Scour effects on monopile lateral behavior under cyclic and monotonic loading

Soil scour can significantly influence the lateral capacity and stiffness of piles in the offshore condition by reducing their embedment depth and soil overburden stress. The effect of scour on monopiles is more severe because of their low embedment depth-to-diameter ratio. The present study employed centrifuge modelling to investigate the effect of scour on the lateral behavior of a monopile. Both cyclic and monotonic loading were performed under different scour geometries for local and general scour. The results showed that the lateral capacity decreased significantly under scour conditions. For example, 1D-local scour caused a 30% reduction in the lateral capacity. The data were used to derive post-scour p-y curves and the results showed that the effect of local scour on the curves was negligible after a specific depth. Cyclic tests revealed the considerable effect of scour on the soil-pile stiffness and accumulated lateral displacement. The data has been used to modify the previously proposed model for accumulated displacement to incorporate the effect of scour.

Automated summary

Soil scour can greatly reduce the lateral capacity and stiffness of offshore piles, particularly monopiles, due to their shallow embedment depth. A centrifuge model was used to investigate the effect of different scour geometries on the lateral behavior of a monopile through cyclic and monotonic loading tests. The results showed a significant decrease in lateral capacity under scour conditions, with 1D-local scour causing a 30% reduction. Post-scour p-y curves were derived and revealed that the effect of local scour on the curves becomes negligible after a specific depth. Cyclic tests also demonstrated the considerable impact of scour on soil-pile stiffness and accumulated lateral displacement, leading to modifications in the previously proposed model for accumulated displacement to incorporate scour effects.