Over break control in underground mines

Abstract

Blasting is an integral part of hard rock mining and remains the most cost effective method of hard rock fragmentation. However, the costs associated with blast damage in terms of safety and productivity of mines are becoming a serious concern. In order to understand the mysterious nature of blast damage prediction and control, field work involved the small scale blasting of physical models and monitoring of blasts in operating hard rock mines. Understanding the factors affecting blast damage is an important step for blast damage control and the refinement of blasting practice and design for damage minimization. Small scale blasting and the monitoring of field blasting practice provided a better understanding of the performance of the blasts in general and identified which aspects of blasting had a significant impact upon over break control. In the light of the field work, following aspects have been discussed to minimize over break in underground excavations. a. Drilling and blasting practice b. Explosive characteristics and distribution c. Explosive products for perimeter control d. Blast design e. Relevance of rock mass characterization to blasting results In addition, based upon the review of the case histories and work done by the author at different sites, a criterion for minor and major blast damage has been proposed.