AE monitoring of a concrete arch road tunnel: Damage evolution and localization

A real-time investigation of damage evolution in two precast concrete arch elements of a road tunnel was carried out by means of a multi-channel AE acquisition system with in-situ data processing and wireless transmission capabilities. The two mainly stressed segments, exhibiting the most evident cracking pattern, were monitored. The investigation was carried out analyzing the trending behaviors of AE synthetic parameters, b-value and βt, extracted from the AE time series. Triangulation techniques for 3D localization of active cracks were successfully applied as well. The results of the analysis demonstrated the existence of irreversible damage processes mainly localized at the bottom of the tunnel and in the lower-central part of the arches. In particular, AE sources localized in subsequent time steps are signatures of macro-crack propagation, suggesting a worsening trend toward instability over time.