Development of a novel empirical approach to control overbreak, surface quality, and slope angle of benches following blasting
Sina Soltanalinejad, Hassan Moomivand
Abstract
Overbreak, slope angle, and quality of a bench behind the boundary of excavation as attractive subjects for mining and civil engineers are the most crucial consequences of the post-blast. But the breakage mechanism of blasting has not originally been well clarified how a desirable slope angle and quality of a bench can be obtained by common drilling and blasting operations and what parameters can quantitatively affect such blasting consequences? The slope angle of the remained bench face ( β ) can be influenced by the overbreak zone between the last row of holes and the remained bench face after blasting. The breakage mechanism and influence of the blasthole parameters, such as hole diameters ( ϕ h ), explosive weight per hole ( Q), burden ( B), spacing ( S), stemming ( S t ), bench height ( K), powder factor ( q), and blastability index (BI) on the width of overbreak zone ( L OZ ), and the difference between hole and bench slope angles ( α ° − β °) and the width of damaged zone (L DZ ) in 15 zones of Sun gun open pit copper mine, Golgohar open pit iron ore mine, Khoy limestone, Rashakan limestone, Bonab silica mine, and Evoghli gypsum mine were investigated. Several parameters were measured in each of 15 drilling and blasting operations. The blasthole parameters varied in a wide range for different mines. Both the inclined and horizontal faces of a bench as two free faces, which are subjected to the shock waves' reflection by blasting, can affect the overbreak and damaged zones. Impact of shock waves' reflection, breakage potential, and overbreak increases from the foot of the bench to the top. L OZ , ( α ° − β °), and L DZ of the results increased by power functions with increasing ϕ h , Q, B, S, S t , and K. But acceptable correlations between each of L OZ , ( α ° − β °) and L DZ with q and BI were not achieved. New multivariable nonlinear relations between each of L OZ , ( α ° − β °), and L DZ with the combination of six blasthole parameters ϕ h , Q, B, S, S t , and K were developed with good correlations. In some cases, with lower values of ϕ h , Q, B, S, S t , and K, both the L OZ and ( α ° − β °) approached to zero value. The new achievements in this study can be important new guides to obtain the desirable bench slope angle and bench faces.