g system of sub-level caving with crushing of coal by overlaying strata: Coal seam is preliminarily broken in upper section by means of sub-level caving (using the same sub-level caving supports as for the operation below, but without the rear conveyor. Bottom section is mined by the basic system of sub-level caving as illustrated above. Typical seam thickness is up to 18m and above.
17－3 Sequence of working
A. The sub-level caving face operates in the bottom of the coal seam to be extracted.
B. The front coal is extracted using a shearer or by blasting in the conventional manner to a depth of 1 or 2 meters.
C. The rear coal is allowed to cave ready for loading.
D. There is provision in the support to give access to drill and fire the roof coal where the coal does not readily break up for loading.
E. A rear conveyor within the support transports the caved coal.
F. Once loading has been completed the rear door is closed and the sequence recommences [11].
17－4 Suitable Conditions of Sub-Level Caving
A. Thickness of coal seams: In general, the sub-level caving is suitable for the thickness of coal seams between 6
