Effects of Surface Live Loads on the Behaviour of Decommissioned Pipelines: Numerical Modelling and Analysis
Date
2020-09-11
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Abstract
Steel pipelines are used throughout the energy industry as the primary means of transporting natural gas, crude oil, and petroleum-related products and chemicals. When a pipeline permanently ceases operation, it is decommissioned and may be abandoned and left in place underground. Over time, the pipeline will degrade due to environmental and in-situ conditions. Corrosion is the principal mechanism for the degradation of decommissioned pipelines. Corrosion and degradation reduce the material strength and stiffness of the pipe section. Degraded pipes may no longer be capable of bearing the loads imposed by groundcover and surface vehicles. Potential collapse of decommissioned pipelines poses a risk to both the public and the environment. The static structural response of buried decommissioned pipelines subjected to surface live load was analyzed using the finite element analysis software ABAQUS. The buried pipeline was modelled within a uniform soil block, eliminating the effects of boundary conditions. Soil-pipe interaction was considered assuming a frictional slippage contact definition. The pipe was subjected to both overburden dead load and surface live load. Surface live load was taken as the maximum axle load of a CL-800 truck using an appropriate dynamic loading factor. The effects of various in-situ parameters including the burial depth, pipe diameter, and wall thickness were investigated. The investigation further expanded to analyze the effects of surface loading magnitude, geometry and direction of travel, along with performing an ultimate limit states analysis. The primary results indicate that for reasonable burial depths, soil stiffness, pipe diameter, and wall thickness, the maximum stresses lie below the elastic limit. However, for shallow burial depths, local deformations and stresses become significant and increase rapidly.
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Keywords
corrosion, finite element analysis, pipeline
Citation
Walsh, C. (2020). Effects of Surface Live Loads on the Behaviour of Decommissioned Pipelines: Numerical Modelling and Analysis (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.