• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.4
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• pp.469-484
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• 2020

This study focused on shielding through inflatable structure in the event of sudden water inflow into the submerged floating tunnels. Currently, there is a lack of measures to deal with unexpected water in tunnels in Korea. Although water treatment facilities such as waterproofing and floodgates in tunnels are installed, there are limitations to the sudden inflow of large amounts of seawater or underground water. Also, floodgates cannot respond quickly to sudden damage due to slow blocking time. Accordingly, a study was conducted on the shielding rate and axial movement distance for inflatable structure. The results of the reduced model experiment confirmed that the number of inflatable structure and internal pneumatic pressure influence on the shielding rate. As the number of inflatable structure increased from one to two, the shielding rate increased by about 35 up to 40 percent. It was also confirmed that the shielding rate increased by about 4 percent as the internal pneumatic pressure increased from 0.2 bar to 0.3 bar. If we verify and further develop the results identified in this study through a real-size experiment, it will be able to be used as an effective waterproof measure for sudden water inflow into the undersea tunnels or underwater tunnels.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.1
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• pp.49-57
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• 2008

One of the most important design concerns for undersea tunnels is to establish design water load and flow rate. These are greatly dependent on the hydraulic factors such as water head, cover depth, hydraulic boundary conditions. In this paper, the influence of the hydraulic design factors on the ground loading and the inflow rate was investigated using the coupled finite element method. A horse shoe-shaped tunnel constructed 30 m below sea bottom was adopted to evaluate the water head effect considering various water depth for varying hydraulic conditions and relative permeability between lining and ground. The effect of cover depth was analysed for varying cover depth with the water depth of 60 m. The results were considered in terms of pore water pressure, ground loading and flow rate. Ground loading increases with an increase in water head and cover depth without depending on hydraulic boundary conditions. This points out that in leaking tunnels an increase in water depth increases seepage force which consequently increases ground loading. Furthermore, it is identified that an increase in water head and cover depth increases the rate of inflow and a decrease in the permeability ratio reduces the rate of inflow considerably.

• The Journal of the Korea Contents Association
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• v.16 no.6
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• pp.507-515
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• 2016

In South Korea, there are a large number of tunnels because of the mountainous terrain, and to overcome this characteristics, lengths of tunnels are more longer than existing tunnels. The need to improvement current tunnel management contents is giving rise for accidents in tunnel section is continuously increased although lots of efforts to reduce the accidents. Conventionally, disaster prevention have been focused on the Tunnel Management Systems, tunnel operators generally tend to depend on CCTV images for most contents of detailed traffic flow managing. In this paper, investigation about current Tunnel Management Systems contents using IPA survey was conducted, and Priority Improvement Contents(Accident Situation Management Support, 2nd Accident Management Support, Traffic Flow Monitoring), which importance are high, but satisfaction are low, are deducted. Also, CCTV images, lack intuitive understanding, are judged as a main cause of low satisfaction of those contents. To overcome those limitations of the existing Tunnel Management Systems, this study sought to develop a technology for the synthesis of road images to derive traffic information from synthesis images, and the contents improvement stragegy is established. Tunnel operators-oriented satisfaction survey on new contents was carried out, and scored 4.2 on a 5-point scale. This has confirmed that the availability of new contents and at this stage, with pushing ahead of long-tunnels and undersea tunnels construction, politic applications are expected.

• Journal of Applied Reliability
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• v.9 no.4
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• pp.275-290
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• 2009

This paper considers accelerated thermal degradation tests which are performed for rubber seal materials used for undersea tunnels constructed by immersion method. Three types of rubber seals are tested; rubber expansion seal, omega seal, and shock absorber hose. Main ingredient of rubber expansion seal is EPDM(Ethylene Propylene Diene Monomer) and that of both omega seal and shock absorber hose is SBR(Styrene Butadiene Rubber). The accelerated stress is temperature and an Arrhenius model is introduced to describe the relationship between the lifetime and the stress. From the accelerated degradation tests, dominant failure mode of the rubber seals is found to be the loss of elongation. The lifetime distribution and the service life of the rubber seals at use condition are estimated from the test results. The acceleration factor for three types of rubber seals are also investigated.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.2
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• pp.347-360
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• 2018

Due to the concentration and congestion of traffic in Seoul metropolitan area, effective utilization of underground space is required, and construction of various underground structures such as a double deck tunnel is increasing. Double deck tunnels are divided into upper and lower runways, and the most important part is middle slab. To investigate seismic behavior of middle slab, experimental study is required because of the complexity of the load and the mechanism of earthquake. In this study, centrifugal model tests were conducted to investigate the response characteristics of earthquake response according to the support conditions of the middle slab of a double deck tunnel. Artificial, Ofunato (short period) and Hachinohe (long period) seismic waves were employed in the experimental study. As a result, it was confirmed that the acceleration attenuation of elastomeric bearings condition was 10.6% in artificial earthquake, 13.6% in Ofunato earthquake, and 10.3% in Hachinohe earthquake. The results indicate that elastomeric bearings have some advantages in the viewpoint of seismic behaviors.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.3
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• pp.503-515
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• 2017

Underground structures that have recently become larger are required to be stable not only during normal times but also during earthquakes. Especially, it is very important to maintain the stability of the subsea tunnels during the earthquake. The objective of this paper is to verify the effectiveness of the flexible segment, which is one of the breakthrough facilities to maintain the stability of the subsea tunnel during the earthquake using the shaking table test. Another goal of this paper is to propose the optimum position of the flexible segment through 3D dynamic numerical analysis based on the verified results from shaking table tests. The 1g shaking table test considering the similarity ratio (1:100) to the cross section of the selected artificial subsea tunnel was carried out considering the Geongju and Artificial seismic waves, longitudinal and lateral wave, and with/without flexible segments eight times or more. As a result of the shaking table test, it was confirmed that the flexible segment is effective in improving the seismic performance of the undersea tunnel in all the experimental results. In addition, 3D dynamic numerical analysis was performed to select the optimum position of the flexible segment which is effective for improving seismic performance. As a result, it was confirmed that the seismic acceleration is attenuated when the flexible segment is installed adjacent to the branch section in subsea tunnel.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.5
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• pp.375-393
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• 2022

This study was deal with blow-out and buoyancy stability evaluation method for slurry shield TBM. When applying a slurry shield TBM for the construction of a shallow tunnel under river or sea, the stability of slurry blow-out and segment lining buoyancy should be evaluated. However, there is a problem in that the currently applied theoretical formula is somewhat complicated, making it inconvenient to calculate in practice. In this study, some simple charts were proposed to easily evaluate the stability of slurry blow-out and segment lining buoyancy. In addition, the buoyancy safety factor of segment lining using the strength reduction method was evaluated and compared with the buoyancy safety factor based on the theoretical formula. The buoyancy safety factor by the theoretical formula was evaluated to be rather small, and it was confirmed that it was on the safe side. The simplified charts for the evaluation of slurry blow-out and buoyancy stability presented in this study are expected to be usefully utilized in the planning and design of undersea tunnels.