• 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 Geotechical Society Conference
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• 2005.03a
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• pp.537-544
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• 2005

We find out many soft ground deep excavation cases where results of careless overexcavation accelerate the advance of loosening zone of adjacent ground, bucklings of struts and bottom heaves happen due to delayed supporting time. This article introduces a soft ground deep excavation case where steel pipe sheet piles were used with struts as an earth retaining system. There were 2 times of buckling in the supporting system and heaving of bottom ground due to overexcavation and insufficient penetration depth of the steel pipe sheet piles. The effort of this article aims to improve and develop the technique of design and construction in the coming projects having similar ground condition and supporting method.

• Korean Journal of Agricultural Science
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• v.28 no.2
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• pp.108-115
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• 2001

In this study, to propose the reasonable evaluation method of degree of consolidation considering the depth of soft ground, the two soft ground areas were chosen and analyzed for the consolidation degree. One was a western coast area in which depth of soft ground was low, and the other was a southern coast area in which depth of soft ground was deep. At the area in which depth of soft ground was low, Barron's and Yoshikuni's methods showed that the evaluation of consolidation degree was large, and it is reasonable that $C_h=C_v$ be recommended to apply the Hansbo's and the Onoue's methods. At the area in which depth of soft ground was deep, it is reasonable that $C_h=C_v$ be recommended to apply the Barron's and the Yoshikuni's methods, and $C_h=(2{\sim}3)C_v$ to apply the Hansbo's and the Onoue's methods. According to the Hansbo's and Onoue's methods, degree of consolidation proved to be applicable with measured data when using the $k_s=(1/3)k_v$ at the area which depth of soft ground was low and using the $k_s=(1{\sim}1/2)k_v$ at the area which depth of soft ground was deep. According to the Hansbo's and Onoue's methods, degree of consolidation was proved to be applicable with measured data when using ds=(3~5)dm at the area which depth of soft ground was low and using ds=2dm at the area which depth of soft ground was deep.

• Journal of the Korean Geotechnical Society
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• v.15 no.5
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• pp.111-124
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• 1999

When deep excavation adjacent to an existing structure is performed, it is very important to minimize damage on the structure through the prediction of ground movement. In this paper, finite element analysis was performed to predict the ground movement, based on the data from site investigation and laboratory tests, when deep excavation close to a buried water tank was carried out in soft clay ground. The movement and stabilities of the soil-cement wall(SCW) and the adjacent structure were checked using the results of the analysis and the field measurement. The comparison between the measured and the predicted ground movements showed the significance of the excavation procedure and lowering of water level in the analytical model. In the future, it is needed to improve the prediction method for better estimation of the ground movement.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.521-532
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• 2008

Supporting system design and construction management for the soft and hard rock layers with fractured zones are very important theme for the safety of temporary retaining wall, surrounding ground and structures in the urban deep excavation for the construction of subway, railway, building etc. The prevailing design method of supporting system for the soft and hard rock layers in the deep excavation is mostly carrying out by simplification without proper consideration for the characteristic of rock discontinuities. Therefore the behaviors of rock discontinuities and fractured zones dominate the whole safety of excavation work in the real construction stage, serious disaster due to the failure of temporary retaining wall can be induced in the case of developing large deformations in the ground and large axial forces in the supporting system. This paper introduces examples of deep excavation where the soft and hard rock layers with fractured zones were designed to be supported by shotcrete and rock bolt, deformations of corresponding ground and supporting systems in the construction period and increments of axial force in the upper earth anchors and strut due to the these deformations were investigated through detailed analysis of measurement data, the results were so used for the management of consecutive construction that led to the safe and economical completion of excavation work. The effort of this article aims to improve and develop the technique of design and construction in the coming projects having similar ground condition and supporting method.

• Journal of Ocean Engineering and Technology
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• v.28 no.2
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• pp.167-176
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• 2014

This paper proposes an optimum curve driving method for adeep-seabed mining robot(MineRo) in deep-sea soft ground. MineRo was designed as afour-row tracked vehicle. A study on the turning methods for the four-row tracked vehicle was conducted using three case by changing the velocity profile of each track. The configuration of the four-row tracked vehicle and soft ground equation are introduced, along with the dynamics analysis models of MineRo and soft ground, which were constructed using the commercial software DAFUL. Because the purpose of this study was to investigate a driving method on soft ground, the marine environment of the deep sea was not considered.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1126-1131
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• 2009

Suction Drain Method is soft ground improvement technique, in which a vacuum pressure can be directly applied to the Vertical Drain Board to promote consolidation and strengthening the soft ground. This method does not require a surcharge load, different to embankment or vertical drain method. In this study, Using Suction-CAIN program, which optimize th Suction Drain method, estimate validity Suction Drain method on deep soft ground

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.7
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• pp.3216-3223
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• 2012

Deep cement mixing method (DCM) is one of the most effective improving methods for deep soft ground. The strength of soft soil can be increased in a short period of time with less noise and vibration. However, it is necessary to determine the stress transferring and concentration ratio of the composite soft ground for estimating the settlement behaviors. In this study, a model test was undertaken to investigate the stress distribution of the improved soil. Results of the model test shows that stresses were concentrated mainly on the improved areas by DCM and the concentration ratios (35.4, 28.6, 27.02) were obtained using several different techniques. These were well in accordance with other previous research results (26.52, 32.5).

• 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.

• Journal of the Korean Geotechnical Society
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• v.38 no.12
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• pp.67-78
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• 2022

In this study, the measurement results of the coastal deep soft ground buried in the upper part of the dredged clay were analyzed and compared with the current specification standards. Based on the results, a suitable proposal was suggested for the selection, installation, data arrangement, and analysis of each instrument used in the deep soft ground improvement construction. The pore water pressure meter has a range of 1.5 times or more of the expected measurement range, considering the field conditions of the soft ground. The groundwater level meter installed in the horizontal drainage layer checks the change in the groundwater level during the embanking as well as the performance of the catchment well and the horizontal drainage layer. Therefore, it is important to manage so that the groundwater level exists inside the horizontal drainage layer during embanking. It is enough to install the inclinometer in the gravel layer below the soft ground or weathered rock with an N value of 40 or more for the deep soft ground. It seems desirable to install a screw type for differential settlement meter. However, the screw type should not settle due to its own weight. Considering that it is a dredged landfill where subsidence occurs significantly, it is sufficient to manage the tolerance of leveling at about 10 mm (L is the one-way distance (km)).