Characterizing pipe leakage with a combination of GPR wave velocity algorithms

• Published in: Tunnelling and underground space technology 2021-03, Vol.109, p.103740, Article 103740
• Main Authors: Lau, Peter King-Wah, Cheung, Bella Wei-Yat, Lai, Wallace Wai-Lok, Sham, Janet Fung-Chu
• Format: Article
• Language: English
• Subjects: Algorithms; Antennas; Ground penetrating radar; Ground penetrating radar (GPR); Hyperbolas; Leak detection; Light speed; Moisture content; Pipes; Propagation; Seepage; Velocity; Velocity analysis; Water utilities; Wave velocity
• ISSN: 0886-7798; 1878-4364
• DOI: 10.1016/j.tust.2020.103740

•Modifies algorithms by full ray-path reflections of diffractive hyperbolas.•Depth of object is no longer required in the algorithm.•Pipe leak is identified through reduction of GPR wave velocity. Moisture content contained in any dielectric media is the most influential factor reducing Ground Penetrating Radar (GPR) wave velocity, which can be measured by the gradients of diffractive hyperbolas as a result of any round-shaped object, such as water carrying utilities. Such characteristic were then used to estimate location of pipe leak where moisture content is higher in localized area compared to the neighbouring no-leak dry area (Cheung and Lai, 2019). However, depth of utilities is required as a known input in the algorithms based on multiple triangular ray paths using common offset antenna (Sham and Lai, 2016). In this paper, we proposed a combination of velocity algorithm for estimation of velocity, followed by characterizing water leak location where wave velocity is reduced compared to non-leak location, without priori information of utility depth. The combination of velocity algorithm was validated firstly using high-frequency 2 GHz antenna in air, where wave velocity is equal to speed of light. The second validation is two full-scale studies of water leakage detection by the proposed velocity analytical approach using a 600 MHz GPR. Results of both studies substantiate the validity of a combination of few velocity algorithms. It reveals the accurate estimation of pipe seepage and leak location, as a result of 5–10% and 20–30% wave velocity reduction, respectively. The algorithms and validation experiments are believed to pave the way for large-scale applications.