Flexible Polyethylene Pipelines for Seismic Resilience

Polyethylene pipe included in Christchurch water and gas reticulation systems performed extremely well in the 2010/11 Canterbury earthquakes. Based on this performance, polyethylene pipe has been used more extensively for repair and reconstruction works. This has required careful consideration of aspects of the design and construction to ensure that the high level of performance is replicated for the wider range of applications.

This paper outlines the design and construction procedures and processes employed by CCC and SCIRT to ensure effective performance in challenging soil conditions for large diameter gravity and pressure pipelines. These processes were utilised on the PM105 project, which included 1940m of DN710 polyethylene pressure main and 1500m of DN800 and DN900 polyethylene trunk sewer. 

The increased use of polyethylene pipe to provide seismically resilient solutions requires careful consideration of a range of first principle design requirements ranging from ground conditions, material specification and potential failure modes of the pipelines. 

Construction control is an essential component of ensuring the design performance of polyethylene pipelines. Particular attention is required to the material quality and the integrity of welded joints.