Key Laboratory of Submarine science and Exploration Technology

Qingdao, China

Key Laboratory of Submarine science and Exploration Technology

Qingdao, China
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Pu J.,Qingdao Geotechnical Investigation and Surveying Research Institute | Xu J.,Ocean University of China | Li G.,Key Laboratory of Submarine science and Exploration Technology
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2013

This paper presents an experimental study on the coupled process between pipe vibration and liquefied silt seabed. The results show that once the disturbing force exceeds a certain threshold, the soil rapidly loses its strength and yields a severe deformation. Liquefied soil has obvious dynamic damping effect on pipeline vibration, and the damping effect is related to pipeline burial depth and load amplitude. The natural frequency of the spanning system changed due to soil liquefactions. Meanwhile, this study also indicates that the traditional supporting method may be deficient in preventing pipeline deformation in liquefied seabed. Copyright © 2013 by the International Society of Offshore and Polar Engineers (ISOPE).


Pu J.,Ocean University of China | Xu J.,Ocean University of China | Li G.,Key Laboratory of Submarine science and Exploration Technology
Journal of Pipeline Systems Engineering and Practice | Year: 2013

The hazardous exposure and self-burial of a submarine pipeline were studied based on the investigation of a submarine pipeline in the sand wave area in the South China Sea, as well as on statistical data and mathematical calculations. The results indicate that the pipeline free span in the area was mainly induced by seabed erosion, sand wave movement, and human disturbance. Extreme weather events cause severe impacts on seabed topography and the pipeline condition. The burial status of the pipe is mainly controlled by the evolution of local seabed topographical conditions, i.e., the amount of sediment load and the movement of seabed sand waves. The migration of the continuous small-scale sand waves facilitates the self-burial of pipes, while the migration of isolated large-scale sand waves creates potential hazards for pipelines because of the existing free span continues to grow on both sides of the sand wave © 2013 American Society of Civil Engineers.


Xu J.,Ocean University of China | Xu J.,Key Laboratory of Submarine science and Exploration Technology | Li G.,Ocean University of China | Li G.,Key Laboratory of Submarine science and Exploration Technology | And 5 more authors.
Journal of Ocean University of China | Year: 2010

The DF1-1 submarine pipeline was investigated using a dual-frequency side-scan sonar and a swath sounder system. More than a hundred scour pits under the pipeline were found, most of which have caused the span of the pipeline to increase and threatened its safety. The maximum allowable free span length (MAFSL) of the pipeline was determined through the limitations regarding maximum allowable stress under static or quasi-static loads and the onset of Vortex Induced Vibrations (VIV) under different hydrodynamic actions. The results show that the MAFSL under static conditions is 56 m. However, the MAFSLs are 30 m and 20 m under ordinary weather conditions and hurricane-induced currents for the 100-year return period, respectively, to avoid VIV as calculated by using the highest safety class factor. It is suggested that spanning pipelines longer than 20 m should be supported. Additionally, eight successive spans which may also threaten the pipeline were proposed. The most hazardous scour pits are along the pipeline section from KP42 to KP51. © 2010 Science Press, Ocean University of China and Springer Berlin Heidelberg.


Xu J.,Ocean University of China | Xu J.,Texas A&M University at Galveston | Li G.,Ocean University of China | Li G.,Key Laboratory of Submarine science and Exploration Technology | And 2 more authors.
Ocean Engineering | Year: 2010

The paper presents an experimental investigation of seabed evolution behavior around a submarine pipeline and the hydrodynamic forces on the pipeline under regular waves. Unlike the previous flume tests that have largely used beds with median sands, this study focuses on fine sediments such as sandy silt and silt. The primary objective of the study was to investigate: (i) the scour process under different wave conditions and with different sediments and (ii) the influence of the bedform evolution on the hydrodynamic forces experienced by the pipeline. In terms of scour and ripple formation, four distinct regimes of the near-field bed evolution behavior are identified which are: (I) no scour, (II) scour without ripples, (III) scour with small ripples and (IV) scour with large ripples. The influence of bedform evolution on wave forces was found to vary significantly in different regimes. In regime I, the wave forces were quite stable; in regime II and III, the wave forces underwent a gradual reduction before reaching their equilibrium values at fairly early stages of the scour process; in regime IV, the wave forces were significantly affected by the migrating ripples and can be rather unsteady throughout the testing period. © 2009 Elsevier Ltd.


Xu J.,Ocean University of China | Xu J.,Key Laboratory of Submarine science and Exploration Technology | Pu J.,Ocean University of China | Li G.,Ocean University of China | Li G.,Key Laboratory of Submarine science and Exploration Technology
Advances in Intelligent and Soft Computing | Year: 2012

The seabed scours around a submarine pipeline on cohesive seabed were studied by analyzing the field investigation data of DF1-1 submarine pipeline off the west coast of Dongfang, Hainan Island. The results show that, the tidal current in the study area can cause the seabed scours on both sides of the pipeline (side scours). The maximum scour depths agree well with that calculated according to the formulae proposed by various researches based on experimental studies with sand or silt beds. It is found that the finer sediments were transported mainly in the form of suspended load in the scour process, while the coarser sediments were mainly as bedload. This process caused a noticeable coarsening process of the local sediments. There exists a large number of scour pits under the pipeline (down scours), which are believed to be caused by hurricanes, but the onset of the scour (piping) is a progressive process, and piping occurs only when the critical piping conditions are exceeded. © 2012 Springer-Verlag GmbH.

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