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Load capacity of caisson anchors exposed to seabed trenching

Load capacity of caisson anchors exposed to seabed trenching
Load capacity of caisson anchors exposed to seabed trenching
Floating structures are often secured in position with a taut mooring system and suction caissons. Large seabed trenches have been observed adjacent to some suction caisson anchors with taut-line mooring systems. The trenches may jeopardise the geotechnical capacity of the caissons and in turn the stationkeeping of the floating structures. Finite-element method is employed to examine the geotechnical capacity of suction caissons in a trenching seabed. The results show that the reduction in the geotechnical capacity becomes more significant with increasing trench width due to the loss of soil support and a change in failure mechanism as the caisson rotates into the trench. For a given trench width, the reduction in capacity becomes more significant as the load inclination angle to the horizontal decreases. However, the shape of the normalised failure envelopes for combined vertical and horizontal load is insensitive to trench width. A strategy to design for inevitable trenching by moving the padeye shallower to reduce the depth of trench formation is not straightforward. The gain from a shallower trench may often be outweighed by the reduction in capacity from rotation of the caisson at failure for loading angles typical of taut moorings.
0029-8018
181-192
Feng, Xiaowei
33d164d1-5589-41f6-995a-9b17374bdd0c
Gourvenec, Susan
6ff91ad8-1a91-42fe-a3f4-1b5d6f5ce0b8
White, David
a986033d-d26d-4419-a3f3-20dc54efce93
Feng, Xiaowei
33d164d1-5589-41f6-995a-9b17374bdd0c
Gourvenec, Susan
6ff91ad8-1a91-42fe-a3f4-1b5d6f5ce0b8
White, David
a986033d-d26d-4419-a3f3-20dc54efce93

Feng, Xiaowei, Gourvenec, Susan and White, David (2019) Load capacity of caisson anchors exposed to seabed trenching. Ocean Engineering, 171, 181-192. (doi:10.1016/j.oceaneng.2018.09.027).

Record type: Article

Abstract

Floating structures are often secured in position with a taut mooring system and suction caissons. Large seabed trenches have been observed adjacent to some suction caisson anchors with taut-line mooring systems. The trenches may jeopardise the geotechnical capacity of the caissons and in turn the stationkeeping of the floating structures. Finite-element method is employed to examine the geotechnical capacity of suction caissons in a trenching seabed. The results show that the reduction in the geotechnical capacity becomes more significant with increasing trench width due to the loss of soil support and a change in failure mechanism as the caisson rotates into the trench. For a given trench width, the reduction in capacity becomes more significant as the load inclination angle to the horizontal decreases. However, the shape of the normalised failure envelopes for combined vertical and horizontal load is insensitive to trench width. A strategy to design for inevitable trenching by moving the padeye shallower to reduce the depth of trench formation is not straightforward. The gain from a shallower trench may often be outweighed by the reduction in capacity from rotation of the caisson at failure for loading angles typical of taut moorings.

Text
2018_Ocean Engineering_Feng et al._Mooring line trenching - Accepted Manuscript
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More information

Accepted/In Press date: 7 September 2018
e-pub ahead of print date: 15 November 2018
Published date: 1 January 2019

Identifiers

Local EPrints ID: 424207
URI: http://eprints.soton.ac.uk/id/eprint/424207
ISSN: 0029-8018
PURE UUID: db53dc51-c6d9-4164-b4ac-e4b021c7638f
ORCID for Susan Gourvenec: ORCID iD orcid.org/0000-0002-2628-7914
ORCID for David White: ORCID iD orcid.org/0000-0002-2968-582X

Catalogue record

Date deposited: 05 Oct 2018 11:34
Last modified: 07 Oct 2020 05:39

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