Rock mass classification systems - Geotechnical Investigation and Design Tables - page 235

Figure 18.2 Cable bolt support (Hutchinson and Diederichs, 1996).

Table 18.17 Approximate support required using Q value (adapted from Barton et al., 1974).

Q Value 0.01 0.01-0.1 0.1-1.0 1-10 10-100 100-1000

Poor Good

Description Poor Fair

Exception Extremely Very OK/Very Ext./Exc.

No rock support

Equivalent span/
height

0.15 0.25-0.8 0.8-2 2-5 5-12 12-30

4-100

4 < ---- Spot bolting ---- > 100
0.15 <---- Systematic bolting ----> 50

1.5-70

0.3-60 0.3 < ------- Bolts and shotcrete ------- > 60

0.15-50 0.15 < ------- Bolts and fibercrete ------- > 50

3 < -- Cast concrete lining -- > 40

3-40

18.18 Prediction of bolt and concrete support using Q values
•

Additional details as extracted from Barton's 2006 graphs are presented
below.