Effect of prior cyclic damage on rock failure exposed to triaxial multistage unloading confining pressure and cyclic loads

Abstract

AbstractA series of triaxial alternative unloading and damage‐controlled cyclic loading tests were conducted on deeply buried granodiorite. The testing results reveal that the prior cyclic loading damage influences rock volumetric deformation, stiffness degradation, damage evolution, and failure modes. Rock volumetric deformation and hysteresis ratio increase with increasing prior cyclic damage, and the subsequent damage propagation is the most severe for a sample subjected to high cyclic damage. A larger hysteresis ratio indicates large plastic deformation and energy loss. In addition, a damage evolution model was proposed based on the irreversible radial strain, and it well describes the damage propagation at the respective cyclic loading stage (CLS) and unloading confining pressure stage (UCPS). Moreover, as prior damage increases, the dominant failure mode changes from shear failure to mixed shear–tensile failure and then to tensile failure. It is suggested that rock failure is cyclic damage dependent; damage fully develops under high cyclic damage.