Bearing capacity of the Yme GBS tank incorporating cyclic pore pressure accumulation with partial drainage

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The Mobile Offshore Production Unit with Storage (MOPUstor) was installed at Yme Gamma in 2011, located 110 km from the Norwegian coastline in the Egersund basin in a water depth of 93 m. It was de-manned in 2012, and the MOPU (topside) was removed in 2016. For the Yme New Development project, it was necessary to evaluate the stability of the gravity base structure (GBS) storage tank without the MOPU. The GBS foundation includes external and internal skirts and a drainage system designed to relieve excess pore water pressures during cyclic loading. Front-End Engineering Design (FEED) for the new development indicated the need for significant ballast to ensure stability under storm conditions. This paper reassesses foundation stability using advanced finite element (FE) analyses. A 3D FE model of the GBS tank was developed using Abaqus. The Partially Drained Cyclic Accumulation Model (PDCAM) incorporated in Abaqus allowed a refined assessment of excess pore water pressures under design cyclic loading conditions. The FE analyses confirmed that the GBS tank meets stability requirements without additional ballast. Limiting equilibrium bearing capacity calculations were also performed to conservatively provide some preliminary estimates and to support the FE results. This study concludes that FE analysis combined with PDCAM can provide an effective and practical tool for evaluating foundation bearing capacity under cyclic loading in partially drained conditions.

5th International Symposium on Frontiers in Offshore Geotechnics (ISFOG2025)

12 - Gravity base foundations, Drag and Plate Anchors