Performance Testing of Trenchless Wastewater Line Spot Repairs

Abstract

The University of Texas at Austin conducted a study for the City of Austin to evaluate the performance of commercially available trenchless spot-repair methods in the City's wastewater pipelines. This paper reports short-term testing procedures and results for two epoxy resin repair methods that were a part of the study. Both methods of repair were proposed by the City of Austin Department of Water and Wastewater, and were field demonstrated in Austin on 200-mm (8-in.) unreinforced concrete wastewater lines. Each process uses remote control, cured-in-place techniques: one method employs a robot to prepare substrate surfaces and to inject epoxy into pipe defects; the other employs an inflatable rubber packer to form a continuous epoxy collar up to 0.6 m in length at the defect. The objective of the study was to evaluate and compare, by field sampling and laboratory testing, the structural integrity and watertightness of the repair processes. A small number of repair samples were obtained by excavation of actual damaged pipe repaired by each method. Tests of the repaired pipe yielded results for bond strength and watertightness of the repair, which differ sharply between the two methods. Possible causes of bond failure are discussed.