Abstract: Deep mining of coal resources is commonly accompanied by high in-situ stress and progressive energy accumulation, which can readily trigger dynamic disasters such as rock bursts. From the perspective of material toughening, elucidating the impact-mitigation mechanisms of coal-based cemented fill materials and establishing an quantitative characterization and evaluation index system for toughening based on the energy dissipation theory are emerging as promising approaches for achieving impact-mitigation control and optimizing material-oriented design. To clarify the impact-mitigation mechanisms, this study employed coal-based solid wastes as the primary constituents and systematically investigated the coupled effects of aggregate gradation, binder-to-aggregate ratio, curing age, and fiber toughening through uniaxial compression tests, energy evolution analysis, rock burst propensity assessment, and scanning electron microscopy (SEM). The results indicate that aggregate gradation, binder-to-aggregate ratio, and curing age exert significant influences on the mechanical performance of the cemented fill. The uniaxial compressive strength grows with the increase in curing age, and rises first and falls subsequently with the increases in Talbot index n and binder-to-aggregate ratio, reaching an optimum at a curing age of 28 d with n=0.6 and a binder-to-aggregate ratio of 2.5∶1. The incorporation of polypropylene fibers markedly enhances the compressive strength and improves post-peak ductility, broadens the energy-dissipation pathways, and enables sustained absorption and dissipation of externally imposed impact energy during the post-peak failure stage. Based on the energy dissipation theory, a FIMI-Lite impact-mitigation evaluation framework comprising five indices (energy dissipation ratio, dynamic toughness index, residual load-bearing ratio, brittleness index, and equivalent vibration isolation coefficient) was proposed to quantitatively characterize the impact-mitigation performance of cemented fill materials. Comparative analyses show that fiber-toughened fills outperform the conventional counterparts across all indices, with the fiber-toughened fill at n=0.4 achieving the highest comprehensive FIMI-Lite score. SEM observations reveal that an appropriate gradation promotes the formation of a dense load-bearing skeleton, whereas the incorporation of fibers conduces to constructing a three-dimensional "particle-cementitious matrix-fiber" network. The synergy of these two factors refines the pore structure, retards crack propagation, and enables stepwise energy absorption and progressive release. The above microstructural findings establish a mechanistic linkage to the macroscopic impact-mitigation performance. The proposed approach provides a scientific basis for optimizing the design of coal-based cemented fill materials and for preventing and controlling coal burst hazards in deep coal mining.