Numerical Simulation Study on Meso-structure Fracture of Waste Rock Tailings Cemented Backfill with Different Initial Defects

Utilizing tailings as aggregate and cementitious material to backfill underground mined‑out areas not only ensures mining safety but also enables large‑scale disposal of tailings solid waste. A thorough understanding of the effect of initial defects on the mechanical properties of cemented backfill can help optimize design while improving engineering safety and stability. This study employed the finite element software ABAQUS to numerically simulate the microstructural evolution of backfill materials. First, a model generation algorithm was used to construct two‑dimensional meso‑numerical models of cemented bodies with varying porosity. A convergence study on mesh size was conducted using pre‑inserted cohesive elements. Subsequently, displacement loading was applied to analyze the complete process from crack initiation to propagation in the numerical models. Finally, an in‑depth investigation of the stress‑strain curves was performed. The results demonstrate that: (1) with increasing porosity, both the number of fractured elements and the total crack length in backfill models under uniaxial compression gradually decrease; (2) when porosity increases from 0% to 1.5%, the compressive strength decreases by 18.6%; (3) although porosity influences crack initiation in backfill specimens, their ultimate failure processes remain similar. The numerical model was validated against experimental data from the literature, showing good agreement in both peak strength and stress‑strain behavior. This provides fundamental support for understanding the stability of tailings‑cemented backfill systems and offers a reference for more complex meso‑numerical studies of cemented backfill materials.