Rock mass classification systems - Geotechnical Investigation and Design Tables - page 237

Table 18.19 P - wave velocity estimate using Q value (adapted from Barton, 2006).

Rock mass quality, Q
value

<0.01 0.01-0.1 0.1-1.0 1 - 10 10 - 100 100 - 1000

Poor Poor/Fair Good

Description

Exception. Extremely Very OK/very Ext./Exc.

P - wave velocity V p (km/s) 1.5 1.5-2.5 2.5-3.5 3.5-4.5 4.5-5.5

RQD %

5%

5-10% 10-40% 40-80% 80-95%

95%

Fractures/metre 27 27-14 14-7 7-3 3

18.20 Prediction of lugeon using Q values
•

The Lugeon values provide an indication of the rock permeability.

•

Chapter 8 related the Lugeon value to the rock jointing characteristics-akey
parameters in the Q value assessment see Table 18.20.

Table 18.20 Average lugeon estimate using Q c value (adapted from Barton, 2006).

Qc Q UCS/100 0.001 0.01-0.1 0.1-1.0 1-10 10-100 100-1000

Poor Poor/Fair Good

Exception. Extremely Very OK/very Ext./Exc.

Description

Hard
porous

Hard
jointed

Hard
massive

Major fault Minor fault

Typical lugeon value

1000-100 100-10 10-1 1-0.1 0.1-0.01 .01-0.001

Lugeon value at depth
1000 m
500 m
100 m
50 m
25 m

~0.01
0.01-0.1
0.1-1.0
1.0-10
10-100

0.01-0.001
0.1-0.01
0.1-0.01
1.0-0.1
~1.0

0.01-0.001
0.01-0.001
0.01-0.001
0.1-0.01
0.1-0.01

0.01-0.1
0.1-1.0
1.0-10
10-100
100-1000

0.01-0.001

18.21 Prediction of advancement of tunnel using Q values
•

The tunnel advancement is proportional to the rock quality.

•

The Q value has therefore been used by Barton to estimate the average tunnel
advancement.

•

The TBM rates decline more strongly with increasing tunnel length.