Critical Review of Axial Resistance in Buried Pipelines Subjected to Transient and Permanent Ground Deformations

Understanding the pipe-soil interaction effects at the pipe-soil interface of a buried pipeline is needed to estimate the stresses and strains on the pipeline subjected to longitudinal transient and permanent ground displacements during a seismic event. In general, pipe-soil interaction effects would be dependent on the actual displacement pattern, pipe-soil interface behavior, configuration of the pipe segments as well as joints, and available axial flexibility within pipe joints. In buried pipelines with uniform pipe barrels, such as in most continuous pipeline situations, axial resistance is primarily contributed by frictional and adhesive behaviors of the pipe-soil interface. However, in certain situations of continuous pipelines (e.g., flanged joints) and in segmented pipelines (e.g., bell- and spigot-type configurations), pipeline cross sections are typically larger than the regular pipeline barrel cross sections. Due to these configurations, the axial resistance in a pipe barrel does not develop solely from pure axial frictional and/or adhesive resistance on the pipe-soil interface. A bearing type resistance (e.g., passive resistance at the enlarged joints) would also be contributing to the axial resistance of the pipe. It should be noted that the maximum passive resistance that could be developed on the pipeline joint is also a function of the relative movement at the pipe-soil interface. While underestimating axial resistance for traditional non-seismic situations mostly yield conservative designs, such is not the case for seismic design conditions. Especially important is the axial resistance contribution in estimating the connection force demand arising from potential seismic hazards acting on a pipeline. Recognizing the importance of accurate estimation of the axial force connection demand on a buried pipeline from a design seismic hazard, a critical review of the approaches to estimate the axial resistance on a pipeline has been completed. This paper presents a summary of the current practice to estimate maximum axial resistance in a buried pipeline, critical review of the resistance components contributing to the axial resistance, and a proposed analytical approach to estimate the maximum axial resistance on a continuous or segmented pipeline with enlarged joints.