• 한국수자원학회:학술대회논문집
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• 한국수자원학회 1993년도 수공학연구발표회논문집
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• pp.483-490
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• 1993

본 논문은 캡슐밀도의 균일성의 영향을 고려하여 관로내에서의 원통형 캡슐 흐름의 특성을 이해하기 위하여 수행된 연구결과를 기술한다. 캡슐의 중심 축방향으로의 밀도변화 영향을 실험적으로나 분석적인 방법으로 연구하였다. 실험은 직경 190mm, 길이 18m인 관에서 수행되었으며, 속도, 캡슐의 기울기, 캡슐바닥과 관과 간격이 여러가지 실험조건하에서 측정되었다. 실험데이타를 해석하기 위하여 무차원 변수로 주어지는 안정성지수(Stability Index)가 유도되었다. 관로에서의 캡슐의 거동은 안정성지수에 크게 영향을 받는다. 실험결과는 안정성지수가 캡슐거동과 캡슐밀도의 균일성과의 상관관계를 잘 설명하여주는 유효한 기준임을 증명하였다.

• 물과 미래
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• 제26권4호
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• pp.97-105
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• 1993

본 논문은 캡슐밀도의 균일성의 영향을 고려하여 관로내에서의 원통형 캡슐 흐름의 특성을 이해하기 위하여 수행된 연구결과를 기술한다. 캡슐의 중심 축방향으로의 밀도변화 영향을 실험적으로나 분석적인 방법으로 연구하였다. 실험은 직경 190mm, 길이 17m인 관에서 수행되었으며, 속도, 캡슐의 기울기, 캡슐바닥과 관과의 간격이 여러 가지 실험 조건하에서 측정되었다. 실험데이타를 해석하기 위하여 무차원 변수로 주어지는 안정성지수(Stability Index)가 유도되었다. 관로에서의 캡슐의 거동은 안정성 지수에 크게 영향을 받는다. 실험결과는 안정성 지수가 캡슐거동과 캡슐밀도의 균일성과의 상관관계를 잘 설명하여주는 유효한 기준임을 증명하였다.

• Journal of Advanced Research in Ocean Engineering
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• 제2권2호
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• pp.86-98
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• 2016

In this study, after the installation of a subsea pipeline, backfilling was performed in the trenched area. During these operations, a stability problem in the subsea pipeline occurred. The pipeline was directly impacted by environmental loading such as waves and currents that were caused by backfill material when scouring or sediment transport and siltation was carried out. Therefore, this study reviewed whether trenching was necessary, and conducted research into an indigenous seabed property that contains granular soil. A study of cohesive soil was also conducted in order to cross-correlate after calculating the values of the critical Shields parameter relevant to elements of the external environment such as waves and current, and the shear Shields parameter that depends on the actual shearing stress. In case of 1), sedimentation or erosion does not occur. In the case of 2), partial sedimentation or erosion occurs. If the case is 3), full sedimentation or erosion occurs. Therefore, in the cases of 1) or 2), problems in structural subsea pipeline stability will not occur even if partial sedimentation or erosion occurs. This should be reflected particularly in cases with granular and cohesive soil when a reduction in shear strength occurs by cyclic currents and waves. In addition, since backfilling material does not affect the original seabed shear strength, a set-up factor should be considered to use a reduced of the shear strength in the original seabed.

• 한국해양공학회지
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• 제21권1호
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• pp.31-39
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• 2007

Recently, the nonlinear dynamic responses among waves, submarine pipeline and seabed have become a target of analyses for marine geotechnical and coastal engineers. Specifically, the velocity field around the submarine pipeline and the wave-induced responses of soil, such as stress and strain inside seabed, have been recognized as dominant factors in discussing the stability of submarine pipeline. The aim of this paper is to investigate nonlinear dynamic responses of soil in seabed, around submarine pipeline, under wave loading. In order to examine wave-induced soil responses, first, the calculation is conducted in the whole domain, including wave field and the seabed, using the VOF-FDM method. Then, velocities and pressures, which are obtained on the boundary between the wave field and the seabed, are used as the boundary condition to compute the wave-induced stress and strain inside seabed, using the poro-elastic FEM model, which is based on the approximation of the Biot's equations. Based on the numerical results, the characteristics of wave-induced soil responses around submarine pipeline are investigated, in detail, inrelation to relative separate distance of the submarine pipeline from seabed. Also, the velocity field around the submarine pipeline is discussed.

• 한국가스학회지
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• 제22권3호
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• pp.53-64
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• 2018

천연가스는 폭발성 유체로 고압의 매설 배관 파손시 심각한 인적/물적 손해를 야기할 수 있으며, 최근에도 실제 매설 배관의 파손으로 상당한 인명피해가 발생한 사례가 보고되고 있다. 국내의 경우, 급속한 성장 및 보급에도 불구하고 천연가스 배관의 운영 길이와 운영기간이 짧아 가스배관의 사고원인 등에 대한 유효한 사고데이터의 확립이 부족한 실정이다. 국내에서 사고 사례에 대한 데이터베이스를 체계적으로 구축하기 위하여 국내보다 천연가스 배관의 운용 역사가 길고, 긴 배관망을 갖고 있는 해외 주요국에서 발생한 최근의 천연가스 배관관련 사고의 원인과 빈도를 분석하는 것이 필요하다. 따라서 본 연구에서는 해외 주요국에서 가스배관의 사고원인별 발생 빈도의 추이를 파악한 후 이를 비교 분석하여 국내 고압가스 운송 배관망의 안정성 확보의 토대를 구축하고자 하였다.

• Structural Engineering and Mechanics
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• 제40권1호
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• pp.29-48
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• 2011

Under large storm loads sections of a long pipeline on the seabed can be uplifted. Numerically this loss of contact is extremely difficult to simulate, but accounting for uplift and any subsequent recontact behaviour is a critical component in pipeline on-bottom stability analysis. A simple method numerically accounting for this uplift and reattachment, while utilising efficient force-resultant models, is provided in this paper. While force-resultant models use a plasticity framework to directly relate the resultant forces on a segment of pipe to the corresponding displacement, their historical development has concentrated on precisely modelling increasing capacity with penetration. In this paper, the emphasis is placed on the description of loss of penetration during uplifting, modelled by 'strain-softening' of the force-resultant yield surface. The proposed method employs uplift and reattachment criteria to determine the pipe uplift and recontact. The pipe node is allowed to become free, and therefore, the resistance to the applied hydrodynamic loads to be redistributed along the pipeline. Without these criteria, a localised failure will be produced and the numerical program will terminate due to singular stiffness matrix. The proposed approach is verified with geotechnical centrifuge results. To further demonstrate the practicability of the proposed method, a computational example of a 1245 m long pipeline subjected to a large storm in conditions typical of offshore North-West Australia is discussed.

• 한국산업융합학회 논문집
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• 제25권5호
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• pp.827-833
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• 2022

In this study, the prediction of the bending angle for the 350 A bellows-type expansion joints and the structural stability according to the load were determined. The stability of the 2km piping system was predicted by applying the allowable bending angle of the expansion pipe joint obtained from the analysis. The maximum bending angle was calculated through bending analysis of the bellows-type expansion joints, and the maximum bending angle by numerical calculation was about 1.8°, and the maximum bending angle of the bellows obtained by comparing the allowable strength of the material was about 0. 22°. This angle was very stable compared to the allowable bending angle (3°) of the expansion pipe joint regulation. By applying the maximum bending angle, the allowable maximum deflection of the 2 km pipe was about 3.8 m. When the seismic load was considered using regression analysis, the maximum deflection of the 2km pipe was about 142.3mm, and it was confirmed that the bellows-type expansion joints and the deflection were stable compared to the allowable maximum deflection of the pipe system. These research results are expected to present design and analysis guidelines for the construction of piping and the development of bellows systems, and to be used as basic data for systematic research.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 1996년도 학술발표회 논문집
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• pp.611-616
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• 1996

• 터널과지하공간
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• 제10권4호
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• pp.533-543
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• 2000

본 연구에서는 지하공간의 굴착에 따른 수직파이프 구조물의 변형거동 및 안정성을 수치해석적으로 검토하였다. 지반의 수직거동은 파이프의 압축변형 및 압축응력을 발생시키며, 수평거동은 파이프의 굴곡변형 및 쉽응력을 발생시킨다. 또한, 지반의 수평응력은 파이프를 압착시켜 접선응력을 발생시킨다. 본 연구의 해석대상 구조물은 지하 천연가스의 생산정으로 서, 인접 지반의 굴착이 파이프에 미치는 영향과 최대 영향 요소를 고찰하였다. 이를 위해 보안탄주의 폭과 가스생산정의 위치가 서로 다른 세 가지 사례를 해석하고 비교하였다. 두께 2.5m인 탄층이 심도 237.5m에 위치할 때 45.8m 폭의 보안탄주는 외경 10$\frac{3}{4}$ in., 두께 0.4 in.인 API-55 강철 파이프 구조물을 안전하게 보호할 수 있다. 또한, 실제로 파괴가 발생한 가스생산정을 검토한 결과, 발생된 전단음력이 강철 재료의 허용음력을 초과하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1666-1671
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• 2003

Exact dynamic stiffness model for a uniform straight pipeline conveying unsteady fluid is formulated from a set of fully coupled pipe-dynamic equations of motion, in which the fluid pressure and velocity of internal flow as well as the transverse and axial displacements of the pipeline are all treated as dependent variables. The accuracy of the dynamic stiffness model formulated herein is first verified by comparing its solutions with those obtained by the conventional finite element model. The spectral element analysis based on the present dynamic stiffness model is then conducted to investigate the effects of fluid parameters on the dynamics and stability of an example pipeline problem.