Influence of load idealisation on strain and pore pressure accumulation in clay

Current design practice for offshore wind turbines (OWTs) simplifies complex, irregular load histories into an idealised sequence of cycles with uniform amplitude and a constant average load, without accounting for variations in the average load or the effects of load idealisation. Consequently, when using element tests to support OWTs design, the variation in average shear stress qave is typically ignored. This paper investigates the impact of qave and the sequence of cycle loading packages on strain and pore water pressure accumulation. A series of undrained triaxial tests was conducted on clay where qave dominates the strain and pore water pressure accumulation. The experimental results show that qave and its variation with the number of cycles significantly affect strain and pore water pressure accumulation. It is suggested that, under the situation of an average-component-dominated design of OWTs, additional safety margins need to be applied to the designed geotechnical parameters to consider the average loading effects.