Modeling Time-Dependent Behavior of Medium-Density Polyethylene Pipes

Medium-density polyethylene (MDPE) pipes are widely used for gas transmission and distribution systems. The behavior of the pipes buried in the ground is governed by soil–pipe interaction. MDPE possesses a time-dependent material property that influences the pipe–soil interaction over time. The current industry practice to account for the time-dependent effect uses secant moduli to calculate the short-term and long-term responses. This method ignores the effect of loading rate, which can have a significant effect on the pipe responses. In the current study, a rigorous finite-element (FE) analysis is employed to investigate the effect of the rate of loading on the pipe behavior. An FE modeling framework for MDPE, developed earlier by the authors, is employed in this study. Two problems, one on a conventional buried pipe subjected to ground and surface load and the other on a pipeline subjected to rate-dependent lateral ground movement, are considered. Based on the investigation, a feasible method of accounting for the time-dependent behavior of MDPE for the pipe–soil interaction problems is developed.