Prospector Trails
Equipment/Underground · Fleet
Many of the world's richest orebodies are too deep for an open pit, so the mine goes underground. Everything there has to fit through a tunnel or down a shaft: drill rigs with long booms, loaders built low and articulated to turn tight corners, machines that bolt the roof, fans that move a river of air, and the hoist that winds it all back to the surface.
01 · The way in
An underground mine starts with a way in: a shaft sunk straight down, or a ramp, called a decline, spiralling down from the surface. Over the shaft stands the headframe, which carries the wheels for the hoist ropes.
This shift of miners posed in front of a headframe at Goldfield, Nevada, around 1905, when the town was in the middle of a gold rush.
02 · 1920
The hoist is a giant winch that winds skips of ore and cages of people up and down the shaft. In this hoist house at the Quincy copper mine in Michigan stands the largest steam mine hoist ever built, which started work in 1920. Its drum is about 9 m across, and it served a shaft about 2.8 km long, sloping down the dip of the copper lode.
Source: ASME.
03 · How deep
The deepest mine is Mponeng, a gold mine near Johannesburg, about 4 km below the surface. The rock there is around 60°C. To keep the air safe to breathe and work in, the mine pumps ice slurry underground and runs refrigeration plants and giant fans.
That is almost five times the height of the Burj Khalifa, the world's tallest building, at 828 m. Kiruna's newest main level is at 1,365 m.
Sources: Guinness World Records; OneMine; LKAB.
04 · Drill
Most hard-rock tunnels advance by drilling and blasting. A drill jumbo drives up to the face and its booms drill a pattern of holes a few metres deep, guided by computer at newer mines. The holes are charged, the face is blasted, and the cycle starts again with the next round.
This jumbo is drilling a face at Panasqueira, a tungsten mine in Portugal.
Source: Drilling and blasting.
05 · Load, before
For much of the 20th century, broken rock underground was shovelled into rail cars, first by hand and then by rail-mounted loaders. This Eimco overshot loader, now on show at the Soudan iron mine in Minnesota, scooped rock from the floor and flung it backwards over its own body into the car behind.
Source: International Mining.
06 · 1958
In 1958 Hidden Splendor Mining in Utah asked Eddie Wagner for a loader that could work in narrow, winding tunnels without rails. He built the MS-1, an articulated, rubber-tyred mining scoop. Its descendants, load-haul-dump machines or LHDs, now do most underground loading.
An LHD is low and long, bends in the middle to turn tight corners, and seats the driver sideways to drive both ways. This Sandvik LH517 stands on the surface, its bucket taller than the ladder beside it.
Source: International Mining, Eddie Wagner.
07 · Hold up the roof
Every new section of tunnel has to be made safe. Rock bolts, steel bars up to a few metres long, are drilled into the roof and walls and fixed with resin, grout or an expanding anchor, often with steel mesh and sprayed concrete. NIOSH counts grouted and mechanical anchor bolts as over 99% of the rock bolts used in US coal mines.
This drill rig is at work in the Pogo underground gold mine in Alaska.
Source: NIOSH.
08 · Air
Fresh air goes down one set of shafts and is pulled out of another by fans, carrying away exhaust, blasting fumes, dust and heat. Smaller fans blow air along ducts to each working face. Pumps do the same for water, which seeps into most mines and must be lifted out.
Ventilation is often a quarter to half of an underground mine's electricity use.
09 · 2019
Diesel exhaust is one of the main reasons underground mines need so much air. Borden, a gold mine near Chapleau in Ontario, opened in 2019 with its diesel mobile equipment replaced by battery-electric machines, built with Sandvik and MacLean Engineering.
Industry reports say Borden needs about half the ventilation of a comparable diesel mine.
Sources: Mining Association of Canada; Engineering News.
10 · Kiruna
Beneath Kiirunavaara, the mountain behind the town of Kiruna, LKAB runs one of the world's largest underground mines. Its newest main haulage level lies 1,365 m below the surface and needed 87 km of new tunnels. Trains, crushers and hoists move the iron ore to the surface.
Read how the mine is moving the town: The Town. Next: longwall mining, the underground method of coal.
Source: LKAB.
The full story
An underground hard-rock mine works in a cycle: drill, blast, ventilate, load and haul, then support the new ground. Each step has its own machines, all built to fit through tunnels a few metres wide and high. Coal mines, which work softer, flat seams, use a different set of machines, from continuous miners to longwall shearers.
Shallow mines are reached by a decline, a ramp that trucks can drive down. Deeper mines sink vertical shafts with a headframe and a hoist that winds skips of ore and cages of people. Large modern hoists are electric.
Drill jumbos drill the face of a tunnel; longhole rigs drill the long fans of holes used to blast big stopes. The holes are charged and blasted by trained crews under strict rules. See drilling and blasting.
Load-haul-dump machines (LHDs) load the broken rock and either tip it down an ore pass or into an underground truck. Some mines haul ore on rail or conveyor to an underground crusher and the shaft. LHDs are increasingly run by remote control or automation, so that operators stay away from freshly blasted areas.
Rock bolts, cable bolts, mesh and shotcrete (sprayed concrete) hold the roof and walls. Bolting rigs drill and install the bolts from a protected cab.
Main fans at the surface move air through the whole mine, auxiliary fans and ducts take it to each face, and deep mines add refrigeration. Pumps lift the water that seeps into the workings. Both run all day, every day, and together they are among a mine's biggest power users.
The main makers include Sandvik, Epiroc, Caterpillar, Komatsu, MacLean and Normet. Names here are facts about who makes what, not a ranking or advice.
More machines: all mining equipment, longwall mining and drilling and blasting. Guides: underground mining in Australia. Places: mining in Sweden, South Africa and Canada.
The main machines are drill jumbos, which drill blastholes in the tunnel face; load-haul-dump machines (LHDs), which load broken rock and carry it to a truck or ore pass; underground trucks; rock bolters and shotcrete sprayers that support the roof and walls; ventilation fans; pumps; and the hoist that lifts ore and people up the shaft. Many mines also use conveyors, rail haulage and crushers underground.
An LHD, or load-haul-dump machine, is a low, articulated front-end loader built for underground tunnels. The driver sits sideways so the machine can be driven in both directions without turning round. Eddie Wagner built the first articulated, rubber-tyred mining scoop, the MS-1, in 1958; the type is often called a Scooptram after one of his models.
Underground air has to be replaced to remove diesel exhaust, blasting fumes, dust and heat, and to give people fresh air. Big fans push or pull air through the tunnels, and in deep mines the air also has to be cooled. Ventilation is often a quarter to a half of an underground mine's electricity use, which is one reason mines are switching to battery-electric machines that make no exhaust.
Guinness World Records lists Mponeng, a gold mine near Johannesburg in South Africa, as the deepest mine, at about 4 km below surface. At that depth the rock is around 60°C, so the mine pumps ice slurry underground and uses refrigeration and large fans to keep the air safe to work in.
Yes. Borden, a gold mine near Chapleau in Ontario, opened in 2019 with its diesel mobile equipment replaced by battery-electric machines, built with Sandvik and MacLean. Canadian sources describe it as the country's first all-electric underground mine, and it needs about half the ventilation of a comparable diesel mine, according to industry reports.
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Pictures in this story: Kaupo Kikkas, Wikimedia Commons (CC BY-SA 4.0); California Historical Society, via Fæ, Flickr (CC BY 2.0); Chris Light, Wikimedia Commons (CC BY-SA 3.0); Nuno Madeira Alves, Wikimedia Commons (CC BY-SA 4.0); Bjoertvedt, Wikimedia Commons (CC BY-SA 3.0); Kelapstick, Wikimedia Commons (CC BY-SA 3.0); Dylan McFarlane, University of Exeter, Wikimedia Commons (CC BY 2.0); Andrew Woodvine, Wikimedia Commons (CC BY-SA 2.0); W. Bulach, Wikimedia Commons (CC BY-SA 4.0). Cover photos from Wikimedia Commons: Bucket wheel excavators by bluecloud9, CC BY-SA 2.0; Draglines by Roy Luck, CC BY 2.0; Haul trucks by Lechhabmed, CC BY-SA 4.0; Autonomous trucks by RobSimmons223311, CC BY-SA 4.0; Drilling and blasting by Siim Roov, CC BY-SA 4.0; Crushers by photosmith2011, Flickr, CC BY-SA 2.0; Ball mills and SAG mills by photosmith2011, Flickr, CC BY-SA 2.0; Froth flotation and tailings by Nina111955, CC BY-SA 4.0; Ore sorting by Tomra Sorting GmbH, CC BY-SA 4.0; Longwall mining by Bochum1805, Flickr, CC BY-SA 2.0; Conveyors, rail and ports by Kabelleger / David Gubler, CC BY-SA 4.0; Who supplies the mines by Alexandre Prevot, CC BY-SA 2.0.
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Cover photos from Wikimedia Commons: Super Pit, Kalgoorlie by Kgbo, CC BY-SA 4.0.
