Study on the Applicability of Currently Used Soil-Pipe Interaction Equations for Segmented Buried Pipelines Subjected to Fault Movement

This study investigates the applicability of force-displacement equations suggested in currently used design codes, based on "Guidelines for the seismic design of oil and gas pipeline systems" of ASCE (1984)[1] as their main reference, to introduce the soil-pipe interaction for segmented type of pipeline systems. Hence, results of finite element method (FEM) analyses are verified by full-scale experiments on a segmented ductile iron pipeline with 93mm diameter and 15m length. Pipeline is installed at a 60cm depth from the ground surface in two types of sandy soil with different values of sub-grade reaction. Adopted fault is a reverse type which has an intersection angle of 60 degrees with pipeline and moves in three same steps to reach its total movement of 35cm. Findings reveal that the aforesaid interaction equations are basically developed for continuous pipelines and the effect of connection joints on the integrated structural behavior of segmented pipelines is not considered in them. Hence, suggesting them by currently used guidelines for seismic design of fault crossing segmented pipelines leads to overestimation of soil resistance against relative downward movement of pipeline in surrounding soil continuum.