Page 344 - Rock Mechanics For Underground Mining

ROCK SUPPORT AND REINFORCEMENT

Figure 11.12 Use of grouted rein-
forcing bars to pre-reinforce a draw-
point in a large mechanised mine.
The brow area, shown shaded, is
blasted last, after reinforcement has
been installed from the drawpoint and
from the trough drive (after Hoek and
Brown, 1980).

important in many underground mining operations. In particular, failure of the brow
of the excavation can result in complete loss of control of the stope draw operation.
Figure 11.12 shows a suitable method of pre-reinforcing the brow area with grouted
reinforcing bars installed from the drawpoint and from the trough drive before the
brow area is blasted.

11.5 Support and reinforcement design

11.5.1 Purpose
Frequently, support and reinforcement design is based on precedent practice or on
observations made, and experience gained, in trial excavations or in the early stages
of mining in a particular area. However, it is preferable that a more rigorous design
process be used and that experiential or presumptive designs be supported by some
form of analysis. Depending on the application, design calculations may be of a
simple limiting equilibrium type or may use more comprehensive computational
approaches involving rock-support interaction calculations and taking account of the
deformation and strength properties of the support and reinforcement system and the
complete stress-strain response of the rock mass. Different design approaches may
be required for three main applications of support and reinforcement:
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