On the buckling propagation and its arrest in buried offshore pipeline crossing strike-slip fault

Abstract

This study focused on buckling propagation and its arrest in buried offshore pipelines crossing strike-slip faults. A buried offshore pipeline with integral arrestors was analyzed using nonlinear vector-form-intrinsic-finite-element-method-based shell elements and modified soil springs. The effects of different external pressures on structural response were investigated. Integral arrestors with different design parameters were tested to prevent flattening and flipping propagation. The results showed seven or five fluctuations in the flattening parameters with alternating orthogonal directions along the pipeline. These fluctuations led to multi-failure modes, including S-shaped and Z-shaped flexures, two local collapses followed by flattening propagations, and a single local collapse followed by flipping propagation. Integral arrestors should be designed specifically to provide sufficient local bending rigidity in the circumferential direction. The arrest mode of flattening propagation is stopping the earliest fluctuations whilst that of flipping propagation is stopping the earliest fluctuations and depressing the downstream reverse ovalities. For the same arrestor thickness, the smallest effective arrestor length to stop flattening propagation was significantly less than that for flipping propagation. The arrest is temporary because of gross deformation of cross-sections at integral arrestors or the downstream pipes, and secondary failure accidents are likely to occur with any external perturbation.