• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.271-278
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• 2002

Recently, deep excavation for high-rise buildings occurs frequently to accommodate the rapidly increasing population in urban area. The stability of the earth retaining structures for deep excavation becomes more critical. The behavior of the earth retaining structures should be accurately predicted in a design stage, but the predicted behavior is different from the measured data due to uncertain soil properties and problems in construction. In this study the back-analysis using Powell's optimization theory was performed to match the measured deflection and results obtained from back-analysis were presented.

• Journal of the Korean GEO-environmental Society
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• v.23 no.4
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• pp.29-39
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• 2022

In order to solve the serious traffic congestion in seoul metropolitan city, large-scale underground space development such as underpasses, deep underground roads, and GTX (Great Train eXpress) is being carried out. In order to minimize the impact of the adjacent seoul metro line A pier foundation and stability due to the construction of the underground road in Seoul, earth retaining structures were reinforced and the foundation was reinforced as well. In this study, three-dimensional finite element mehtod analysis was performed to evaluate the effect on adjacent construction and to review the stability of the underpass excavation work. The reinforcement effect was quantitatively analyzed through numerical analysis. As a result of the analysis, compared to the result of performing the existing reinforcement when overlapping CIP and ground reinforcement grouting were performed, the displacement of the earth retaining structures was reduced by more than 50%, and stress of the foundation piles were also reduced by more than 45%. Based on the analysis of the numerical analysis results, it was confirmed that the displacement of the walls of earth retaining structures during adjacent construction should be strictly controlled.

• Geomechanics and Engineering
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• v.7 no.3
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• pp.263-277
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• 2014

In the conventional design of retaining structures in a seismic zone, seismic inertia forces are commonly assumed to act upwards and towards the wall facing to cause a maximum active thrust or act upwards and towards the backfill to cause a minimum passive resistance. However, under certain circumstances this design approach might underestimate the dynamic active thrust or overestimate the dynamic passive resistance acting on a rigid retaining structure. In this study, a new analytical method for dynamic active and passive forces in c-${\phi}$ soils with an infinite slope was proposed based on the Rankine earth pressure theory and the Mohr-Coulomb yield criterion, to investigate the influence of seismic inertia force directions on the total active and passive forces. Four combinations of seismic acceleration with both vertical (upwards or downwards) and horizontal (towards the wall or backfill) directions, were considered. A series of dimensionless dynamic active and passive force charts were developed to evaluate the key influence factors, such as backfill inclination ${\beta}$, dimensionless cohesion $c/{\gamma}H$, friction angle ${\phi}$, horizontal and vertical seismic coefficients, $k _h$ and $k_v$. A comparative study shows that a combination of downward and towards-the-wall seismic inertia forces causes a maximum active thrust while a combination of upward and towards-the-wall seismic inertia forces causes a minimum passive resistance. This finding is recommended for use in the design of retaining structures in a seismic zone.

• Journal of the Korean Geotechnical Society
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• v.31 no.4
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• pp.19-29
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• 2015

Nowadays, the importance of the information management of construction sites to achieve the goal of safety construction. This management uses the collaborated analysis of in-situ monitoring data and numerical analysis, especially of an earth retaining structures of excavation sites. In this paper, the fractal theory was applied to actually monitored data from various excavation sites to develop the alternative interpolation technique which could predict the displacement behavior of unknown location around the monitoring locations and the future behavior of the monitoring locations with the steps of excavation. Data, mainly from inclinometer, were collected from various sites where retaining structures were collapsed during construction period, as well as from normal sites with the characteristics of geology, excavation method etc. In the analyses, Hurst exponent (H) was estimated with monitored periods using the Rescaled range analysis (R/S analysis) method applying the H in simulation processes. As the results of the analyses, Hurst exponents were ranged from 0.7 to 0.9 and showed the positive correlation of H > 1/2. The simulation processes, then, with the Hurst exponent estimated by Rescaled range analysis method showed reliable results. In addition, it was also expected that the variation of Hurst exponents with the monitoring period could instruct the abnormal behavior of an earth retaining structures to directors or operators. Therefore it was concluded that fractal theory could be applied for predicting the lateral displacement of unknown location and the future behavior of an earth retaining structures to manage the safety of construction sites during excavation period.

• Geotechnical Engineering
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• v.13 no.5
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• pp.35-44
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• 1997

A finite element computer program is developed for the specific analysis of earth retaining structures in urban excavation. Unlike the existing multi -purpose FEM programs, the newly developed program (EM) consists of very simple and easy data processing system for the urban excavation. A non-linear material model(GDHM, Generalized Decoupled Hyperbolic Models is deviloped and implemented in the program EM. The results of large scale model tests for earth retaining structures are used for the vertification of EM along whit GDHM, and the results were satisfactory, but it was found that the program EM needs minor modification for the improvement of its accuracy.

• Geomechanics and Engineering
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• v.13 no.5
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• pp.715-742
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• 2017

Earth berms are often left in place to support retaining walls or piles in order to eliminate horizontal struts in excavations of soft soil areas. However, if the excavation depth is relatively large, an earth berm-supported retaining system may not be applicable and could be replaced by a multi-bench retaining system. However, studies on multi-bench retaining systems are limited. The goal of this investigation is to study the deformation characteristics, internal forces and interaction mechanisms of the retaining structures in a multi-bench retaining system and the failure modes of this retaining system. Therefore, a series of model tests of a two-bench retaining system was designed and conducted, and corresponding finite difference simulations were developed to back-analyze the model tests and for further analysis. The tests and numerical results show that the distance between the two rows of retaining piles (bench width) and their embedded lengths can significantly influence the relative movement between the piles; this relative movement determines the horizontal stress distribution in the soil between the two rows of piles (i.e., the bench zone) and thus determines the bending moments in the retaining piles. As the bench width increases, the deformations and bending moments in the retaining piles decrease, while the excavation stability increases. If the second retaining piles are longer than a certain length, they will experience a larger bending moment than the first retaining piles and become the primary retaining structure. In addition, for varying bench widths, the slip surface formation differs, and the failure modes of two-bench retained excavations can be divided into three types: integrated failure, interactive failure and disconnected failure.

• Journal of the Korean Society of Safety
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• v.24 no.2
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• pp.48-54
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• 2009

Structures to support against slop failures or resist earth pressure like masonry retaining walls or retaining walls have continued to advance and evolve to new eco-friendly, easy-to-construct, crib retaining walls with varied forms and construction methods, meeting the needs of the times. Researches until now, however, have focused on the analyses of site displacement or stability of the whole site including structures like retaining walls, and thus, researches on rational design or method for stability analysis are lacking. Therefore, this study was conducted on a number of stability analyses, such as the visual power line or stability on sliding, being presented for bin walls, which enable vegetation to grow and were developed and applied in varied forms, meeting the development demands for eco-friendly retaining wall structures. This study compared the results of stability analyses, determined their feasibility, and evaluated their stability according to the height and facade slope of retaining walls. According to the results of this study, traditional masonry retaining wall analysis showed rather conservative stability evaluation results in the stability evaluation of bin walls, and the method using the visual power line seems to be objective because it produced similar results to the stability evaluation method on sliding or turnover.

• Geomechanics and Engineering
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• v.36 no.4
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• pp.329-341
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• 2024

Retaining structures are one of the most important elements in the stabilization of excavations and slopes in various engineering projects. Mechanically stabilized earth (MSE) walls are widely used as retaining structures due to their flexibility, easy and economical construction. These benefits are especially prominent for projects built on soft and weak foundation soils, which have relatively low resistance and high compressibility. For high retaining walls on weak foundations, conventional design methods are not cost-effective. Therefore, two alternative solutions for different foundation weakness are proposed in this research: optimized multi-tiered MSE walls and single tier wall with foundation improvement. The cost optimization considers both the construction components and the land price. The results show that the optimal solution depends on several factors, including the foundation strength and more importantly, the land price. For low land price, the optimized multi-tiered wall is more economical, while for high land price (urban areas), the foundation improvement is preferable. As the foundation strength decreases, the foundation improvement becomes inevitable.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.49-83
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• 2005

ESCP Project showed an urban excavation case and introduced design method for case of Soil-Structure behavior in urban excavation. In this case, a retaining structures design to analysis the behavior of retaining wall and adjacent structures in urban excavations was applied by using a Elasto-plastic beam and limit Equilibrium analysis and soil-structure interaction analysis. Reliable design of earth retaining structures and the ground adjacent to braced wall in urban excavation are often difficult due to many variable factors. The ground settlement and the damage of adjacent structures in urban excavation has been an imprtant issue. Therefore, the stability of the adjacent structures must be secured with the excavation support and research on the protection of adjacent structure is necessary.

• Proceedings of the Korean Geotechical Society Conference
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• 1990.10a
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• pp.129-144
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• 1990

This paper is an introduction of measured samples of a peripheral ground displacement resulting from excavation work, and the work carried out to minimize the displacement of the earth retaining wall and the adjacent structures.