Fracture evolution during rockburst under true-triaxial loading using acoustic emission monitoring

Abstract

This paper investigates the fracture evolution during rockbursts of granodiorite and basalt that appeared to be representatives of two different rockburst modes under true-triaxial loading using acoustic emission (AE) analysis. In the experiments, with the macroscale ejection and failure features captured and presented by the high-speed video imaging and failed specimens, the inside micro- or meso-scale fracturing was detected and analyzed in detail by AE in terms of intensity, temporal-spatial distribution, and mechanism. The experimental results and AE analyses show that the fracture evolution during rockburst (particularly in granodiorite) exhibits hierarchical characteristics: during early loading, small local microfractures developed progressively and stably mainly by tension and clustered preliminarily; around and after the point of the crack damage stress, large-scale fractures developed and coalesced rapidly and unstably with increasing shear mechanism, and nucleation zones significantly developed; upon rockburst failure, rocks near the free face buckled or fractured and ejected rapidly, and shear ruptures suddenly ran through. The findings help facilitate the rockburst prediction and control.