What is auger mining?
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Auger mining is a surface mining technique used to recover additional coal from a seam located behind a highwall produced either by excavation or previously mined areas. An auger is a drilling device that consists of a rotating helical screw blade called a “flighting” that is used to move granular material, such as coal, from the highwall back to the entrance of the mine.
The auger is mounted on a rig that is capable of moving horizontally along the highwall, and it is equipped with a cutting head that bores into the coal seam as the auger rotates. As the auger advances, the coal is broken up and carried back to the entrance of the mine by the flighting.
Auger mining is typically used to extract coal from seams that are too thin or steep to be mined using traditional surface mining techniques, or when the coal seam is located in an area that is not suitable for surface mining due to environmental or logistical constraints. It is a relatively low-cost and low-risk mining method, and it can be used to recover coal that would otherwise be left behind during traditional surface mining operations. However, auger mining can be less efficient than other surface mining methods, as it leaves much of the coal in place and can result in lower recovery rates
⚫Auger Mining
🔷Auger mining means a method of mining coal at a cliff or highwall by drilling holes into an exposed coal seam from the highwall and transporting the coal along an auger bit to the surface and includes all other methods of mining in which coal is extracted from beneath the overburden by mechanical devices located at the face of the cliff or highwall and extending laterally into the coal seam, such as extended depth, secondary recovery systems
As the auger rotates and advances forward, coal is cut and pushed out of the hole by the rotating action of the auger.
🔹The action is similar to that of a carpenter boring a large hole in wood using an auger bit, and that is where the name derives.
🔷Auger mining recovers around one-third of the coal under the highwall, for whatever depth of penetration is achieved.
🔹 Auger cutting heads can be as large as 7 feet in diameter and may be drilled to a depth of more than 300 feet.
When the ultimate pit limit is reached, it is difficult to “pack up and leave” when you see the exposed coal seam.
🔹 So, in some regard, the company looks at this secondary recovery technique, i.e., auger mining, as the “icing on the cake.
🔹” It amounts to coal recovery at a very low cost. It is, however, somewhat problematic and controversial.
🔷The low recovery, less than 35%, means that the majority of the reserve remains in place, but it has been sterilized, i.e., left in a condition where it will be essentially impossible for anyone to recover the remainder in the future.
🔹The holes into the side of the hill create drainage holes for acid-laden water, and that is a big problem.