Blast optimization and stability enhancement through geotechnical mapping at Highland Valley Copper

CIM Bulletin, Vol. 85, No. 962, 1992

S. Daly and D. Assmus, Highland Valley Copper, Logan Lake, British Columbia

Poor fragmentation, high toe areas, excessive shovel wear and tear and frequent re-drilling and blasting of certain tough waste rock zones in the Lornexpit in the early 1980s necessitated a better understanding of these zones. A combination of geotechnical mapping, penetration rate data, toe elevation contouring and observations on shovel and drill performance were used to determine the character and extent of these zones. This complementary information was brought together by the geotechnical mapper and the explosives supervisor. Distinct zones with particular geological characteristics were determined. A classification system with three types of blast and dig-ability was developed for the Lornex pit and later applied to the Valley pit, with considerable success. The three blast zone types are called "poor", "fair", and "good". This system will be described in detail. The explosives supervisor adjusted the blasting parameters to each zone, in particular, pattern spacing and burden. The resulting powder factors showed considerable variation between the poor, fair and good zones within each pit as well as between the two pits. Pattern geometry and length of collar were also adjusted to improve fragmentation. Cost savings resulted from less re-drilling and less wear and tear on drills and shovels in the poor zones and more efficient use of explosives in all the zones. An annual estimated cost savings of well in excess of $1,000,000 is realized at Highland Valley Copper. A by-product of the mapping was the determination of unstable structures and water flowing zones. Blasting was then adapted to this information for enhanced slope stability.