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A pillar method of working suitable for seams 4 ft (1.2 m) and over in
thickness. Three or more narrow headings are driven rapidly with machines
at about 30-yd (10-m) centers with crosscuts for ventilation. The headings
are 10 ft (3 m) or more wide and 5 to 6 ft (approx. 2 m) high or seam
thickness. Upon reaching the boundary, the pillars formed by the headings
are extracted, again with machines, on the retreat. This method is favored
in the United States and the heading work is quite as productive, if not
more so, than pillar working. See also: entry;
longwall retreating.
Nelson
Source:
Dictionary of Mining, Mineral, and Related Terms
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