Seismic performance of shared suction caisson anchors installed in liquefiable sand for floating offshore wind turbines

Abstract

Shared anchors will reduce the levelized cost of energy for floating offshore wind (FOW) arrays currently under active development in various seismically active regions. This study investigates the seismic performance of a shared suction caisson anchor installed in liquefiable sand for a FOW array using a nonlinear dynamic 3D finite element analysis. The advanced UBC3D-PLM constitutive model was calibrated against cyclic element tests then validated with centrifuge experimental data. Strong ground motions with orthogonal horizontal and vertical components were applied to the model with varying frequency content, peak ground acceleration (PGA), and orientation. The model captured the stress–strain response of the soil and evolution of excess pore pressure to the onset of liquefaction, which occurred after application of a PGA of 0.2 g and above. Despite significant liquefaction caused by a PGA of 0.8 g, displacement of the anchor remained within around 10% of anchor diameter. The results suggest some resilience to pull-out during seismic loading in liquefiable soils, even with vertical tensile loading on the anchor developed by the inverse catenary. Further investigation could be carried out under specific site conditions and serviceability criteria to optimize the size of the caisson and reduce costs while ensuring anchor performance during seismic loading.