Numerical simulation of the seismic response of corroded pipelines crossing faults

Buried steel pipelines serve as core infrastructure for oil and gas transportation. Their corrosion-fault coupling failure under seismic fault activity poses a severe threat to energy security. The present study focuses on an X52 pipeline. The establishment of a finite element model of an internally corroded pipeline crossing a normal fault is based on the ABAQUS finite element software. By comparing the strain responses of corrosion-free and corrosion-defective pipelines, the failure mechanism under the coupled action of normal faults and corrosion is revealed. Through contrasting the failure modes and corrosion locations of reverse-faulted pipelines, the most vulnerable position of corrosion-affected pipelines under normal faulting is verified. Additionally, the study analyzes the influence of stepwise corrosion-characterized by the simultaneous evolution of three parameters: corrosion depth (h/t), corrosion width (w), and corrosion length (l)-under positive faulting on the strain behavior and failure mechanisms of pipelines. The results indicate that local corrosion defects significantly intensify the concentration of compressive strain in the pipeline, triggering local buckling, thereby weakening the pipeline's overall deformation capacity and stability. Compared with tensile failure, normal fault action is more likely to cause compressive failure of the pipeline. The positioning of the corrosion defect at the peak compressive strain region on the pipe crown, consistent with the worst-case principle, can facilitate the accurate revelation of the pipeline failure mechanism under normal fault action. This, in turn, provides a basis for the optimisation of the pipeline's anti-buckling design. Escalation in corrosion stage expedites the deterioration of the pipeline's mechanical performance, evidenced by an earlier onset and more accelerated progression of local buckling, consequently diminishing the pipeline's capacity to resist fault displacements. The present study reveals the critical influence of more realistic corrosion forms and fault coupling effects on pipeline failure behavior, providing theoretical support for the safety assessment and seismic design of corroded pipelines in practical engineering.