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Room and Pillar Mining

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Mining Processes

Room and pillar is a method employed in underground mining in which rooms are cut into the coal bed and pillars of ore are left to provide support. This method is usually employed when ore is positioned in flat and narrow deposits. The room and pillar method also helps control the flow of air within the mine. Most underground coal mining is completed by this method.

One of the most famous instances of a room and pillar operation is what is referred to today as the SubTropolis, the largest underground business complex in the world. Based in Kansas City, it is the result of space created by a room and pillar mining operation to remove 270-million year old limestone. Left behind were 25-foot (7.6-m) square pillars on 65-foot (20-m) centers, spaced 40-feet (12.2 m) apart. The concrete floor to the ceiling spans 16 feet (4.9 m) and have been engineered to provide sufficient stability and lighting. The SubTropolis, home to many businesses, is owned by Hunt Midwest, run by Lamar Hunt and his family.[1]

[edit] Types

There are two different types of room and pillar mining. The first involves the conventional method of drilling holes into the coal, blasting the rock and loading it into carts to be transported out of the mine; the second, known as continuous mining, involves a continuous miner machine cutting coal from the mine’s face in a continuous flow, eliminating drilling and blasting equipment.[2]

[edit] Process

Room and pillar mining is usually used while extracting coal, iron, and copper ores; it is best suited for deposits that are relatively flat. Rooms generally are 2,067 feet (630 m) wide and pillars are up to 328 feet (100 m) wide; pillars, and subsequent grid-like patterns, are formed as mining advances.

This type of mining requires care and precision to ensure the pillars left behind are of the correct size to enable miners to extract enough ore with the support of the pillars but not so much that they leave behind a substantial amount of valuable ore.

When mining with this method, miners must consider the height of the pillar, the conditions of the roof and the likelihood that it could cave, as well as the type of mineral that is being extracted. It is important that all of the pillars are supportive, as one falling pillar will result in subsequent collapsing of the cave, a disaster that is known to occur in this method of mining.

Sometimes the pillars are filled with backfill or waste material to provide additional support. Other times, timber and steel supports are elevated alongside the pillar. Self-supporting pillars can stand without additional support.

Ore located in the pillars is usually abandoned and not recovered, for doing so could result in the collapse of the mine.[3]

[edit] References

  1. Suptropolis Site Plan. Subtropolis. 2008-09-08
  2. Coal. Earth Science Australia. 2008-09-08
  3. Whyte, John and Cumming, John. Mining Explained. Northern Miner: Don Mills: 2004.