A macroelement model for predicting load–displacement reponses of suction anchors under combined horizontal–vertical–torsional loading in clay

This paper presents a plastic-hardening, nonassociated macroelement model for predicting the load–displacement responses and padeye trajectories during the monotonic pullout process of suction anchors under horizontal–vertical–torsional loading ( H–V–T) in clay. The closed-form formula of the three-dimensional H–V–T failure surface is established through comprehensive finite-element analyses, extending from the conventional two-dimensional horizontal–vertical failure envelope and considering the influence of anchor aspect ratio and reduction factor of interface shear strength. Subsequently, appropriate forms of loading surface and hardening rule are selected based on this failure surface. A nonassociated flow rule is adopted with a modified plastic potential that accurately captures the padeye kinematic trajectories. Only one test is required for determining and calibrating model parameters, along with recommended loading conditions provided. Finally, rigorous validation against numerical tests conducted in this study, as well as physical model tests and numerical simulations from other studies, demonstrates satisfactory agreement between the model predictions and experimental results. The proposed macroelement model offers researchers and engineers a straightforward and effective tool, particularly useful in scenarios involving suction anchors subjected to torsional load.