The laboratory scaled-down model of a ground-penetrating radar for leak detection of water pipes

To evaluate the potential of a ground-penetrating radar for leak detection of water pipes, well-controlled experiments allowing flexibility of the involved parameters are necessary. To accomplish this purpose, a laboratory scaled-down model of the radar under leak conditions is proposed here. The laboratory system consisted of a dry sand tank, a pipe and a simulated zone of leakage adjacent to the pipe. The size and burial depth of the pipe were scaled down to about 1/6 of the real world condition. An equivalent leakage model was employed using an acrylic plastic box filled with methanol. A support for the model was provided by acrylic plastic plates and tubes with dry sand filling. The electrical properties of the equivalent leakage and support were verified by measuring their complex permittivities. B-scan radar images were displayed by background removal and neighbouring difference of raw data. For three cases of leaky pipes, the images showed the superimposition of nearly symmetric and inverted hyperbolas produced by non-leaky pipes and the blurring effects caused by the leakage. Thereafter, diffraction tomography was also applied to B-scan images to improve resolution of the pipe and leakage zone.