Page 583 - Rock Mechanics For Underground Mining
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EXAMPLES OF MONITORING ROCK MASS PERFORMANCE
Figure 18.16 Microseismic event
locations in the period 28–30 June
2001 at (a) stope 20, and (b) stope
26, Williams Mine, Ontario, Canada
(after Bawden and Jones, 2002).
On 17 December 1999, a 2.6 Mn rockburst occurred in the same general area at the
location shown in Figure 18.15. SMART cables installed on the 9450 level above the
previously heavily damaged 9415 level, showed instantaneous load increases of up to
70% of yield. Even though the load increases in some locations were substantial, the
reinforced shotcrete was virtually undamaged. This event was followed by a series
of events having magnitudes of 1.6 to more than 3.0 Mn as detailed by Bawden and
Jones (2002). Figure 18.16 shows the locations of events recorded in the period 28–30
June 2001 on vertical sections through stopes 20 and 26. A 3.1 Mn event occurred
on 28 June 2001. It will be noted that at stope 20 towards the eastern side of the sill
pillar, microseismic activity was restricted to the footwall while at stope 26 further to
the west, microseismic events were recorded in both the ore and the footwall.
Figure 18.17 shows the displacements recorded over an almost two year period in
a SMART cable installed in the stope 24 cross-cut on the 9390 level. Displacements
565
