FALCONBRIDGE AT TIMMINS: KIDD CREEK: DEVELOPMENT AT DEPTH

Despite the mining of 12 million tons of ore and the passage of nearly three years, there has been only one change in mining methods since we reported on Kidd Creek in the July, 1988 issue.

On the other hand, mine development is a different story and a major shaft-sinking program is under way. This opening will see mining carried out initially to 6,000 ft. (1,830 metres) below surface and it will also establish a base for the exploration of the orebody between the 6,000-ft. and 7,000-ft. horizons.

Newcomers to the mine may be puzzled by references to No. 1 and No. 2 mines, concluding that there are two separate mines. This is not the case. The mine is blocked out in this manner for planning and administrative purposes; thus the No. 1 mine extends from 800 ft. to 2,600 ft. (244 to 792 metres). The 800-ft. elevation is the base of the open pit. This section is serviced by the No. 1 shaft. The No. 2 mine extends from 2,600 to 4,600 ft. (792 to 1,400 metres) and is serviced by the No. 2 shaft. The No. 3 mine is being developed by a new internal shaft and will sevice mining from 4,600 to 6,950 ft. (1,400 to 2,120 metres).

The reference to a change in mining methods concerns the trial of the Avoca method. The inclined cut-and-fill method was possible for the No. 2 mine but was not adopted. The first experimental stopes were much lower in productivity than expected because of slower face advance, and there was heavy dilution originating from the placed fill. Stoping is therefore a blasthole method similar to that used in the upper parts of the mine. It is best described as a cut-and-fill method breaking 60,000- to 80,000-tonne cuts with an extra-long cut cycle.

Unlike the two shafts already serving the mine, the No. 3 is an internal shaft. It is now being sunk from the 4,700-ft. level with anticipated completion of rock work in late October of this year at a depth of 6,950 ft. (2,120 metres). It will be fully operational in June, 1992 and, like its two predecessors, will be equipped with a “tower-mounted” friction hoist.

It is around the shaft that most interest is centred. Here, J.S. Redpath is using a new technique with its distinctive hardware to achieve a better-than-average advance in a safe, uncluttered environment. The principal items responsible for the improvement are: full-face blasting; the application of the burn cut; a custom-designed, 2-boom hydraulic jumbo; and a long-reach mucker of basic Cryderman design.

The Kidd Creek winze is 5.5 metres (18 ft.) in diameter and lined with concrete. The shaft bottom was at the 56th level in mid-April (5,600 ft. or 1,707 metres below surface). A 14-ft. round is drilled with a 2-boom hydraulic jumbo and four to six burn cut holes reamed from 1.75 to four inches. A total of 105 holes is required. The jumbo was designed and built by MacLean Engineering to meet Redpath’s specifications and one machine is capable of covering the entire shaft bottom in the event of the failure of the second machine. Mucking is by a redesigned Cryderman machine with a 0.75-cu.-yard (0.57-cu.-metre) bucket and a reach of 13 ft. (four metres). The machine, the “Brutus,” is the largest of a series of three that are manufactured by O.J. Industries of Salt Lake, Utah.

A complete cycle comprising drill-blast-muck-concrete varies between 20 and 24 hours for a 14-ft. (4.3-metre) advance.

The hoist is a separate story and an interesting one. It was originally installed as a 3-rope, 151-inch-diameter friction hoist at Inco’s Coleman mine and was later replaced by a larger model. Falconbridge purchased the 2,000-hp dc motor and brakes, but the rope reel was too big to be taken underground at Kidd Creek and a new one had to be designed. G.L. Tiley & Associates of Hamilton designed a new 134-inch reel for the now 4-rope hoist that is currently installed. Of particular interest is the use of the friction hoist for single-drum shaft-sinking service. The friction reel is temporarily fitted with a grooved shell to take the hoisting rope, and the versatile arrangement is now handling a 6-tonne sinking bucket.

To what extent the winze will extend the life of the mine remains to be seen. Quoted reserves of 41.2 million tonnes to the 5,600-ft. level, a speculated extraction rate of 3.5 million tonnes per year and complete extraction indicates 12 years. Advancement from the 5,600-ft. level to the 6,800-ft. level (the lowest level established from the current sinking) should extend this by another three to five years.

This is a healthy margin of time for new discoveries and if Kidd Creek should follow the oft-quoted maxim that orebodies rarely occur in isolation, then three to five years may well translate into as many decades.