BLAST FRONT PARAMETERS AS AN ALTERNATIVE TO THE BOREHOLE SPACING RATIO IN DRILL AND BLAST DESIGN

Abstract

The article substantiates the necessity of abandoning the traditional borehole spacing-to-burden ratio as the primary calculation parameter when designing short-delay blasting patterns in open-pit mines. It is demonstrated that with the transition from detonating cord to non-electric initiation systems and electronic blasting systems, this ratio loses its informative val-ue, as it fails to unambiguously define the re-quired charge initiation sequence within a blast block. As an alternative, two independent parameters are proposed. The first parameter represents the angle of deviation of the blast front relative to the bench free face. The second parameter determines the velocity of this front propagation through the rock mass. The combined application of these two parameters enables accurate realization of the engineering intent of blasting operations, regardless of the adopted borehole pattern and the type of initiation systems utilized. The procedure for calculating delay intervals for each blasthole based on its plan coordinates is outlined. The calculation can be implemented both in standard spreadsheets and in specialized CAD/geoinformation software for blast engi-neering. Additionally, a solution to the inverse problem is presented, allowing the determination of actual blast front angle and velocity values based on known borehole pattern parameters and assigned delay times. The efficiency of the proposed approach is demonstrated through trial industrial blasts conducted at the Western and Main open pits of the Kachkanar Mining and Processing Plant. It has been established that applying the blast front angle and velocity parameters in combination with electronic blasting systems ensures a more than twofold reduction in oversize yield. Furthermore, the prediction of muckpile shape and dimensions is enhanced, blasting safety is improved through the integrity control of the in-hole initiation network, and positive effects are achieved at downstream technological stages, including reduced truck unloading times and improved ore crushing performance at the processing plant.