Blast performance in small tunnels - A critical evaluation in underground metal mines

Tunnels can be classified by size as small, medium or large. Blast design parameters and blast performance are considerably influenced by tunnel size. Though parallel cut is more suitable for a higher advance in small drivages, wedge cut proved to be more productive than parallel cut in the small drivages of a manganese mine (no. 1) because of the need for greater charge and more holes per unit of cut area. A double wedge cut pattern. is suggested efor improved blast results in these drivages. Analyses of blast results in around 600m of small rectangular tunnels driven in the host rock and the ore body of true metal mines led to development of an empirical relation for precise prediction of powder factor and specific drilling with wedge cut and parallel cut considering rock strength parameter, Q and hole depth. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.