Numerical Analysis on Seismic Response of Buried Pipelines with Defects in Liquefiable Sites

Abstract

The rapid expansion of long-distance oil and gas pipeline networks has led to increased pipeline crossings of high-seismic-risk regions. Soil liquefaction substantially degrades pipe–soil interaction restraint, triggering significant axial deformation of buried pipelines. In addition, local corrosion defects generated during long-term service reduce pipe wall cross-sectional area and induce severe stress concentration, considerably exacerbating pipeline failure hazards under seismic conditions.In this study, a finite element numerical model is established to investigate the seismic response of buried pressure pipelines with local corrosion defects in liquefiable soils. Solid elements are employed to discretize the pipeline structure, while nonlinear spring elements are adopted to characterize soil confinement effects. The stiffness degradation of soil in liquefied zones is realized by reducing the stiffness of soil springs, which accurately simulates the attenuation of soil bearing capacity during liquefaction. The maximum axial strain is selected as the critical evaluation index to quantify the tensile and compressive deformation of pipelines during liquefaction-induced uplift. By comparing the calculated axial strain with the material yield strain, the plastic development degree and bearing capacity degradation of defective pipelines can be quantitatively identified. Parametric analyses are systematically conducted to explore the effects of liquefied zone length, corrosion defect depth, and internal operating pressure on pipeline axial strain responses.The numerical results demonstrate that the expansion of the liquefied zone weakens pipe–soil constraint stiffness and enlarges pipeline axial deformation, with the maximum axial strain increasing monotonically with liquefied zone length. Deepened corrosion defects significantly reduce the local structural stiffness of the pipe wall and aggravate strain concentration at defect locations. Moreover, elevated internal pressure raises the initial circumferential stress of pipelines, which further amplifies the axial strain of defective sections under seismic excitation. This study provides a reliable theoretical reference for the seismic safety assessment and risk mitigation of defective buried pipelines in liquefaction-prone areas.