While technology and equipment have improved significantly over the last century, the basic principles of mining have remained - find ore and remove it. Mine engineers develop drill or blasting patterns to best extract ore from the earth. These patterns are utilized daily by miners underground. The extraction process is strenuous and time-consuming. Miners spend hours prepping and drilling at the face (the working end of a drift or stope) before blasting happens. Red Lake's producing mines have often utilized two shifts of miners, completing the blasting sequence twice daily.
There are four main stages in the blasting process:
There are four main stages in the blasting process:
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Prep Before miners can begin drilling, the worksite needs to be secured and cleaned. The area is mucked out and the ore is transported to an ore bin for storage. The walls and back (ceiling) are scaled, removing any loose rocks. While traditionally completed with a scaling bar, today, scaling is often completed with a machine. After any loose rocks have been removed, miners use drills or jumbos to attach screening to the walls and back with large rock bolts. The screen is used to catch any rocks that shift during drilling. Historically, miners did not use screening but would stop multiple times per shift and re-scale their workspace. With a secure worksite, miners paint a grid-like drill pattern on the blasting face. Holes cannot be drilled more than once. To avoid this, miners cross out the previous blast's cut (the first set of holes to be detonated). Remnants of old blast holes or bootlegs are also highlighted and circled. If there was a misfire at the face, the miners have to remove the detonators carefully and flush the holes of explosives. Drilling near explosives can be fatal. |
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Jumbo drilling at a face - Photo courtesy of Goldcorp
The blasting wall and artifact display from the Beneath It All: Red Lake's Mining Story exhibition - A powder loader can be seen at the bottom left corner of the blasting wall
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Drilling
With the drill pattern spray painted on the face, miners drill dozens of 6-8 feet (1.8-2.4 metre) deep holes. The preset drill pattern dictates the amount and placement of the holes. Depending on the size of the face, 35 to 50 holes may be needed. Since its introduction in the mining industry, the jackleg drill has been the main drill that miners have used. However, depending on the situation and type of mining, drifters and stopers were also used. Today, companies are beginning to shift away from manual drills, preferring to utilize drilling machines like the jumbo. Loading Once the drill holes are completed, they are primed and loaded with blasting powder, a blasting cap and a fuse. Blasting powder is usually ANFO powder, a combination of ammonium nitrate and fuel oil. However, the explosive used may differ depending on the mine. Historically, blasting caps were attached to long fuses or electrical wires (depending on the type of cap used) and hooked up to a blasting machine for detonation. Today, mines use a combination of electric and non-electric blasting caps. Wires containing small amounts of explosives connect the blasting caps. The electronic blasting caps are connected to a central blasting system and set off the other blasting caps when detonated. |
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Blasting Historically, miners would light fuses and 'run like hell' to get away before the explosion. Electric detonators or blasting machines allowed miners to be farther away from the blast. Today, detonation takes place on the surface through a central system. Everyone has to be safely out of the mine and 'tagged out' before blasting can happen. Charges or holes are set off in a specific order to allow the rock space to expand and break. The most important set of holes are known as the cut. The cut is blown first to ensure that the remainder of the face has the space to expand. The rest of the holes are blasted in succession. Lifter holes (the bottom row of holes) are set off last to lift and break up the fallen rock. After the mine safely settles from the blast, the process begins again. |
Warning sign at Red Lake Gold Mines - Photo courtesy of Goldcorp
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