地下矿山采矿方式underground_mining_methods

Underground Mining Methods

(Animations courtesy of Sandvik Tamrock Canada, accompanying text by Terry

Gong, UBC Mining Engineering student)

Room and Pillar Mining

Ramps (inclined tunnels) are excavated to connect the surface to the

underground orebody. Drifts (horizontal tunnels) are excavated at different

elevations to surround the orebody. Next, stopes (tunnels that have direct

access to mining the ore) are mined to gain access to the ore. All tunnels are

excavated by drilling and blasting. Jumbos are in charge of drilling the holes in

the rocks and filling them with explosives. The loose rock, also called muck, is

transported by either dump trucks or Load Haul Dump (LHD) vehicles back up

to the surface for either waste disposal or processing. As mucking progresses,

rooms (tunnels) are cut into the ore body. In order to provide safe roof support

for mining, pillars of material around the rooms are left standing to hold up the

rock ceiling above. Some parts of the mine roof can be particularly weak and

fragile. In addition to pillar support, a jumbo is then brought back in for rock

bolting of the roof to ensure safety. When all the ore in the stopes has been

transported up to surface, some pillars can be removed, since they still have

valuable mineral content, while some must be left standing to provide active

support for the ceiling. In some room and pillar mines, pillars are all excavated as

mining nears completion, to allow the natural collapse of the roof.

Cut and Fill Stoping

In cut and fill stoping, the orebody is retrieved in horizontal slices beginning at

the very bottom and advancing upwards towards the surface. Ramps (inclined

tunnels) are excavated to connect the surface to the underground ore body.

Drifts are excavated to come in contact with the ore slices. The slices are drilled

using a jumbo, blasted by charging the drill holes with explosives, and ore is

removed by using dump trucks or Load Haul Dump (LHD) vehicles. The ore is

dumped into an ore pass, an inclined tunnel where ore is transported to a lower

elevation in the mine. The ore is picked up at the other end of the ore pass by a

LHD to be transported out of the mine through a ramp (inclined tunnel). Once a

slice is completely mined out, the empty space is partially backfilled hydraulically.

The backfill material used can be a mixture of sand and rocks, waste rock with

cement, or dewatered mill tailings (rejected low grade ore from processing,

usually fine and sandy). The backfill underground serves to keep the mine walls

stable and also as the floor for mining the next slice. Mining continues upwards

towards the surface until the orebody is depleted.

Sublevel stoping

Sublevel stoping is a mining method in which ore is blasted from different levels

of elevation but is removed from one level at the bottom of the mine. Before

mining begins, an ore pass is usually drilled from a lower to a higher elevation.

Jumbos selectively drill holes into the roof of the drift and fill them with

explosives. When the roof is blasted, loose rocks, or muck, fall through the

drilled ore pass. A Load Haul Dump (LHD) vehicle transports the muck to

another ore pass where it falls to a hopper that feeds a crusher. The crushed ore

is then elevated (raised) to the surface in a skip. As the muck is taken out, more

drilling of the now higher roof continues. The roof is blasted till it is so high that it

cannot be reached by a jumbo. Then a jumbo working in a higher elevation drift

is used to intersect the stope. After blasting, the ore falls down to the lower drift

where LHDs can drive in to load the muck and dump it at an ore pass. Drilling

and blasting continues until the stope is completely excavated. Once the stope is

completely hollowed out, it is backfilled from the bottom, up. The backfill material

used can be a mixture of sand and rocks, waste rock with cement, or dewatered

mill tailings (rejected low grade ore from processing, usually fine and sandy). The

backfill material must have a lot of strength to support the roof of the empty

stope.

Sublevel Caving

Sublevel caving is usually carried out when mining of the orebody through an

open pit method is no longer economically feasible. Mining now proceeds

underground, underneath the open pit. At first, both a raise and a network of

tunnels are made. At different sublevels, jumbos are used for long hole drilling,

drilling directly upwards into the roof. These holes are then charged with

explosives and blasted. As the roofs cave in, the rock from the ground surface

will cave in to the underground as well. Load Haul Dump (LHD) vehicles

transport the muck, loosened rocks, to an ore pass where the rocks are lifted to

the surface. Drilling and blasting takes place at different underground levels of

the mine at the same time. As the blasted rock, muck, is continuously

transported to the ore pass, more blasting will encourage the roof to cave in to

the void and further into the drift. This is repeated until blasting, caving and

transporting depletes the entire orebody.

Glossary

Bolting

Crusher

Drift

Drilling and blasting

drilling a hole, and inserting a bolt to strengthen the

ceiling and walls of an underground mine

a machine used to crush ore before it is transported

a horizontal underground tunnel that follows a vein or ore

body

the process of using a drill to create long, narrow

cylindrical holes in the rock, and filling these holes with

explosives which are then detonated to fragment the rock

a drill which is capable of drilling more than one hole at a

time and is especially useful in preparation for blasting.

Jumbo

Load Haul Dump

Mineral

a vehicle with a large bucket on the front used for

transporting ore to crushing stations and mucking

naturally occurring chemical compound with a unique

three dimensional crystalline structure and chemical

composition; component or rocks

waste rock that has been broken by blasting

a naturally occurring concentration of minerals that can

be mined at a profit

a vertical or inclined passage that is used for transporting

ore down to a lower level or hoist

the columns of rock that are left to support the ceiling in

room and pillar mining

a vertical or inclined opening from one level of a mine

that is driven toward the level above

inclined tunnels used to transport ore or machinery

the open areas left open by blasting in room and pillar

mining

a self-dumping bucket used in a shaft for hoisting ore or

rock

an underground excavation from which ore has been

removed

materials rejected from a mill after the recoverable

valuable minerals have been extracted.

Muck

Orebody

Ore pass

Pillar

Raise

Ramp

Room

Skip

Stope

Tailings

Glossary References: Mineral Resources Education Program of British Columbia, Social Studies 10/11:

Mining in BC A Resource Unit; The Northern Miner, Mining Explained: A Layman’s Guide (1996)