Numerical study on the pullout capacity of plate anchors in clay: Effect of soil-anchor interface tension

Plate anchors are a promising choice to moor floating offshore wind turbines due to their high pullout capacity relative to their weight. Previous studies and industry guidelines have not included soil-anchor interface tension in anchor capacity predictions, but simplistically assume two extreme conditions: immediate breakaway and no breakaway, corresponding to zero and infinite interface tension, respectively. This study utilises finite element analyses to investigate the effect of intermediate interface tension on the pullout capacity of plate anchors in clay, incorporating a tensile strength threshold to describe the breakaway condition. The findings reveal that increasing interface tension leads to a transition in the failure mechanism, ranging from immediate breakaway to no breakaway conditions. A design formula for anchor capacity is proposed, incorporating interface tension and applicable to both weightless and weighted soil conditions. The results indicate that soil overburden pressure suppresses the effect of interface tension compared to weightless soil. Additionally, a critical interface tension factor is identified, beyond which further increases in interface tension do not enhance the pullout capacity. The findings highlight the critical impact of interface tension on pullout capacity, offering valuable insights for engineers in anchor design. • Interface tension effects on anchor pullout capacity assessed via FE modelling. • Proposed anchor capacity formula includes varied breakaway conditions. • Interface tension shown to significantly impact plate anchor capacity in clay.