Abstract: To address the massive waste rock and tailings generated during ore mining processes, this study conducted Brazilian splitting tests on waste rock-tailings backfill specimens to achieve efficient utilization of general solid waste in mines and gain insights into the influence mechanisms of tensile strength and energy dissipation characteristics in waste rock−tailings backfill. Response surface methodology was employed to analyze experimental results regarding tensile strength and energy dissipation. The research systematically investigated the effects of varying waste rock addition rates, ash-sand ratios, slurry concentrations, and curing ages on the backfill’s tensile strength and energy dissipation. Results demonstrate that stress–strain curves of waste rock-tailings backfill exhibit distinct four-phase features including compaction, elastic deformation, yielding, and fracture. Under identical slurry concentrations, tensile strength increases with rising ash-sand ratios, waste rock addition rates, and prolonged curing ages, with the ash-sand ratio at 1∶4 showing the most significant impact under controlled conditions. The response surface-based tensile strength prediction model of the backfill achieves a multiple correlation coefficient of 0.968 7, revealing the influence hierarchy: curing age > ash-sand ratio > waste rock addition rate. Elastic strain energy density accounts for over 98 % of total energy during backfill fracture, indicating that abrupt release of internal elastic strain energy constitutes the primary failure mechanism in Brazilian splitting tests. The research results can provide a theoretical basis for the optimization of waste rock−tailings backfill ratio in underground mines and for maintaining the stability of underground goafs and stopes.