Lesson 4 Coal Underground Mining Flashcards
a highly mechanized underground mining system for extracting coal.
Longwall mining
In Longwall Mining, a layer of coal is selected and blocked out into
an area known as a ______, usually _____ m long X ______ m wide and is set with a mining equipment, typically ________ meters in width and _______ meters high
consisting of a coal shearer mounted on conveyor operating underneath a series of self-advancing hydraulic roof supports.
panel; 3000 m long X 250 m wide; 150-250; 1.5 to 3
In Longwall Mining, extraction is an almost continuous operation involving the use of self-advancing hydraulic roof supports
sometimes called _____.
shields
The system may advance into an area of coal, or more commonly, retreat back between development tunnels (called “______”) allowing the roof behind the supports to collapse in a planned and controlled manner.
Gate roads
Why is it we need to collapse the support in a longwall mining after extracting the coal?
to prevent continuous build up of back pressure and prevent massive collapse that is equivalent to a bomb explosion
This technique is considered as the most common supported pillar method, designed and used primarily for mining flat-lying seams, or tabular orebodies
like coal and is most advantageous for shallow orebodies –as a means of preventing surface subsidence.
Room and Pillar Mining
This mining method accounts for less than 1% of deep coal production. This technique involves the use of a continuous mining machine with moveable roof
supports, similar to longwall.
Shortwall Mining
In Shortwall Mining, continuous miner shears coal panels ______ feet wide and more than a half-mile long.
150 to 200
In this method, pillars are left in place in a regular and systematic pattern as support of the roof while the rooms are mined out.
Room and Pillar Mining
A method with low recovery rate as large percentage of ore remains in place underground.
Room and Pillar Mining
The pillars are taken out starting at the farthest point from the stope
access, allowing the roof to collapse and fill in the stope. This process is called ___________. Although this allows for greater recovery as less ore is left behind in pillars, the risk of surface subsidence is a problem.
retreat mining
Room and Pillar Mining is well adapted to mechanization and is sometimes referred to as ________
continuous mining
This is an older practice of coal mining that uses explosives such as dynamite to break up the coal seam and accounts for less than 5% of total underground production in the U.S. today.
Blast Mining
This process consists of a series of operations that begins with “cutting” the coal bed so it will break easily when blasted with
explosives. Broken coal is then gathered and loaded onto shuttle cars or conveyors for removal to a central loading area.
Blast Mining
After a brief increase in 2017, production in the United States decreased by _____ in 2018,
continuing the long-term trend that has seen production fall by more than one third since 2008.
2.5%
