Controlled blasting to minimize overbreak with big boreholes underground

CIM Bulletin, Vol. 75, No. 838, 1982

P.P. DAY and W.K. WEBSTER Explosives Division, C-I-L Inc. Toronto, Ontario

The introduction of large boreholes underground initially involved taking the techniques of open-pit bench blasting to the production slope, but with deeper boreholes and narrower slopes more controlled techniques must be developed in order to maintain good slope walls and prevent dilution of ore or structural damage to pillars due to blasting overbreak. The points discussed are drilling accuracy and drill pattern, the relationship between open-pit wall control and underground mining, the varied explosives products and initiation devices available, and some of the many ways that variations in loading, such as deck charging, etc., can produce desirable results.
Keywords: Underground mining. Blasting, Controlled blasting, Over-break, Boreholes, Large-diameter boreholes, Drilling, Deck charging, Air spacers, Seismic monitoring.