Session: 04-04-06 Pipe-Soil Interaction

Paper Number: 124740

124740 - Pipe-Soil Interaction for Viv of Free Spans in Carbonate Silty Sand 

Pipeline engineers have to manage free-spans - i.e. sections of the pipeline which are or which may become unsupported by the seabed - during their operational lifetime. Free-spans can make the pipeline susceptible to in-line (horizontal) or cross-flow (vertical) Vortex-Induced-Vibrations (VIV) that can potentially lead to fatigue failure, which leads to the requirement for regular pipeline inspections and expensive mitigation of critical spans. Modelling of free-spans and assessing their fatigue life requires understanding of the system response, including interactions with the seabed at the free-span shoulders – i.e. sections of continuous support on either side of a free-span – normally characterized in terms of spring stiffness values and damping values

The paper will report on an experimental investigation into the variation of soil stiffness and damping ratio during simulated in-line and cross-flow VIV motions for pipeline ‘elements’ (representing parts of the free-span shoulder) for different pipelay modelling scenarios in order to improve design practice.

A set of geotechnical centrifuge model tests has been performed with a section of a model pipeline first being installed to different initial embedment values, either dynamically or by over-penetration in a layer of carbonate silty sand. Following the installation, sets of horizontal cyclic episodes with varying displacement amplitude were applied. Different initial embedments, pipeline weights and pipelay modelling methods were investigated to examine the difference in the load-displacement curves, from where the soil stiffness and damping ratio are derived. The obtained results will contribute to a better understanding of pipe-soil-interaction for free-span shoulders and improved selection of non-linear soil springs and dampers.

Presenting Author: Vasileios Papavasileiou The University of Western Australia

Presenting Author Biography: Vasileios is a PhD candidate at the University of Western Australia, focusing on offshore geotechnics.
Prior to his PhD, he obtained a bachelors degree from the Alexander Technological Educational Institute of Thessaloniki and a masters degree from Alaborg University.

Authors:

Vasileios Papavasileiou The University of Western Australia
Fraser Bransby The University of Western Australia
Zhechen Hou The University of Western Australia
Michael O'neill The University of Western Australia
Phil Watson The University of Western Australia
Han Eng Low Fugro
Ralf Peek Peek Solutions
Andrew Rathbone Wood PLC