Monopiles supporting offshore wind turbines are subjected to intermittent episodes of cycling and reconsolidation during the lifetime. The cyclic lateral behavior of the monopiles have been investigated by many researchers, however, the effect of episodes of cycling and reconsolidation on subsequent cyclic lateral pile behavior is not well acknowledged. For this reason, a series of centrifuge tests on two monopiles (4 and 6 m) in soft clay is carried out to investigate the effects of episodic cycling and reconsolidation on the evolution of cumulative displacement, stiffness and p-y curves of the monopiles. The experimental results show that the lateral pile-soil stiffness degrades during the initial cycling episode, but it entirely recovers during the subsequent reconsolidation to exceed the initial stiffness, with a percentage increase up to 50%. After two episodes of cycling and reconsolidation, the cumulative pile displacement induced by the 3/sup rd/ episode of cycling can be 63% smaller than that due to the 1/sup st/ episode. These observations indicate that, ignoring the episodes of cycling and reconsolidation effects may lead to a conservative monopile design.
Y. Q. Lai, L. Z. Wang, Y. Hong, B. He and H. Wang
Keywords: centrifuge modeling, monopile, soft clay, cyclic loading, reconsolidation
Publisher: DFI