Dynamic properties and fragmentation mechanism of cemented tailings backfill with various particle size distributions of aggregates

Abstract

The stability of cemented tailings backfill (CTB) is susceptible to dynamic loading from excavation or blasting. In this study, we investigate the strain rate and particle size distribution of aggregate effects on mechanical properties and fragmentation mechanism of cemented tailings backfill, in which the gradations of aggregate particles satisfy the Talbot gradation theory. The characteristic stress–strain curves, dynamic peak compression strength (DPCS), energy variations, macroscopic fragmentation characteristics and microstructure characteristics of CTB with various strain rates and gradations of aggregate particles are investigated by split Hopkinson pressure bar (SHPB), scanning electron microscope (SEM), and fragment distribution of CTB after impact. The results show that strain rate has a linear increase on both DPCS and total input energy but a negative correlation on the average particle size of fragments λ. A decrease in the average particle size means an increase in the degree of damage. The relationship between the aggregate grade and the DPCS of the CTB is approximated as a quadratic function and the gradation Talbot index of 0.5 has the best DPCS, the least dissipated energy, the lowest degree of fragmentation and the densest microstructure, which means it has the best dynamic mechanical properties and resistance to fragmentation mechanism. These results can provide an essential reference for the design of the underground mining backfill.