Spatial acoustic emission evolution of red sandstone during multi-stage triaxial deformation

Multi-stage triaxial compression tests for cylindrical red sandstone specimens (diameter of 50 mm, height of 100 mm) were carried out with a rock mechanics testing system and spatial acoustic emission (AE) locations were obtained by adopting an AE monitoring system. Based on spatial AE distribution evolution of red sandstone during multi-stage triaxial deformation, the relation between spatial AE events and triaxial deformation of red sandstone was analyzed. The results show that before peak strength, the spatial AE events are not active and distribute stochastically in the specimen, while after peak strength, the spatial AE events are very active and focus on a local region beyond final microscopic failure plane. During multi-stage triaxial deformation with five different confining pressures, the spatial AE distribution evolution in the red sandstone was obtained. The obtained spatial AE locations of red sandstone at the final confining pressure agree very well with the ultimate failure experimental mode. Finally, the influence of confining pressure on the spatial AE evolution characteristics of red sandstone during triaxial deformation was discussed. The AE behavior of red sandstone during multi-stage triaxial deformation is interpreted in the light of the Kaiser effect, which has a significant meaning for predicting the unstable failure of engineering rock mass.