underground mining

The drift mining is possible where the coal seam intersects the surface. It enters the seam in a horizontal direction following the coal. Shaft mining is a common method accessing a coal seam in which elevators provide access to mines. The room and pillar mining is nearly half the coal is left behind to support the mine roof. The pillars can squeeze and put pressure on adjacent pillars leading to roof collapse. Continuous mining machines can be used with drift or room and pillar mines. One miner can operate a contintuous miner to a rotating steel drum with tungsten carbide teeth to mine 5 tons of coal per minute. Longwall mining or retreat mining is highly efficient. The huge mining machines support the roof with hydraulics as it removes coal. When the coal is remover the machine retreats allowing the roof to fall behind it. Longwall mines extract much more of the coal than room and pillar mines.




advantages-well-drained, required less machinery and less initial effort. Its easy way to mine, its a cheap way to mine.
disadvantages-its not the safest way to mine as the tunnels may collase killing and trapping miners.
   Shaft Mining
advantages-that mining can be done as deep as possible and that it reduces the rock bursts or mines from falling off the ground.
disadvantages-it cost too much.


 Room and Pillar Mining
advantages-this cycle maximizes face utilization.
disadvantages-there is no face-to-face shift handover.

 

   Continuous Mining
advantages-flexibility and its adaptability to various mining conditions.
disadvantages-complexities, its inability to clean up adequately while advancing the face and its slow mining rate, a function of its small area of face attack.


advantages-safety of the miners enhanced by being under the hydraulic roof supports when they are extracting coal.
disadvantages-surface subsidence, which may considerably alter the landscape above the mine which can damage natural or man-made structures or features

information
http://www.coalcampmemories.com/miningmethods.html
http://rachealjane.wix.com/racheal-jane
http://www.ask.com/answers/304896681/advantages-and-disadvantages-of-adit-and-shaft-mining
http://www.saimm.co.za/Conferences/Pt2010/231-238_Pickering.pdf
 http://www.illawarracoal.com/technology.htm
http://www.sourcewatch.org/index.php?title=Longwall_mining

picture
http://elpmm.blogspot.com/
http://library.thinkquest.org/05aug/00461/shaft.htm
http://kids.britannica.com/comptons/art-1519/Room-and-pillar-mining-of-a-horizontal-ore-body
http://www.coalleader.com/continuous_mining.htm
http://www.umwa.org/?q=content/longwall-mining