Hoop strain-Based Approach to Detecting Leak Phenomena

Detecting leakage in aging underground pipeline remains challenging due to limited accessibility and complex hydraulic conditions. This study explores a transient damping-based method for leakage detection using both internal water pressure and external hoop strain measurements. Field tests were conducted on 5.5 km pressurized pipeline during pump-stopping operations. Harmonic components are extracted from pressure and strain signals using band-pass filtering, and leakage-induced damping factors are calculated. Leakage locations are estimated based on damping ratios across the first, third and fifth harmonic components. Pressure-based estimation yielded high accuracy (errors: 6.1-13.3%), while strain-based estimation showed similar trends despite lower accuracy. These results demonstrate that hoop strain can indirectly capture pressure transient behavior, offering a non-intrusive alternative for leakage detection. The proposed method enables practical application of transient damping-based techniques to in-service pipelines, especially where access is limited or reflection-based methods are ineffective.