Failure mode analysis of X80 buried steel pipeline under oblique-reverse fault

As the main way of oil and gas long-distance transportation, buried pipelines will inevitably pass through the active fault zones. Fault displacement induced by earthquake, especially the oblique-reverse fault displacement, will cause large compressive, tensile and bending strain in the pipeline, resulting in buckling, rupture or warping, which seriously threaten the safety operation of pipelines. A 3-D numerical model considering the role of underground rock stratum was proposed for failure mode analysis of X80 buried steel pipeline under oblique reverse fault displacement. Referring to the engineering parameters of the Second West-to-East Gas Pipeline Project (China), the strain evolution of X80 steel pipeline for local buckling, tensile fracture and cross-section ovalization failure was obtained, and the effects of fault dip angle, pipeline diameter-thickness ratio, burial depth and internal pressure on the failure modes were discussed. Finally, according to the failure criteria of buried steel pipeline, the critical fault displacements corresponding to different failure modes were obtained, and the conversion relationships between different failure modes were further derived, which provide a reference for failure analysis and safety design of pipelines crossing oblique-reverse faults.