Abstract: In order to reveal the meso-mechanical characteristics during the fracture process of the cemented waste rock-tailings backfill (CWRB) of metal ore and the synergistic mechanism of the tail-sludge cementation, uniaxial compression real-time CT scanning mechanical test was carried out to visualize and digitize the damage evolution process of the filling body with waste block proportions (WBP) of 0% (full tailings cemented backfill), 30%, 50% and 70%. The mesoscopic mechanism of mesoscopic damage and cracking and fracture evolution of CWRB was revealed. The results show that the WBP in the CWRB could affect the stress-strain response. As the WBP increases, the strength of the filling body increases. The main reason for the increase in strength is attributed to the propagation of the curved fracture surface in the sample. Related geomechanical effects, the crack morphology after the cracking of the filling body was affected by the shape, size and distribution of the waste rock. The matrix-block interface is the weakest part of the filling body. The formation and propagation of cracks eventually lead to the stress dilatancy behavior of CWRB. The damage and cracking on the interface control the crack propagation path and strength characteristics. The strength effect of CWRB depends on the content of block stone. The interaction between waste rock and waste sand controls the increase of sample strength, and the interlocking effect between blocks and rocks has an important impact on improving the overall stiffness of the sample. The research results have theoretical significance for the green disposal of solid waste and sustainable development of mineral resources

Key words: cemented waste rock-tailings backfill (CWRB), in-situ CT scanning, uniaxial compression test, meso-mechanical properties, fracture evolution