ABSTRACT
There is a restriction for longer rounds of blasts in rock tunnels or drifts due to confinement proportional to area of cross section of the opening. However, plenty of new ideas and efforts are being experimented to improve the yield per blast round and implemented in coal and rock tunnels. It is known that in solid blasting, a cut is blasted initially towards which the rest of the shots are fired. The confinement, which is maximum in the cut holes in absence of any free face, is released to a great extent one the cut is developed and hence, the balance holes are blasted with minimised confinement. The efficiency of a blasting round vastly
1 INTRODUCTION
It is high time to focus upon underground mining vis-à-vis blasting, as the cost of opencast mining is going to increase in near future due to higher stripping ratio as well as environmental concerns. The ever growing demand for metals and minerals is pressing the need for progress of underground blast rounds. But, there are some technical constraints associated with underground blasting. The chances of explosive malfunctioning are high in solid blasting due to close proximity of charges. In coal mine blasting statutory provisions indicate that desensitization of blastholes was very frequent in coal mine when the blastholes were closer than 0.6 m. Katsabanis & Ghorbani (1995) found that the sympathetic detonation might occur if differ-
depends on the success of cut development. Innovations in various explosive accessories like relays, shock tubes and others are applied in opencast blasting not yet introduced in underground metal mines due to field constraint. Hence, blast rounds deeper than 3 m, are not common in India considering the prevalent restrictions. The pull to hole depth ratio also lies in a mediocre range of 0.6-0.7. This paper deals with the case study of successful implementation of two new blasting methods for improved pull as well as pull percentage in a hard rock metal mine.
