A method of of coal mining depends on the depth of its bedding:
- open cast mining (open pit), if the depth of coal seams does not exceed 100 meters;
- underground coal mining (mine).
Excavation of coal consists of breaking and loading of chipped fossil. When a surface method is used there are three types of excavation: mechanical, drilling and hydraulic. The choice of method of breaking depends on the physic-mechanical properties of the coal seam, the stability of host rocks, availability of appropriate equipment.
The most widespread method is mechanical process of breaking in which mining machines destroy the layer by means of cutters, crowns. Methods of mechanical separation of coal from solid also includes breaking jackhammers.
A coal pit is a mining enterprise used to develop fields by open cast
method. In a coal pit all the manufacturing processes necessary for extraction
of coal from the depths, are made on the surface. Preparation of rocks for
excavation includes: separation of rocks from solid and hoeing. Mined rock is
loaded into vehicles by means of different hoisting mechanisms: excavators,
loaders, rotary systems. Transportation of rocks is made by: rail, automobile,
pipeline and hydraulic transport, skip hoists, cable-ways.
Hydraulic coal mining is a process of underground coal mining, and transportation of coal up to the surface using high-speed liquid jets issuing from water monitors. As a source of fluid they also use inflow of groundwater into the mine. Over the past years there has been steady growth in the development of techniques and technologies of destruction of coal, rocks by means of high-speed jets with continuous, pulsating and impulsive action.
Hydraulic coal mining, as an independent technological direction, has the following advantages:
- high labor productivity,
- low cost,
- improvement of labor and safety of mining in preparatory slaughterings.
Mechanical hydraulic recess can be used in the extraction of robust, low-fissured coals when mechanical and hydraulic breaking is ineffective, and it has a lower power consumption. Its advantages:
it is independent or dependent on a lesser extent on geological disturbances;
it provides for practice of inclined formations;
it has lower production costs with a significant reduction of injuries and the complexity of work.
At mine development of a coal field the way of dredging directly depends on properties of containing breeds and a layer and conditions that are applied to the coal standards. They can use the following types of excavation: manual, drilling, geotechnological, and a number of mixed methods.
Depending on the direction of access to the coal seam they distinguish several ways of deposit opening: by tunnel (horizontal underground workings), or by vertical or inclined mine shafts.