• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.1039-1049
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• 2010

Excavation support systems are the temporary earth retaining structures that can prevent the lateral movement of soils. The systems are initially performed before other construction operations and have a great impact on the entire construction period. The temporary support system in Korea have been carried out generally along with installing supports, which are struts, tiebacks, and rakers. However, most of existing support systems in application relatively have limitations such as cost increase, construction configuration, and displacement occurred with support systems. Thus, a new retaining support system (referred to as the SSR, New Construction Technology No. 533) was developed to solve the aforementioned problems. This study introduces the design, construction, and maintenance of the SSR system under the different construction conditions. The behavior and characteristics of the SSR system were identified based on the case studies.

• Journal of the Korean Geotechnical Society
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• v.34 no.12
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• pp.7-17
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• 2018

Test bed additional wall combined with PHC-W pile retaining wall has been constructed. To determine the dimensions of test bed additional wall, bending and shear tests of full scale core members of additional wall were tested. Basement additional walls utilizing PHC-W pile retaining wall, which were developed by modifying the cross-section of PHC piles, were classified into the composite additional wall and the non-composite additional wall. Their tests were conducted to obtain bending strength and shear strength of basement additional walls ultilizing PHC-W pile retaining wall. Since bending strengths and shear strengths of the composite additional wall and the non-composite additional wall were similar, it could be confirmed that the non-composite additional wall could be applied instead of the composite additional wall. Full-scale model additional wall was 200 mm thick, thus the thickness of additional wall combined with PHC-W pile retaining wall could be reduced by 100~200 mm.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.96-103
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• 2002

In this study, design concepts of Seoul Subway Construction (901∼914) are reviewed in relation to the cases for temporary soil support wall systems which are revealed in highly developed design competitions such as Turnkey and Alternative based on. Especially soil and rock properties, various design schemes for dealing with soil and water pressures, new technology adopted etc are discussed very profoundly and broadly for the better understanding and additional clues for constructing new design technologies.

• Journal of the Korean Geotechnical Society
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• v.15 no.4
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• pp.43-56
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• 1999

The use of berms can be an effective method to restrain excessive movements of wall and ground caused by deep excavations in urban area. But generally in construction sites, no berm remains for the sake of construction convenience or the geometry and magnitude of remaining berm is determined by individual experiences due to scarce research results. In this research, laboratory model tests and numerical analyses are used mainly for sandy soils. And efficient berms for restraining excessive movements by deep excavations are analyzed. Model tests were performed for the cases of cantilever and braced wall excavations, and the behaviors of retaining wall were analyzed according to the geometry and magnitude of berms. And also, numerical methods were used for analyzing efficient berms which are available in the soil and construction conditions in urban areas of Korea.

• Journal of the Korean Geotechnical Society
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• v.33 no.2
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• pp.5-15
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• 2017

PHC-W retaining wall method is one of the economical retaining wall methods. PHC-W pile used in PHC-W retaining wall method has special shape with flat surfaces so that the PHW-C retaining wall, with overlapped piles, shows outstanding vertical control and impermeability. In order to evaluate two types of retaining walls, numerical analysis were performed. The selection of cases depended on N values of the ground and ground properties, and two types of PHC-W retaining walls (defined as type A and B) were constructed. For a case that consists of inorganic clay and sand with less than 30 of N value, the maximum excavation depths for type A and B were respectively 10.5 m and 11.0 m. At the other case of which N value is above 30, the depths were 17.0 m and 19.5 m. From the results, it was found that maximum excavation depth, horizontal displacement, and safety factor for flexural strength of the wall were influenced by ground properties.

• Journal of the Korean Geotechnical Society
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• v.23 no.10
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• pp.121-131
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• 2007

This study is to investigate the damage assessment of adjacent structures due to excavation in urban environment. Model tests were carried out for 2 story masonry building and frame structures in various shapes and locations. The damage level of adjacent structures were very differently estimated in accordance with the shape ratio (L/h) of structures, construction stages, and various locations. Therefore the most weak part (bay) of structure must be heavily instrumented and monitored in more details at early stage of constructions. The progressive crack development mechanism at various construction stages was revealed through model tests and crack size indicated more conservative side of damage level on the damage level graph.

• Journal of the Korean Geotechnical Society
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• v.15 no.1
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• pp.31-40
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• 1999

The bracing system using screw jack is not effective for the restraining of adjacent ground displacement. since the screw jack dose not induce sufficient preloading on struts. In order to protect excessive displacement of adjacent ground at braced excavation, new preloading jack was developed in the country. In this paper, the new preloading jack and the measurement results of the lateral displacement of braced wall at three deep excavation sites in Seoul city are introduced. The measurement results showed that the maximum displacements of braced wall are smaller than 0.15% of excavation depth, therefore the wall displacements can be minimized by preloading which is acted on bracing. If the bracing system with new preloading jack is used in braced excavation, it is effective for reducing the cost and period of construction.

• Journal of the Korean Geotechnical Society
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• v.27 no.5
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• pp.17-31
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• 2011

This paper presents the results of a numerical investigation on the behavior of earth retaining wall system with emphasis on the groundwater lowering. Using the 2D stress-pore pressure coupled analysis, the effects of ground excavation and groundwater interaction were examined using wall horizontal deformation, ground surface movement, plastic strain pattern, effective stress distribution and axial stress of strut. In addition, based on the results from a parametric study on a wide range of soil profile and initial ground water table level, the ranges of wall displacement and ground deformation were suggested quantitatively.

• Journal of the Korean Geotechnical Society
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• v.38 no.11
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• pp.119-135
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• 2022

This paper used dynamic centrifuge tests to examine the seismic response for a deep temporary retaining wall with four input motions of 100, 1,000, and 2,400 years of return periods. The centrifuge model was designed based on an actual deep excavation design with a 50 m maximum excavation depth. The model backfill was prepared with dry silica sand at a relative density of 55%, and the retaining wall was modeled as a 24.8 m height diaphragm wall supported by struts. Acceleration response was amplified at the backfill surface, top of the wall, and near bedrock. However, in the middle of the model, input motion was de-amplified. The member forces of the wall and strut induced by the seismic load, which excited, were compared with the member force at rest condition. The wall's maximum negative and positive moments were increased to 36% and 10% compared to the maximum moment at rest. The maximum axial force increases to 70% of the at rest axial force on the bottom strut. The equivalent static analysis using Mononobe-Okabe (M-O) and Seed-Whitman (S-W) seismic earth pressures were compared to the centrifuge results. Considering the bending moment, the analysis results with the M-O theory underestimates but that with the S-W theory overestimates.

• Journal of the Korean Geotechnical Society
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• v.38 no.12
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• pp.45-65
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• 2022

In this paper, a diaphragm wall that supports soils and rock was modeled using FLAC, a finite difference analysis program, to evaluate the seismic behavior of temporary retaining structures in a deep excavation. The appropriateness of the numerical model was verified by comparing its results with those of the centrifuge test performed in a similar condition. The bending moment distribution along the diaphragm wall shows a very similar tendency, and the maximum acceleration obtained at the backfill and top of the wall shows a difference within 5%. Based on the developed model, a parametric study was conducted in various input earthquake, ground, and excavation conditions. The maximum structural forces and bending moment under earthquake loading were compared with the maximum values during excavation, from which the critical condition that requires a seismic design was roughly sorted out. The maximum bending moment of a wall that retains soil layers increased 17%. Particularly, the axial force of struts located in loose soils increased 32% under 100 years return period of an earthquake event, which strongly is estimated to require seismic design for structural safety.