• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.285-292
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• 1999

Recent development cases of transportation utilities using tunnelling method in metropolitan sites have been increased due to the heavily complex environments and restrictions of construction works. The progress of tunnel design and construction to be supported by the tunnel analysis and measurement techniques using computers have increased adoptions of large section tunnels. In this paper, many factors to be considered in designing large section tunnels are discussed and the case of the construction of the subway station tunnel which is recently completed is introduced. This tunnel has a width of 24 m, a height of 16 m, and a excavation section area of 366 ㎡.

• Tunnel and Underground Space
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• v.27 no.4
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• pp.195-204
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• 2017

This case study introduces the construction of large cross section tunnel for underground ventilation system in Sillim-Bongcheon Tunnel Project. In order to grant the safety and efficiency in connecting the ventilation shaft (7.8 m of width, and 6.6 m of height) to a tunnel for axial fan facility (20.8 m of width, and 12.3 m of height), gradual enlargement of tunnel cross section was employed between those and temporary support method was determined based on Q system. In addition, some original designs were revised during construction stage to improve the efficiency of excavation in large cross section tunnel. The advance length was optimized and top heading of the tunnel was excavated without partition in accordance with ground condition and numerical stability analysis results. It is believed that some experiences and considerations in this case study will be useful for the future design and construction in similar large cross section tunnel such as large underground ventilation system or road tunnel with four lanes.

• 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.

• Explosives and Blasting
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• v.22 no.3
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• pp.65-70
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• 2004

Lately, the length of tunnel, the number of long-large tunnel over 3 lanes are steeply increased because of the request for high-speed and straight road. Therefore, the maximization of excavation efficiency is needed in tunnel construction. The sapaesan tunnel (4 lanes with the length of 4km) construction was delayed with environmental conflict far 2 years. For making-up delayed construction period, various new methods were adopted to improve excavation length, look-out and blasting efficiency. This study introduced bulk explosive which is new method in tunnel blasting and verified the efficiency of bulk explosive far long-large tunnel.

• Geomechanics and Engineering
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• v.38 no.6
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• pp.583-591
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• 2024

To properly simulate the excavation process and evaluate the structural stability of the tunnel, rigorous large deformation analysis method is necessary. This study applies two most widely used numerical approaches capable of modelling and considering the large deformations behavior during excavation process to analyze and evaluate the structural stability of circular tunnel based on tunnel boring machine (TBM) excavation. By comparing and combining the results from two numerical approaches, the deformation of the excavated ground will be analyzed. The stability of the circular tunnel from TBM tunneling was assessed based on the maximum deformation occurred during the excavation process. From the numerical computation it was concluded that although the range of the damage on the ground done during excavation was found to be larger under hard rock condition, maximum deformation within the circular tunnel structure was larger under weak ground conditions and deeper tunnel depths.

• Earthquakes and Structures
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• v.15 no.6
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• pp.655-665
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• 2018

Shield tunnels are widely used throughout the world. However, their seismic performance has not been well studied. This paper focuses on the seismic response of a large scale model tunnel in compacted sand. A 9.3 m long, 3.7 m wide and 2.5 m high rigid box was filled with sand so as to simulate the sandy soil surrounding the tunnel. The setup was excited on a large-scale shake table. The model tunnel used was a 1:8 scaled model with a cross-sectional diameter of 900 mm. The effective shock absorbing layer (SAL) on the seismic response of the model tunnel was also investigated. The thickness of the tunnel lining is 60 mm. The earthquake motion recorded from the Kobe earthquake waves was used. The ground motions were scaled to have the same peak accelerations. A total of three peak accelerations were considered (i.e., 0.1 g, 0.2 g and 0.4 g). During the tests, the strain, acceleration and soil pressure on the surface of the tunnel were measured. In order to investigate the effect of shock absorbing layer on the dynamic response of the sand- tunnel system, two tunnel models were set up, one with and one without the shock absorbing layer of foam board were used. The results shows the longitudinal direction acceleration of the model tunnel with a shock absorbing layer were lower than those of model tunnel without the shock absorbing layer, Which indicates that the shock absorbing layer has a beneficial effect on the acceleration reduction. In addition, the shock absorbing layer has influence on the hoop strain and earth pressure of the model tunnel, this the effect of shock absorbing layer to the model tunnel will be discussed in the paper.

• Journal of Industrial Technology
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• v.24 no.A
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• pp.239-250
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• 2004

Numerical analysis were performed to investigate the stability and internal movement of tunnel located beneath the base of abutment of bridge according to the method of supporting tunnel. Two supporting methods of the multi-staged grouting method with steel pipes and the large diameter of pipe supporting method were used in the centrifuge model tests. The slip form of model lining, specially built to simulate the process of tunnel excavating under the condition of accelerated g-level, was used in the centrifuge model tests. Four centrifuge model tests were performed, changing the supporting methods of the multi-staged grouting method with steel pipes and the large diameter of pipe supporting method and the location of model abutment base of bridge. For internal displacement of tunnel, movements of the crown. The left and the right sides of spring line were measured during the proceeds of excavating tunnel in centrifuge model tests. Test results were compared with numerically estimated values of internal displacement of tunnel by using the commercially available FEM software of PENTAGON-3D. It was found that they were in good agreements and the large diameter of pipe supporting method was more stable than the multi-staged grouting method with steel pipes with respect to the internal movement of tunnel.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.33-37
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• 2003

This paper presents the characteristics of large-scale fading in a tunnel environment. The Ray-Launching Method has been used to analyze the characteristics of the tunnel. For a curved tunnel, The concept of RDN (Ray Density Normalization) is introduced in order to obtain more accurate results. For our purposes, the structure of tunnel is assumed to be either a straight or curved tunnel having rectangular cross-section. A large scale fading has been presented shown in several tunnel cases.

• Tunnel and Underground Space
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• v.19 no.2
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• pp.132-145
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• 2009

Faults in rock mass have strong influences on the behaviors of rock structure such as rock slope, tunnel and underground space. Thus, it is very important to analyse for the characteristics of fault rocks in design for tunnel. But, due to the limitation of geotechnical investigation in design stages, tunnel engineers have to carry out the face mapping and additional geological survey during tunnel excavation to find the distribution of faults and the engineering properties of faults for support and reinforcement design of tunnel. In this study, various geological survey and field tests were carried out to analyse the characteristics of the large thrust fault zone through the large sectional tunnel is constructed in mica-schist region. Also, the distribution of structural geology, the shape of thrust faults and the mechanical properties of fault rock were studied for the reasonable design of the reinforcement and support method for the highly fractured fault zone in the large-span tunnel.

• 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.