A 3D experimental study of the wave-induced seabed response around a monopile foundation based on pore pressure measurements under regular wave loading

Pore pressures in the seabed soil around monopile foundations are critical for assessing seabed stability and optimising the design of offshore structures. This study presents the set-up, applied methodology and findings of 3D experiments on the wave-induced pore pressures around a scaled monopile foundation subjected to regular wave loading, under various wave conditions. Sand sediment from the Belgian part of the North Sea is used to resemble realistic seabed conditions, enhancing the practical relevance of the study. The experimental results are used to investigate the influence of varying wave conditions on the pore pressures around the monopile. A semi-empirical model is subsequently developed to predict the wave-induced pore pressures in the tested soil sediment under different wave scenarios. The model accounts for the presence of the monopile structure while maintaining a connection to the underlying theoretical principles. The experimental results indicate that the common design assumption of undrained soil behaviour may be overly conservative for the type of sand tested, as significant pore pressure accumulation was not observed during the experiments.