Effects of Axial Relative Ground Movement on Small Diameter Polyethylene Piping in Loose Sand

Auchib Reza,Ashutosh Sutra Dhar

doi:10.3390/infrastructures6120168

Auchib Reza, Ashutosh Sutra Dhar

Open Access

https://doi.org/10.3390/infrastructures6120168

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Journal: Infrastructures	Publication Date: Dec 1, 2021
License type: CC BY 4.0

Affiliation: Memorial University of Newfoundland

Abstract

Small diameter (42 mm) medium density polyethylene (MDPE) pipes are widely used in the gas distribution system in Canada and other countries. They are sometimes exposed to ground movements resulting from landslides or earthquakes. The current design guidelines for evaluating the pipes subjected to ground movement were developed for steel pipes of larger diameters and may not apply to flexible MDPE pipes. This paper evaluates 42 mm diameter MDPE pipes buried in loose sand under axial relative ground movement for developing a design method for the pipes. MDPE is a viscoelastic material; therefore, the behaviour of MDPE pipes exposed to landslides would depend on the rate of ground movements. In this research, full-scale laboratory tests were conducted to investigate the responses of buried pipes under various rates of relative axial displacement. Finite element modelling of the tests was used to interpret the observed behaviour using the continuum mechanics framework. The study revealed that the pulling force on the pipe depends on the rate of relative ground displacement (pulling rate). The nondimensional pulling force possessed a nonlinear relationship with the pulling rate. A rate-dependent interface friction angle could be used to calculate the maximum pulling forces using the conventional design guidelines for the pipes in loose sand. Based on the pulling force, the pipe wall strains can be estimated using the methods available for larger diameter pipes.

Highlights

Pipelines are a safe, reliable, and environmentally friendly way of transporting liquids and gas
When the direction of ground movement is parallel to the pipe axis, the pipelines are subjected to longitudinal forces resulting from the friction between the pipe and the moving ground, causing axial strains in the pipe wall
The longitudinal force along the pipeline depends on the relative axial displacement between the soil and pipe, which is evaluated in the current design practices (i.e., [2,3,4]) based on an evaluation of the normal stresses acting on the pipe wall and the frictional characteristics of the soil–pipe interface

Summary

Introduction

Reliable, and environmentally friendly way of transporting liquids and gas. Reza and Dhar [21] examined 60 mm diameter MDPE pipes further, monitoring the length of shear strength mobilization during axial pullout and investigating the pulling rate effect on the pullout resistance. Finite element analysis was employed to capture the features that could not be measured during the tests, including the contributions of the soil, pipe, and interface parameters to the pipe behaviour It revealed that the interface friction angle depends on the pulling rate due to the time-dependent property of the pipe material. The current study focuses on the assessment of 42 mm diameter MDPE pipes in loose sand subjected to axial relative ground movement. The objective of the current study is to develop a database and an improved understanding of the behaviour of small diameter MDPE pipelines subjected to axial ground movements. The applicability of the method proposed in Reza and Dhar [21] for the prediction of pipe responses was examined for the 42 mm diameter pipes

Test Facility

Experimental Force–Displacement Responses

Finite Element Analysis

Comparison of Results

Strain Calculations

Findings

Conclusions