For Underground mine we have a term and definition in Energy.

Underground Mine (Energy)

A mine where coal is produced by tunneling into the earth to the coalbed, which is then mined with underground mining equipment such as cutting machines and continuous, longwall, and shortwall mining machines. Underground mines are classified according to the type of opening used to reach the coal, i.e., drift (level tunnel), slope (inclined tunnel), or shaft (vertical tunnel).
Underground mining equipment:
A coal-cutting machine is used in conventional mining to undercut, topcut, or shear the coal face so that coal can be fractured easily when blasted. It cuts 9 to 13 feet into the bed.
Continuous auger machine is used in mining coalbeds less than 3 feet thick. The auger has a cutting depth of about 5 feet and is 20 to 28 inches in diameter. Continuous auger mining usually uses a conveyor belt to haul the coal to the surface.
Continuous mining machine, used during continuous mining, cuts or rips coal from the face and loads it into shuttle cars or conveyors in one operation. It eliminates the use of blasting devices and performs many functions of other equipment such as drills, cutting machines, and loaders. A continuous mining machine typically has a turning "drum" with sharp bits that cut and dig out the coal for 16 to 22 feet before mining stops so that the mined area can be supported with roof bolts. This machine can mine coal at the rate of 8 to 15 tons per minute.
There are of two types of conveyor systems:
1. A mainline conveyor, which is usually a permanent installation that carries coal to the surface.
2. A section conveyor, which connects the working face to the mainline conveyor.
Face drill is used in conventional mining to drill shotholes in the coalbed for explosive charges.
Loading machine is used in conventional mining to scoop broken coal from the working area and load it into a shuttle car, which hauls the coal to mine cars or conveyors for delivery to the surface.
Longwall mining machine shears coal from a long straight coal face (up to about 700 feet) by working back and forth across the face under a movable, hydraulic-jack roof-support system. The broken coal is transported by converyor. Longwall machines can mine coal at the rate of 1,000 tons per shift.
Mine locomotive, operating on tracks, is used to haul mine cars containing coal and other material, and to move personnel in specially designed "mantrip" cars. Large locomotives can haul more than 20 tons at a speed of about 10 miles per hour. Most mine locomotives run on electricity provided by a trolley wire; some are battery-powered.
Ram car or shuttle ram is a rubber-tired haulage vehicle that is unloaded through the use of a movable steel plate located at the back of the haulage bed.
Roof-bolting machine, or roof bolter, is used to drill holes and place bolts to support the mine roof. Roof bolting units can be installed on a continuous mining machine.
Scoop is a rubber-tired haulage vehicle used in thin coalbeds.
Shortwall mining machine generally is a continuous-mining machine used with a powered, self-advancing roof support system. It shears coal from a short coal face (up to about 150 feet long). The broken coal is hauled by shuttle cars to a conveyor belt.
Shuttle car is a rubber-tired haulage vehicle that is unloaded by a built-in conveyor.
Underground mining methods:
* A drift mine is driven horizontally into coal that is exposed or accessible in a hillside. In a hydraulic mine, high-pressure water jets break the coal from a steeply inclined, thick coalbed that would be difficult to mine with the usual underground methods. The coal is then transported to the surface by a system of flumes or by pipeline. Although currently not in commercial use in the United States, hydraulic mining is used in western Canada.
* A punch mine is a type of small drift mine used to recover coal from strip-mine highwalls or from small, otherwise uneconomical, coal deposits. A shaft mine is driven vertically to the coal deposit. A slope mine is driven at an angle to reach the coal deposit.
* In a room-and-pillar mining system, the most common method, the mine roof, is supported mainly by coal pillars left at regular intervals. Rooms are places where the coal is mined; pillars are areas of coal left between the rooms. Room-and-pillar mining is done either by 1) conventional mining, which involves a series of operations that require cutting the working face of the coalbed so that it breaks easily when blasted with explosives or high-pressure air, and then loading the broken coal or 2) continuous mining, in which a continuous mining machine extracts and removes coal from the working face in one operation. When a section of a mine has been fully developed, additional coal is extracted by mining the supportive pillars until the roof caves in; the procedure is called room-and-pillar retreat mining.
* In a longwall mining system, long sections of coal, up to about 700 feet, are removed and no pillars are left to support the mined-out areas. The working area is protected by a movable, powered roof support system. The caved area (gob) compacts and, after initial subsidence, supports the overlying strata. Longwall mining is used where the coalbed is thick and generally flat, where surface subsidence is acceptable.
* A shortwall mining system generally refers to the room-and-pillar mining in which the working face is wider than usual but smaller (less than 150 feet) than that in longwall mining.
Roof support and mine ventilation are paramount in all underground mining operations. Roof bolting is the principal method of supporting the mine roof. In roof bolting, long bolts, 2 to 10 feet long with an expansion shell or with resin grouting are placed in the mine roof. The bolts reinforce the roof by pulling together rock strata to make a strong beam or by fastening weak strata to strong strata. Mine ventilation, accomplished with fans, is essential to supply fresh air and to remove gases and dust from the mine. To reduce the possibility of coal dust explosions, rock dust is sprayed in an underground coal mine. Rock dust is a very fine noncombustible material (pulverized limestone).

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