Identifying the real fracture hidden in rock microcrack zone by acoustic emission energy

Abstract

Identifying the real fracture of rock hidden in acoustic emission (AE) source clusters (AE-depicted microcrack zone) remains challenging and crucial. Here we revealed the AE energy (representing dissipated energy) distribution rule in the rock microcrack zone and proposed an AE-energy-based method for identifying the real fracture. (1) A set of fracture experiments were performed on granite using wedge-loading, and the fracture process was detected and recorded by AE. The microcrack zone associated with the energy dissipation was characterized by AE sources and energy distribution, utilizing our self-developed AE analysis program (RockAE). (2) The accumulated AE energy, an index representing energy dissipation, across the AE-depicted microcrack zone followed the normal distribution model (the mean and variance relate to the real fracture path and the microcrack zone width). This result implies that the nucleation and coalescence of massive cracks (i.e., real fracture generation process) are supposed to follow a normal distribution. (3) Then, we obtained the real fracture extension path by joining the peak positions of the AE energy normal distribution curve at different cross-sections of the microcrack zone. Consequently, we distinguished between the microcrack zone and the concealed real fracture within it. The deviation was validated as slight as 1–3 mm.