Paired Impulse Response Function and Layer-Peeling Method for Anomaly Detection and Condition Assessment of Pipelines

Abstract

Water transmission and distribution pipeline systems are one of society’s most important infrastructure assets. They consist of buried pipes that are often old and deteriorating and their condition is extremely difficult and expensive to determine. This PhD thesis focuses on developing non-invasive and cost-effective methods to both detect anomalies in water pipelines and to assess the condition of pipelines that will allow for predictive repair. The first stage of the research is to identify and localize anomalies in the pipelines. The second stage is to assess the detailed condition of the pipe wall or the size of a blockage if the anomalies in the pipeline are deteriorated sections or blockages. In the thesis, a novel paired impulse response function (termed paired-IRF) technique has been developed for anomaly detection in pressurised pipelines. This is the first time that a transient-based method has been experimentally validated to be able to fully eliminate the effects from background pressure fluctuations and noise. The technique has a high spatial resolution by transferring the anomaly-induced wave reflections into sharp spikes. It has a high detectability by making use of a continuous signal as the injected wave. The continuous wave injection leads to continuous wave reflections and thus provides a large amount of information for signal analysing. The technique can be applied in pipe networks with arbitrary configurations and achieves a wide detection range. The advantages listed above make the technique potentially attractive for field applications. A layer-peeling method has also been developed for condition assessment in pressurised pipelines. The layer-peeling method, which has previously been applied to the inspection of musical instruments and the design of optical fibers, has in this thesis for the first time been applied to water pipelines. It considers the frequency-dependent dissipation and dispersion of the transient waves in the pipeline and enables a bi-directional reconstruction of pipelines with branches. To compensate the cumulative errors which can occur in the layer-peeling method, a fast inverse transient method is developed. To improve the spatial resolution and the tolerance to background pressure fluctuations and noise, the paired-IRF technique has been combined with the layer-peeling method in the thesis. To assist in applying the techniques in the field, a voice-coil-based transient generation system has been developed to generate transient waves and a customized in-pipe optical fiber sensor array has been used for transient pressure measurement. The transient generation and measurement system has been applied in the laboratory and will be used to validate the proposed techniques in the field in the future.