Seismic Resiliency Evaluation of a Structural Cured-in-Place Pipe Liner for Water Mains

This paper presents the results of a seismic resiliency evaluation program of water mains lined a structural Cured-in-Place Pipe (CIPP) technology, which was used for deteriorated legacy water main renewal and strengthening against earthquake and natural hazard effects. This CIPP product is a composite lining consisting of an inner and outer layer or jacket, produced by circular weaving of continuous textile yarns, impregnated with an epoxy. This product is used to renew water mains by insertion at access pits, without the need for complete excavation of the pipe to be replaced, and was evaluated through a series of large-scale tests at Cornell University's Large-Scale Lifelines Laboratory, ultimately involving large-scale fault rupture. During the fault rupture test, the CIPP-lined water main was progressively subjected to very large tensile and bending loads, resulting in the water main failure due to joint opening, until debonding and full detachment of the CIPP from the water main, leading to extensive extension and bending of the CIPP. Debonding loads of at least 120 kN were evaluated by means of direct tension testing on CIPP-lined water mains, with lining extension at a water main joint of at least 60 mm prior to debonding. Despite such large deformations the product remained structurally sound and retained water pressure as no water leakage was observed. Post-fault-rupture testing performed on liner samples taken from the highest deformation joint area indicated that residual mechanical properties were similar to pristine liner properties.