Definitions for "Longwall"
Keywords:  shearer, goaf, coal, gob, stowing
The coal seam is removed in one operation by means of a long working face or wall, thus the name. The workings advance (or retreat) in a continuous line which may be several hundreds of yards in length. The space from which the coal has been removed (the gob, goaf, or waste) is either allowed to collapse (caving) or is completely or partially filled or stowed with stone and debris. The stowing material is obtained from any dirt in the seam and from the ripping operations on the roadways to gain height. Stowing material is sometimes brought down from the surface and packed by hand or by mechanical means.
Series of equipment, including hydraulic jacks and a shearer, used to mine coal in an underground mine.