Multi-springs model for suction caisson under monotonic lateral loading

Suction caisson has been widely used as the foundation for the offshore wind turbines. The behaviors of suction caisson under lateral loading caused by the combined effects of wind, wave and current, are quite significant for engineering design. In this paper, a novel multi-springs model is proposed to estimate the foundation displacement behavior and soil resistance distribution under lateral loading. In the proposed model, the p-y and t-z springs are divided into multiple groups and their combined effect is considered to reflect the uneven distribution of interface normal stress outside the caisson. In this way, the enhancement and direction reversal of vertical friction resistance can be reflected, which is also validated by the centrifuge tests of suction caisson. Afterwards, the multi-springs model is adopted to study the static performance of suction caisson under monotonic lateral loading. It is found that the soil displacement field is gradually dominated by the caisson rotation, whose rotation centre moves upwards and stabilizes at about 0.7-0.8L. Compared to p-y and Q-z springs, t-z spring plays the key role in resisting the foundation overturning at the slightly rotation angle of caisson.