Page 352 - Rock Mechanics For Underground Mining

ROCK SUPPORT AND REINFORCEMENT

Figure 11.19 Permanent support requirements for underground excavations, using precedent practice. Barton et al.
and reinforcement recommendations proposed 38 categories of support based on their tunnelling quality index, Q, and the
based on the Q system of rock mass excavation support ratio, ESR, which varies with the use of the excavation and the
classification (after Barton, 2002).
extent to which some degree of instability is acceptable. These proposals have been
discussed in detail by Hoek and Brown (1980) who point out the dangers involved in
blindly adopting their provisions, particularly where the nature of the excavation and
the properties of the rock mass differ from those in the case histories that were used
in developing the recommendations.
Figure 11.19 shows the recommendations for the support and reinforcement of
permanent excavations offered by Grimstad and Barton (1993) and Barton (2002)
which update the original recommendations of Barton et al. (1974) and allow for, in
particular, subsequent advances in shotcrete technology.

Comprehensive analysis of general or systematic reinforcement. In a rock mass
subject to fracture and yield, the spatially-extensive model of reinforcement is more
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