Major Research Elucidation of the horizontal resistance characteristics of pile foundations for offshore wind power plants under various fluctuating loads

Offshore wind power plants that are built directly on the seabed are subjected to a variety of variable loads simultaneously for extended periods, including wind, waves, earthquakes, etc. As each such variable load has a unique load amplitude, frequency band, number of repetitions, acting position, etc., the horizontal load affecting pile foundations also consists of complex factors.
 
In practice, the beam spring model in which the lower ends of piles are fixed has been mostly used. However, as it is unclear whether large-diameter piles could exhibit a similar resistance mechanism, the non-linear ground spring model that is used cannot demonstrate the deformation characteristics of ground that are manifested when subjected to repetitive loads. In addition, as it has not yet been clarified the change of mechanical properties of ground during pile-driving, at present we must treat ground as virgin ground for design purposes.

Therefore, the objective of this study is to evaluate bearing capacity while taking into consideration the history of pile-driving and external variable loads for offshore wind power plant having a pile foundation.

During this fiscal year, we produced test equipment that can apply horizontal loads to the piles, utilizing the large soil tank experiment planned for execution in the next fiscal year, and also developed a numerical analysis code that can simulate the pile-driving process.