LAUSR

Cast iron pipe breaks are an increasing concern as water distribution networks installed in the nineteenth and twentieth centuries continue to deteriorate. Breaks can be caused by a number of factors, but two of the most critical are corrosion and differential ground movement causing bending. In this study, two tests were conducted to investigate the application of distributed fiber optic sensors to measure the influence of simulated corrosion pits and differential ground movements on buried pipe behaviour to provide information on the impact of corrosion as part of a larger monitoring and assessment strategy. A 154 mm-diameter steel pipe was used as both a ‘control’ specimen and a ‘deteriorated’ specimen after two 25.4 mm (1 inch)-diameter holes were drilled into the pipe to simulate corrosion pits. Distributed fiber optic strain sensors were installed longitudinally along the pipe at the crown, invert, and springlines as well as around the circumference of the simulated corrosion pits. The longitudinal behaviour of both specimens passing across a normal ground fault was similar, although higher strains and curvatures (6% higher) were measured for the deteriorated pipe on the stationary side of the ground displacement. The Kirsch solution was applied to estimate the strain distribution around the holes. On the moving side, the results assuming uniaxial stress (i.e., pure bending producing a plane stress condition) from the Kirsch solution were in good visual agreement with the measured strains. On the stationary side, the measured strain results indicated a biaxial compressive stress condition that was not captured by the plane stress approach.