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The objective of this paper is to derive analytical solutions for buckle propagation and fracture of a pipeline subjected to hydrostatic pressure. Rigid-plastic approximations are used to determine the plastic deformation of the pipeline. Because the transition zone of buckle propagation occurs over a finite region, the plastic collapse of a pipeline of finite length is first considered. The deformation model for the finite-length pipe is then extended to buckle propagation in pipelines of infinite length. Closed-form solutions for the steady-state buckle propagation pressure are derived by considering plastic work dissipation due to both circumferential bending and longitudinal stretching. Analytical predictions of the propagation pressure are within 5% of the experimental data on mild steel pipes. The present model is an improvement over previous analytical solutions, in which the longitudinal stretching resistance of the pipeline was ignored. It has been found that the plastic work due to longitudinal stretching accounts for 20% to 30% of the propagation pressure in the pipelines considered in this study. Finally, approximations of the maximum strains are made from the assumed deformation field. Fracture criteria based on the uniaxial rupture strain or the combinations of biaxial rupture strains are suggested to predict cracks in the pipe. INTRODUCTION When damaged locally by dropped anchors and other offshore drilling equipment, a pipeline may experience buckle propagation at hydrostatic pressures that are lower than the elastic buckling pressure for a perfect cylinder. As the pipeline buckles into a circumferential dog-bone pattern, it undergoes large plastic deformation. Plastic strains at the outer lobes of the buckled pipeline may be very high, exceeding the fracture strain, and result in cracks or leaks in the pipeline. Pipeline rupture due to a propagating buckle is referred to as a wet buckle (Kyriakides and Babcock, 1980). Because the cleaning and repairing processes after wet buckling are costly and time-consuming, several steps have been taken to design pipelines against propagating and wet buckles.
- Well Completion > Hydraulic Fracturing (1.00)
- Reservoir Description and Dynamics (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Offshore pipelines (0.88)
The objective of this paper is to derive analytical solutions for the indentation, buckle propagation, and fracture of a plastically deforming pipeline. Rigid-plastic approximations are used to find the plastic deformation of a collapsed pipeline. Circumferential bending and longitudinal stretching are the only two dominant load resisting mechanisms considered in evaluating the rate of plastic work dissipation. The load-deformation response of the pipeline is characterized by a bending term which is independent of the deformation and a membrane term which increases linearly with pipeline deformation. It is shown that very long pipelines are susceptible to buckling, while longitudinal stretching resistance stabilizes plastic collapse in short pipelines. A closed-form solution for the steady-state buckle propagation pressure of an infinitely long pipeline is derived from this model. Analytical predictions of the propagation pressure are within 5 % of the experimental data. The plastic work due to longitudinal stretching accounts for 20–30 % of the propagation pressure, and the present model is an improvement of previous approximations which ignored longitudinal stretching. Finally, approximations of the maximum strains are made from the deformation field and a fracture criterion based on a critical rupture strain is used to predict fracture of a steel pipeline. INTRODUCTION When damaged locally by dropped anchors and other offshore drilling equipment, a pipeline may experience buckle propagation at hydrostatic pressures that are lower than the elastic buckling pressure for a cylinder. As the pipeline buckles into a circumferential "dogbone" pattern, it undergoes large plastic deformation. Plastic strains at the outer lobes of the buckled pipeline may be very high, exceeding the fracture strain. and result in a crack or leak in the pipeline. Pipeline rupture due to a propagating buckle is often referred to as "wet buckle" (Kyriakides and Babcock, 1980).
- Well Completion > Hydraulic Fracturing (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Offshore pipelines (0.46)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Piping design and simulation (0.34)