Analytical solution for controlled lateral buckling of unburied subsea pipelines

Unburied subsea pipelines designed to operate under high temperature and high pressure (HT/HP) conditions tend to relieve their axial compressive force by forming lateral buckles. Uncontrolled lateral buckling can lead to pipeline failure, such as collapse. Thus, controlled lateral buckling is an effective and inexpensive method to accommodate axial thermal expansion and to control pipeline lateral buckling. In this study, analytical solutions for uncontrolled and controlled lateral buckling of unburied subsea pipelines are derived. And the interaction between two adjacent buckles for controlled lateral buckling is considered. The typical behaviors of uncontrolled and controlled lateral buckling with different lengths of feed-in zone are illustrated and analyzed. The effects of length of feed-in zone and lateral soil resistance on controlled lateral buckling are also presented. The results show that shorter length of feed-in zone and smaller lateral soil resistance will lead to smaller lateral buckling amplitude, maximum bending moment and maximum axial compressive stress. Therefore, reducing the length of feed-in zone or lateral soil resistance can be an appropriate method to be used to control lateral buckling. Finally, the analytical solutions are validated by use of the finite element modelling. The analytical results show good agreement with finite element analysis results.