Design of Scamp for Development &Depillaring in Underground Coal Mines
After pillars have been formed on the bord and pillar system, consideration has to be given to the extraction of coal from the pillars; the operation is known as pillar extraction. It is also referred to as depillaring, pillar-cutting or broken working.
In a method of depillaring, known as the caving method, the coal of the pillars is extracted and the roof is allowed to break and collapse into the voids or the decoaled area, known as goaf. As the roof strata about the coal seam break, the ground surface develops cracks and subsides, the extent of damage depending upon depth, thickness of the seam extracted, the nature of strata, thickness of the subsoil and effect of drag by faults.