ABSTRACT:

In quarries and mines, blocky rock masses are transformed by fracture of intact rock by the action of the detonation pressure of explosives, the blastpile fragment size distribution ultimately controlling the economics. Rock fragmentation prediction and blast design continues to this day to follow largely empirically calibrated equations. One source of inaccuracy of models such as Kuz-Ram is likely to be the lumping together of so-called uncontrollable i.e. geological parameters into one blastability factor to characterize the rock mass. Recent developments in numerical modelling have introduced the sophistication necessary to capture more of the key nonlinear and coupled processes that occur during rock blasting and to consider intact rock properties and jointing or discontinuities independently. The discontinuous computational approach adopted here is based on the combine finite-discrete element method (FEMDEM) coupled to a FEM multi-phase gas flow model with full equation of state. The fragment size distributions are compared for idealised scenarios drawn from simulated blasts with isotropic intact rock, rock with persistent and impersistent discontinuity sets i.e. with rock bridge ratios and different discontinuity spacing, all for identical detonation gas pressure. Results are discussed in the context of the rock structure’s effect on the dominant mechanisms of fragmentation.

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