Episodes of Cycling and Reconsolidation Effects on Cyclic Lateral Behavior of Monopiles in Soft Clay: Centrifuge Modeling-Paper

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The study investigates how repeated episodes of lateral cycling and intervening reconsolidation affect monopiles in soft clay. Centrifuge tests at 100 g modeled 4 m and 6 m diameter monopiles. Each cyclic test applied three loading amplitudes—25%, 45%, and 65% of the pile’s monotonic ultimate capacity—with 100 cycles per episode and reconsolidation between episodes.<br /><br />During cycling, cumulative pile displacement and excess pore-water pressure increased, while unloading stiffness degraded. The effects were strongest early in each episode and diminished as the response stabilized. During reconsolidation, excess pore pressure dissipated and the surrounding soil strengthened and stiffened. Consequently, later cycling caused less displacement accumulation and stiffness degradation.<br /><br />After two cycling–reconsolidation sequences, displacement during the third episode was up to 63% lower than during the first. Unloading stiffness recovered and reached 1.5 times its initial value—an increase of up to 50%. Reconsolidation also increased lateral soil resistance represented by the p-y curves. This gain was greater for the larger pile and decreased with depth.<br /><br />The API (2014) p-y curves underestimated measured soil resistance by up to 24% during the first cycling episode and by up to 52% after two reconsolidation periods. The findings indicate that accounting for reconsolidation may improve monopile design accuracy; ignoring its beneficial effects can lead to conservative designs.

Keywords

monopile

soft clay

lateral cycling

reconsolidation

centrifuge tests

p-y curves

excess pore-water pressure

unloading stiffness

pile displacement

soil resistance