Understanding the Triaxial Behavior of Cemented Tailings Backfill Reinforced with Fibers

Fiber-reinforced cemented paste backfill (FRB), a composite material incorporating fibers and cement into mine tailings, is extensively utilized in mine backfilling to ensure underground excavation stability. The triaxial mechanical properties and behavior of FRB, however, are not fully validated. This study investigates FRB specimens with varying fiber (1%, 2%, and 3%) and cement (3.0%, 4.5%, and 6.0%) contents, cured at room temperature. Consolidated drained (CD) and consolidated undrained (CU) triaxial tests were conducted on specimens cured for up to 28 days. The results show that axial strain–stress behavior transitioned from strain-softening to strain-hardening with increased curing time, fiber content, cement content, and confining pressure. The shear strength parameters determined using the Mohr–Coulomb criterion were consistent across CD and CU tests. Notably, 15% deviatoric stress and cohesion increased with fiber content and curing time, while the friction angle remained largely unaffected. Volumetric strain and pore-water pressure evolution revealed an initial contractive phase, followed by dilation in all specimens, highlighting the dependence of stress–dilatancy behavior on curing time and fiber content. Other key observations include the induction of stronger bonds by FRB hydration products and a shift from CPB softening to hardening patterns, underscoring significant advancements from prior studies. These findings enhance the understanding of FRB’s triaxial behavior and contribute to designing safer, cost-effective FRB structures for underground support.