Deepwater pipeline global walking refers to the phenomenon that a pipeline, subjected to multiple start-up/shut-in thermal and pressure cycles, gradually moves toward one direction. The fundamental mechanism of walking is complex and is affected not only by the thermal/pressure loading and pipeline structural behavior (e.g., lateral buckling), but also by the pipeline-soil interaction (PSI) which varies both spatially and temporally. The complex nature of walking makes the prediction of pipeline walking a challenging task, and the prevention of pipeline walking, which may be unnecessary, requires significant financial budget and increased risk exposure from offshore installations. Therefore, the motivation of this paper is to offer insights into PSI to help the engineering design of pipeline walking. The objectives of the paper are to re-visit the axial soil stiffness model (characterized by the axial mobilization displacement) recommended in the SAFEBUCK guideline and to propose a new model for the axial mobilization displacement for walking analysis. The recommended mobilization displacement is based on a simple energy method and is calibrated with a PSI analytical model, SAFEBUCK JIP model tests, in-house proprietary tests, and test results available in the literature.
Jinbo Chen, David White, Chris Hadley, Kevin Ouyang, Jason Newlin, Shuang Hu, David Bruton and Meng Luo
Keywords: pipe-soil interaction, walking, axial stiffness, mobilization displacement
Publisher: DFI