Finite Element Modeling of Axial-Vertical Interaction Behavior of Buried Pipelines in Dense Sand
- Sheikh Sharif Ahmed (University of California, Davis) | Sheikh Shahriar Ahmed (State University of New York at Buffalo)
- Document ID
- International Society of Offshore and Polar Engineers
- International Journal of Offshore and Polar Engineering
- Publication Date
- March 2019
- Document Type
- Journal Paper
- 70 - 77
- 2019. The International Society of Offshore and Polar Engineers
- axial-vertical interaction, modified Mohr-Coulomb model, numerical analysis, dense sand, Buried pipeline, Abaqus
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Three-dimensional finite element (FE) analysis of axial–vertical interaction behavior of buried pipelines in dense sand is performed. The commercially available FE software package Abaqus/Explicit is used to accommodate large displacement and to avoid convergence problems. In addition, a user subroutine is utilized to capture the pressure dependent stress–strain behavior of dense sand. The numerical model is verified by comparing the results with experimental results available in literature. The effects of pipeline burial ratio, angle of attack, and pipeline surface roughness are discussed. A normalized axial–vertical interaction diagram is also proposed.
The use of subsea buried pipelines for transporting high-pressure and high-temperature hydrocarbons has increased rapidly in recent years all around the globe. The safe operation of such buried pipelines is a prime concern for the oil and gas industry. The minimization of adverse effects on the mechanical response and integrity of pipelines as a result of geohazards is one of the major challenges. Permanent ground deformation as a result of geohazards such as landslides and earthquakes can cause relative movement between the pipeline and surrounding soil, which may impose geotechnical loads onto the pipe. The geotechnical load onto the pipe increases the level of stress and strain in the pipeline, which may hinder the safe operation of the pipeline system.
In the current engineering practice (e.g., American Lifelines Alliance, 2001; Honegger and Nyman, 2004), the soil/pipe interaction is idealized by structural modeling. The mechanical response of pipeline is assessed by specialized beam elements, and the soil behavior is evaluated by discrete nonlinear springs with load-displacement relationships provided for principal directions (i.e., longitudinal or axial, lateral or horizontal, vertical upward, and vertical downward). These springs are independent and cannot account for the combined effects during a three-dimensional (3D) soil/pipe relative movement (i.e., movement under oblique loading) despite the fact that, in reality, the movement can occur in all three directions simultaneously. The oblique soil/pipe interaction cases include axial–lateral, axial–vertical, and lateral–vertical soil/pipe relative movements, which are specific cases of a general 3D (axial–lateral–vertical) soil/pipe relative movement.
|File Size||1 MB||Number of Pages||8|