Buried pipelines may be subjected to various complicated combinations of forces and deformations. This may result in localized curvature, strains, and associated deformations in the pipe wall. As a result, wrinkles may form. The wrinkled pipeline may then develop a fracture and even rupture in the pipe wall and lose its structural integrity if it is subjected to further sustained deformation. An NPS 10 field line pipe ruptured due to tearing in the pipe wall in the wrinkle region.
It was felt that the wrinkle was subjected to shear deformation that resulted in tearing type rupture. Numerical study using non-linear finite element (FE) method was carried out to study the possible loaddeformation history that may cause this type of failure. A detailed FE model was developed and analyzed to study the behavior of a wrinkled pipeline subjected to axial and shear deformation. The study shows that the combination of axial and shear deformations can introduce tearing type rupture in the wrinkle region the way the NPS10 field line pipe ruptured. This paper discusses the FE modeling technique and the results obtained from the FE analysis.
Field observations of buried pipelines indicate that it is not uncommon for geotechnical movements to impose large displacements on buried pipelines resulting in large localized deformations, strain, and curvature in the pipe wall. Such displacements may be associated with river crossings, unstable slopes, or regions of discontinuous permafrost. Often the deformation of the pipe wall results in local buckling and, in its post-buckling range of response, wrinkles develop rapidly and can be of significant magnitude. This can occur under loading conditions that may be idealized as combinations of variable internal pressure, compressive axial load, shear load, and moment.
