to reduce the required time for consolidation of the soft ground. Especially, the PBD (Plastic Board Drain) has been widely used among in the vertical drain method. In this study, a behavior of characteristic was evaluated by operating a compound drainage capacity test about the PBD (Plastic Board Drain) method applied in soft clay in deep depth. As a result, the settlement gradually occurred with increase of surface load. The consolidation settlement was processed with dissipation of pore pressure after surface load of $500kN/m^2$. Accordingly, it was found that change of settlement through load steps was resulted from dissipation of pore pressure. It was also found that the drainage capacity of vertical drains was considerably reduced with pressure increase and time elapse.

• 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

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.809-814
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• 2009

Deep mixing method has been used for ground improvement and foundation system for embankment, port and harbor foundations, retaining wall, and liquefaction mitigations. It has attractive benefits because it is not only improved strength of soft ground but superior for prevention of settlement. However, the quality controls of improved mass affect to the efficiency of the deep mixing method is not properly established. These effects vary depending upon the construction environments and conditions of agitation in consideration of an agitator. The strength and shape of the improved column are not unique and these are affected by mechanical properties of agitators. In this study, in order to investigate the efficiency of deep mixing method for ground improvement on a soft clay ground, experimental studies are performed considering mechanical properties of agitator; the location of exit-hole of admixtures, an angle of mixing wing and a speed of revolution. The experiments are conducted with the simulated apparatus for deep mixing plant that reduced the scale in 1:8 of the real plant. According to the results, the diameter and shape of improved column mass vary depending on the mechanical properties and operating conditions of agitator. Its quality is better when the exit-hole of admixtures is located in the mixing wing, when an angle of mixing wing is large, and when the speed of revolution is rapid.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.151-154
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• 2003

This paper reviews depositional environments and consolidation characteristic of Soft Dredged Clay fill and then analytical solution of self-weight consolidation is made to find consolidated state. It's known that Soft Dredged Clay Ground is in the under-consolidated state under $U{\fallingdotseq}30%$ from analytical solution. It is effective for higher consolidation rate that the time of Dredge is shorter ani the time of leave is longer. It is conclude that the under-consolidated state should be considered in prediction of consolidation settlement.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.09a
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• pp.9-16
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• 2000

Applicability of the cross shaped drain in a soft clay ground is examined using the laboratory discharge capacity test, column consolidation test and 3-D numerical flow analysis. The equivalent diameter of the tested drains is back-calculated from the laboratory experiment and compared with those calculated from the formula suggested in the literature. The effective range of the cross shaped drain about the discharge capacity and coefficient of permeability is analyzed. The results of numerical analysis show that the cross shaped drain which has a cross-sectional area twice of the band shaped drain can reduce the consolidation time by 30% from that for the band shaped drain in a soft clay ground that K is over 1${\times}$10$\^$-7/cm/sec

• Journal of the Korea Institute of Building Construction
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• v.1 no.1
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• pp.160-168
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• 2001

This study aims at the development of computer program for the deformation analysis of soft ground, and using this computer program, study the constraint effect of deformation heaving, lateral displacement of the soft ground reinforced with improvement of soft ground up to hard strata, under intact state(natural). The following results are obtained. 1. Improvement of soft ground to the hard strata works well against the settlement of neighboring ground. 2. the larger the rigidity or width of improvement of layer to hard strata is, the less settlement occurs. 3. Improvement of soft ground to the hard strata is of no use.

• Geomechanics and Engineering
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• v.34 no.3
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• pp.303-316
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• 2023

With the development and utilization of urban underground space, the artificial ground freezing technology has been widely used in the construction of underground engineering in soft soil areas. The mechanical properties of soft clay changed greatly after freezing and thawing, which affected the seismic performance of underground structures. In this paper, a series of triaxial tests were carried out to study the dynamic response of the freezing-thawing clay under the seismic load considering different dynamic stress amplitudes and different confining pressures. The reduction factor of dynamic shear stress was determined to correct the amplitude of the seismic load. The deformation development mode, the stress-strain relationship and the energy dissipation behavior of the soft clay under the seismic load were analyzed. An empirical model for predicting accumulative plastic strain was proposed and validated considering the loading times, the confining pressures and the dynamic stress amplitudes. The relevant research results can provide a theoretical reference to the seismic design of underground structures in soft clay areas.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.09a
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• pp.61-69
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• 2000

It is not easy to find a good soil condition due to the shortage of suitable land for construction work. The earth structure and buildings can be constructed over the soft soil. The soft soil must be treated either using the reinforcement element or dewatering. Most of land reclamation projects are being implemented along the south coast or west coast of the Korean Peninsula. The soils in these areas are covered with the soft marine clay, so soil and site improvement is the most important things to do. Pile foundation at the bottom of embankment can be constructed either in the soft ground or in the soil contaminated area. The purpose of this research is to develop "geogrid-reinforced piled embankment method" to prevent the differential settlement and increase the bearing capacity of soil. In this study, the effectiveness of the geogrid-reinforcement was studied by varying the space between piles and reinforcement conditions. Also, the geotechnical engineering properties of the embankment material and foundation soil were determined through the laboratory tests as well as the field tests. As a result, the site that the pile-spacing S = 3b with geogrid reinforcement is the most effective to reduce the differential settlement and increase load bearing capacity.