Spatio-temporal evolution and precursory indicators of rock failure processes using acoustic emission tomography

Abstract

The characterization of stress and crack development plays important part in monitoring disasters. To capture the instability enlightenment from the spatio-temporal evolution of rock damage, this paper constructs the velocity field of key nodes in the rock failure process with the active and passive collaborative acoustic emission (AE) tomography method. It realizes the exploration of the micro-crack propagation law and its potential connection with the stress environment, combining the velocity field, the AE density field, and the energy field. Furthermore, from the spatial integrity and directional evolution of the velocity field, the mutation trend coefficient (MTC) and deformation coefficient (DC) of the velocity field are proposed as precursor indicators of rock instability, respectively. Results show that the anisotropy of the velocity field increases with the aggravation of rock damage, and the stress environment controls the spatial heterogeneity of the velocity field. The most important feature of spatial heterogeneity is that there are the continuous decrease and extension of low-velocity regions and the transformation from the high velocity to the low velocity. Real-time acoustic emission monitoring of the velocity field with MTC and DC can early identify rock instability precursors and principal stress direction, which provides vital pre-alarm information for geotechnical engineering.