Analytical solutions for lateral global buckling of deep-sea pipelines based on multi-stage soil resistance model

Abstract

The offshore oil and gas resources are mainly transported by deep-sea pipelines. In practice, the high temperature and pressure (HTHP) are applied on the pipelines, and large axial force is accumulated in the pipeline sections due to the influence of HTHP and the restriction of seabed soil. Once the axial force reaches the critical buckliong force, the pipeline will experience the lateral global buckling deformation, and lateral buckling threatens the safety of the pipeline system. The former analytical solutions of lateral buckling of deep-sea pipelines are usually based on the elastic-plastic soil resistance model, which has a difference with the practice. This paper improved the analytical solutions based on a more realistic multi-stage soil resistance. The analytical solution for solving the first-order buckling, which is developed from a first-order imperfection, and the analytical solution for solving the third-order buckling, which is developed from a first-order imperfection, are proposed, and the proposed two analytical solutions are more suitable for evaluating the lateral buckling deformation in engineering practice. According to the proposed analytical solutions, the peak value of the soil resistance enhances the critical buckling force. In addition, unlike the results according to the analytical solution based on elastic-plastic soil resistance model, the buckling force of the third-order buckling deformation is always higher than the first-order buckling deformation at the same temperature. That explains why the shift of buckling mode has not happened frequently and why the first-order more likely occurs in practice.