Undrained bearing capacity of deeply embedded foundations under general loading

Zhang, Y., Bienen, B., Cassidy, M.J. and Gourvenec, S. (2011) Undrained bearing capacity of deeply embedded foundations under general loading. In Frontiers in Offshore Geotechnics II - Proceedings of the 2nd International Symposium on Frontiers in Offshore Geotechnics. pp. 691-696 .

Abstract

The foundations of offshore mobile jack-up drilling rigs are subject to combined vertical (V), horizontal (H) and moment (M) loading conditions. In soft soil, spudcans penetrate deeply (up to 2.5 diameters) and soil flows back on top of the foundations. This is generally believed to provide additional bearing capacity. However, the current industry guideline evaluates bearing capacity based on shallow foundation mechanisms regardless of the spudcan penetration, and the potential benefits associated with deep failure mechanisms are unaccounted for. This results in conservatism within site-specific assessments. In this study, the combined undrained bearing capacity of a deeply embedded spudcan foundation in normally consolidated clay is investigated using small strain finite element analyses. The effects of footing shape and aspect ratio on the failure mechanisms and combined bearing capacity are highlighted. To conclude, a closed-form expression is proposed to describe the shape of the VHM failure envelopes.

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Contributors

Author: S. Gourvenec

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