Mechanical Responses and Assessment of Fatigue Life for Submarine Suspended Pipelines

Abstract As an essential component for the transportation of oceanic oil and gas supplies, it is crucial to ensure the efficient operation of submarine pipelines. The fatigue failure of submarine pipelines occurs frequently under the combined effects of currents, waves and soil. Firstly, a pipe-soil interaction suspended pipeline model was developed, which could be used to simulate the mechanical behavior of pipes and the dynamic response of the combined loads of waves and currents. Then, the effects of soil properties, current direction and suspended length on the stress distribution and dynamic mechanical response of submarine suspended pipelines were investigated. In addition, the vibration characteristics of suspended pipelines affected by soil were revealed. At last, according to the vortex-induced resonance evaluation and fatigue life assessment method, the critical length of suspended pipelines for the Bohai sea was determined. The results show that the stress change in the center of the suspended section reaches the most significant for the pipeline with a length of less than 20m. When the suspended length exceeds 20m of the pipeline, the connection between the suspended section and the buried section shows the most dramatic stress fluctuations. Meanwhile, the cumulative damage of the submarine suspended pipeline entering the soil becomes the maximum, and fatigue failure often occurs in this position. The results are expected to provide an important theoretical basis in safe operation and repair decision of submarine pipeline.