Centrifuge modelling of a tetrapod jacket foundation under lateral cyclic and monotonic loading in soft soil

Abstract

The tetrapod jacket foundation is one of the most common types of foundations used for offshore structures. Although the static bearing capacity of the jacket foundation is important, a safe design must be taken into consideration for accumulative deformation and stiffness degradation during cycling. To address this, a set of centrifuge model tests of a tetrapod jacket foundation subjected to cyclic and monotonic loading was conducted in kaolin. The test results mainly reveal (i) the influence of loading history on the lateral bearing capacity of the jacket foundation; (ii) the evolution of accumulative deformation of the jacket foundation during cycling; (iii) the stiffness degradation of soil–pile interaction under cyclic loading. Comparing typical “lateral soil resistance”–“pile lateral displacement” (p–y) curve approaches with test results, a hyperbolic tangent p–y curve method is adopted to calculate the soil–pile interaction of the jacket foundation. The values of the p-multipliers of leading-row and trailing-row piles in soft soils are clearly lower than that in sands. Finally, a cyclic p–y curve method related to cycles and embedded depths is developed for the jacket foundation in the hope of providing guidance for the design of the jacket foundation in soft soil.