Detecting water leaks in underground pipelines by radar and dielectric analysis

Water leaks in underground pipelines not only lead to economic losses from wasted water but can also cause structural damage to urban infrastructure. In this study, we present a non-destructive radar-based detection for locating water leaks beneath the soil at various scales. First, as the radar detection relies on the dielectric contrast of soils with different saturation degrees, it is important to understand how the presence of water affects the dielectric permittivity and conductivity of unsaturated soils. To investigate this, the dielectric properties of three soil types: sand, loam, and a sand-loam-aggregate mixture, were analyzed by an open-ended probe to establish the relationship between the water saturation and the soil dielectric permittivity. Second, a stepped frequency radar (SFR) was employed in a controlled laboratory setting to monitor signal changes caused by water leaks in the three soil types. Finally, field tests were conducted at a site (8 × 5 m²), where a ground-penetrating radar (GPR) was used to locate leaks in two plastic pipelines buried over 1 m deep, with varying leak speeds. Based on these multi-scale experimental results, we aim to demonstrate the potential application of radar-based measurement for water leak detection. Additionally, we discuss the signal variations caused by wet soils, soil deformation, and the accuracy of detection in different scenarios.