• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.587-590
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• 2005

This study investigates the efficient construction scheme of the immersed tunnel focusing on the hydration heat. In this respect, some alternatives in curing, temperature condition and removing of the forms are compared together to meet the required criteria. It is addressed that the strict construction stage analysis considering the placing scheme of concrete is one of the key factors to trace the realistic structural behavior for the hydration heat.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.1
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• pp.95-105
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• 2014

Reinforced concrete (RC) shield tunnel lining must be designed for fireproof performance because the lining is sometimes exposed to very high temperature due to traffic accidents. Both experimental and numerical studies are carried out to evaluate fire resistance performance of precast RC tunnel lining systems. In the experimental studies, six full-scale precast RC tunnel segments are exposed to fire in order to examine the influence of various parameters on the fire resistance performance of precast RC tunnel lining. We used the temperature curve of the RABT criteria, which are severe conditions of fire temperatures. The fire test showed that the explosive spalling was not observed by substituting concrete to PP fiber reinforced concrete. A transient heat flow analysis was carried out in consideration of the material properties that change with temperature, and the results showed good agreement with the test results.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1774-1781
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• 2007

In this study, Matsuda's formula, which has been used to evaluate the acting load on the concrete pillar in 2-Arch tunnels, is investigated and a load reduction factor $({\alpha})$, which has been estimated from numerical parametric studies, is proposed for a better design of 2-Arch tunnels in the future. Numerical parametric studies show that the concrete pillar is subjected to a stress concentration on the excavation side during the first tunnel driving and when tunnel excavation is completed, the induced stress on the pillar in a poor quality of ground condition is 1.5 to 1.8 times the stress developed during the first tunnel driving. In addition, the numerical studies indicate that the acting load on the pillar is in the range of $14{\sim}83%$ of the load estimated by Matsuda's formula. From these results, a load reduction factor $({\alpha})$ is determined and it would make 2-Arch tunnel design more economically.

• Journal of the Korean Society for Railway
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• v.17 no.6
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• pp.410-414
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• 2014

In this study, the behavior of urban subway tunnels is measured using instrumentation sensors installed in the lining concrete inside subway tunnels in order to analyze their behavior according to temperature variations. It is observed that the stresses of the concrete lining, tunnel convergence, and cracks change according to the temperature variations. However, the crack deformation differs depending on the size and status of the crack. In addition, this study proposes a correction formula for the lining stress and tunnel convergence through numerical analyses of the concrete lining according to the temperature variations. The results of this research can be used in the tunnel maintenance considering the tunnel behavior depending on the temperature variations in the tunnel.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.5
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• pp.69-78
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• 2009

Since the blast vibration induced by explosives of the powder possibly provide damage of the nearby structures adjacent to the tunnel, the stability of the nearby structures should be estimated. In this study, the stability of the tunnel based on the allowable peak particle velocity of the structures as well as allowable stress of the structures presented in the concrete structural design standard was estimated with respect to the stress of the concrete lining and axial force of the rockbolt during the blasting operation at the ground surface of the pre-existing tunnel. The analyses were carried out by using $FLAC^{2D}$ which is one of the programs developed based on the finite difference method. The bending compressive stress and shear stress of the concrete lining and axial force of the rockbolt were rapidly increased when the blasting operation was conducted near the tunnel.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.537-540
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• 2008

Tunnel structures are constructed even longer and more extensive these days than they were in the past. Because of this reason, breaking out a large scale of fire in tunnel structures is frequently. Recently, a noticeable event is reported that the temperature of inside of tunnel rises significantly when an oil car detonated in the tunnel and it reached 1,350$^{\circ}$C. It did damage to people who used the tunnel at that time and caused many demaged parts of tunnel to recover. To improve a fire resistance of tunnel, many methods are studied focused refractory concrete and mortar. This study deals with refractory mortar and is a part of initial basic step. In this study mechanical properties are considered before fire resistance test. As result of test for examination of mechanical properties, it is considered that a consistency and strength of refractory mortar in this study are suitable to construct.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.373-378
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• 2003

The cement-based composites have relatively low tensile strength and toughness. The fiber addition is one of the most important ways of increasing the toughness of concrete. The steel fibers have been used conventionally in the shotcrete of tunnel lining. Recently, the structural synthetic fibers were developed and used frequently in some actual tunnel shotcreting in foreign countries. Now types of synthetic fibers have been developed in this study. The purpose of this study is to explore the strength and toughness characteristic of the concrete reinforced with synthetic fibers developed in this study. The result were compared with those of steel fiber reinforced concrete. It is seen that the performance of synthetic fiber reinforced concrete is good as much as that of steel fiber reinforced concrete, while the synthetic fibers have advantages in corrsion resistance and economy.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.5
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• pp.369-378
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• 2010

This paper presents a new approach of closing the tunnel face with sprayed concrete to reduce the stress at the tunnel face and displacement occurring at the ground surface during tunnel excavation. In order to carry out this research, the experimental and numerical studies are performed. In the experimental study, the model tests are carried out according to the closure ratio of tunnel face, tunnel depth and tunnel excavation length. The model test results are analyzed and interpreted by numerical calculation in order to verify both results obtained from experimental and numerical studies. It is clearly found that the tunnel face stability is decreased in decreasing the closure ratio of tunnel face. The results also show that the tunnel face is stable when the closure ratio of tunnel face is larger than 80%. This research will be very useful to develop the economical tunnel face closing system.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.6
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• pp.653-664
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• 2015

When the structural analysis is performed for the concrete lining of the water pressure tunnel, many parameters are considered such as relaxed ground loads, internal water pressure, external water pressure, the shrinkage of the concrete lining, grouting pressure, etc. But, there are no standards and manuals for the structural analysis for the concrete lining of the water pressure tunnel. Above all, the external water pressure has an much effect on the stability of tunnel. So, in case that permeability of ground is large, the external water pressure should be decreased by installation of weep hole, or reinforced ground by ground improvement grouting should be pressed by the external water pressure instead. But, when weep hole is installed to reduce the external water pressure, the many problems may me occurred. Thus, reasonable approach for treatment of the external water pressure is necessary if weep hole is not installed. Therefore, the purpose of this study is to analyze design cases and studies for treatment of the external water pressure in performing structural analysis for the concrete lining of the water pressure tunnel, and to find reasonable method for tunnel lining modeling which is the treatment of the external water pressure according to permeability of ground and consequently the design of ground improvement grouting.

• Structural Engineering and Mechanics
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• v.45 no.3
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• pp.337-354
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• 2013

For shield TBM (Tunnel Boring Machine) tunnel lining, the segment joint is the most critical component for determining the mechanical response of the complete lining ring. To investigate the mechanical behavior of the segment joint in a water conveyance tunnel, which is different from the vehicle tunnel because of the external loads and the high internal water pressure during the tunnel's service life, full-scale joint tests were conducted. The main advantage of the joint tests over previous ones was the definiteness of the loads applied to the joints using a unique testing facility and the acquisition of the mechanical behavior of actual joints. Furthermore, based on the test results and the theoretical analysis, a mechanical model of segment joints has been proposed, which consists of all important influencing factors, including the elastic-plastic behavior of concrete, the pre-tightening force of the bolts and the deformations of all joint components, i.e., concrete blocks, bolts and cast iron panels. Finally, the proposed mechanical model of segment joints has been verified by the aforementioned full-scale joint tests.