Engineering measures for preventing upheaval buckling of buried submarine pipelines

Abstract

In-service hydrocarbons must be transported at high temperature and high pressure to ease the flow and to prevent the solidification of the wax fraction. The high temperature and high pressure will induce the additional stress in the pipeline, which results in the upheaval buckling of the pipeline. If such expansion is resisted, e.g., by the frictional effects of the foundation soil over a kilometer or of a pipeline, the compressive axial stress will be set up in the pipe-wall. When the stress exceeds the constraint of the foundation soil on the pipeline, suddenly-deforming will occur to release the internal stress, similar to the sudden deformation of the strut due to stability problems. The upheaval buckling may jeopardize the structural integrity of the pipeline. Therefore, effective engineering measures against this phenomenon play an important role in the submarine pipeline design. In terms of the pipeline installation and protection measures commonly used in Bohai Gulf, three engineering measures are investigated in great details. An analytical method is introduced and developed to consider the protection effect of the anti-upheaval buckling of the pipeline. The analysis results show that the amplitude of the initial imperfection has a great effect on the pipeline thermal upheaval buckling. Both trenching and burial and discrete dumping are effective techniques in preventing the pipeline from buckling. The initial imperfection and operation conditions of the pipelines determine the covered depth and the number of layers of the protection measures.

Static and dynamic analysis on upheaval buckling of unburied subsea pipelines

“…Loading time is a significant factor in dynamic analysis especially when dynamic effect is prominent (Liu et al, 2012). As a result, the influence of loading time on snap buckling is discussed first.…”

Reliability Analysis of Subsea Pipeline against Upheaval Buckling

“…When the lateral restraint of a trenched pipeline exceeds the vertical restraint force against vertical displacements created by the pipeline submerged weight, the pipeline bending stiffness, and the covered soil resistance, the pipeline tends to move upward, and considerable uplift movement may occur. This phenomenon is called upheaval buckling [6,7,8], which is a failure mode that has to be taken into account in the design of buried and trenched pipelines. The pipeline moves upward due to upheaval buckling, leading to possibly unacceptable local plastic deformations or collapse or vulnerability to fishing gear and other third-party activities.…”