Page 375 - Rock Mechanics For Underground Mining

UNDERGROUND MINING METHODS

Figure 12.5 Schematic layout for
sublevel open stoping with ring-
drilled blast holes (after Hamrin,
2001).

selective mining is precluded by the requirement for regular stope outlines, which are
associated with the use of long blast holes. Blast hole penetration of stope walls, due
to drilling inaccuracy, leads to dilution. Dilution from this source is, relatively, a more
significant problem in narrow orebodies. The resulting minimum orebody width for
open stoping is about 6 m.
Pillar recovery is common practice in open stoping. Backfill of various qualities
may be placed in the primary stope voids, and pillar mining performed by exploiting
the local ground control potential of the adjacent fill. Alternatively, pillars may be
blasted into adjacent stope voids, with the possibility of extensive collapse of the
local country rock. Successful ore recovery would then require draw of fragmented
ore from beneath less mobile, barren country rock.

12.4.3 Cut-and-fill stoping (Figure 12.7)
In the most common form of cut-and-fill stoping, mining proceeds up-dip in an
inclined orebody. (An alternative, less common, method involves down-dip advance
of mining.) The progress of mining is linked to a closely controlled cycle, involving
the sequential execution of the following activities:
357