An experimental investigation on stress-induced cracking mechanisms of a volcanic rock

In underground excavations, different failure features can be induced by complex geological stresses. Therefore, many researchers have investigated rock behaviour and failure mechanisms under high-stress conditions. This study investigated the different failure characteristics to determine the stress-induced cracking mechanisms. Accordingly, a series of tests were performed on a volcanic rock (rhyodacite) under one- to three-dimensional stress states. The results indicated that the samples exhibited different failure characteristics/modes under different stress states. Under 1-D and 2-D compression, the rock exhibited unstable brittle failure induced by tensile cracking (Mode I fracture). Under axisymmetric triaxial stress (sigma(1) > sigma(2) = sigma(3) > 0), the rock exhibited stable failure, and as sigma(3) increased, the failure mode transitioned from Mode I fracture to Mode II fracture to distributed cataclastic failure. In contrast, under a three-dimensional differential stress state (sigma(1) > sigma(2) > sigma(3) > 0), the risk of unstable failure increased with increasing sigma(2), and the rock exhibited localized shear failure (Mode II fracture). Based on the acoustic emission (AE)-based cracking classification method, further studies were also conducted on the failure mechanism. Finally, based on the energy release and cracking propagation, the mechanism of the sigma(2) effect on unstable failure was assessed.

Automated summary

The study investigated the different failure characteristics of volcanic rock under high-stress conditions, revealing various failure modes under different stress states. It found that the rock exhibited unstable brittle failure under 1-D and 2-D compression, stable failure under axisymmetric triaxial stress, and localized shear failure under a three-dimensional differential stress state. The research also assessed the effect of sigma(2) on unstable failure based on energy release and cracking propagation.