• Structural Engineering and Mechanics
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• v.65 no.6
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• pp.741-750
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• 2018

The aim of this study was to investigate the mechanical responses of a high-speed railway shield tunnel subjected to impact by a derailed train, with emphasis on the protective effect of the secondary lining. To do so, the extended finite element method was used to develop two numerical models of a shield tunnel including joints and joint bolts, one with a cast-in-situ concrete secondary lining and one without such a lining. The dynamic responses of these models upon impact were analyzed, with particular focus on the distribution and propagation of cracks in the lining structures and the mechanical responses of the joint bolts. The numerical results showed that placing a secondary lining significantly constricted the development of cracking in the segmental lining upon the impact load caused by a derailed train, reduced the internal forces on the joint bolts, and enhanced the safety of the segmental lining structure. The outcomes of this study can provide a numerical reference for optimizing the design of shield tunnels under accidental impact loading conditions.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.5
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• pp.553-561
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• 2015

In this study, the performance assessment criterion for reasonable maintenance of shield TBM tunnel was presented. The performance assessment items such as crack, leakage, breakage, spalling, exfoliation/detachment, efflorescence, quality condition, exposure of steel, carbonation, faulting step, bolts condition, drainage condition, ground condition, contact section condition and conduit condition were selected by analyzing domestic and foreign performance assessment criterions and investigating segment lining deterioration cases through the site investigation and in-depth inspection analysis result on the shield TBM tunnel. In addition, the reasonable weight using AHP (Analytic Hierarchy Process) were estimated.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.6
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• pp.683-697
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• 2012

In this paper, a risk analysis methodology applicable to shield TBM tunnels was studied. Fault Tree Analysis (FTA) was utilized to identify all risk items and to calculate the probability of failure of each item and Analytic Hierarchy Process (AHP) was used to obtain the impact of each risk item. Finally, a risk level of each risk item can be assessed. Developed methodology is applied to a Seoul subway site in which EPB shield tunnel method was utilized and it was found that risk analysis results matched reasonably well with field data.

• Geomechanics and Engineering
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• v.17 no.1
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• pp.97-107
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• 2019

Based on the results of Han et al. (2016), in the failure zone ahead of the tunnel face it can be obviously identified that a shear failure band occurs in the lower part and a pressure arch happens at the upper part, which was often neglected in analyzing the face stability of shield tunnel. In order to better describe the collapse failure feature of the tunnel face, a new improved failure mechanism is proposed to evaluate the face stability of shield tunnel excavated in layered soils in the framework of limit analysis by using spatial discretization technique and linear interpolation method in this study. The developed failure mechanism is composed of two parts: i) the rotational failure mechanism denoting the shear failure band and ii) a uniformly distributed force denoting the pressure arch effect. Followed by the comparison between the results of critical face pressures provided by the developed model and those by the existing works, which indicates that the new developed failure mechanism provides comparatively reasonable results.

• Geomechanics and Engineering
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• v.18 no.2
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• pp.215-224
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• 2019

Excavation of long tunnels by shielded TBMs is a safe, fast, and efficient method of tunneling that mitigates many risks related to ground conditions. However, long-distance tunneling in great depth through adverse geological conditions brings about limitations in the application of TBMs. Among various harsh geological conditions, squeezing ground as a consequence of tunnel wall and face convergence could lead to cluttered blocking, shield jamming and in some cases failure in the support system. These issues or a combination of them could seriously hinder the performance of TBMs. The technique of excavation has a strong influence on the tunnel response when it is excavated under squeezing conditions. The Golab water conveyance tunnel was excavated by a double-shield TBM. This tunnel passes mainly through metamorphic weak rocks with up to 650 m overburden. These metamorphic rocks (Shales, Slates, Phyllites and Schists) together with some fault zones are incapable of sustaining high tangential stresses. Prediction of the convergence, estimation of the creeping effects and presenting strategies to overcome the squeezing ground are regarded as challenging tasks for the tunneling engineer. In this paper, the squeezing potential of the rock mass is investigated in specific regions by dint of numerical and analytical methods. Subsequently, several operational solutions which were conducted to counteract the challenges are explained in detail.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.6
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• pp.385-392
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• 2021

When ordering a slurry shield TBM to be used for power cable tunneling, the client organizes an evaluation committee composed of experts, suggest the criteria and evaluation method for technical specifications for supplier selection, and based on the manufacturer's technical proposal were attempted to evaluate and select. It is expected to be referred to as a guideline for future projects to using Shield TBM as one of the methods of verifying performance and quality in advance and securing economic feasibility in the shield TBM tunneling in the recent increasing trend.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.3
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• pp.677-683
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• 2016

In urban areas, underground tunnel construction sites have spread widely to accommodate rapidly increasing traffic volume along with a high-degree economic growth. Earth tunneling might be adapted frequently for the underground space securing, and various tunneling methods have been developed to stabilize the tunnel face and crown. Among them, the DSM (divided shield method) is gaining popularity for its enhanced stability and construction efficiency. This method has its foundation from the Messer Shield method, which is one of the trenchless special tunneling methods. This study examined the effects of face reinforcement on construction the sequence through a large scale soil chamber test and numerical analyses. The chamber has a size of a 1/2 scale of the real tunnel. Surface settlements were measured according the tunneling process. Commercially available software, MIDAS GTS, was used for numerical analysis and its result was compared with the values obtained from the chamber test. The results of the study show that both settlements of the embanked soils and the stress of the tunnel girder are located within the safe criteria. Overall, this study provides basic data and the potential of using a reinforced tunnel face to enhance DSM applications.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.10
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• pp.1748-1753
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• 2010

This paper suggests an improved technique to establish the modeling regarding steady and transient state on three phase-in one cryostat type HTS(High Temperature Superconducting) cable. The proposed modeling is established using EMTP/ATPDraw and TACS and MODELS provided by that. It has higher accuracy than the conventional method, as the actual HTS cable is modelled. Steady and transient state analysis performed by EMTP/ATPDraw calculate the current of conductor, shield and former, respectively. In case of the transient state modeled quench state occurred by a single line-to-ground fault, current of conductor shield and former are also calculated, respectively. Especially, various fault resistances and angles are considered to improve the reliability during transient state analysis. Analysis results reveal that the proposed technique improves the accuracy of modeling.

• Journal of the Korean institute of surface engineering
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• v.27 no.6
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• pp.340-346
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• 1994

The method of uniforming current distribution in Hull cell are studied by using auxiliary anode, current shield bipolar electrode, and combinings bipolar electrode with current shield in order to find a way of uni-form deposition. The current density distributions are measured by each ammeter of the same inner resistance connected to divided cathode pannel respectively. The current density distributions of cathode electrode divided into five sections with 5mm width have a tendency of linear inclination, and that of twenty sections have a tendency of smoother curve than the curve of original Hull cell pannel. Their results showed lower value on the high current density portion and higher value on the low portion than that original Hull cell pannel. The current distribution in Hull cell is able to unify by using auxiliary anode, or combining bipo-lar electrode with current shield, but not efficient in using one of both individually.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.29-50
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• 2002

Based on the investigation results on the damages of some underground structures due to the severe Kobe Earthquake it concludes that the aseismicity of underground is far superior to that of aboveground structures. Therefore, at first, necessity to reconstruct strong cities especially by good use of underground space will be discussed. Then two non-circular shield-tunneling projects in Japan are discussed. The first is construction of the world's first shield driven double track subway tunnel of rectangular shape for the Kyoto Municipal Subway. This paper presents a report on the overall planning, the tests that were performed in the process of planning, and the results of driving. The second is the design of the Hirakata Tunnel, with three traffic lanes and shoulders on one side, which will be constructed as one of the tunnels for The New Meishin (Nagoya-Kobe) Expressways. This paper presents the feasibility study of the shield tunneling method, using the same design criteria as the non-circular, horseshoe section of mountain tunnel, to the equivalent section of the Hirakata Tunnel.