Numerical investigation of blast-induced rock fragmentation

Optimum fragmentation of rocks during blasting is pivotal for the productivity of mining and civil engineering systems. Extensive studies on the ubiquitous fragmentation phenomena in nature and artificial processes have attested to the dominant control of the effective dimensionality and material brittleness on the size distribution of fragments. In this study, by further demonstrating that the impact of brittleness on fragmentation is physically inherent in the material dimension, we present new mechanistic insights into the blast-induced rock fragmentation via integrated analytical modelling, finite element simulation and image processing. A continuous-surface viscoplastic cap model was first calibrated step-by-step against rock behavior in different pressure and strain-rate regimes on various scales. Then, rock blasting was simulated under various bench dimensions and the fracture patterns were image-processed to provide quantitative insights into blast fragmentation. Our findings suggest that the fragments become smaller and rounder while their size distribution becomes more uniform as the rock dimensions decrease. We demonstrated that at smaller rock dimensions, the equivalent increase in energy density and suppression of pressure-induced ductility can conspire to assist crack bifurcation and thus create successively finer fragments towards the unbreakable limit. We also identified significant correlations between the fragment aspect ratio and its size and uniformity of distribution, highlighting the potential use of fragment shape as an indicator for evaluating blasting performance alongside conventional grading analysis.