Subsea Pipeline Walking: The Effect of a Bi-Linear Seabed Friction Model-Paper

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The paper examines how a bi-linear, elastic–plastic seabed friction response affects axial walking of subsea pipelines. Existing analytical methods generally treat pipe–soil friction as rigid–plastic, neglecting the displacement required to mobilise full resistance. The authors first use ABAQUS finite-element analyses to reproduce established predictions for walking driven by steel catenary riser (SCR) tension, seabed slope and thermal transients, confirming the numerical model’s agreement with existing solutions.<br /><br />They then incorporate axial friction mobilisation displacement into the analytical treatment. Analyses show that greater mobilisation displacement reduces pipeline walking and changes the axial force profile. For a sloping seabed, the authors derive an updated expression in which the rigid–plastic walking prediction is reduced by twice the mobilisation displacement per cycle. Numerical comparisons show that this correction also predicts walking driven by SCR tension and thermal transients.<br /><br />The proposed approach therefore extends conventional analytical design tools to represent a more realistic elastic–plastic soil response, while retaining a simple means of estimating walking rates. The study focuses on short pipelines and the three stated walking mechanisms; additional effects, such as slope combined with liquid hold-up, are identified as potential subjects for future work.

Keywords

subsea pipelines

axial walking

elastic-plastic seabed friction

pipe-soil interaction

mobilisation displacement

finite element analysis

ABAQUS

steel catenary riser tension

seabed slope

thermal transients