Beam-on-spring modeling of buried MDPE pipes in sand subjected to lateral loads at a pipe junction

Abstract

Buried pipelines in landslide areas may experience excessive stresses or strains that depend on a complex soil-pipe interaction. The simplified beam-on-spring analysis is recommended in current pipe design guidelines to assess buried pipes subjected to ground movements. The recommended method was developed based on observations of buried steel pipes. The applicability of the methods was not evaluated for Medium-Density Polyethylene (MDPE) pipes that are widely used in gas distribution systems. This paper evaluates the applicability of the beam-on-spring modeling technique for MDPE pipes experiencing relative ground movements observed in laboratory tests. Finite element analysis was performed, modeling the pipes as beams and the soil reactions using the pipe-soil-interaction (PSI) elements in Abaqus, representing springs. The study reveals that while the beam-on-spring analysis can simulate the pipe responses, the spring parameters recommended in the design guidelines are not applicable to buried MDPE pipes. The required magnitudes of peak axial and lateral spring forces and the yield displacements for MDPE pipes are larger than those recommended in the design guidelines. Based on the simulation of experimentally measured pipe responses, modifications to the recommendations of existing design guidelines for estimating the spring parameters are proposed for application to the MDPE pipe assessment.

Keywords

• Gas distribution pipes
• Medium density polyethylene (MDPE)
• Ground movements
• Lateral branch
• Beam-on-spring