Rock Fragmentation by Blasting – A Review

Abstract

The rock fragmentation process in mining currently being practiced in India needs re-examination to improve the productivity of the mine. This is of immense importance that we should develop a better understanding of the explosive used and the rock mass to be blasted. The improved productivity cannot be achieved by following the traditional practice of following rules of thumb such as powder factor (cubic meter of rock broken with a kg of explosive) or describing the target rock as weak, medium or strong, or specifying a delay interval in multi-hole blasting. In order to overcome this problem, a long-term R&D projects for understanding and quantifying the real detonation behaviour of the variety of commercial explosives currently in use, under actual field conditions is the need of the hour. The current use of explosive energy figures supplied by manufacturers is woefully inadequate, as these are based on the maximum chemical energy available in a given explosive composition, which has only a very qualitative correlation with the effective energy available to fragment rock efficiently. The same would apply for selection of appropriate delay systems (shock tube or electronic), more specifically the delay interval and its correlation with fragment size distribution and digging and hauling efficiency. These studies are in their infancy, and there is little attempt in linking blast design, fragment size and loading efficiency. This paper comprises some recent R&D developments on rock fragmentation analysis and its application. The experiments were performed at Noamundi, Joda East, Katamati and Khondbond iron mines of Tata Steel Limited.