Bearing capacity of a suction anchor in sand under dynamic wave-current coupling

This study investigated the coupled wave-current effects on the vertical bearing capacity of suction anchor in sandy seabed through scaled flume experiments (geometric ratio 1:17.5) using Bohai Bay sand, based on Froude similarity criterion. Departing from conventional static scour pit simulations, dynamic hydrodynamic loading scenarios—hydrostatic, current-only, wave-only, and combined conditions—were systematically examined. Key findings reveal: (1) The ultimate vertical capacity under hydrostatic conditions decreased by 48.9% due to pore pressure-induced reduction in effective stress. (2) Current loading induced nonlinear bearing capacity degradation (R² = 0.997), with a 14.52% reduction at 0.29 m/s and an incremental 5% loss per 0.1 m/s velocity increase. (3) Wave height governed bearing capacity through a compaction-softening competition mechanism, yielding a 5.73% average capacity increase per 0.05 m wave height increment, whereas wave period exhibited negligible influence. (4) Wave-current coupling demonstrated non-additive interaction, reducing capacity loss by 15.30% compared to linear superposition predictions. Wave-induced seabed compaction suppressed current-driven scour, mitigating embedment loss, while coupling effects intensified capacity degradation with increasing flow velocity. These findings provide critical insights for offshore wind foundation design, emphasizing the necessity of coupled hydrodynamic analysis in coastal engineering practice. The experimental framework establishes a benchmark for evaluating foundation performance under complex marine environmental loads.