Soil Loads on Polyethylene Natural Gas Pipelines Subjected to Relative Axial Ground Displacements

The performance of buried natural gas pipeline systems in areas subjected to permanent ground displacements is an important engineering consideration since geotechnical hazards can be a major cause of damage to these utilities. Although pipe-soil interaction models exist, there is only limited experience with pipeline materials other than steel, and particularly in relation to polyethylene (PE). With this background, a detailed research program involving full-scale physical model testing of buried pipeline systems was undertaken, and performance of straight PE pipes subject to relative axial soil movement was investigated as a part of this work. A closed-form solution was derived to account the nonlinear material response of MDPE pipes subject to relative axial soil movement, and the analytical results are compared with the results obtained from the full-scale testing. This closed-form solution provides a rational framework to estimate the response of the pipe (level of strain, force) and even the mobilized frictional length along the pipe for a known amount of ground displacement. The approach, in turn, could be used in estimating the relative axial soil displacement needed for pipe failure, which is an important consideration in the evaluation of the field performance of MDPE pipe systems located in areas of potential ground movement.