Investigating the backbreak and reduction in the bench dip respect to the blastholes dip, and parameters affecting them in surface mines

Backbreak and subject of reduction in the bench dip respect to the blasthole dip have the important role on the stability and design of remained bench wall after blasting. Effects of parameters of blastholes and charging due to surface mines including: blasthole diameter, blastholes spacing, burden, stemming, blasthole length, blasthole dip, under drilling, charge quantity in each delay and powder factor on the backbreak distance and varying the reduction of bench dip angle (β) respect to the blastholes dip angle (α) have been investigated by various blasting operations in Eyvughly gypsum mine, Rashakan limestone mine, Sungun copper mine and Gholghohar iron mine in this research. Each parameter of backbreak distance (Lb) and varying the reduction of bench dip respect to the blastholes dip increases with an increase of blasthole diameter, blastholes spacing, burden, stemming and blasthole length. The parameters of Lb and () show better correlations with the blasthole diameter and blastholes spacing (S). The parameters of Lb and dont show correlation with the three parameters of under drilling (U), charge quantity in each delay and powder factor. The multivariable relationships between parameters of backbreak distance (Lb) and varying the reduction of bench dip respect to the blastholes dip () with the combination of five blasthole parameters including: diameter, blastholes spacing (S), burden (B), stemming and blasthole length were obtained by statistic analysis using SPSS program with correlation coefficient (R) of 0.948 and 0.960 respectively. The amount of backbreak distance (Lb) and varying the reduction of bench dip respect to the blastholes dip can be predicted and controlled using the obtained multivariable relationships. The parameters of blastholes have important effects on the backbreak and dips of mine benches, and proposed relationships can be useful for stability analysis and design of mine benches due to the blasting operations.