Buckling failure analysis for buried subsea pipeline under reverse fault displacement

Buckling failure analysis of buried subsea pipeline under reverse fault displacement was investigated by the Vector Form Intrinsic Finite Element method in this paper, considering nonlinear soil–pipeline interaction in slit with sand and the multifold nonlinearities of nonlinear material, large deformation, large displacement and self-collision/contact. Two typical conditions discussed were the operation condition and the empty waiting state during installation, maintenance, and operation. Effects of soil properties, pressure loadings, diameter–thickness ratios and dip angles on local buckling formation, tensile strain and cross-sectional distortion were investigated. The results show that subsea pipelines obtain a large deformation capacity and the flexure curve shape is usually S-shape. The external pressure is more unfavorable than the internal pressure since it aggravates the compression strains but alleviates the tension strains. A small fault dip angle results in serious axial compression and can lead to local collapse in the empty waiting states. For big diameter–thickness ratios or great pressure level, external pressure will cause local collapse and even buckle propagation along the pipeline. Seven different modes of collapse and propagation are discovered in the empty waiting state. They can be classified by the first collapse location, buckle propagation direction and further propagation sustainability. The cross-sectional shapes after collapse and during propagation are mainly determined by the compression or tension state around the circum. These results can be used for the development of performance-based design methodologies for buried subsea pipelines.