Influence of mechanical and aggregate properties of rock on powder factor in rock blasting

Abstract

Profit margins in metal quarrying have drastically reduced in Sri Lanka due to high powder factors recorded in recent rock blasting activities. Importance of analysing the influence of mechanical and aggregate rock properties on the powder factor arises in this context to determine suitable rocks in which expenditure on blasting is minimal during the production stage. Eight quarries operated under the close supervision of qualified Mining Engineers were selected for this study to ensure that a proper blasting geometry and configurations have been properly managed during the period of study. Random core samples were obtained from each quarry site and tested for Density, Uniaxial Compressive Strength (UCS), Tensile Strength and Aggregate Impact Value (AIV) and Rock Mass Rating (RMR). Explosive consumption and drilling records for the past six months were obtained from each quarry for the calculation of powder factor. Powder factor was plotted against each selected rock property and regression analysis was performed to understand their standalone influence. Results of the analysis concluded that the aggregate rock properties, especially Aggregate Impact Value (AIV) have a greater influence on the powder factor. Relationship established in this research can be used to predict powder factor of a fresh rock before conducting any blasting activity.