Applicability of the strain accumulation procedure for the geotechnical foundation design of zero-radius bend triggers

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Abstract

Geotechnical design of offshore shallow foundations is generally based on a cyclically degraded shear strength, typically determined from a shear strain or pore pressure accumulation procedure based on contour diagrams derived from laboratory tests. The procedure was initially developed for gravity-based structures and is now used for a wider range of offshore applications including shallow foundations for subsea structures that are subjected to different cyclic loading regimes. The applicability of the traditional equivalent cyclic shear strength approach based on the accumulation procedure is investigated for a specific type of subsea structure, the Zero-Radius Bend (ZRB) trigger. A series of centrifuge tests have been performed on a shallow skirted foundation on normally consolidated kaolin clay under a range of horizontal cyclic load sequences typical of those applied to foundations of ZRB triggers during pipe-laying. The observed performance from the centrifuge tests is compared with predictions of foundation performance using the traditional strain accumulation procedure. It is shown that the traditional procedure over predicts strength degradation at the end of the particular cyclic load sequences. The findings indicate that a performance-based approach may be more appropriate for the geotechnical design of these foundations and other foundations with a high tolerance to displacement.

Original languageEnglish
Article number106062
JournalOcean Engineering
Volume186
DOIs
Publication statusPublished - 15 Aug 2019

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Cyclic loads
Centrifuges
Shear strength
Kaolin
Pore pressure
Shear strain
Gravitation
Clay
Pipe
Degradation

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title = "Applicability of the strain accumulation procedure for the geotechnical foundation design of zero-radius bend triggers",
abstract = "Geotechnical design of offshore shallow foundations is generally based on a cyclically degraded shear strength, typically determined from a shear strain or pore pressure accumulation procedure based on contour diagrams derived from laboratory tests. The procedure was initially developed for gravity-based structures and is now used for a wider range of offshore applications including shallow foundations for subsea structures that are subjected to different cyclic loading regimes. The applicability of the traditional equivalent cyclic shear strength approach based on the accumulation procedure is investigated for a specific type of subsea structure, the Zero-Radius Bend (ZRB) trigger. A series of centrifuge tests have been performed on a shallow skirted foundation on normally consolidated kaolin clay under a range of horizontal cyclic load sequences typical of those applied to foundations of ZRB triggers during pipe-laying. The observed performance from the centrifuge tests is compared with predictions of foundation performance using the traditional strain accumulation procedure. It is shown that the traditional procedure over predicts strength degradation at the end of the particular cyclic load sequences. The findings indicate that a performance-based approach may be more appropriate for the geotechnical design of these foundations and other foundations with a high tolerance to displacement.",
keywords = "Centrifuge modelling, Cyclic loading, Shallow foundations",
author = "Dimitra Zografou and Meysam Banimahd and Susan Gourvenec and Conleth O'Loughlin",
year = "2019",
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AU - Zografou, Dimitra

AU - Banimahd, Meysam

AU - Gourvenec, Susan

AU - O'Loughlin, Conleth

PY - 2019/8/15

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N2 - Geotechnical design of offshore shallow foundations is generally based on a cyclically degraded shear strength, typically determined from a shear strain or pore pressure accumulation procedure based on contour diagrams derived from laboratory tests. The procedure was initially developed for gravity-based structures and is now used for a wider range of offshore applications including shallow foundations for subsea structures that are subjected to different cyclic loading regimes. The applicability of the traditional equivalent cyclic shear strength approach based on the accumulation procedure is investigated for a specific type of subsea structure, the Zero-Radius Bend (ZRB) trigger. A series of centrifuge tests have been performed on a shallow skirted foundation on normally consolidated kaolin clay under a range of horizontal cyclic load sequences typical of those applied to foundations of ZRB triggers during pipe-laying. The observed performance from the centrifuge tests is compared with predictions of foundation performance using the traditional strain accumulation procedure. It is shown that the traditional procedure over predicts strength degradation at the end of the particular cyclic load sequences. The findings indicate that a performance-based approach may be more appropriate for the geotechnical design of these foundations and other foundations with a high tolerance to displacement.

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KW - Centrifuge modelling

KW - Cyclic loading

KW - Shallow foundations

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