Computational Modelling of Unburied Offshore Pipelines Crossing Active Tectonic Faults-Paper

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The study uses three-dimensional nonlinear finite-element simulations to assess unburied steel pipelines resting on soft clay and crossing active offshore faults. The models account for nonlinear soil–pipe interaction, steel behavior, large deformations, operational pressure, and possible buckling. The authors examine normal and reverse faulting and vary fault dip, pipe-wall thickness, soil strength with depth, and pipeline pressurization.<br /><br />Under normal faulting, the pipeline withstands fault displacements of up to 5 m with axial strains remaining below the adopted safety limits and no evident buckling. Strains increase with steeper fault angles and thinner pipe walls. Internal operating pressure also increases the strain demand compared with unpressurized conditions.<br /><br />Reverse faulting produces a substantially more hazardous response. Compression can trigger global buckling, followed by local buckling and concentrated deformation. For the modeled cases, buckling occurs at approximately 0.4–0.6 m of fault displacement, corresponding to earthquake magnitudes of roughly 6.6–6.8. Thinner-walled pipes are particularly vulnerable to local wrinkling and strain localization.<br /><br />The results show that fault type strongly governs pipeline performance: normal-fault displacement may be accommodated safely in the scenarios studied, whereas relatively modest reverse-fault displacement can lead to failure. The authors emphasize the importance of accounting for fault geometry, pipe thickness, and operating conditions when routing and designing offshore pipelines.

Keywords

three-dimensional nonlinear finite-element simulations

unburied steel pipelines

soft clay

offshore faults

soil-pipe interaction

normal faulting

reverse faulting

pipeline buckling

operating pressure

pipe-wall thickness