Undrained capacity of shared triple-bucket anchor foundations under combined horizontal and torsional loading

Shared anchors offer a promising solution for reducing mooring system costs in floating offshore wind arrays. However, their capacity may be reduced by varying resultant horizontal and torsional mooring loads under complex environmental loading. Numerical analyses are conducted to clarify the undrained capacity and failure mechanisms of shared triple-bucket anchor foundations under combined horizontal and torsional loading. The effects of embedment ratio, spacing ratio, horizontal loading direction and torsional load magnitude on the H x - H y failure envelopes are examined. Under pure horizontal loading, the capacity is insensitive to loading direction. As torsional load magnitude increases, the H x - H y failure envelopes contract progressively, and their shape evolves from circular to triangular. The effects of embedment ratio and spacing ratio on the shape of normalised H x - H y failure envelopes are limited. Based on the optimal centreline loading depth, a theoretical method is proposed for predicting the H x - H y failure envelopes under torsional loading, and an example application is provided to illustrate its use in practice. The proposed method provides a theoretical basis for the preliminary design of shared-anchor systems.