Study on the Stability of Cemented Backfill Under Blasting Disturbance: A Case Study of Makeng Iron Mine

The stability of cemented backfill during secondary extraction depends on its response to coupled static and blast-induced loading, yet the required strength and dominant failure mechanisms remain uncertain. Using the Makeng Iron Mine as a case study, we combined mix-design tests, analytical strength assessment, split Hopkinson pressure bar (SHPB) tests, static and dynamic FLAC3D simulations, and field monitoring. A slurry mass concentration of 78% and a binder-to-tailings ratio of 1:8 produced a 28-day uniaxial compressive strength of 2.69 MPa. Six self-supporting models yielded a conservative design strength of 2.45 MPa, slightly higher than the theoretically estimated blast-transmitted stress of 2.40 MPa. In the SHPB tests, the dynamic peak stress increased from 4.09 to 19.15 MPa as the average strain rate rose from 50 to 152 s−1, while the dynamic increase factor increased from 1.52 to 7.12, demonstrating a pronounced rate-strengthening effect. Numerical simulations identified the orebody–backfill interfaces as the principal zones of stress-wave reflection, deformation incompatibility, and shear-dominated plastic deformation. Flexible mesh reinforcement reduced the maximum lateral displacement of the exposed backfill from 18.85 to 7.24 mm (61.60%) and reduced the extent of the shear-failure zone by approximately 39.72%. Field monitoring recorded a maximum lateral displacement of 8.97 mm, with no large-scale backfill instability observed. These findings provide a case-specific framework for selecting backfill strength and controlling interface instability under blasting disturbance.