Coal mining The cycle of coal
{"Image DocumentName": "Coal mining The cycle of coal", "Image ImageDescription": "Coal is mined by two main methods: underground (or \u2018deep\u2019) mining and surface (or \u2018strip\u2019) mining. The majority of the world\u2019s coal reserves are recoverable by underground mining. The choice of mining method is determined by the geology of the coal deposit. There are two main methods of underground mining: room-and-pillar (\u2018bord\u2019-and-pillar) and longwall mining. With the room-and-pillar approach, coal deposits are mined by cutting a network of \u2018rooms\u2019 or panels into the coal seam and leaving behind \u2018pillars\u2019 of coal to support the roof of the mine. Surface mining operation in Australia. Longwall mining involves the use of mechanised shearers to cut and remove the coal at the face, which can vary in length from m. Self-advancing, hydraulic-powered supports temporarily hold up the roof whilst the coal is extracted. The roof over the area behind the face, from which the coal has been removed, is then allowed to collapse. Surface mining, economic only when the coal seam is near the surface, recovers a higher proportion of the coal deposit than underground methods. The equipment used includes: draglines, which remove the overburden (the term given to the strata between the coal seams and the surface); power shovels; large trucks, which transport overburden and coal; bucket wheel excavators; and high capacity conveyors. Surface mining equipment has increased dramatically in size over recent years. However, the high capital cost of importing this equipment can favour the selection of underground mining.", "Image XResolution": "37", "Image YResolution": "37", "Image ResolutionUnit": "Pixels/Centimeter", "Image Software": "SlidePlayer", "Image YCbCrPositioning": "Centered"}