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Sedimentation-induced burial of subsea pipelines: observations from field data and laboratory experiments

Sedimentation-induced burial of subsea pipelines: observations from field data and laboratory experiments
Sedimentation-induced burial of subsea pipelines: observations from field data and laboratory experiments

Sediment transport-induced changes to the embedment of three 26 km long sections of subsea pipeline are analysed and subsequently explained using model scale experiments. Rather than the scour and scour-induced sinking and sagging traditionally thought to dominate post-lay pipeline spanning and embedment change, the change for these pipelines is shown to be caused by sedimentation. The pipelines traverse a range of metocean and soil conditions; the variation in embedment correlates well with the variation in metocean conditions, with most change occurring in an area where multidirectional high-velocity short-duration flows associated with internal waves propagate at near-perpendicular angles to the pipeline. To understand the mechanism driving these changes, a series of model scale tests in O-tube flumes have been completed under flow conditions mimicking those recorded in the field. Good agreement is found between the field and laboratory results, both in terms of the process timescale and the post-sedimentation profile. The consistency of the embedment changes between the pipelines, their correlation with metocean conditions, and the ability to replicate these changes in model scale tests suggests that such changes can be accounted for in more effective pipeline design. Spans are relatively rare along the pipelines but where they do occur fish rather than scour are shown to be the principal agent of span formation.

On-bottom stability, Pipe-soil interaction, Pipeline embedment, Scour, Sediment transport, Sedimentation
0378-3839
137-158
Leckie, Simon H.F.
2f62ed53-abf1-461d-879f-9b9e0134cb0f
Mohr, Henning
2afb09e1-17c7-4875-ac8a-cd15850c1e91
Draper, Scott
efe46b7d-3989-403b-8b19-0b17dd54194f
McLean, Dianne L.
bffb8e42-012d-4243-8b1a-6a9f15c8f39a
White, David J.
a986033d-d26d-4419-a3f3-20dc54efce93
Cheng, Liang
0ce99dcc-f682-4ec6-97aa-59fd87174385
Leckie, Simon H.F.
2f62ed53-abf1-461d-879f-9b9e0134cb0f
Mohr, Henning
2afb09e1-17c7-4875-ac8a-cd15850c1e91
Draper, Scott
efe46b7d-3989-403b-8b19-0b17dd54194f
McLean, Dianne L.
bffb8e42-012d-4243-8b1a-6a9f15c8f39a
White, David J.
a986033d-d26d-4419-a3f3-20dc54efce93
Cheng, Liang
0ce99dcc-f682-4ec6-97aa-59fd87174385

Leckie, Simon H.F., Mohr, Henning, Draper, Scott, McLean, Dianne L., White, David J. and Cheng, Liang (2016) Sedimentation-induced burial of subsea pipelines: observations from field data and laboratory experiments. Coastal Engineering, 114, 137-158. (doi:10.1016/j.coastaleng.2016.04.017).

Record type: Article

Abstract

Sediment transport-induced changes to the embedment of three 26 km long sections of subsea pipeline are analysed and subsequently explained using model scale experiments. Rather than the scour and scour-induced sinking and sagging traditionally thought to dominate post-lay pipeline spanning and embedment change, the change for these pipelines is shown to be caused by sedimentation. The pipelines traverse a range of metocean and soil conditions; the variation in embedment correlates well with the variation in metocean conditions, with most change occurring in an area where multidirectional high-velocity short-duration flows associated with internal waves propagate at near-perpendicular angles to the pipeline. To understand the mechanism driving these changes, a series of model scale tests in O-tube flumes have been completed under flow conditions mimicking those recorded in the field. Good agreement is found between the field and laboratory results, both in terms of the process timescale and the post-sedimentation profile. The consistency of the embedment changes between the pipelines, their correlation with metocean conditions, and the ability to replicate these changes in model scale tests suggests that such changes can be accounted for in more effective pipeline design. Spans are relatively rare along the pipelines but where they do occur fish rather than scour are shown to be the principal agent of span formation.

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More information

Accepted/In Press date: 16 April 2016
e-pub ahead of print date: 14 May 2016
Published date: 1 August 2016
Keywords: On-bottom stability, Pipe-soil interaction, Pipeline embedment, Scour, Sediment transport, Sedimentation

Identifiers

Local EPrints ID: 419538
URI: http://eprints.soton.ac.uk/id/eprint/419538
ISSN: 0378-3839
PURE UUID: 9387de2c-1d85-4f77-810c-9e48d87efef0
ORCID for David J. White: ORCID iD orcid.org/0000-0002-2968-582X

Catalogue record

Date deposited: 13 Apr 2018 16:30
Last modified: 18 Mar 2024 03:42

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Contributors

Author: Simon H.F. Leckie
Author: Henning Mohr
Author: Scott Draper
Author: Dianne L. McLean
Author: David J. White ORCID iD
Author: Liang Cheng

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