Analysis of energy evolution and failure mechanism of cemented tailings backfill with voids

To investigate the influence of pore defects on the mechanical properties and failure mechanisms of cemented tailings backfill(CTB), this study systematically analyzed the stress-strain response, energy evolution, and crack propagation characteristics of cemented tailings backfill with voids (CTBV) through uniaxial compression tests and particle flow numerical simulations. Single-pore Samples with varying pore diameters (D = 5, 6, and 8 mm) and double-pore Samples with different arrangement angles (0°, 45°, and 90°) and swapped primary and secondary pore positions were prepared. The experimental results demonstrated that the presence of pores significantly reduced the compressive strength of the backfill. Specifically, the peak strength of single-pore Samples exhibited a linear decrease with increasing pore diameter (reduction of 7.4%ཞ21.6%), and the elastic modulus decreased by 22.4%ཞ55.3%. Among the double-pore Samples, the 90° vertically aligned structure exhibited the optimal mechanical performance, with its strength approximately 15% higher than that of the single-pore 8 mm specimen, indicating that vertical alignment can delay the propagation of the main crack by optimizing the superposition effect of the inter-pore stress field. Based on the aforementioned changes in mechanical properties, energy analysis revealed that pores altered the energy storage-dissipation pattern. The peak absorbed energy of the double-pore Samples increased by 11.2% compared to the single-pore Samples, and the energy release in the post-peak stage was primarily dominated by dissipated energy. The numerical simulation results indicated that crack initiation originated from tensile stress concentration around the pores, propagating obliquely at a 45° angle. The damage evolution process conformed to the Weibull distribution, which is in agreement with the stress-strain curve characteristics observed in the experiments. The damage accumulation rate of the 90° aligned specimen was 30% slower than that of other double-pore structures. These findings provide a theoretical basis for the structural design of mine backfill and defect repair, particularly regarding the influence of pore geometry on energy dissipation and the potential for stress field optimization to enhance backfill stability.