Rock fragmentation in which the fragment size distribution of blasted rock material used in the quarry and mining industry as an index to estimate the productivity of blasting activity. The aim of this study is to investigate the effect of burden to hole diameter ratio on rock fragmentation induced by blasting. Numerical investigation was carried out by utilizing the Discrete Element Method (DEM) and Particle Blast Method (PBM) approaches in LS-DYNA software, on the response of rock fragmentation. In bench blasting simulation, the rock media was modelled using DEM and the blast loading was modelled using PBM. Parametric study was carried out on the hole diameter and burden was kept constant. The comparison of rock fragmentation distribution has been made between numerical analysis and fieldwork data. It was observed that uniformity index increases with the decreases in burden to hole diameter ratio. It can be concluded that by increasing hole diameter without changing burden will increase the powder factor which in turn yields finer fragmentation. The numerical model has successfully showed the crack propagation of rock which can form the rock fragments and helps to predict fragment size distribution of rock.
Fragmentation is one of the most important aspects on explosives engineering. The mean fragment size of rock should not too high or too low. This is because oversize rock and very fines rock will occur. Rock fragmentation plays a critical role in large-scale quarrying operations because of its direct effects on the costs of drilling, blasting, secondary blasting and crushing (Dershowitz, 1993; Goodman & Shi, 1985; Faramarzi et al. 2013). The optimum-blasting pattern to excavate a quarry efficiently and economically can be determined based on the minimum production cost, which generally estimated according to rock fragmentation.
Factors influence the blast result divided into controllable and uncontrollable factors. Blast design parameters and explosive charge characteristics grouped under controllable parameters. Whereas, properties of rock mass, discontinuities and geomechanical characteristics of the intact rock are under uncontrollable factors. Controllable parameters for blast results was listed by Bakhtavar (2014) which are the burden, spacing, bench height, stemming length hole diameter, delay sequence, firing pattern, explosive per hole and powder factor.
