Analytical study on anchor force for pipeline walking laid on inclined seabed

Abstract

Unburied subsea pipelines under cyclic thermal loading are often prone to axial walking. The axial movements accumulate over operational cycles, which can lead to potential failure at the mid-line or end connections. Anchoring is a commonly adopted method to -control pipeline walking, however, it requires accurate estimation of anchor force for efficient pipeline design. In view of this, the present study proposes a calculation method for anchor force of full mobilized lengths for different anchoring positions. Furthermore, the anchoring mechanism for partial mobilized lengths is analyzed. The anchor force is then determined using a strain diagram method for partial mobilized lengths. Finally, an analytical solution for anchor force based on the strain diagram method is derived and validated against finite element results. The results show that the mobilized length ratio of pipeline anchor force increases with the loading temperature and seabed slope but decreases with the pipeline length. The proposed analytical solution for anchor force which has advantages over traditional analytical solutions can comprehensively consider the effects of pipeline parameters, load parameters, and contact parameters.