Quantitative Visualization Monitoring of Cracks at Shotcrete-Rock Interface Based on Acoustic Emission

To investigate the possibility of quantitative monitoring of the fracture process zone (FPZ) at the shotcrete-rock interface, the acoustic emission (AE) and digital image correlation (DIC) are used to monitor the three-point bending test of shotcrete-rock specimens. Firstly, the AE intensity signal characteristics during damage to the shotcrete-rock interface are analyzed. Then, the spatial b-value of AE is used to visually characterize the shotcrete-rock interface damage, and the interface damage characteristics of two specimens, shotcrete-granite and shotcrete-sandstone, are analyzed using this analysis method. The analysis reveals that not only the AE spatial b-value can determine the location of microdamage within the interface but it can also characterize the degree of damage. Finally, a new parameter, Tb-value, is constructed based on the AE spatial b-value to quantitatively characterize the FPZ, and the newly established characterization method is validated with the FPZ monitored by DIC. The results show that the Tb-value not only locates and visually characterizes the location of the FPZ within the specimen but also enables the quantitative determination of the FPZ. This provides a new idea for localizing and quantitatively monitoring cracks and FPZs inside structures using AE techniques.