Validating “Fully Structural”: Development and Testing of a New Carbon Composite in situ Pressure Barrier for Trenchless Rehabilitation of Small-Diameter Pressure Pipelines

Abstract

Trenchless technologies similar to Cured in Place Pipe (CIPP) continue to be embraced for pipeline repair and rehabilitation since the first installation in the early 1970’s. The varying levels of repair from corrosion mitigation, leak protection, to semi-structural and fully structural repair systems require alternating levels of strength, stiffness and durability properties under loading conditions. ASTM F1216 is widely used in water and wastewater pipelines to determine the required thickness of composite liners for semi structural (class II and III) and fully structural (class IV) repair/rehabilitation systems as defined in AWWA M28 Appendix A. It is important to understand the initial assumptions and limitations of these design guidelines. The ASTM F1216 was developed for felt-epoxy CIPP systems that demonstrate quasi-isometric properties. Likely because of this, longitudinal loading is not considered in this design process. As CIPP products continuously develop to resist increasing external and internal loading conditions, stronger materials are used in specific orientations to meet those increasing demands. When unidirectional glass and carbon reinforced polymers (GFRP and CFRP’s) are used to meet the demands of high internal and external loading conditions, additional design criteria are required to cover both hoop direction and longitudinal loading. These additional design criteria extend beyond ASTM F1216. Thus, theoretical calculations from existing and developing pipeline standards, and experimental validation is required to demonstrate the capabilities of new technology utilizing high strength and high stiffness materials like CFRP. This paper will address the additional design considerations appropriate for CFRP pull-in-place rehabilitations and the validation of a fully structural CFRP in situ pressure barrier for small diameter (six to fourteen inch) pressure pipe.