• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.4
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• pp.499-511
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• 2015

A room-and-pillar underground structure is characterized by its grid-type array of galleries. As a result, its construction and economical efficiency can be governed by excavation sequence of galleries. Therefore, this study aims to study the optimum excavation scheme of a room-and-pillar underground structure by considering its various design factors such as ground conditions and excavation sequences. Drill-and-blast method is assumed as a excavation method for a room-and-pillar underground structure. In addition, two kinds of excavation patterns corresponding to a concurrent and a sequential excavation patterns are considered in this study. For the assumed conditions, the structural stability and the construction efficiency based on the number of faces and the travel distance of a jumbo drilling machine are analyzed for the two excavation patterns. Even though the two kinds of excavation patterns show almost the same structural stability as each other, the concurrent excavation pattern is relatively preferable to the sequential excavation pattern in terms of the number of faces in operation and travel distance of a drilling jumbo.

• Journal of Korean Tunnelling and Underground Space Association
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• v.26 no.1
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• pp.1-17
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• 2024

Analyzing the tunnel excavation behavior and its effect on the surrounding ground involves large deformation behavior. Therefore, in order to properly simulate the tunnel excavation process and rigorously investigate the actual effect of excavation on surrounding ground and tunnel structure large deformation analysis method is required. In this study, two major numerical approaches capable of considering large deformations behavior were applied to investigate the effect of tunnel boring machine excavation on the surrounding ground: coupled Eulerian-Lagrangian (CEL) and the automatic remeshing (AR) method. Relative performance of both approaches was evaluated through the ground response due to TBM excavation. The ground response will be quantified by estimating the range of the excavation damaged zone (EDZ). By comparing the results, the range of the EDZ will be suggested on the vertical and horizontal direction along the TBM excavation surface. Based on the computed results, it was found that the size of EDZ around the excavation surface and the tendencies was in good agreement among the two approaches. Numerical results clearly show that the size of the EDZ around the tunnel tends to be larger for rock with higher RMR rating. The size of the EDZ is found to be direct proportional to the tunnel diameter, whereas the depth of the tunnel is inversely proportional due to higher confinement stress around the excavation surface.

• Proceedings of the Korean Geotechical Society Conference
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• 1994.09a
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• pp.158-168
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• 1994

This report describes aspects of recent braced excavation constructed in built up areas where adjacent buildings or underground utilities are likely to be subjected to settlement and damages. Trends and choice of earth retaining structures for deep excavation are present, and some desigen and construction techniques are introduced in order to minimise possible adverse effects to the urban environment. Some problems in design and construction of braced excavation in urban area are closely examined and remedial measrures are proposed.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1993.04a
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• pp.207-212
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• 1993

In the construction of underground structures, it is critical to accurately predict the ground deformations during excavation. In this paper, a finite element procedure for the computation of solid displacement and fluid pore pressure during incremental excavation is presented based on Biot's theory. The numerical formulation is done using the virtual work principle. The proposed procedure is applied to some example problems with different excavation rates and permeabilities.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1992.10a
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• pp.174-179
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• 1992

In this paper a discussion is presented about excavation responses of underground openings for radioactive waste disposal. The effects of excavation methods, stress redistribution, thermal change, and backfill materials are reviewed. Comparisons of computational models for discontinuous reek masses and discussions on numerical simulation techniques for the excavation of underground openings are also described. Finally, the application of the CAD system to the planning, design and construction of underground openings fop radioactive waste disposal is introduced.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.85-95
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• 2002

A substantial portion of the cost of deep excavations in urban environments is devoted to prevent ground movements and their effects on adjacent buildings and utilites. Prediction of ground movements and assessment of the risk of damage to adjacent structures has become an essential part of the planning, design, and construction of a deep excavation project in the urban environments. This paper presents damage assessment techniques for buildings and utilities adjacent deep excavation, which can be readily used in practice.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1301-1306
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• 2009

Recently, urban excavations are one of most frequent geotechnical work according to construction of a high rise building and subway. These kind of excavation affect to a adjacent ground or structure and it can trigger various severe accidents. Generally, the ground is closer to the excavation site, the deformation become larger. In this study, special ground settlement case due to adjacent ground excavation is presented and a cause of deformation is examined by various geotechnical exploration, lab-testing and numerical analysis.

• Journal of the Korean Geotechnical Society
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• v.15 no.6
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• pp.71-86
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• 1999

The displacements of soil nailed wall and the nail tensile force for 11 soil nailing sites were investigated by using measurements obtained from inclinometer and strain gauge. The maximum horizontal displacement which occurred between 5% and 15% of the final excavation depth was found to be below 0.3% and 0.2% of excavation depth for well and poorly constructed sites. It was also found that the maximum horizontal displacements for 0.4%, 0.3% and 0.2% of excavation depth occurred when the ratios of nail length to final excavation depth were 0.5, 0.5~0.6 and 0.6~0.7. But the maximum horizontal displacement increased by 0.3% of excavation depth when the ratio was above 0.7. This was probably due to the shallow excavation depth and the deep soil stratum. The non-dimensional maximum tensile force of nail, K, from ground surface to $(0.6H_f)$ of the final excavation depth was less than 0.8 and decreased linearly between $(0.6H_f)$ and the final excavation depth. Also, the maximum tensile force was found to reach up to 60% of the ultimate tensile force at final excavation.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.4
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• pp.435-450
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• 2020

The divergence section of a double-deck tunnel can be divided into a 'widening pre-divergence section', a large cross-section with a cap shape and a 'post-divergence section' where the separation between the main and the branch tunnel is made. Since the cross-section of the widening pre-divergence section is considerably larger than that of the post-divergence section, the influence of excavation due to the different sizes and shapes in the cross-section should be considered in the examination of the tunnel stability. In this study, the effect of the preceding excavation, that is the excavation of the widening pre-divergence section, on excavation stability of the post-divergence section was examined by varying the excavation methods and bench lengths through 3D finite element analysis. The results showed that although the effects of the excavation methods and the bench lengths are not significant on the variation of principal stresses, the preceding excavation causes a relatively large variation on the stresses which may have an impact on the stability of the post-divergence section from the comparison of Stress-Strength Ratio (SSR) between the cases with and without the consideration of the preceding excavation effect by 2D finite element analysis.

• Journal of the Korean Geosynthetics Society
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• v.21 no.4
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• pp.101-109
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• 2022

This study describes the results of model experiment to analyze the effect of backfill material types on the behavior of underground facility. In the model experiment, backfill materials around the existing underground facility were applied with soil (Jumunjin standard sand) and CLSM. The displacement of underground facility was analyzed for each excavation stage considering the separation distance between the excavation surface and the backfill area based on the experimental results. When soil was applied as a backfill material, the soil on the back of the excavation surface collapsed by excavation and formed an angle of repose, and the process of slope stability was repeated at each excavation stage. In addition, the displacement of underground facility began to occur in the excavation stage that the failure line of soil passes the installation location of the underground facility. When CLSM was applied as a backfill material, there was almost no horizontal and vertical displacement of the ground regardless of the separation distance from the excavation surface even when excavation proceeded to the backfill depth. Therefore, this result showed that it can have a resistance effect against the lateral earth pressure generated and the collapse of the original ground by adjacent excavation, if a backfill material with high stiffness such as CLSM is applied.