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Roger Weller, geology instructor
by A. Nonymous
There are Different types of mining methods the main two being, first, underground methods and the second being surface mining methods. Within these two methods are different sub types of mining that are used for different conditions and locations of the desired resource.
The first method of mining is
underground, which takes place when, rocks, minerals, or precious gems are too
far underneath the surface to mine. In this situation, underground access takes
place by either a drift mine, a slope mine, or a shaft mine. Drift mines enter
horizontally, or from the side into a hill or mountain and mine the coal within
the hill. “Slope mines usually begin in a valley bottom, and a tunnel system
slopes down to the coal to be mined. Shaft mines are the deepest mines; a
vertical shaft with an elevator is made from the surface down to the coal”
(Kentucky Geological Survey).
After gaining access to the desired deposits of ore, mineral, or gemstones different types of mining takes place. These consists of Room and Pillar mining and Longwall mining.
· Room and Pillar Mining, a Continuous miner is typically used for this type of mining. Two phases are used, first pillars being left behind and then slowly partially extracted nearing the end of excavation.
o A network of rooms is cut out by the miner, the miner loads coal at the same time and loads the coal onto a ram car. Eventually the coal makes its way to the surface after being placed onto a conveyer belt.
o Pillars made of coal are left behind to support the ceiling, and each room has a pillar of grater width to support the further depth or distance of the tunnels.
o Pillars of equal size to the room are optimal to avoid collapse
o Roof bolts are bolted into the ceiling to add additional support to the roof further decreasing the chance of ceiling collapse.
o After the bulk of excavating the pillars are slowly decreased/or partially excavated to maintain safely and increase profits on the resources available.
· “Longwall mining is wear shearers are used to cut and remove coal at the face of the mine” (Kentucky Geological Survey). Or in other words the shears cut the surface of the mine back and worth similar to grinding the wall away but on a larger scale.
o After coal is removed it is dropped on a conveyer which moves it to another until it finally reaches the top” (Kentucky Geological Survey).
o Hydraulic-powered, or water powered, roof supports are used to hold the roof up until the mining extraction is over
o Bolts are used just like with Room and Pillar mining, but are only used for the main tunnels.
Side tunnels are allowed to collapse after mining has been done.
Also as the machine moves forward the hydraulic lifts move forward allowing the
tunnel or the side tunnel to collapse increasing proficiency and reducing costs.
Surface mining is a broad category of mining in which soil and rock overlying the mineral deposit are removed. Surface mining includes strip mining, open-pit mining and mountaintop removal mining. Surface mining is practiced throughout the globe but bulk of it is practiced in North America. Heavy machinery is used that is capable of moving tons of earth, these machines consist of dragline excavators that extract the mineral, and earthmovers that remove overburden.
· Strip mining includes area stripping (area mine) and contour stripping (contour mine).Strip mining is most commonly used for mining coal and lignite.
o Area Stripping: is used on flat terrain, to extract deposits over a large area
§ The overburden from each strip of land is placed in the previous strip to reduce land destruction and produce clean up efficiency.
o Contour Stripping: involves removing the overburden above the mineral seam near the outcrop in hilly terrain, where the mineral outcrop usually follows the contour of the land
§ Overburden: soil and rock overlying the mineral deposit
o Open pit mining is a method of extracting rock or minerals from the earth through their removal from an open pit or borrow.
o used when valuable resources are found near the top
o Open pit mines that produce building material are often referred to as Quarries.
· Mountaintop removal mining is a form of coal mining that mines coal seams beneath mountaintops by first removing the mountaintop overlying the coal seam
o Very destructive method that usually involved explosives to break up the rock, the over burden in put into valley usually leaving a flatter landscape then previously had.
· Highwall mining is another form of surface mining that evolved from auger mining.
o Highwall mining is an intermediate between surface and underground mining. Usually is considered too costly to continue surface mining so different machines are brought in.
o Highwall mining uses continuous miners to penetrate into the side of the mountain whereas Auger Mining used Augers.
When the coal seam is exposed from the side of a hillside a
continuous miner is brought in to excavate the coal from the seam and fed back
out so it can be hauled off.
Continuous Miner, used for Room and pillar mining and highway mining
"Frontier Trails of The Old West." Frontier Trails of The Old West. N.p., n.d. Web. 28 Nov. 2016.
Hustrulid, William Andrew. "Strip Mining." Encyclopedia Britannica Online. Encyclopedia Britannica, n.d. Web. 28 Nov. 2016.
Kentucky Geological Survey, Univeristy of Kentucky, Coal. "Methods of Mining. University of Kentucky." Methods of Mining. University of Kentucky. N.p., 1 Aug. 2012. Web. 28 Nov. 2016.