Structural analysis methods used in the design of buried pipelines for the discontinuous permafrost regions need to handle the unique conditions that can arise; in particular thaw subsidence and frost heave. As a chilled gas pipeline traverses from a frost stable soil zone to a frost susceptible zone, frost bulbs are formed around the pipe and cause the pipeline to heave. If there is significant differential heave, pipe bending across the interface between these two zones could result in pipe strains exceeding design limits, or in extreme cases, buckling or tensile fracture.
For pipelines subjected to geotechnical hazards, characterization of strain demand is an integral part of the strain-based design process. This paper describes a simplified finite element model that was developed to predict compressive and tensile strain demand of gas pipelines subjected to frost heave. By using features that are typically available in general-purpose finite element analysis software, the proposed pipe-soil interaction model addressed issues that are essential for predicting pipeline strain demand. These issues include pressure-dependent heave displacement, and geometrically non-linear load-displacement response of steel pipe. The simplified model was validated by comparing model predictions to the Caen tests.
Author: Chen, Q
Publisher: The Twenty-fourth International Ocean and Polar Engineering Conference, 15-20 June, Busan, Korea
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