Details

MANNER OF EXTRACTION OF PILLARS

(Cir. Tech. 14/1975) The following conditions are usually incorporated in depillaring permission letters while specifying the manner of extraction of pillars in caving system-

(i) Each pillar shall be split into two equal parts by driving a central split gallery, not 

exceeding 3.6 metres in width.

(ii) Each half of a pillar shall then be extracted by driving slices, not exceeding 4.5 metres in width, so however that the area or roof exposure at any one working place shall not 

exceed 60 sq. m. at any time.

(iii) While driving slices, a rib of coal, not less than 1.8 m in thickness shall be left against the adjacent goaf. This rib may, however, be reduced judiciously on retreat.

(iv) Not more than one slice shall be driven in a pillar at a time, and the extraction of a half of a pillar shall not be commenced until extraction boons of the adjoining inbye half 

of the pillar has been completed.

 As would be seen, a coal rib of 1.8 m in thickness is recommended to be left against the goaf in each slice which is to be judiciously reduced on the retreat consistent with 

safety. Similar precautions should be taken while establishing a connection of a split gallery which is to join into a goaf. Some fatal accidents have occurred recently when this 

precaution was not taken. Thickness of rib to be left in the split may perhaps be same as that required to be left in slices. As in the case of ribs left in slices, the same could be 

reduced judiciously in the split galleries also after setting strong breaker line of cog(s) and/or other means of artificial support adjacent to it.