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Limit analysis of the undrained bearing capacity of offshore pipelines

Limit analysis of the undrained bearing capacity of offshore pipelines
Limit analysis of the undrained bearing capacity of offshore pipelines

The ultimate bearing capacity of a rigid, plane-strain pipe segment embedded in undrained clay is studied using numerical limit analysis. The pipe is considered to be 'wished in place' at invert penetrations ranging from zero to five pipe diameters, thus providing coverage of both on-bottom (partially embedded) and trenched (fully embedded) offshore pipelines. The soil is modelled as a rigid-plastic Tresca material with either uniform strength or strength proportional to depth. The effects of soil weight, interface roughness and interface tensile capacity are investigated in a systematic manner. All calculations are performed using the finite-element limit analysis code OxLim, which uses adaptive mesh refinement to compute tightly bracketed lower- and upper-bound plasticity solutions. The velocity fields from the upper-bound analyses provide the corresponding failure mechanisms. The paper initially focuses on purely vertical loading (penetration and uplift), and then addresses combined vertical and horizontal loading. A comprehensive set of design curves and failure envelopes is presented, with the results explained in terms of the changing failure mechanisms. These results are immediately applicable in practice. In particular, current industry-standard procedures for design against pipeline upheaval are critically reviewed, and are shown to have potentially unconservative shortcomings.

Bearing capacity, Clays, Numerical modelling, Offshore engineering, Pipelines
0016-8505
847-863
Martin, C.M.
0e7cd727-c254-4d4e-af61-7704dff627d0
White, D.J.
a986033d-d26d-4419-a3f3-20dc54efce93
Martin, C.M.
0e7cd727-c254-4d4e-af61-7704dff627d0
White, D.J.
a986033d-d26d-4419-a3f3-20dc54efce93

Martin, C.M. and White, D.J. (2012) Limit analysis of the undrained bearing capacity of offshore pipelines. Géotechnique, 62 (9), 847-863. (doi:10.1680/geot.12.OG.016).

Record type: Article

Abstract

The ultimate bearing capacity of a rigid, plane-strain pipe segment embedded in undrained clay is studied using numerical limit analysis. The pipe is considered to be 'wished in place' at invert penetrations ranging from zero to five pipe diameters, thus providing coverage of both on-bottom (partially embedded) and trenched (fully embedded) offshore pipelines. The soil is modelled as a rigid-plastic Tresca material with either uniform strength or strength proportional to depth. The effects of soil weight, interface roughness and interface tensile capacity are investigated in a systematic manner. All calculations are performed using the finite-element limit analysis code OxLim, which uses adaptive mesh refinement to compute tightly bracketed lower- and upper-bound plasticity solutions. The velocity fields from the upper-bound analyses provide the corresponding failure mechanisms. The paper initially focuses on purely vertical loading (penetration and uplift), and then addresses combined vertical and horizontal loading. A comprehensive set of design curves and failure envelopes is presented, with the results explained in terms of the changing failure mechanisms. These results are immediately applicable in practice. In particular, current industry-standard procedures for design against pipeline upheaval are critically reviewed, and are shown to have potentially unconservative shortcomings.

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More information

Published date: September 2012
Keywords: Bearing capacity, Clays, Numerical modelling, Offshore engineering, Pipelines

Identifiers

Local EPrints ID: 419673
URI: https://eprints.soton.ac.uk/id/eprint/419673
ISSN: 0016-8505
PURE UUID: 1d2d98da-c35d-4f98-8cc7-87adcf0b8809
ORCID for D.J. White: ORCID iD orcid.org/0000-0002-2968-582X

Catalogue record

Date deposited: 19 Apr 2018 16:30
Last modified: 01 Oct 2019 00:25

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Contributors

Author: C.M. Martin
Author: D.J. White ORCID iD

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