• Journal of Korean Tunnelling and Underground Space Association
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• v.3 no.4
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• pp.3-15
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• 2001

Generally, it has been noted that underground structures have a consistent record of suffering much less damage than surface facilities during earthquakes; but it is still necessary to illustrate the dynamic response of tunnel structures subject to earthquake loadings and to provide the appropriate method for the seismic analysis of underground tunnel structures since many types of underground structures have been and will be constructed in countries situated within seismic zones. In this study, first, seismic analyses for underground tunnel structures are performed by using quasistatic analysis method and dynamic analysis method. Second, seismic analyses in tunnel portals are performed by using above methods. The results of seismic analyses for the tunnel structure show that the tunnel structure conforms to ground deformation and that seismic design by using the quasi-static analysis method is more conservative than that by using the dynamic analysis. The results of the dynamic FEM analysis for the tunnel structure show that the simplified 2-D FEM analysis using a sine wave rather than the 3-D FEM analysis can be adopted for seismic analysis. Finally, the results of the dynamic FEM analysis in tunnel portals show that the force acting on the lining is largest near to the tunnel portal when an earthquake wave propagates parallel to tunnel axis.

• Geotechnical Engineering
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• v.11 no.4
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• pp.125-140
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• 1995

Generally, the groundwater pressure is not considered in the design of concrete lining of bottom drainage tunnel. This design method implies that the phreatic surface is drawdown to the bottom of tullnel. When tile groundwater is continually supplied without changing of groundwater table, there is a possibility at which the groundwater pressure acting on the tunnel lining after the completion of tunnel. Therefore, the safety of tunnel lining must be checked in this case. In this paper, the stability of bottom drainage tunnel which is affected by groundwater discharge is analzed by using of the Finite Element Method at the 2 sections of subway where the groundwater level has a tittle change during the construction. As the result of analysis, the grouting for the water tightness and the permanent monitoring system of tunnel are required for maintaining of long-term stability of bottom drainage tunnel for the case of groundwater plassure acting on the tunnel lining is greater than that of design stage.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.5
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• pp.611-620
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• 2019

The shield tunnel was mostly applied to cable tunnel with a diameter of 3~4 m, recently 7.8 m diameter shield tunnel was constructed in the lower section of the Incheon International Airport runway and is planning or under construction to roads and railway tunnels in the lower section of the Han River. Segments are also becoming larger as the shield tunnel cross-section increases, which causes a number of problems in the design, construction, and performance evaluation of segments. In this study, segment lining structural safety, criteria for serviceability check considering axial forces and quality control method for approximately 8 m in diameter shield tunnel were reviewed by field measurements and full scale bending test.

• Tunnel and Underground Space
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• v.9 no.2
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• pp.102-113
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• 1999

Two-dimensional and three-dimensional DEM programs, UDEC and 3DEC, were used to investigate the mechanical stability of the conceptual design of deposition drift and deposition holes constructed in a crystalline rock mass. From the simulations, the influence of discontinuities, the number of deposition holes, and deposition hole interval on the stability of deposition drift and deposition holes could be determined. From the two-dimensional and three-dimensional analysis. it was concluded that three-dimensional analysis should be carried 7ut fur deriving reliable conclusions. Even though the deposition hole interval changed from 8 m to 3 m, which did not damage the mechanical stability of the deposition drift.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.10
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• pp.1017-1024
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• 2002

In this paper, we present the analysis of radio wave propagation characteristics in curved tunnels. Tunnel propagation models are performed in two cases which are using ray-tracing method for straight tunnels and geometrical optics extension to the standard hybrid waveguide model for curved ones. By regression analysis for measured power based on distance between the transmitter and the received antenna in tunnels that have 3.5 m $\times$ 6 m cross section and limited wall depth path loss are 0.19 dB/m for straight section and 0.68 dB/m for curved ones. By comparing model analysis with measurement in tunnels, it has been shown that the simulated results of tunnel propagation models are similar to the measured values.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.3
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• pp.92-98
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• 2012

This study shows details of a specific space truss frame structure devised to carry out maintenance and repair temporary works in tunnels. The purpose of this study is to verify structural safety and function of the innovative truss structure through an analysis tool, i.e.. ABAQUS, which is a suite of software application for finite element analysis and computer aided engineering. And then optimized size, i.e., thickness and diameter of truss members is evaluated in practice. In this study, construction methods in the temporary works are additionally represented by using the new space truss frame structure.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.6
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• pp.599-612
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• 2013

This study aims to investigate an economical efficiency of two excavation methods with respect to the room-and-pillar method for the underground space and conventional excavation method, i.e. 2-arch tunnelling method. For feasibility study, an excavation cost for both room-and-pillar method and 2-arch tunnelling method was estimated when the same space in operation was required. It was assumed that properties of reinforcements and rock were adopted from literatures. However, an excavation shape of the room-and-pillar method was assumed not to be the rectangular shape which is a general type in the room-and-pillar method but to be an arch shape in order to compare with the conventional excavation method (2-arch tunnelling) and to achieve the maximum bearing capacity of the structure during excavation. Consequently, the wider space in use or required and the better condition of rock we assumed, the more economical advantage we have in the room-and-pillar method than the 2-arch tunnelling method.

• Geophysics and Geophysical Exploration
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• v.6 no.1
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• pp.13-22
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• 2003

TSP (Tunnel Seismic Profiling) survey is a technique for imaging and characterizing geological structures ahead of a tunnel face. The seismic modeling algorithm and the synthetic data could be helpful for TSP surveys. However, there is few algorithm to describe the propagation of the elastic waves around the tunnel. In this study, existing 2-dimensional seismic modeling algorithm using finite element method was modified to make a suitable algorithm for TSP modeling. Using this algorithm, TSP modeling was practiced in some models. And the synthetic data was analyzed to examine the propagation characteristics of the elastic waves. First of all, the modeling for the homogeneous tunnel model was practiced to examine the propagation characteristics of the direct waves in the vicinity of the tunnel. And the algorithm was applied to some models having reflector which is perpendicular or parallel to the excavation direction. From these, the propagation characteristics of the reflected waves were examined. Furthermore, two source-receiver arrays were used in respective models to investigate the properties of the two arrays. These modeling algorithm and synthetic data could be helpful in interpreting TSP survey data, developing inversion algorithm and designing new source-receiver arrays.

• Tunnel and Underground Space
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• v.19 no.1
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• pp.19-30
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• 2009

For the purpose of determining the thickness of concrete lining and detect of the cavity where may be located behind tunnel lining, IE (Impact-Echo) method it effectively useful in the tunnel safety diagnosis and the quality control during the construction. As a part of case study, we applied IE method to various tunnel structure types such as road tunnel and subway tunnel constructed by NATM (New Austrian Tunnelling Method) and ASSM (American Steel Support Method). As tunnel specifications estimated from this method were compared with coring data, design drawing and other survey results, it was very good agreement with each other. In conclusion, we verified that IE method shows an accurate and reliable result. The conventional interpretation of IE method in frequency domain gives only vertical information at a certain point. However, the interpretation using time-frequency analysis and depth section imaging technique from two dimensional profiling surveys can show more reliable information about structure inside.

• Journal of the Korean Geotechnical Society
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• v.21 no.3
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• pp.99-108
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• 2005

One of the most important and difficult tasks in designing underground structure is the estimation of engineering properties of the ground. The main purpose of this study is to propose a new back-analysis technique in tunnelling to estimate geotechnical parameters around a tunnel. In this study, the Extended Bayesian Method, which appropriately combines objective information with subjective one, is adopted to optimize engineering parameters. By using only relative convergence data measured during tunnelling as input values in back-analysis, inevitable errors in absolute convergence estimation are excluded and 3-dimensional numerical analysis is applied to consider a trend of relative convergence occurrence. Finally, 3-dimensional back-analysis technique using relative convergence is proposed and evaluated using a hypothetical site.