Macro/mesofracture and instability behaviors of jointed rocks containing a cavity under uniaxial compression using AE and DIC techniques

To better understand the macro/mesofracture and instability behaviors of the jointed surrounding rock of a cavity, a series of uniaxial compression tests on jointed granite samples with openings were conducted using acoustic emission (AE) and digital image correlation (DIC) techniques. The experiments indicated that with increasing joint angle, the peak strength and elastic modulus first decreases and subsequently increases, reaching a minimum as the joint angle approaches 45 degrees. The linear transition point of the AE cumulative count before the peak stress is related to crack initiation or interpenetration, while each instantaneous increase in the AE count after the peak stress is associated with the stress drop caused by the localization of high strain or the formation or further development of visible cracks. The accelerated release of AE energy probably has a better early warning ability for the prediction and forecast of rock instability and failure. Moreover, the prominent strain localization bands indicate crack initiation, and the crack extension behavior signifies the gradual evolution of the strain localization bands. The existence of joints changes the stress distribution patterns in the samples, and the high stress concentration areas formed at the joint tips and around the cavities interact and jointly dominate the fracturing process, eventually leading to complex failure modes. The unstable failure of the specimens is mainly induced by tensile cracks around the caverns and the joint tips, accompanied by local shear failure.

Automated summary

Uniaxial compression tests were conducted on jointed granite samples with openings to investigate the macro/mesofracture and instability behaviors. The results showed that the peak strength and elastic modulus of the samples first decreased and then increased with increasing joint angle, reaching a minimum at around 45 degrees. The AE cumulative count before the peak stress was related to crack initiation or interpenetration, while the instantaneous increase in the AE count after the peak stress was associated with the stress drop caused by high strain localization or the formation of visible cracks. The accelerated release of AE energy can provide early warning for rock instability and failure. The existence of joints changed the stress distribution patterns and interacted with high stress concentration areas to dominate the fracturing process.