Pore water pressure accumulation due to cyclic horizontally loaded monopiles with large diameters

Pore water pressure accumulation due to cyclic horizontally loaded monopiles with large diameters. Monopiles, i.e. single piles with large diameter of up to 8 m, are suitable foundations for offshore-wind power plants built in up to 40m water depth. Cyclic loading of the monopile-soil system induced by extremely strong wind and water waves causes a change in pore water pressure. Current design practice does not account for such effects. In this paper the interaction behaviour of monopile-soil systems subjected to extreme loading is analyzed using a finite element model. A fully coupled two-phase model and a hypoplastic constitutive model for the sandy soil are used in the numerical analyses. Results from the numerical studies are presented and they include the variation of loading amplitude, frequency, number of cycles and loading type as well, initial density and permeability of the sand as well as the diameter of the monopile. The own numerical results are compared with design equations for cyclic horizontally loaded piles from other references. Based on these investigations the importance and relevance of the consideration of pore water pressure accumulation with monopile-soil systems subjected to offshore loading conditions is demonstrated.