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Why must the floor and slope of a coal seam meet certain conditions for hydraulic 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.
In hydraulic mining, the floor and slope of a coal seam must meet specific conditions to ensure the process is both functional and efficient:
- Floor Stability: The floor must be composed of material that does not deteriorate when it comes into contact with water. If the floor softens or breaks down due to the water used to dislodge the coal, the mining operation cannot be successfully maintained.1
- Seam Gradient: The slope of the seam must be sufficiently steep to allow gravity to assist the water in flushing the broken coal away from the working areas. This gradient is essential for transporting the coal through channels to a collection point, ensuring the system remains productive and economical.1
When these conditions are met, high-pressure water jets can effectively fragment the coal and transport it, a method used extensively for steeply pitching deposits.21