Underground mining (soft rock) refers to a group of underground mining techniques used to extract coal, oil shale, potash and other minerals or geological materials from sedimentary ("soft") rocks.
Longwall mining equipment consists of a coal shearer mounted on conveyor operating underneath a series of self-advancing hydraulic roof supports.
Room-and-pillar mining or continuous mining is commonly done in flat or gently dipping bedded ores. Pillars are left in place in a regular pattern while the rooms are mined out.
The picture to the left is that of room and pillar mining. In this instance the mining is done by machines. The ceiling demonstrates the pattern of a machine removing the rock.
Blast mining is an older practice of coal mining that uses explosives such as dynamite to break up the coal seam, after which the coal is gathered and loaded onto shuttle cars or conveyors for removal to a central loading area.
Shortwall mining is a method that accounts for less than 1% of deep coal production, shortwall involves the use of a continuous mining machine with moveable roof supports.
Coal skimming is no longer in general use, because of the massive amount of water needed and environmental damage thereof, in the late 1930s.
