ABSTRACT

The increase in investment in offshore wind farms and floating wind turbines due to environmental and energy needs has resulted in increased size of the rotors and going farther out to the sea where the winds are stronger. Consequently, the mooring systems must be designed for larger loads and deeper waters. With the trend towards deeper water applications, depending on the distance between the wind turbines in an offshore wind farm, the mooring load angle at the anchor's padeye can vary from 30° in catenary systems up to more than 45° from the horizontal plane in taut systems. This fact highlights the importance of designing anchor systems with large vertical load components. A parametric investigation of the mooring capacity of inclined piles in comparison with vertical piles driven in extremely soft to very soft clay is conducted using finite element methods (FEM). The results show that pile inclination up to 30° can increase the mooring capacity by more than 50%. The study shows that the reduced mooring capacity due to large mooring angle of taut systems can partially be compensated by pile inclination. In addition, simple empirical models are developed to predict anchoring capacity and inclination efficiency. The model for anchoring capacity can estimate the capacity calculated by FEM with very good accuracy.

INTRODUCTION

The increase in investment in offshore wind farms and floating wind turbines due to environmental and energy needs has resulted in increased size of the rotors and going farther out in the sea where the winds are stronger (Equinor, 2023). While European trends show a clear tendency towards wind power projects being consented and planned in deeper waters, developing wind power projects in some areas poses technical challenges. Mooring difficulties related to deep waters, larger loads due to excessive wave heights, and non-homogeneous seabed conditions are identified as the main challenge (NVE, 2013).

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