فهرست نشریات علمی دسترسی آزاد ایران

In most open pit mines, the first step in the operation cycle of a mining unit is drilling and blasting. One of the most important results of blasting in mines is rock fragmentation. The dimensions of the crushed parts, resulting from the blast, are effective in the costs of loading, haulage, and crushing operations. Many studies have been done in relation to understanding the blasting mechanism and introducing different charging patterns. One of the most practical charging methods that is used today in production blasts in mines is placing an air column along the charging column. This method leads to a change in blast mechanism compared to continuous charging by producing secondary pressures. In this research, the ratio of the optimal length of the air column in the limestone mass has been numerically studied in terms of rock damage. For the analysis and validation of the numerical model of the single blast hole, the field studies of other researchers have been used. In the present simulation, the length of the air column is designed between 0.3 and 0.9 meters. The results represent that by escalating the length of the air column up to 0.7 meters, the pressure applied to the stemming column and fly rock velocity increase with the rate of 1.18 and 1.3, respectively. For longer lengths, this rate increases to 1.58 and 2.39, respectively. It is caused by excessive reduction of the stemming length. The radius analysis of damage in the limestone mass around the blast hole demonstrates that the maximum damage is achieved for the air column with a length of 0.7 meters (air column length ratio was 21.9).