Assessment of Axial Pullout Force for Buried Medium-Density Polyethylene Pipelines

Abstract

The maximum axial force on a pipeline subjected to axial ground movement is commonly calculated using a design equation developed without proper consideration of soil-pipe interaction. The authors’ recent work revealed that soil-pipe interaction significantly contributes to the axial pullout load, particularly for flexible pipes. In this study, a three-dimensional finite element (FE) analysis is used to explore the pullout mechanism of a buried medium density polyethylene (MDPE) pipe to develop a rational method of calculating the pullout forces for the pipe. The FE model is developed through validation with experimental data available in the literature for MDPE pipes. The study reveals that axial elongation and diameter reduction occur during axial pullout of the MDPE pipe. The normal stress on the pipe surface from the ground is affected by the axial elongation and the diameter reduction, which also depends on the relative stiffness of the pipe to the surrounding soil and the shear strength parameters of the soil. A simplified method to calculate the normal force for MDPE pipe under various ground conditions is developed using FE analysis for rationally assessing the ground resistance to the pipeline.