When you want to ventilate the deepest levels of a mine or when you’re in charge of mining the highest-grade uranium deposit in the world, you’re pretty well limited to one kind of machine to get the job done right.
“We’ve considered several different mining methods to extract ore from the Cigar Lake deposit,” Cigar Lake Mining Corp General Manager George Peebles says of this rich pocket of uranium ore in northern Saskatchewan, which averages 14% U3O8. But because of the mine’s unique ground conditions, ventilation and ore- handling requirements as well as gamma ray and radon daughter exposure limits, efforts have been concentrated on the raise-boring method. In its simplest form, a raise-boring drill would be located in a drift above the ore zone, Peebles explains. A vertical, 10-inch-diameter pilot hole, 50 m deep, would be drilled from this drift into another drift below the ore zone. A large-diameter reaming head would then be attached to the drill string and the pilot hole reamed to the top of the ore. Fragments of ore fractured by the cutters on this reaming head would fall to the drift below into transport containers, which would then be hauled by truck to the shaft and hoisted in the cage.
Cigar Lake Mining is taking a close look at raise-bore manufacturers worldwide. They include: Wirth Mas chinen- und Bohrgerate-Fabrik GmbH of West Germany, Koken and Tone, both of Japan, Tamrock of Finland (which has recently re-entered the market) and The Robbins Co in the U.S. Stoping is scheduled to start at Cigar Lake in late 1990.
What makes the raise-bore drill an appropriate choice for mining the Cigar Lake deposit is the machine’s proven track record. Raise-bore drills have been used in underground hardrock mines since the early 1960s — usually for driving long ventilation raises, ore and waste passes and backfill raises. As several major companies begin developing orebodies at greater and greater depths, they are beginning to acquire expertise in this area of mine excavation. Cominco Ltd, for example, reamed a total of 3,492 m of raise (1.83 m in diameter) last year at the Polaris mine alone. The machine used was a 73RM-AC, manufacturered by Robbins. Mining contractors Dynatec Mining, Thyssen Mining Construction, J.S. Redpath and Patrick Harrison & Co all have active raise-boring divisions. Jim Seeley, an area manager for Dynatec who has worked as a foreman for both Redpath and Dynatec, says “raise boring is very busy right now.”
Redpath Raiseboring, a company wholly-owned by the Redpath Group, bores more than 9,000 m per year worldwide, according to Micheal Kelly, manager of Redpath Raise boring. That’s the most of any single contractor outside of South Africa and is 68% of the total footage contracted out in 1987. The company owns five Robbins machines and Redpath Manufacturing manufactures a small-diameter machine of its own design. One of the Redpath-operated Robbins machines, an 82-R, has just finished a 638.5-m raise, 7 ft in diameter, at a copper mine in Freeport, Indonesia. Redpath has been working on this multi-raise project since 1979. The company owns another 82R machine which is operating at the Page-Williams mine in Hemlo, Ont. It will be completing the last of more than 15 raises there ranging from 7 to 12 ft in diameter. The other three Redpath-operated Robbins raise-bore machines are two 71Rs, one of which is at the Caribou mine in New Brunswick, the other of which is in Tasmania; and a 61R, which is at the Curriagnalt mine in Ireland.
Redpath Manufacturing is building its sixth and seventh 4-ft-diameter raise-boring machine. Called the Redbore 40 (or RB40 for short), it is a special-application machine developed in-house by Redpath for certain contracting jobs (the first machine was manufactured in September, 1987). One RB40 has been used at the David Bell mine in Hemlo, the Belmoral mine in northwestern Quebec and the Caribou mine in New Brunswick. Since then, it has created a market for itself. Lac Minerals purchased the first machine this month and a test application at Inco Ltd in Sudbury was so successful that Redpath has won its first contract with the nickel giant since it sank the Creighton shaft in 1965. “We’re having a hard time keeping up with demand,” Kelly says.
Competing with Redpath in the small-diameter market is Machines Roger International of Val d’Or, Que. Besides selling a number of machines here in Canada, this company has broken into the international marketplace with a novel raise-boring concept. Instead of using a full-face cutter head, the Roger Machine uses two or three (depending on the raise diameter) in-the-hole hammers which rotate about a central axis. The concept saves considerable weight and therefore requires very little site preparation work as a result.
Since the company started marketing its machine last fall, it has made a sale in Australia, according to Lorrent Gaudet, director-general of Machines Roger. Lac Minerals has used the machine steadily at the Bousquet No 1 mine, according to that com pany’s annual report, driving 60-ft raises in only two shifts.
Machines Roger is also working on an $11-million research program, which should span about three years, to develop a machine for drilling horizontal openings in rock using the same in-the-hole hammer concept.
Dynatec, which has been reaming raises since 1982, is attacking the other end of the market — the high-risk market for large-diameter (12.5-ft) raises. No one else is in this market in Canada. Using one of only four Jarva raise-bore machines ever manufactured, Dynatec plans to drive a 604-ft ventilation raise at the Bousquet mine at this larger diameter. The mac hine is in Dynatec’s shop being converted back to dc drive which should give it 216,000 ft-lb of torque. The Bousquet project is one of two in which Dynatec is involved. The other is at Minnova’s Ansil mine, also in northwestern Quebec. Another Jarva machine is being used there to drive two 2,000-ft fill raises, 7 ft in diameter. To accomplish the difficult task of reaming holes to more than 12 ft, Dynatec has learned to go slow and not over-stress the reaming head, Area Manager Seeley says. “We average about 1 ft per hour.” Dynatec is also using a Subterranean 009 at Ansil to drive various ore and waste passes at the Ansil mine. Some of those are at shallow angles of 55 to 56 . Dynatec has also acquired a 32R raise-bore for 4-ft-diameter raises.
Before the advent of raise-bore drills, raises and manways in hardrock mines where driven by jackleg and stoper miners. Their work, in the dark, wet, confined space of a raise on a timber platform on top of a timber cribbing, was demanding and dangerous. Retractable steel platforms called Alimak raise-climbers have reduced the risk of injury while driving raises using the blasting method, but raise- boring is still considered the safest method. Another method, which uses explosives, is called drop-raising.
These older methods are still used today, sometimes competing successfully for raise-boring projects in hardrock. But they are usually in large- diameter applications and where a raise fully equipped with manways is required on completion. But where accuracy, speed and a smooth wall is required raise-bore drills are the technology of choice. In a ventilation raise, a smooth wall reduces friction losses. Other advantages of the raise- bore method include lower costs, greater safety and quicker completion times. The rule-of-thumb used by some contractors is to quote a per- vertical-foot cost based on $50 to $60 for every foot of diameter. But that varies.
The longest raise-bore project in the country (in the 10-ft diameter class) has been let to Patrick Harrison & Co of North Bay. Four raise-bore machines, all from Robbins (two 61Rs, one 71R and a 97LR) will be used on the project. It will consist of four, 2,000-ft ventilation raises through some of the hardest rock in the world, at Falconbridge Ltd’s Craig deposit north of Sudbury, Ont. Earlier this year, Falconbridge formed a 5-year joint-venture partnership with Harrison to do all of the mining company’s raise-boring work. The Craig project alone should cost in the order of $8 million and take 16 months to complete. About $15 million worth of equipment will be used.
One of the more demanding aspects of this deal is the requirement to be within one half of 1% of design targets on each of the four raises (that means the pilot hole must be within 10 ft of the target at the 2,000-ft depth). To accomplish this, Harrison has im ported some expertise from South Africa. Wilf Davies, former director of the large diameter hole division of Rockbore of South Africa, is in Sudbury providing technical direction for the Craig project. He is well-known in the world of raise-boring. Many of his technological feats in bored raises (including the largest, 6.3 m in diameter using a Wirth machine) have yet to be matched. He says he has supervised a number of hardrock projects, but expects to learn more drilling in the hard Sudbury norites. Tamrock has been selected to provide the reaming heads for the project and the disc- cutters will be supplied by Dresser Industries. At presstime, the first pilot hole (133/4 inches in diameter) had reached the 1,580-ft level. An in-hole multi-shot gyro survey indicated the bit is 7 inches off target (that’s four one-hundredths of one percent off target — well within Falco bridge’s specifications).
The 97R unit is being installed underground on the 2050 Level. There is only one other machine like this in the mining world. It is working in an old underground gold mine in Ghana. Robbins has designed this machine to ream 610-m raises, so the Falco/ Harrison project at the Craig orebody will be pushing the machine to its limits.
With two new machines sold in the last two months (a Rhino 200 and a Rhino 2000) Tamrock is experiencing somewhat of a comeback in the raise boring field. This major mining equipment manufacturer, based in Finland, has sold a total of eight raise bore machines worldwide. Six of those have been running since the 1970s, according to William Lainsberry of Tamrock Canada in Sudbury. He says it is only a matter of time before a Rhino is sold to a Canadian contractor or mining company. “We’re quoting the machines here now. It’s a very competitive market.”
The number of manufacturers competing for that market has been culled since the recession. The raise-bore division of Ingersoll-Rand was bought out by Robbins, and last year Tamrock bought out Dresser, a major supplier of raise-bore cutters. One mining contractor which owns three Ingersoll- Rand built machines (RBM7-SPs) is Thyssen Mining Construction of Regina, Sask. This western mine contractor also owns a Subterranean 003 and a Robbins 61R.
Thyssen is involved in one of the more challenging raise boring projects in the country. They have won a contract to ream six holes ranging from 6 to 10 ft in diameter at the Namew Lake mine in northern Manitoba. What makes the project unique is the angle of some of those holes. Not only is Hudson Bay Mining & Smelting using raise-bore machines to drive ventilation raises and ore passes at this big new mine, but an ambitious plan to mine the 2.8-million-ton nickel-copper orebody there from raises driven in the ore at 45 angles has captured the attention of many in the industry. Kenneth Wilconson, who has worked for Thyssen for nine years is confident it can be done with sufficient accuracy. He supervised the reaming of penstocks in sedimentary rocks at the Mica Dam project in B.C. which were driven an 45 . The ore at Namew Lake is buried under a se quence of Paleozoic limestones and sandstones. The initial phase of the Namew Lake project is worth about $2 million, according to John Pearce, projects manager for Thyssen. It should be completed in June or July, 1989. After that, depending on the success of the test-mining, Thyssen could be on the project for another three years.
Be the first to comment on "Specs WANNA RAISE?"