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How does auger mining extract coal from a contour strip mine?

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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 contour strip mining, auger mining is used to recover coal from a seam at the base of a highwall where traditional stripping has become uneconomical.12

The process functions similarly to a carpenter’s bit:
* Drilling: A large auger head bores horizontally into the exposed coal seam.23
* Extraction: As the cutting head rotates, it shears the coal, producing shavings that are carried out along the spiral of the auger stems.23
* Extension: As the head penetrates deeper—sometimes reaching 60 to 100 meters—additional auger stems are attached to the assembly.23
* Collection: Once the coal discharges from the spiral at the surface, it is collected for transport.3

To maintain structural integrity and support the overlying rock, webs of intact coal must be left between adjacent holes, resulting in limited recovery rates. While effective for reaching deeper reserves, the method is associated with environmental concerns such as subsidence and water pollution.32