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How are thick coal seams divided into slices for underground mining?
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coal mining
Schematic diagram of an underground coal mine, showing surface facilities, access shafts, and room-and-pillar and longwall mining methods.
When a coal seam exceeds the thickness that can be extracted in a single pass (typically five to seven metres), it is divided into multiple slices for underground mining. These slices, which generally range from three to four metres in thickness, are extracted using longwall, continuous, or conventional mining methods.1
The extraction process follows these key practices:
- Sequence: Slices may be removed in either ascending or descending order.1
- Void Management: While caving is the preferred practice to manage the space left behind, backfilling is employed if roof conditions or the risk of spontaneous combustion require that no caving occur. In such cases, the backfill material serves as an artificial floor or roof for the subsequent slice.12
- Methodology: The specific approach to extracting the complete seam varies, but the goal remains the systematic removal of the coal in manageable layers to ensure safety and efficiency.1