• Geomechanics and Engineering
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• v.24 no.4
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• pp.323-335
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• 2021

This paper aims to estimate the range of the excavation damaged zone (EDZ) formation caused by the tunnel boring machine (TBM) advancement through dynamic three-dimensional large deformation finite element analysis. Large deformation analysis based on Coupled Eulerian-Lagrangian (CEL) analysis is used to accurately simulate the behavior during TBM excavation. The analysis model is verified based on numerous test results reported in the literature. The range of the formed EDZ will be suggested as a boundary under various conditions - different tunnel diameter, tunnel depth, and rock type. Moreover, evaluation of the integrity of the tunnel structure during excavation has been carried out. Based on the numerical results, the apparent boundary of the EDZ is shown to within the range of 0.7D (D: tunnel diameter) around the excavation surface. Through series of numerical computation, it is clear that for the rock of with higher rock mass rating (RMR) grade (close to 1st grade), the EDZ around the tunnel tends to increase. The size of the EDZ is found to be direct proportional to the tunnel diameter, whereas the depth of the tunnel is inversely proportional to the magnitude of the EDZ. However, the relationship between the formation of the EDZ and the stability of the tunnel was not found to be consistent. In case where the TBM excavation is carried out in hard rock or rock under high confinement (excavation under greater depth), large range of the EDZ may be formed, but less strain occurs along the excavation surface during excavation and is found to be more stable.

• Geomechanics and Engineering
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• v.30 no.2
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• pp.153-167
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• 2022

This study proposes a method to analyze the distribution of coal porosity disturbances after the excavation of ultra-large-diameter water jet boreholes using a coal wetting and softening model. The high-pressure jet is regarded as a short-term high-pressure water injection process. The water injection range is the coal softening range. The time when the reference point of the borehole wall is shocked by the high-pressure water column is equivalent to the time of high-pressure water injection of the coal wall. The influence of roadway excavation with support and borehole diameter on the ultra-large-diameter jet drilling excavation is also studied. The coal core around the borehole is used to measure the gas permeability for determining the porosity disturbance distribution of the coal in the sampling plane to verify the correctness of the simulation results. Results show that the excavation borehole is beneficial to the expansion of the roadway excavation disturbance, and the expansion distance of the roadway excavation disturbance has a quadratic relationship with the borehole diameter. Wetting and softening of the coal around the borehole wall will promote the uniform distribution of the overall porosity disturbance and reduce the amplitude of disturbance fluctuations.

• Explosives and Blasting
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• v.20 no.3
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• pp.59-71
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• 2002

The points of this design case are the planning and excavation method of a new double-tracked railroad tunnel which is approx. 11∼22 meters apart from existing single-tracked railroad tunnel. For the optimum excavation method some needs are required in design stage, such as the reduction of noise and vibration, public resentment, damage of buildings and construction costs. Hence the estimation and application of allowable noise and vibration criterion is important. The ground coefficient (K, n) of this site is determined by field trial blasting. The excavation method is chosen to satisfy the allowable noise and vibration criterion. In addition, in order to ensure the stability of existing single-tracked railroad tunnel, the instrumentation of maintenance level is accompanied during the construction stage. As a result of this design condition, central diaphragm excavation with line drilling and pre-large hole boring blasting is applied to the area within 15 meters apart from existing tunnel. And above 15 meters apart, pre-large hole boring blasting is designed.

• 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 KSR Conference
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• 2010.06a
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• pp.1500-1505
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• 2010

The objective of this study is controlling of the large diameter Shield TBM excavation for subway tunnels. In this paper, it will focus on the selection of Shield TBM and the problems of excavation due to unusual abrasion of the Disk Cutters and the distorted Cutter Mounts, in mixed layer of soil in below and hard rock in above, and in rock layer. And also, it will be discussed that the type of ground improvement to change and repair the Disk Cutters and the distorted Cutter Mounts, Advance Rate, Cutter Torque, etc. The results of this study will be using controlling of the excavation in various large diameter Shield TBM for subway tunnels.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.643-650
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• 2009

The necessary consequence by the rapid economic growth in large-scale urban excavation is increasing. If the site is the congested in downtown, the scale of excavation will get the large-scale and the extreme depth. We have achieved a high level technology internationally by the design and construction of underground excavation since 1980's. But the accidents during excavation are frequently occurring. So, this demage instigates the human life loss as well as economical loss. The recent accident is come about the damage for public facilities such as the railroad, subway and etc. in addition to the loss of life and property. For these reasons, the recent accident is being caused the damage of copious social overhead capital. The reasons of collapse during excavation can be classified roughly into the administrative part(sanction, permission), the investigation and design, the construction and management and etc. In this study the close check for the cases of the recent collapse is performed and the improvement course for the prevention of collapse is found.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.1087-1094
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• 2010

With recent growth of population and industry, urban development grows into grand scheme of excavation and construction in urban area. As the development progress advanced, the developments get large and deepen. With a progress of technology development in geotechnical engineering in Korea, most our grand scheme of projects follows great progress. On the other hand, some excavation in construction site caused direct or indirect event that affects the adjacent or surrounding structures by excavation from time to time. This event usually happens around residential and commercial area where underground tunnel, subway station, commercial building, and high-rises excavation site is, could lead great damage on economy as well as personal injury or human casualties. In order to prevent this event, the study has to be done with analysis on various events of excavation and its cause. In this paper, the research has collected the various excavation events and their causes to analyze on each site and event to define emphasis on surrounding environment.

• Journal of the Korean Society of Safety
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• v.31 no.2
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• pp.57-63
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• 2016

Recently, subways in the city are formed a vast underground network which is interfered with construction when large-scale infrastructure will be planned to nearby existing subway tunnels. Researches have been restricted to estimate stability of existing subway tunnel due to adjacent excavation causued by small construction such as buildings. In this paper, OO underpass is planned on the top of existing subway tunnel, which will be need large-scale excavation, is selected as a subject of study. And the purpose of this study is to analyze the effects on existing subway tunnel due to excavation by stages on construction of underpass. The 3D-numerical analysis was performed by using the MIDAS/GTS program. The stability on existing subway tunnel caused by sequential excavation is analysed using numerical results. Based on the analysis, the excavation orders and reinforcement methods was suggested for stability of exiting subway tunnel.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.521-532
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• 2008

Supporting system design and construction management for the soft and hard rock layers with fractured zones are very important theme for the safety of temporary retaining wall, surrounding ground and structures in the urban deep excavation for the construction of subway, railway, building etc. The prevailing design method of supporting system for the soft and hard rock layers in the deep excavation is mostly carrying out by simplification without proper consideration for the characteristic of rock discontinuities. Therefore the behaviors of rock discontinuities and fractured zones dominate the whole safety of excavation work in the real construction stage, serious disaster due to the failure of temporary retaining wall can be induced in the case of developing large deformations in the ground and large axial forces in the supporting system. This paper introduces examples of deep excavation where the soft and hard rock layers with fractured zones were designed to be supported by shotcrete and rock bolt, deformations of corresponding ground and supporting systems in the construction period and increments of axial force in the upper earth anchors and strut due to the these deformations were investigated through detailed analysis of measurement data, the results were so used for the management of consecutive construction that led to the safe and economical completion of excavation work. The effort of this article aims to improve and develop the technique of design and construction in the coming projects having similar ground condition and supporting method.

• Journal of the Korean Society of Safety
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• v.19 no.2
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• pp.112-118
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• 2004

Recently, when being constructed the large structures, the deep excavations have performed to utilize the underground space. As the ground excavation is deeper, the damage of the adjacent structure and the ground is frequently occurred. the Analysis of the retaining structures is necessary to safety of the excavation works. There are many methods such as elasto-plastic theory, FEM, and FDM to analyze the displacement of the retaining structure. In this thesis, GEBA-1 program by the Nakamura-Nakajawa elasto-plastic method was developed. The lateral displacement of the wall was analyzed by the developed program GEBA-1, SUNEX, and EXCAD, and compared with the measured displacement bye the Inclinometer. The monitored fields were three excavation work site in S-I, S-II, and S-III area. Excavation method of each site is braced retaining wall using H-pile. Excavation depth is 14m, 14m, and 8.2m.