• Tunnel and Underground Space
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• v.21 no.6
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• pp.427-438
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• 2011

Segment lining is a key permanent lining structure to maintain the shield tunnel stability in shield tunnel operation. Moreover, segment lining generally accounts for the largest proportion in the shield tunnel construction costs. As a result, technical improvements to increase its economic feasibility have been actively carried out. This study aims to propose the development directions of high-performance segments from their recent cutting technologies. In addition, based on over 2,100 world-widely collected segment design data, a series of statistical analyses of segment key design parameters such as thickness, width and the number of divisions as well as segment materials were carried out to approximately estimate them in a design stage.

• Journal of the Korean Geosynthetics Society
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• v.17 no.4
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• pp.251-265
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• 2018

This paper concerns the development of an optimized NATM secondary lining design system for a subsea tunnel. The subsea tunnel is normally laid down under the sea water and submarine ground which consists of soil or rock. The design system is the series of process which can predict lining member forces by ANN (artificial neural network system), analyze suitable section for the designated ground, construction and tunnel conditions. Finally, this lining design system aims to be connected for designing the subsea tunnel automatically. The lining member forces are predicted based on the ANN which was calculated by a FEM (finite element analysis) and it helps designers determine its lining dimension easily without any further FEM calculations.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.462-469
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• 2011

The design of high-depth and large-section tunnel facilities has been increased lately. The purpose of the design is to avoid inference of existing facilities, enhance public relations and reducing the size of the station, which is advantageous for effective use of underground spaces. Diverse downtown tunnel experience, advanced excavation equipment, reinforcement methods, monitoring technologies and numerical analysis made the design possible. This paper is to introduce the design of high-depth and large-section tunnel facilities via Gimpo airport area of Deagok-Sosa railway BTL project of double-tracking.

• Geomechanics and Engineering
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• v.22 no.5
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• pp.433-439
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• 2020

Tunnels are one of the most important constructions in civil engineering. The damage to these structures caused enormous costs. Therefore, the safe and economic design of these structures has long been considered. However, both applied loads on the tunnels as well as the resistance of the structural members are naturally uncertain parameters, hence, the design of these structures requires considering the probabilistic approaches. This study aims to determine the load and resistant factors of lining tunnels concerning the earthquake extreme events limit state function. For this purpose, tunnels that have been designed according to the previous design codes (AASHTO Tunnel LRFD 2017) and using reliability analysis, the optimum reliability of these structures for different loading scenarios is determined. In this paper, the tunnel is considered circular. Finally, the proper load and resistance factors are calculated corresponding to the obtained target reliability. Based on the performed calibration earthquake extreme events limit state function, the result of this study can be recommended to AASHTO Tunnel LRFD 2017.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.1007-1013
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• 2004

A three-arch NATM tunnel with a total length of 53.5m has been constructed for a metropolitan subway station in Daejon, Korea. The tunnel, whose crown is located 22m below the ground, crosses the old Daejon station underneath. Since the tunnel comprises a very large section (10${\times}$28 m; largest in Korea), it shows complicated mechanical behaviors, especially near portal, due to its short length relative to width. As far as its construction step is concerned, the center tunnel is excavated with pre-excavated pilot tunnel, which is a unique feature of this tunnel (first in Korea) to secure safety during construction and prevent excessive settlements. The both side tunnels are then excavated along with the center tunnel. Since significant amount of settlement was predictable from the design stage, extensive monitoring was performed during construction. During excavation of the side tunnels, unexpected large settlements up to ${\~}$140mm (estimated 41.8 mm at design stage) was measured at the center tunnel. In this paper, we study the causes of this unusually large ground settlement. We believe that the extra-wide tunnel excavation increases the stress influence zone of portal in longitudinal direction and consequently add more settlements to the existing due to excavation and consolidation.

• Tunnel and Underground Space
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• v.6 no.3
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• pp.197-208
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• 1996

Due to the constraints in pre site-investigation for tunnel, it is essential to redesign the support structures suitable for rock mass conditions such as rock strength, ground water and discontinuity conditions for safe tunnel construction. For the selection of optimum support, it is very important to carry out the rock mass classification and in-situ measurement in tunnelling. In this paper, in a mountain tunnel designed by NATM in hard rock, the selectable system for optimum support has been studied. The tunnel is situated at Chun-an in Kyungbu highspeed railway line with 2 lanes over a length of 4, 020 m and a diameter of 15 m. The tunnel was constructed by drill & blasting method and long bench cut method, designed five types of standard support patterns according to rock mass conditions. In this tunnel, face mapping based on image processing of tunnel face and rock mass classification by RMR carried out for the quantitative evaluation of the characteristics of rock mass and compared with rock mass classes in design. Also, in-situ measurement of convergence and crown settlement conducted about 30 m interval, assessed the stability of tunnel from the analysis of monitoring data. Through the results of rock mass classification and in-situ measurement in several sections, the design of supports were modified for the safe and economic tunnelling.

• Earthquakes and Structures
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• v.26 no.3
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• pp.229-237
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• 2024

This paper studied the subgrade spring stiffness and its influencing factors in the seismic deformation method of circular tunnel. Numerical calculations are performed for 3 influencing factors: stratum stiffness, tunnel diameter and burial depth. The results show that the stratum stiffness and tunnel diameter have great influence on the subgrade spring stiffness. The subgrade spring stiffness increases linearly with stratum stiffness increasement, and decreases with the tunnel diameter increasement. When the burial depth ratio (burial depth/tunnel diameter) exceeds to 5, the subgrade spring stiffness has little sensitivity to the burial depth. Then, a proposed formula of subgrade spring stiffness for the seismic deformation method of circular tunnel is proposed. Meanwhile, the internal force results of the seismic deformation method are larger than that of the dynamic time history method, but the internal force distributions of the two methods are consistent, that is, the structure exhibits elliptical deformation with the largest internal force at the conjugate 45° position of the circular tunnel. Therefore, the seismic deformation method based on the proposed formula can effectively reflect the deformation and internal force characteristics of the tunnel and has good applicability in engineering practice.

• Journal of the Korean GEO-environmental Society
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• v.3 no.3
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• pp.5-13
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• 2002

In tunnel design, geotechnical survey of over 200m tunnel depth is required because of its characteristical topography. For this reason, there are difficulties in collecting information of basic data in tunnel design because of large-scale costs in borehole tests, of limits to a geotechnical analysis by the existing refraction seismic survey and of analytical errors in steep mountainous area. Seismic tomography has many advantages as follows; 1) seismic velocity as absolute value is more reliable than electrical resistivity, 2) geotechnical analysis in deep tunnel depth is available by seismic velocity, 3) analytical errors is reduced in steep mountainous area. In this paper, it was found out a correlation of seismic velocity and Q in tunnel design in the neighborhood of the National Capital region and the reduction effect of tunnel construction cost using reliable rock quality by seismic tomography compared with by borehole data and electricity resistivity data.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.3
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• pp.282-290
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• 2013

A primary air pollutant as an indicator of air quality released from incomplete combustion is Carbon monoxide. A study of the distributions of CO concentration with no heat source in a tunnel model closed at left end side is simulated with a commercial CFD code. The tunnel model is used to investigate the CO concentration distributions at three Reynolds numbers of 990, 1970, and 3290. which are computed by the inlet velocities of 0.3, 0.6 and 1.0 m/s. The CFD predictive approaches can be useful for a better design to analyze the distributions of CO concentrations. In the case of the tunnel model closed at left end side alone, the concentration changes of x/H=-5 and -2.5 have the similar laminar characteristics like the case of the tunnel model closed at both end sides expecially at low values of Reynolds number. Irregular average CO concentration variations at Re=1790 are considered that the transition from laminar to turbulent flow occurs even in three different tunnel models.

• Proceedings of the Korean Geotechical Society Conference
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• 1994.09a
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• pp.235-246
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• 1994

At pre-construction design stage, most of the design data are based on the site investigation results or property estimation which often does not provide satisfactory output for the tunnel analysis. Nonlinear FEM tunnel analysis was cariied out by Hoek-Brown model which is principly semi-empirical design method based on insitu rock descriptions, rock test results as well as field measurement data. The results of the analytical methods from Hoek-Brown model and Mohr-Coulomb model are compared with the sige measurement data from two-NATM tunnel construction sites. It was found that the Hoek-Brown model can be satisfactorily adopted as a feed back analysis technique in order to examin the safety of NATM tunnel at any construction stage.