Abstract
The article describes an analytical method for determining the particle size composition of the rock mass exploded by blasthole breaking of rocks in horizontal underground workings (tunnels). It is based on taking into account the size of the zones of intensive crushing of rocks around the blasthole charge and the presence of natural jointings in the rock mass. The radii of the zones of intensive crushing are calculated using the preset physico-mechanical properties of the blasted rocks and the physico-chemical characteristics of the applied explosive materials (EMs). The particle size composition of natural jointings is calculated using the average size of the jointing in the rock mass. Based on the combined consideration of these components, an analytical method has been developed for the first time in mining that allows to determine each rock class by size in terms of the blasted rock in the course of driving of horizontal underground workings (tunnels).A software program has been developed for the automated determination of the particle size composition of the blasted rock mass, which interconnects the influence of the physico-technical properties of the blasted rocks, the physico-chemical characteristics of the EM used, and the parameters of layout of charges in the rock mass. With this program, calculations were carried out in relation to the anticipated particle size composition of rocks under various parameters of drilling and blasting operations at the Zhezkazgan mines of Kazakhmys Corporation LLP. The comparison of the theoretical and experimental data types has demonstrated a high degree of their identity. These findings confirm that the proposed theoretical approach to determining the particle size composition of the blasted rocks takes into consideration the actual mechanism of destruction of the real rock mass by explosion in the course of driving of horizontal underground workings (tunnels).