• Journal of the Korean Geotechnical Society
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• v.21 no.2
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• pp.27-36
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• 2005

The performance of innovative prestressed support (IPS) earth retention system applied in urban excavation was presented and investigated. The IPS wales provide a high flexural stiffness to resist the bending by lateral earth pressure, and the IPS wales transfer lateral earth pressure to Corner struts. The IPS wale provides a larger spacing of support, economical benefit, construction easiness, good performance, and safety control. In order to investigate applicability and stability of the IPS earth retention system, the IPS system was instrumented and was monitored during construction. The IPS system applied in urban excavation functioned successfully. The results of the field instrumentation were presented. The measured performances of the IPS earth retention system were investigated and discussed.

• Journal of the Korean GEO-environmental Society
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• v.10 no.7
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• pp.43-51
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• 2009

This paper holds three objects. The first is to analyze surveys of concerning zone and promotion department. The data were collected through an examination of construction excavated in coastal soft (marine) clay and measurements obtained during excavating construction. The second is to observe the appropriate selection and the application of support system on earth retaining wall in soft clay. Lateral deformation behavior during the excavating construction according to the differences in a soft ground pressuring degree was investigated. The third is to compare the results with those of numerical analysis. Therefore, the purpose of this study is to analyze the characteristics of lateral deformation when soft ground improvement for the expansion of infrastructure in object of study zone has been incompleted. Also, it is to identify the relationship between the degree of consolidation of soft ground and lateral deformation, in a method of displacement quantity in compliance with the numerical analysis and a quatitative analysis. In conclusion, displacement of excavated section after consolidation was fewer 60% averagely than section under consolidation.

• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.15-26
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• 2003

Urban excavation requires highly reliable prediction technique for the design and construction of earth retaining structure in order to protect adjacent structures around deep excavation. Application of the pre-loading of bracing for deep excavation has been reported, and the known beneficial effects are not fully understood and recognized by many practitioners. Model tests have been carried out to evaluate the efficiency of pre-loading system in reducing ground settlement as well as prediction of structural damage around excavation in sand. The test results revealed that the applied pre-loading of 50% and 70% showed about 20% of reduction in horizontal wall displacement and 30∼40% reduction in ground settlement. Also, bracing forces and earth pressure distribution behind the wall have been monitored during pre-loading at various excavation stages.

• Proceedings of the Korean Geotechical Society Conference
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• 2007.09a
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• pp.115-123
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• 2007

설계 하중이 큰 대형 구조물의 기초로 많이 사용되는 현장타설말뚝은 현장에서 지반을 굴착하여 조립된 철근망을 삽입한 후, 콘크리트를 타설하여 제작되므로 복잡한 시공 과정과 현장의 특수한 지하수 및 지반 조건으로 인하여 현장타설말뚝의 내부에는 결함이 포함될 수 있다. 발생 가능한 대표적인 결함으로 연약한 말뚝 선단, 말뚝체 콘크리트의 품질 저하, 말뚝과 지반의 접촉 불량, 주 철근의 부식 등이 있으며, 이들 결함을 감지하기 위한 건전도 시험법으로 공대공초음파 검층, 충격반향시험, 충격응답시험, 감마-감마 검층법 등이 있다. 결함은 말뚝의 수평지지력을 감소시키며, 일반적으로 발생하는 비대칭단면 결함에 의한 응력 집중현상과 수평 하중에 의한 휨모멘트는 연직지지거동에 영향을 준다. 따라서 결함을 감지하고 평가하는 것이 현장타설말뚝의 품질관리에 있어 매우 중요하다.

• Proceedings of the Korean Geotechical Society Conference
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• 1991.10a
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• pp.133-151
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• 1991

In this paper an analytic discussion was made for a finite element analysis performed for the case study of Seoul subway NATM tunnel. The effects mainly discussed on the ground deformation analysis were the staged tunnel excavation and the excavated distance from a tunnel facing. The concept of ground characteristic line has been applied to properly consider the loading condition given by staged tunnel excavation so that the imaginary supporting pressure is applied on the excavated tunnel face. Discussions on the results of the performed finite element analysis were mainly made with respect to the ground settlement, tunnel displacement, earth pressure, stress mobilized in supporting members. And the three dimensional supporting effect due to the tunnel facing was evaluated based on an elastic closed-form solution and a result of two dimensional axisymmetric finite element analysis.

• Journal of the Korean Geosynthetics Society
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• v.14 no.4
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• pp.23-33
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• 2015

Together with the wall stiffness, a berm has the role of deciding the stability of a temporary retaining wall before structure installation after excavation. Especially in case of loose or soft soil excavated ground, the role of berm is very important. In this study, the measurement data obtained from the temporary retaining wall in the bermed excavation site in urban and numerical analysis are used to investigate the effects of berm's dimension (width and slope), excavation depth and ground property on the maximum horizontal displacement of the temporary retaining wall. The measurement data indicated that the wall displacement varied to the berm's width. That is, as the berm width decreased, the wall displacement increased. As a result of numerical analyses, the maximum wall displacement increased as slope increased and berm width decreased. This means that the berm is effectively restrained to the wall displacement. As excavation depth increased, the effect of berm's slope and width increased. In case of the same berm condition, the wall displacement restrained as ground property increased.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.1
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• pp.175-183
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• 2014

This study investigates the response of structures to tunnelling-induced ground movements in clay ground, varying tunnel excavation condition (tunnel depth and diameter), tunnel construction condition (ground loss), and tunnel ground condition (soft clay and stiff clay). Four-story block-bearing structures have been used because the structures can easily be characterized of the extent of damages with crack size and distribution. Numerical parametric studies have been used to investigate of the response of structures to varying tunnelling conditions. Numerical analysis has been conducted using Discrete Element Method (DEM) to have real cracks when the shear and tensile stress exceed the maximum shear and tensile strength. The results of structure responses from various parametric studies have been integrated to consider tunnel excavation condition, tunnel construction condition, and tunnel ground condition and provide a relationship chart among them. Using the chart, the response of structures to tunnelling can easily be evaluated in practice in clay ground.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.2
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• pp.175-187
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• 2015

In this paper, the development of trench shield machine for near-surface railway construction were presented. The Near-surface railway can be constructed by cut and cover construction method, because it is installed at the depth of 5~7 m below roads. The cut and cover construction method mostly use temporary supports. The limitation of the cut and cover method is high installation cost and long construction period. To overcome these disadvantages, development of the trench shield machine is proposed and expected to shorten the construction time and cost of near-surface railway system. The sliding retaining wall of trench shield equipment replaces the role of temporary support (solider piles and lagging) and excavator equiped to the bottom front of the machine shorten the excavation time. This paper deals with design of the bit attached to the excavator and required capacity of the motor.

• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.4
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• pp.305-317
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• 2011

In this study, both the model test and the numerical analysis were carried out to figure out the physical behaviour of the model pile during the tunnelling. As a result, both the vertical and the horizontal displacements were simultaneously occurred in the model pile which is subjected to the working load during the volume loss. Consequently, the phenomenon of inclination took place in the model pile. The degree of inclination of the model pile depends on volume loss due to tunnel excavation, pile tip's offset from the tunnel centre, and bearing ground conditions in which pile tip is located. Therefore, in the planning stage of urban tunnelling not only the ground behaviour with respect to the pile locations, but also the physical behaviour of pile itself should be carefully analysed to avoid damage of adjacent buildings.

• Journal of the Korean Geotechnical Society
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• v.33 no.1
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• pp.5-15
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• 2017

Skin friction may be one of the most critical factors in designing the prebored and precast pile. Special attention was given to the interface behavior of cement milk-surrounding soil during the installation of prebored and precast pile. Small-scale field model pile test was conducted for the case of single pile. The size and geometry of the small-scale field model piles were designed with pile length 1.3m, boring diameter 0.067 m. Quick maintain-load test was conducted for the cases of boring diameter 150, 125, 90, 86, 74 mm and water-cement ratio 90, 70, 60%. It was shown that the bearing capacity of the pile increased as the cement-water ratio and cement milk thickness increased. Considering the scale effect between the small-scale model test and the actual construction site, it was found that cement milk thickness of 0.1~0.4D (50~200 mm) was reasonable for the stability of the structure. Also, the proper cement paste water / cement ratio was about 70% when considering the results of this study and quality control.