Field validation of water-pipe leakage detection through spatial and time-lapse analysis of GPR wave velocity

Detection of leakage in a buried water pipe is a crucial issue, as underground pipes become aged and these pipes are often used as pathways for aggressive chemical agents. Non-destructive geophysical methods for identifying such underground leakages are of vital importance. Leakage detection in buried water pipes is sometimes carried out through specific acoustic methods. In this research, we have used ground-penetrating radar as an alternative to such acoustic methods, because of the high sensitivity of electromagnetic waves to the presence of water in soil. This paper presents a methodology, illustrated by field-scale ground-penetrating radar experiments. Four water leakage points in a buried, ductile, iron, main-water pipe were pre-designed within a full-scale (20 m long x 10 m wide) experimental set up. This facility was paved half by reinforced concrete and half by other pavement blocks. Four ground-penetrating radar antennae with five nominal frequencies 200, 250, 400, 600 and 900 MHz were tested. Using a modified algorithm for common offset ground-penetrating radar antennae, in this work, we measure the changes in electromagnetic wave velocity and wave reverberation, which sense upward and downward leakages, respectively. Leakages could be identified most clearly in the 600 MHz ground-penetrating radar data. Our result suggests two potential applications in terms of detecting and defining the extent of multiple leakages in old water pipes, and testing and commissioning new pipes before and after pressurized tests.