Compression behavior and microscopic damage mechanism of waste rock-tailings matrix composites: Experiments and models

Waste rock-tailings matrix composites used for goaf filling are a significant approach to promote solid waste recycling in mines and achieve safe and environmentally friendly production. In this study, the effects of waste rock content (WRC) and size (WRS) on the compressive mechanical properties of cemented rock-tailings backfill (CRTB) were investigated by experiment. Additionally, PFC3D numerical simulation software is utilized to visualize the micro-crack extension mechanism and microscopic damage characteristics of CRTB. The results indicate that irregularly shaped waste rock exhibits bridging and interlocking effects within CRTB, effectively increasing the uniaxial compressive strength and elastic modulus. However, excessive WRC and WRS lead to a looser skeleton structure in CRTB, thus compromising its load-bearing capacity. The optimum WRC and WRS are 30% and 4–6 mm, respectively. The incorporation of irregularly shaped waste rock effectively suppresses the Poisson effect, and as the WRC increases, CRTB failure gradually transitions from tensile failure to complete shear failure. Numerical simulation results demonstrate that irregularly shaped waste rock redirects and seals crack expansion, resulting in a distinct X-shaped distribution of the main crack after CRTB damage. The findings of this research provide valuable guidance for the efficient application of waste rock-tailings matrix composites in mines.