• 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.

• Tunnel and Underground Space
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• v.18 no.5
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• pp.366-374
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• 2008

Tunnelling under water table induces many geotechnical problems because of groundwater. In subsea tunneling, reduction of face stability can induce flooding in the vicinity of a fracture zone characterized by high permeability and high water pressure. In this study, the effects of high water pressure on the stability of a tunnel face in a limited zone with high permeability(hazardous zone) are analyzed. On the basis of the 'advance core' concept, the seepage force acting on a hypothetical cylinder ahead of a tunnel face is modeled. This study focuses on the hydraulic behavior of the ground ahead of the tunnel face by three-dimensional steady-state seepage analyses. The impact of the hazardous zone on the seepage force and stability of the tunnel face are simulated and analyzed. In light of the analysis results, it is estimated that the distance from the tunnel face to the exterior boundary limit, which the seepage force significantly affects the stability of the tunnel face, of a hypothetical cylinder is approximately 5 times the tunnel radii. Despite the restrictive assumptions of this study, the results are highly indicative regarding the risks of hazardous zones.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.1
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• pp.70-82
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• 1995

A multi-layer simulation program is developed to estimate the ocean current considering sea bottom geometry. The so-called $\sigma$ coordinate system is introduced in vertical direction to describe sea bottom topography more accurately and effectively. Leapfrog scheme combined with Euler backward scheme is used to reduce computation error which may be possibly accumulated in time evolution by Leapfrog scheme alone. In this paper, very simple examples of rectangular basins with various bottom geometries were taken and the effect of sea bottom geometry on vertical structure of the ocean tidal current and its direction were investigated. Through comparisons between the present three dimensional calculation in which bottom topography is directly taken into consideration and the two dimensional calculation in which depth average concept is employed, it was found that magnitude of surface current and its direction could be largely affected by the sea bottom topography, particularly in shallow region with complex bottom shape.

• Tunnel and Underground Space
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• v.17 no.1 s.66
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• pp.1-8
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• 2007

In Norway, about 30 subsea tunnels have been constructed over the last 20 years. The minimum depth of 17 subsea tunnels is 56 m and rock cover are between 23 and 49 m. As the project areas for subsea tunnel are covered by water, special investigation techniques need to be applied and the investigation results are more uncertain than that of most conventional tunnel projects. The indefinite potential of water inflow and the salinic character of ingress water represent considerable problems for tunnel equipment and rock support materials. The least stable conditions are represented by major faults or weakness zones containing heavily crushed rock and clay gouge. This paper introduces the Oslofjord subsea tunnel project including minimum rock cover requirement, risk of water inflow, investigation costs, construction costs, and traffic & operation costs.

• Proceedings of KOSOMES biannual meeting
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• 2007.05a
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• pp.51-56
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• 2007

It has generally used the burial method for the protection methods of submarine cable. Especially in Korea, It has used the protection methods of various types according to fisheries and fishing implements. Present day, All the protection methods-burial, continuous concrete mattress, cast iron pipes, U-duct, concrete bags, Rock Berm, mortar bags, FCM apply to the submarine cable, but these methods just focus on the safety of submarine cable against the external damages not the characteristics of ocean environment and the protection of environment. This research is going to present the protection methods of submarine cable according as the characteristics of ocean environment-external damages, depth of water, seabed condition, wave power and the protection of environment.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.8 no.1
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• pp.81-86
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• 1996

Subsea pipelines have an important role in the overall tasks of offshore oil and gas production but arc exposed to various hazards with high potential risks of damage resulting in serious economic loss and impact on ocean environment. In this paper, the dynamic free span is analysed, which is one of main risk factors against the safety of subsea pipelines and the allowable length of dynamic free span which is important for the design of subsea pipelines is determined. The allowable free span length is examined by considering the relationship between vortex shedding frequency and natural frequency of pipeline free span, and the variation of the allowable length is analysed for different boundary conditions of pipe ends. The free span is regarded as a beam on elastic foundations and the boundary condition of the beam is generalized by modelling as restrained by linear and rotational spring at each end. A non-dimensionalized curve is obtained to facilitate the determination of exact allowable length of dynamic free span for subsea pipelines and is applied to the pipelines which is to be installed in the gas fields of the south of East Sea of Korea.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2009.03a
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• pp.113-119
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• 2009

• Magazine of korean Tunnelling and Underground Space Association
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• v.25 no.3
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• pp.17-27
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• 2023

• Proceedings of the KIEE Conference
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• 2008.11a
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• pp.400-402
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• 2008

제주도의 지속적인 전력수요 증가에 능동적으로 대처하고자 육지-제주간 초고압 직류연계(HVDC) 추가 건설사업이 추진 중에 있다. 초고압 직류 송전계통을 신뢰성 있게 운전하기 위해 양측 변환소에 설치될 제어 및 감시계통간 정보전송로의 화보는 매우 중요하다. 본 논문에서는 고품질, 대용량화 되어가는 전력데이터를 안정적으로 전송하고 해저케이블 고장감시 및 향후 정보 통신 분야의 부가가치 창출을 위한 최적의 해저광통신케이블을 소개하고자 한다.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.572-573
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• 2011

본 논문에서는 신안군 도서지역의 안정적 전력공급 및 해저송전선로 건설기술 국산화를 위하여 국내 최초로 제작, 설치된 154kV급 AC 해저송전선로에 대한 케이블 구조, 시스템 및 보호공법 등 전반적인 내용에 대하여 소개하였다.