Abstract: Utilizing mine solid waste as backfill aggregate represents a key pathway towards green mining and waste recycling, in which the coarse aggregate replacement ratio directly influences the mechanical properties and engineering safety of cemented backfill with mixed aggregates. To clarify this influence, uniaxial compression tests were conducted on backfill specimens with different coarse aggregate replacement ratios. The mechanical characteristics were analyzed based on stress-strain curves, and a damage evolution equation along with a piecewise constitutive model were subsequently developed. The results indicate that: (1) The compressive failure process of the backfill sequentially undergoes five stages: initial pore compaction, secondary pore compaction, linear elastic deformation, plastic yielding, and post-peak failure. (2) The peak stress damage value, toughness index, elastic modulus, and compressive strength all increase initially and then decrease with the rise of the coarse aggregate replacement ratio, reaching their optimum at a replacement ratio of 60%. (3) The established piecewise constitutive model agrees well with the experimental curves, effectively characterizing the complete damage and failure process of the backfill. (4) Based on the evolution characteristics of stress and damage, the damage process can be divided into four stages: initial damage, stable damage growth, accelerated damage growth, and damage failure.