• Journal of the Korean Geosynthetics Society
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• v.8 no.3
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• pp.9-16
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• 2009

In generally, ground surface strengthening such as using geotextile is needed to secure trafficability of construction equipment. Several calculation methods for bearing capacity for very soft ground improved by geotextile have been proposed already but they are not established yet. In this paper, elastoplastic finite element analysis is carried out to estimate bearing capacity improvement for very soft ground reinforced by geotextile. In conclusion, by reinforcing with geotextile the bearing capacity improvement of very soft ground is increased with the increase of the settlement after yielding. And it is enough that the length of geotextile is about 3~4 times of the loaded width for the effect to the bearing capacity improvement. Finally, the biggest tensile force of geotextile occurs at an edge of the uniform load.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.2
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• pp.605-610
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• 2011

Soft ground improvement is essential to enhance strength of ground for construction in reclaimed land or shore. There are many method of soft ground improvement, and vertical drain method was widely used in many countries including korea. As vertical drain method is to plant many Prefabricated Vertical Drains in soft ground, it promotes consolidation and enhances strength. The PBD(Plastci Board Drain) that is excellent economy and workability was widely used in many countries as Prefabricated Vertical Drains. Construction quality of PBD is affected installation depth, pressure, perpendicularity. This paper describes the system developed that can automatically measure installation depth, pressure and perpendicularity for PBD. This system can reduce fraction defective of construction by auto faulty alarm and keeps the safety of operator by auto control system.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.264-271
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• 2005

Sand pile method, such as sand drain method and sand compaction pile method, has been popularly used as an improvement method for soft clay grounds. The effect of accelerating consolidation of soft clay grounds has been evaluated with Barron's solution. By the way, the consolidation behavior of soft clay ground with sand piles strongly depends on both the nonlinear mechanical interaction between sand piles and surrounding clays and the degradation permeability of clays. In this paper, the method for determining consolidation parameters of soft clay ground with sand drains by using Barron's solution was proposed, through a series of numerical simulations. Through the method, the change in both volume compressibility and permeability during consolidation was reasonably evaluated.

• Journal of the Korean Geosynthetics Society
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• v.15 no.4
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• pp.89-96
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• 2016

Compressive axial behavior of the variable cross-section soft ground reinforced foundation is investigated from the field load test results at ${\bigcirc}{\bigcirc}$ construction site in Incheon city. Variable cross-section soft ground reinforced foundation is a type of partial-displacement pile formed by mixing bidding material with in situ soils to obtain a rigid and strong variable cross-section column in a relatively soft ground. The foundations are usually constructed as a group; however in this study, only single foundation was installed and tested under compressive axial load on foundation head. For the comparison of the variable cross-section soft ground reinforced foundation axial behavior, behavior of typical Pretensioned spun high strength concrete (PHC) pile constructed on a relatively soft ground near the surface was analyzed. It was concluded that variable cross-section soft ground reinforced foundation efficiently resists against axial load with sufficient stiffness and strength within a considerable range of axial load magnitude.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1167-1174
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• 2008

Vertical drain method, which is one of the soft ground improvement methods, shorten s drain path to accelerate consolidation process and is applied in many sites. At a recent, composite discharge capacity experiment that analyze discharge amount by consolidation behavior with overburden pressure of soft ground in laboratory, simulates similarly with actuality. Geotechnical engineering problems such a s soft ground improvement are solved by numerical analysis by development of computer and numerical analysis techniques. Numerical analysis does that result is contrary by user's inexperience for choice of constitution model and application of analysis method. Therefore, this thesis experiments on composite discharge capacity test and study discharge capacity of drain and consolidation behavior of soft ground installed prefabricated vertical drain boards. Also, This thesis studied reasonable input parameters and constitution model by compare results of composite discharge capacity test and numerical analysis using PLAXIS that is 2D finial element numerical analysis program.

• Journal of the Korean GEO-environmental Society
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• v.2 no.4
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• pp.63-72
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• 2001

As construction cases on soft ground are increasing, the necessity of ground improvement is also increasing. Granular pile is one of the methods for soft clay and for loose sandy soil. In our country, SCP(Sand Compaction Pile) method using sand material has been mainly used to improve soft ground, but Granular pile with crushed-stone was not used much. However, alternative material such that crushed-stone is needed to substitute for sand due to the environmental and economical problems. In this study, staged load test and consolidation test were performed in the laboratory to observe the behavior of soft ground improved by Granular pile. In order to evaluate the characteristics such as bearing capacity, drainage, and settlement, sand and crushed-stone were applied as each pile material. The test results show that crushed-stone has higher bearing capacity and less settlement than those of sand under similar pore water pressure condition. Therefore, crushed-stone is determined to be appropriate as substitute for sand.

• Journal of the Korean Geotechnical Society
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• v.17 no.6
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• pp.53-67
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• 2001

In this study the pilot test of CGS as injection method by low slump mortar was performed and the results were analyzed in order to find out the application of this method and effect of settlement restraint. The site far pilot test is adjacent to apartments supported by pile foundations. Sand drain method was performed previously as countermeasures against settlement, but settlement occur continuously because this ground is very soft. Site investigations such as SPT, DCPT and vane shear test were performed to determine the characteristics of ground improvement. Field measurements and FDM analysis were performed on purpose to find out the displacement of ground during injection works. From the results of this study, CGS method can be optimized by the control of diagram, space, depth, injection material, and injection pressure. CGS improved soft ground compositely by the bearing effect of CGS columns and reinforcement of adjacent ground. Considering that increase of N value is about 2.1, CGS can be considered as an effective method to increase the bearing capacity as well as to stop the settlement of soft ground. It is also expected to be economic and effective in improvement of ground when it is used in applicable sites.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.701-708
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• 2003

Recently, piezocone penetration test is frequently conformed in order to estimate the characteristics of soft ground with standard penetration test, generally used in the past. The soil characteristics, such as cone penetration resistance, friction resistence and excessive pore water pressure, can be evaluated continuously through the piezocone penetration test. In Incheon International Airport 2nd phase site preparation, standard penetration test and piezocone penetration test were used in order to increase the confidence for determination of soft ground depth. And the compressible layer was determined by the comparison between the preconsolidation pressure and the designed increase pressure. As the results, the relation between standard penetration test and piezocone penetration test shows q$_{c}$=(1.09~l.63)N at the soft ground, determined by 5/30 N value. And q$_{c}$=(1.21~l.98)N was shown at the point of compressible layer, evaluated by the preconsolidation pressure. These results were applied to determination for the depth of soft ground and to design the improvement for the soft clay.lay.

• Proceedings of the Korean Geotechical Society Conference
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• 1993.10a
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• pp.51-56
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• 1993

This paper presents the FEM anlysis results performed to assess the applicability of Horizontal Jet Grout Roofing, and of ground improvement methods for tunneling in soft ground. Horizontal Jet Grount Roofing Method is applicable to ensure the stability of tunnel face in non-cemeted alluvial strata under high ground water pressure. For applying this method, to ensure the reliability, the Horizontel Jet Grout Roofing should be double lined with pre-grouting to reduce the water inflow during the jet grouting.

• Proceedings of the Korean Geotechical Society Conference
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• 1997.11a
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• pp.87-96
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• 1997