Page 420 - Rock Mechanics For Underground Mining

PILLAR SUPPORTED MINING METHODS

Figure 13.29 (a) Stope and pil-
lar layout for an extraction sequence
based on primary stoping and pil-
lar recovery in secondary stopes. The
‘1-3-5’ sequence involves primary
stoping of each second ore block. (b)
Pillarless mining sequence in which
ore blocks are mined to maintain a
‘chevron’ mining front (after Morri-
son, 1996).

convergence behind the advancing face is relatively uniform. According to Morrison
(1996), although the sequence does not eliminate large seismic events and associated
rockbursts, it can significantly reduce the magnitudes of such events.
An interesting example of sequencing of extraction in a complex mining geometry
is provided by Andrieux and Simser (2001). The Brunswick Mine is characterised
by states of stress which lead to damaging seismicity and rock structure which poses
instability problems in zones of stress reduction. In two dimensions, the extraction
sequence resembles one half of the chevron pattern illustrated in Figure 13.29. The
stopes are mined ‘en-echelon’, by pillarless stoping, with overall progression of stop-
ing towards the final abutments for the extracted orebody. In three dimensions, the
orderly displacement of the abutment stress is provided by a sequence called pyrami-
dal pillarless mining, as illustrated in Figure 13.30. Implementation of the sequence

Figure 13.30 Three-dimensional
representation of the pyramidal
pillarless mining sequence at the
Brunswick Mine (after Andrieux and
Simser, 2001).
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