Strategies for quantifying the installation reliability of skirted subsea foundations

Bransby, M.F., White, D.J. and Xie, Y. (2015) Strategies for quantifying the installation reliability of skirted subsea foundations. In Offshore Technology; Offshore Geotechnics. vol. 1, The American Society of Mechanical Engineers. 8 pp . (doi:10.1115/OMAE2015-42340).

Abstract

An increasing number of well-related and pipeline-related subsea structures (e.g. PLETs, ILTs, buckle initiators, etc.) are being placed on the seabed. Many of these structures are founded on unskirted and skirted mudmat foundations as a costeffective, low risk solution. Much attention has been placed in the literature on the geotechnical capacity of subsea mudmat foundations, but less attention on how these types of foundations are installed. In some soil conditions this can be a critical aspect of design: the requirement to add skirts to ensure sufficient foundation capacity comes with the penalty of increasing the necessary foundation weight to ensure that these skirts can be reliably installed. The addition of weight to a foundation increases its installation and fabrication cost and so requires careful treatment in design. As an example of this design optimization process, attention is given to dealing with uncertainty associated with variable soil conditions. It is shown how probabilistic geotechnical analysis can give a clearer perspective of cost and risk and how carefully targeted site investigation can also be used in this context.

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Contributors

Author: D.J. White

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