Page 411 - Rock Mechanics For Underground Mining
P. 411
THE ELLIOT LAKE ROOM-AND-PILLAR MINES
Figure 13.21 Relation between pil-
lar factor of safety and pillar perfor-
mance (after Hedley and Grant, 1972).
Figure 13.22 Effect of mining depth
on pillar width and volume extraction
ratio (after Hedley and Grant, 1972).
mined area is shown in Figure 13.23. The mining sequence in the area involved the
extraction of seven level stopes up-dip of the trackless area, the eight level stopes,
the trackless area, and then the nine level stopes. Mining of the nine level stopes
was in progress when pillar disintegration commenced in the trackless area. Pillar
disintegration progressed from this area, involving initially stable pillar failure, and
subsequently unstable failure and pillar bursting in the seven level sill pillars.
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