Assessment of blasting quality for lateral development in underground mines

Safety, stability, and functionality of mine excavations depend on the structural integrity of the surrounding rock mass. Various explosives and perimeter control blasting techniques have been developed in order to minimize rock damage associated with the conventional drilling and blasting operations. Mining engineers have little or no control over the rock mass characteristics, but proper selection of blast design and explosives parameters results in blasts producing minimum disturbance to the remaining rock mass.; Assessment of blast performance in mine operations requires a simplified methodology combining pre-blast rock conditions and post-blast observations. A new Blast Quality Index (BQI) quantifying the blast-induced rock mass damage is proposed. Based on the data available at the time of the study, the BQI incorporated the Rock Mass Rating as a rock mass quality parameter and post-blast observations such as Half Cast Factor, overbreak, scaling time, scaled volume, and sounding with a scaling bar.; The developed methodology is not site specific and combines several easy to obtain damage assessment parameters. It can be easily applied to evaluate the performance of different blasting techniques for various rock mass conditions in underground hard rock mines. The BQI values are relevant only to the site being analyzed. The application of the BQI was demonstrated for determination of the optimum blast design parameters for the rock mass conditions at two case studies. Blasthole spacing to diameter (S/D) ratio, Perimeter Powder Factor (PPF), blasthole spacing (S), and burden to spacing (B/S) ratio yielding minimum disturbance to the rock mass at the blast sites were obtained.