Enhancing Leak Location in Buried Water Pipes using Array Signal Processing Techniques: the Effect of Wave Velocity Variation

Leakage in buried pipelines is a significant cause of water wastage in distribution systems, resulting in water losses ranging from 30% to 50% in many countries. To address this issue, techniques have been developed to detect leaks in buried pipes over the last few decades. The leak detection procedure typically involves three steps: (1) leak detection, which involves analysis of water pressure/flow measurements along the pipelines; (2) estimation of the approximate region where the leak occurred through local pressure variations; and (3) pinpointing the estimated location of the leak to perform maintenance procedures. Acoustic pinpointing techniques are among the most effective ones to deal with the latter step. These techniques exploit the delays in time of arrival of acoustic waves, caused by the leak, between different sensors placed around the suspected leak. By calculating the cross-spectral densities (CSDs) between sensors and analysing their phase difference over frequency, it is possible to infer the estimated location of the radiating source. Existing methods rely on access points to the pipeline through correlators. However, the buried pipe acts as a radiating source, and its location could also be estimated through ground vibration signals. Although array signal processing techniques applied to source localization are well-established in the acoustics field, their adaptation to the vibroacoustic field is less well developed. Among the many challenges, the identification of wave velocity is one of the most troublesome. In this paper, the effect of the wave velocity variation on the leak pinpointing is investigated and tested against numerical data. Results show that the estimation of the leak position is sensitive to the wave velocity variabilities. The pinpointing error is found to be more significant in terms of the depth of the pipe, compared to the error on the ground surface.