Energy damage evolution and mesoscopic failure mechanism of cemented waste rock tailing backfill under axial compression

Cemented waste rock tailing filling is an important means to achieve efficient and waste-free mining in mines. In this study, uniaxial compression tests and discrete element numerical simulations were carried out on cemented waste rock tailing backfill (CWTB) to investigate the effect of waste rock content V a (0 %, 10 %, 20 %, 0 %, 40 % and 50 %) on the mechanical properties and microscopic damage mechanism of CWTB. The results show that the waste rock aggregate improves the energy storage limit, crack resistance and compressive strength of CWTB, and the optimum V a is 30 %. With the increase of V a , the phenomenon of surface spalling is increasingly significant at the final failure of CWTB, and the failure mode is transitioned from tensile to tensile-shear composite failure. The appropriate amount of waste rock aggregate can inhibit the conversion of elastic energy to dissipated energy, and the damage constitutive model based on energy dissipation can effectively characterize the stress-strain response of CWTB. The numerical results show that the contact force increases before the peak and decreases after the peak under axial compression, and its distribution has an obvious dominant orientation, suggesting that the change of contact force is the microscopic reason leading to the evolution of the mechanical properties of CWTB. Increasing the strength of the mortar is more significant in improving the CWTB properties compared to aggregates and interface transition zone (ITZ).