Different methods of coal mining are adapted to dig out the natural coal from the earth. Among them, Surface mining method is applied for producing coal of about nearly 40% in the world. The coal deposits are found on the surface of the earth and make the mining easier for the coal-miners. The various types of coal mining are contour, mountaintop removal and strip mining.
Strip mining is adopted in areas, which has leveled landscape. The surface coal is exposed when the earth covering them is removed in strips. When the whole earth concealing is removed from the surface the coal that lay beneath is exposed. They appear in blocks and are usually extracted either by drilling or blasting. Once the strip is free of coal or goes empty, the strip mining process is continued with the next strip that lay adjacent to the former.
The contour mining is used to remove coal from the layer following the contours found along the ridges of a hill or landscape. The commonly used places for this type of mining are areas with rolling to steep terrain. This method may create landslides and erosion troubles. Using the freshly cut overburden to refill the mined areas rectifies these problems. Strip mining has its own limitations and when the process of strip mining reaches a specific stripping ratio, it may not yield you profit when continued.
Mountaintop removal coal mining can be understood by its name. Removing the mountaintops exposes the coal. This method also involves disposing of mining overburden that is associated with mountaintops removal in nearby valleys. This method is a combination of area and contour strip mining methods. This process creates adverse changes in the topography like creating head of hollow hills and filling valleys with mining wastes.
Latest open cast methods can reveal higher proportion of coal deposit than the underground mining methods.
Deep mining or underground mining is applied to dug out coal that lay underneath the surface of the earth. The primary underground mining ways are Continuous, Longwall, Shortwall, Retreat and Blast Mining.
Longwall mining method is adopted for about 50% of underground mining. This method involves a complex machine with a revolving drum that sways mechanically back and forth across the coal deposit. This method yields high production and ensures safety. This method has sensors that can detect the quantity of remaining coal in the seam and robotic controls contribute to the efficiency of the process.
Continuous mining method is applied for about 45% in underground coal mining. The machine used in this method has a huge revolving steel drum that is facilitated with tungsten carbide teeth to extract the coal from the seam.
Blast mining occupies less than 5% of the whole underground mining in USA. Explosives are used to break the coal seam in this method. The extracted coal is collected and transported to the central area using conveyors or shuttle cars.
Shortwall mining covers 1% and the method is somewhat similar to longwall mining. Retreat mining method employs pillar or coal ribs to support the roof of the mine. This is the most dangerous method as it involves risk of falling roofs that might trap or crush the workers in the mine.