Research on Fatigue Damage of Suction Pile in Deep Sea Drilling

Abstract In recent years, the use of suction pile foundations in deep-sea drilling operations has been increasingly adopted worldwide. Suction piles have a long service life and are difficult to maintain, so there is a risk of fatigue failure during drilling. This necessitates a study of the mechanical properties and cumulative fatigue damage of suction piles during drilling. Based on a flexible deformation model of the riser, and considering environmental load effects, mechanical analysis models for the platform-riser and the subsea wellhead suction pile foundation are established separately using a decoupling method. This allows for the analysis of fatigue hotspots in suction piles. Through the dynamic response analysis of the system, the fatigue damage of the suction pile foundation is calculated. A parametric case study is presented for a deep-water block in the South China Sea, discussing the influence of the suction pile's aspect ratio on hotspot locations and fatigue damage.The results show that under drilling conditions, fatigue hotspots are located on the inner conductor walls at the front and rear sides of the suction pile, just below the top plate. The smaller the aspect ratio of the suction pile, the closer the hotspots are to the top plate. Additionally, the aspect ratio of the suction pile has a minimal effect on structural fatigue, with fatigue damage values at hotspots increasing as the aspect ratio increases.The novelty of this study lies in exploring the fatigue damage laws of suction pile foundations in deep-sea drilling, ensuring operational safety, and guiding the design and application of suction piles in the South China Sea.