Investigation of the dynamic mechanical properties and damage mechanisms of fiber-reinforced cemented tailing backfill under triaxial split-Hopkinson pressure bar testing

The filling method is a widely-used mining technique, and the performance of cemented tailings backfill (CTB) determines the quality of filling. However, the mechanical properties of conventional CTB are limited in terms of their crack resistance and toughness under complex stress environments. Polypropylene fiber-reinforced cemented tailing backfill (PFRCTB) is a filling type that is currently receiving significant attention. This paper investigates PFRCTB dynamic mechanical properties and damage mechanisms under different strain rate conditions using a triaxial Hopkinson pressure bar test apparatus at five confining pressures (0–4 MPa). The results indicate that the strain rate enhancement effect of PFRCTB under dynamic loading is very significant with the enhancement effect of confining pressure, and the presence of confining pressure significantly changes the stress-strain curve. In the absence of confining pressure, the specimens showed outwardly expanding circular table-like damage with increasing strain rate, and the crack volume and surface area increased in a stepwise manner, and the hollow cylindrical polypropylene fibers showed flat damage, at which time the polypropylene fibers were subjected to ultimate strain rates ranging from 206.5s−1 to 232.3s−1. When the confining pressure gradually increased, the outward expansion of the specimen was gradually curbed until there was no obvious damage inside. At this time the fibers appear to split, bend and pull out.