• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.4
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• pp.323-336
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• 2003

Recently, the development of tunnel reinforcement method has been required relating to the shallow tunnelling in soft ground. In this study, the improvement method on tunnel stability is proposed by evaluating the efficiency of face reinforcement which enables to control extrusion of advance core, however, it is often neglected in urban tunnelling under the poor ground conditions. Systematic pre-confinement ahead of the face improves the tunnel stability, subsequently, displacement of the crown and surface settlement can be restrained by proper method. 3-dimensional numerical analysis including horizontal reinforcement modelling on a face is applied to estimate the behaviour of a tunnel in relation to the ground and reinforcement conditions. Consequently, extrusion at the face decreases significantly after using the horizontal reinforcement and the effect of reinforcement is much increased in case of applying the supplemental reinforcement ahead of the face together. Especially, confinement effect around the tunnel and the core is proved by means of the core reinforcement in poor ground conditions.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.79-86
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• 2000

This paper presents the results of a parametric study on the behavior of tunnel face reinforced with horizontal pipes. A series of reduced-scale model tests was carried out to in an attempt to verify previously performed three-dimensional numerical modeling and to investigate effects of reinforcement layout on the tunnel face deformation behavior The results of model tests indicate that the tunnel face deformation can significantly reduced by pre-reinforcing the tunnel face with longitudinal members and thus enhancing the tunnel stability. In addition, the model tests results compare fairly well with those from the previously performed three-dimensional finite element analysis. Therefore, a properly calibrated three dimensional model may effectively be used in the study of tunnel face reinforcing technique.

• Journal of the Korean Geotechnical Society
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• v.16 no.6
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• pp.127-139
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• 2000

In the study, an expert system was developed to predict the safety of tunnel and select proper tunnel reinforcement system using fuzzy quantification theory and fuzzy inference rule based on tunnel information database, For this development, many tunnelling sites were investigated and the applied countermeasures were studied after building tunnel database. There will be benefit for the deciding tunnel reinforcement method in the case of poor ground condition. The expert system developed in the study has two main parts, pre-module and post-module. Pre-module is used to decide input items of tunnel information based on the tunnel face mapping information which can be easily obtained in in-situ site. Then, using fuzzy quantification theory II, fuzzy membership function is composed and tunnel safety level is inferred through this membership function. Post-module is used to infer the applicability of each reinforcement methods according to the face level. The result of the predicted reinforcement system level was similar to measured ones. In-situ data were obtained in three tunnel sites including subway tunnel under Han River. Therefore, this system will be helpful to make the mose of in-situ data available and suggest proper applicability of tunnel reinforcement system to development more resonable tunnel support method without dependance of some experienced experts opinions.

• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.2
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• pp.91-100
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• 2002

This paper presents the results of laboratory investigation on the deformation behavior of tunnel face reinforced with longitudinal pipes. A series of reduced-scale model tests was carried out to investigate the effect of reinforcement layout on the tunnel face axial displacement as well as the surface settlement. Among other things, the results of the model tests indicate that the axial displacement of tunnel face as well as the ground surface settlement can significantly be reduced by pre-reinforcing the tunnel face with longitudinal pipes, suggesting that the pre-reinforcing technique may effectively be used as a positive ground control method in the urban environments. Also illustrated is that the reinforcing effect is significantly influenced by the reinforcement layout. The implications of the findings from this study are discussed in a great detail.

• Journal of Korean Tunnelling and Underground Space Association
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• v.2 no.2
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• pp.32-40
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• 2000

This paper presents the results of a parametric study on the behavior of tunnel face reinforced with horizontal pipes. A series of reduced-scale model tests was carried out to in an attempt to verify previously performed three-dimensional numerical modeling and to investigate effects of reinforcement layout on the tunnel face deformation behavior. The results of model tests indicate that the tunnel face deformation can significantly reduced by pre-reinforcing the tunnel face with longitudinal members and thus enhancing the tunnel stability. In addition, the model tests results compare fairly well with those from the previously performed three-dimensional finite element analysis. Therefore, a properly calibrated three dimensional model may effectively be used in the study of tunnel face reinforcing technique.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.185-192
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• 1999

This paper presents the results of a parametric study on the behavior of tunnel face reinforced with horizontal pipes. A three-dimensional finite element model was adopted in this study to capture the three-dimensional nature of tunnel face behavior under various boundary conditions. A parametric study was peformed on a wide range of boundary conditions with emphasis on the effect of reinforcing layouts on the deformation behavior of tunnel face. The results of analysis such as tunnel face deformation behavior under various conditions were thoroughly analyzed, and a database for the behavior of tunnel face under different reinforcing conditions was established for future development of a semi-empirical design/analysis method for the tunnel face reinforcing technique. The results indicated that there exits an optimum reinforcing layout for a given tunnel condition, which must be selected with due consideration of tunnel geometry and ground condition.

• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.3
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• pp.259-267
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• 2004

The practice of introducing and grouting reinforced fiber glass pipes or bar into the core to be excavated to maintain stable the tunnel face during excavation has been applied to many tunnels, where difficult geotechnical conditions are present, with good results in terms of safety and speed of works. This reinforcing technique, initially developed to be used jointly with the mechanical precut in clay, has been widely used with other geotechnical conditions as the only type of reinforcement or joined with other ground consolidation and/or reinforcement techniques (i.e. steel pipes or jet-grouting umbrella). At present same numerical researches have been carried out to find which are the real working conditions of the reinforcing elements but no final results have been obtained for the definition of the best design approaches. In this work the results of a three dimensional parametric numerical model is presented.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.1
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• pp.11-22
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• 2009

Tunnel excavation with several sections and appropriate auxiliary measures such as face bolt and pre-grouting are widely used in case of weak and less rigid ground for the stability of a tunnel face during excavation. This papers first described the evaluation methods proposed in technical literature to maintain the tunnel face stable, and then studied by FEM analysis whether face reinforcement is need in what degree of ground deformation and strength features for the stability of a tunnel face when excavating by full excavation with sub-bench. Lastly, a three dimensional FEM analysis was performed to study how the tunnel face itself and the ground around the tunnel behave depending on different bolt layouts, length of bolts, number of bolts. There were relative differences in comparison of results on the stability of a tunnel face by a theoretical evaluation methods and FEM analysis, but the same in reinforced effect of face. It was found that the stability of a tunnel face can be obtained with face bolt installed longer than 1.0D (tunnel width), bolt density of about 1 bolt per every $1.5\;m^2$ (layout of grid type), and reinforcement area of $120^{\circ}$ arch area of upper section.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.101-108
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• 2000

In this study, an expert system was developed to predict the safety of tunnel and choose proper tunnel reinforcement system using fuzzy quantification theory and fuzzy inference rule based on tunnel information database. The expert system developed in this study have two main parts named pre-module and post-module. Pre-module decides tunnel information imput items based on the tunnel face mapping information which can be easily obtained in-situ site. Then, using fuzzy quantification theory II, fuzzy membership function is composed and tunnel safety level is inferred through this membership function. The comparison result between the predicted reinforcement system level and measured ones was very similar. In-situ data were obtained in three tunnel sites including subway tunnel under Han river, This system will be very helpful to make the most of in-situ data and suggest proper applicability of tunnel reinforcement system developing more resonable tunnel support method from dependance of some experienced experts for the absent of guide.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.5
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• pp.359-368
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• 2010

Unlike in Korea where steel pipe-reinforced multistep grouting is of commonly used methods for tunnel reinforcement, face bolt method is more widely used due to its better workability and lower construction cost in other countries. In this paper, the effects of both methods after tunnel failure were numerically analyzed and verified based on the oversea construction experiences. As a result it is concluded that the face bolt method may be effective to reinforcement especially when there are some fractured zones developed in the face of tunnel.