Dynamic Mechanical Properties and Damage Constitutive Model of Layered Cemented Backfill Under Blasting Disturbance
In this study, we explore the static and dynamic mechanical responses of layered cemented backfill subjected to blasting loads. Variable-rate uniaxial compression tests and Split Hopkinson Pressure Bar (SHPB) numerical simulations were performed on specimens with three different interlayer cement-to-tailings ratios. All samples were cured for 28 days before testing. The test results reveal that uniaxial compressive strength rises and then falls with increasing loading rates, and mixed tensile-shear failure dominates quasi-static loading conditions. The interlayer cement-to-tailings ratio dominates the bearing capacity of backfill. At the test loading rate of 0.02 mm/s, lowering the interlayer ratio from 1:4 to 1:8 sharply reduces peak strength from 5.595 MPa to 1.285 MPa, with a total drop of 77.0%. SHPB simulation results show obvious strain-rate hardening under dynamic impact. For samples with an interlayer ratio of 1:4, dynamic compressive strength increases from 5.38 MPa to 6.16 MPa as impact velocity rises from 4 m/s to 13 m/s, a 14.5% improvement caused by rapid compaction of internal micropores. Combining damage mechanics and energy conservation principles, we establish a dynamic damage constitutive model that couples inherent layered interfacial damage with blasting-induced dynamic disturbance. Model predictions match experimental measurements well. The peak strength error is only 1.3% at a loading rate of 0.005 mm/s, and peak deviations for all test cases are controlled within 5.0%. This work quantitatively clarifies the static and dynamic mechanical evolution of layered cemented backfill, and provides solid theoretical support for mixture proportion design and blasting stability assessment in high-stage sequential backfilling mining.