Underground Coal Mining - The underground coal mining refer into underground mining technique group that used for extracting coal, potash, shale, and many other minerals or geological source from underground.
Types of underground coal mining
There are 3 main types of underground coal mining, there is shaft mines, drift mines and slope mines. To decide what type of mine that will construct is depend on the coal seam depth and the terrain surround.
- Drift mine is mine that have horizontal entries to the coal seam from the hillside.
- Slope underground coal mining usually come with medium deep, and inclined from the coal seam surface.
- Shaft mines, is the deepest mine that have vertical access to the coal seam that use elevator that carry worker and mine equipment to the mine inside.
Most of underground coal mining are less than 1000 feet deep, but there are some mines that reach depths about 2000 feet.
Method of underground coal mining
There are three method of underground coal mining. This is due to the sedimentary rocks that commonly layered and it relatively less hard that require different methods.
- Long wall mining. The set of long wall mining equipment is consisting with coal shearer that mounted in conveyor and operated in series of self-advancing of hydraulic roof supports. The entire process in long wall mining is almost automated. Long wall mining machines are typically in 150-250 meters in width and it has 1.5 to 3 meter high. The long wall miners extract the panel rectangular coal blocks as wide as the equipment face installed insert and as long as certain kilometers. The long wall mine can advance to the coal area and commonly it retreat back to the tunnels development.
- Blast mining is the older coal mining practice that use explosive to break up the coal seam such as dynamite. After which coal gathered and loaded into shuttle cars or conveyors it will removal the central loading area. The process of blast mining consist of operation series that start with cutting the coal bed that make it break easily when it is blasted with explosive. There are less of 5% from total underground coal mining in US today with this practice.
- Room and pillar mining or the continually mining is the mining that commonly done in flat or smooth dipping bedded ores. The pillars are left in place with regular pattern while the room in mined out. The pillars will take out, and start from the farthest point into the mine exit. The room and pillar method is adapted well into mechanization and use for deposit of coal, phosphate, salt, oil, uranium ores and potash.
- Short wall mining is the coal mining that measure less than 1% of coal deep production. The short wall mining involves the use of continually mining machine with the moveable roof supports that similar to long wall mining. The panel f continuous mine shears coal panels into 150-200 feet wide and more than half mile long.
- Coal skimming is the no longer practically use because it use massive water and environmental damage.
The underground coal mining also differ with the surface mining.