Experimental study of acoustic emission multi-parameter information characterizing rock crack development

Monitoring the acoustic emission (AE) signals released during rock fracture process can reflect the crack development and damage in the rock in real time. As that there are few rock damage indicators at present, it is unsuited to in-situ monitoring and early warning. Based on small-scale AE uniaxial compression experiments in the laboratory, through adopted phased AE source location and wave velocity tomography, it was found that the process of crack development and stress evolution in the rock would show discrete stages, and the regional damage and excessive local stress difference in the rock would accelerate failure of the rock. The phasic variation of the AE multi-parameter indicators introduced from the field of seismology can better characterise the four internal stages of the rock crack development (crack compaction-crack elastic deformation-crack expansion-crack propagation"), which is coupled with the internal crack distribution and degree of damage. The acoustic emission activity (AEA) and the acoustic emission fault total area (AEFTA) are positively correlated with AE signal amplitude, number of AE events and release AE energy of micro-fracture, while the AE b value is negatively correlated therewith. Based on this, the AE multi-parameter damage evaluation indicators which are suitable for actual engineering guidance of excavation and support operations can be established. In practical application, a large amount of data gathered on site is needed to correct the precursors of failure, so as to make the AE monitoring and warning more accurate.