Comparison Testing of Reinforced Non-Circular CIPP Liners

Abstract

The use of cured-in-place pipe (CIPP) reinforced liners in non-circular applications has become more common as the technology has developed, especially with the implementation of design standard ASCE MOP 145 and its ability to specifically address non-circular scenarios. The QA/QC testing of non-circular reinforced liners creates unique challenges as the existing testing standards have been created for flat plate testing or round pipes with a consistent radius throughout. Non-circular pipe samples often combine characteristics of both circular and flat samples. Adding to the difficulty, the use of reinforced lining system (commonly utilized in larger non-circular sewers) requires that test samples be orientated in the correct alignment to obtain material properties in the circumferential direction. The complexities of sampling and testing of non-circular liners has resulted in significant uncertainty with testing results on these critical liners. To gain some clarity, Insituform Technologies (Insituform) and Stantec Consulting Ltd (Stantec) have undertaken testing on liners installed as part of a non-circular large diameter contract recently completed for the City of Winnipeg (City). Sample sets which included plate samples and direct cut samples, both with and without backing plates, were prepared from five large non-circular liner inversions. These samples were sent to three different testing labs in North America for testing using both ASTM D790 and ISO 11296-4. The results of the findings are presented along with lessons learned and suggestions for best practices going forward.