Strength and deformation characteristics of rock-backfill-rock composites under uniaxial compression: experiments and three-dimensional models

Pillar-backfill-pillar systems govern backfill-mining stability, but their internal stress evolution remains unclear. Rock-backfill-rock composite (RBRC) specimens with different cement-to-tailings ratios by mass (CTR) and backfill structures were investigated using uniaxial compression tests and three-dimensional discrete element simulations. As CTR decreased from 1:4 to 1:6 and 1:8, the uniaxial compressive strength (UCS) of RBRC decreased by 15.78% and 12.02%, while peak strain increased by 22.06% and 37.35%. Layered backfill caused only a 4.81% UCS difference but accelerated pre-peak damage. Simulations revealed delayed internal normal-stress peaks, direction-dependent tangential stress, interface-controlled shear bands, and post-peak stress transfer to backfill.