Influence of Soil Backfill on Vibration-Based Pipeline Leakage Detection

An estimated 20% of treated fresh water is lost through leakage in distribution pipeline infrastructure in the United States. As a result, significant research has been devoted to developing technologies that will assist water utilities in detecting and locating leakages in their distribution systems. The authors recently developed and demonstrated a technique referred to as the leakage detection index (LDI) technique to determine the presence of leakage through temporal comparison of the cross-spectral density (CSD) of pipeline acceleration response measured at multiple locations along the pipeline length. One major limitation of the experimental setup in the previous study was the lack of soil backfill. Consideration of the backfill is important because it could alter the vibrational features of the buried pipeline. In this study, the authors determined the effect of the surrounding soil backfill on the vibrational characteristics of a buried PVC pipeline and subsequently determined the influence on LDI for various leakage severities. A comprehensive experimental campaign was conducted using a two-loop PVC pipeline test bed comprising multiple pipe sizes, multiple bends, T-joints, and valves. Multiple cover depths and multiple leakage sizes were investigated in this study. Confirming our hypothesis, the results revealed that the soil backfill intensifies the dampening effect of pipeline vibrations. Furthermore, irrespective of the soil cover depth, the LDI metric exhibited a monotonic increase as the severity of the leakage increased, and it could be further developed to be suitable for leakage detection in real-world buried PVC pipelines.