On the fracture and energy characteristics of rock–backfill composite structure specimens exposed to fatigue–creep interaction loading

Abstract A series of stress‐controlled fatigue–creep interaction loading tests were performed on rock–backfill composite structure (RBCS) samples. The testing results reveal the influence of cement/tailing (c/t) on deformation, energy dissipation, damage evolution, and macro–meso failure patterns. The equivalent lifetime of RBCS is the largest for a sample with smaller stiffness filling, a smaller stiffness filling leads to weaker volumetric expansion. Additionally, strain energy is relatively large for larger stiffness filling, indicating a larger proportion of energy release at failure. A dissipated energy‐based damage evolution model is proposed to describe damage propagation at the entire fatigue–creep process which fits well with the experimental data. Moreover, the macro–meso failure pattern reveals the interactions between surrounding rock and filling material, failure seems to change from tension splitting to shear with increasing c/t. Good agreement was found among the volumetric deformation, energy dissipation, and failure pattern. It is suggested that flexible backfilling is benefit to prevent rock spalling and collapse.