Impact of Blast Design Parameters on Rock Fragmentation in Building Stone Quarries

Crushed stone aggregates are indispensable construction material which is produced by crushing of raw stone boulders raised from stone quarries through the process of drilling and blasting. Proper size of boulders fed to the crusher is important to eliminate congestion in the crushing circuit and obtaining the desired productivity. Drill-blast design parameters have a considerable effect on the degree of post-blast fragmentation. Bench height, spacing, burden, stemming, bench stiffness ratio and powder factor are controllable blast design parameters which considerably influence the fragmentation. By controlling these design parameters, optimum fragmentation can be achieved. Extensive field trials followed by scientific analysis have been done in this study which reveals the relation between drill-blast design parameters and post-blast fragmentation. Burden, spacing, stemming, bench stiffness ratio and powder factor were varied over a range of 30–45% which in turn caused distinctions in the mean fragment size in the range of 50–200% approximately. For optimum mean fragment size, the burden was found to be 21 times the blast hole diameter. Spacing dimension of 1.3 times the burden produced the optimum mean fragment size. Stemming length of 0.91 times of burden generated the optimum fragmentation. Mean fragment size was most optimum at powder factor of 1.02 kg/cum.