The effect of cyclic stress amplitude on macro-meso failure of rock under triaxial confining pressure unloading

This work aims to explore the impact of cyclic stress amplitude (CSA) on the macro-meso failure characteristics of deeply buried rock under confining pressure unloading process. The experimental results show that the deterioration of rock structure is influenced by the disturbed stress amplitude. It is found that the lateral expansion induced by confining pressure unloading has a great impact on rock volumetric deformation, damage propagation, and failure characteristics. Additionally, a damage evolution model is proposed and expressed using the irreversible lateral strain. The model is available to express the progressive damage evolution pattern. Finally, CT images investigate the complexity of the crack network, and it decreases with increasing CSA. It is suggested that the final volumetric deformation does not simply depend on the stimulated crack pattern but also on the failure modes. A specimen with the pure shear failure mode has the largest volumetric deformation.