Field performance monitoring of a sliplined watermain

A field instrumentation system was successfully installed to monitor the performance of a HDPE sliplined 83-year old 910-mm diameter cast iron watermain in Ottawa. This monitoring system included various sensors to measure strains in both pipe walls, the internal hydrostatic pressure, the in-situ soil moisture contents and the temperature profiles in the soil backfill. The work included the insertion of sections of the HDPE pipe with sensors and cables attached during the rehabilitation of the entire 1.5-km water line. The installation therefore required the collaborative effort of the research team, the owner, the consultant and the general contractor for the rehabilitation project. About 50% of the installed strain gauges and about 95% of the installed thermocouples survived the installation process. The preliminary results based on the first four-month data show that the measured strain ranges in the HDPE pipe were within the ranges predicted using the short- and long-term modulus of elasticity of the HDPE material. The results have confirmed the assumption that bonding at the interfaces between the HDPE and the grout and between the grout and the cast iron pipe was negligible. The results also show that the granular ?C? backfill material above the pipe had little insulation capacity and that the soil around the watermain is likely to freeze over the winter.Peer reviewed: YesNRC publication: Ye