A study on rock throw phenomena in boulder controlled blasting

Abstract

In construction industries, blasting is the predominate method for fragmentation when dealing with protruded rock. The issue of fly-rock is critical to the operation of all sites that employ this method especially if it is near to highly sensitive or populated area. This paper takes a risk-based approach to identifying, analysis and managing the fly-rock hazard. The outcomes of the boulder blast should not be underestimated as the fly-rock hazard is less predictable than the primary blasting. A study in the United Kingdom mines and quarries inspectorate (2007) revealed that more than 80 percent of incidents were associated with this type of blasting. The basic cause of fly-rock generation is mismatch between the energy available and the work to be done. This mismatch can be caused by an abrupt decrease in rock resistance (geological weakness), overcharging, inappropriate blast design and inaccurate drilling. In this study, 6 cases of actual blasting operation and their effect of throw due to the amount of explosive used to break a certain volume of rock (powder factor) is examined. A range of various amount of powder factor and distance of throw from initial position of blast are presented. It can be concluded that the wild fly-rock risk can be controlled by managing the powder factor for a given blasting situation.