The role of joints and rock mass quality in perimeter control

The quality of a rock mass has a direct influence on its blasting characteristics. Though each specific rock mass occurrence is unique yet there are common features in rock masses which can influence the outcome of controlled blasting in a similar way. A field study was conducted which involved blasting of small scale models, drift rounds in a geologically dominant rock mass and assessment of blast damage at several operating mines. The effects of rock strength, rock quality designation (RQD), and joint parameters on perimeter control have been described. The influence of number and thickness of weak layers on overbreak control has been discussed in the light of the practical data. In addition, critical particle velocity ranges for damage to rock masses with different qualities have also been outlined in this paper.