Engineering geology aspects for design and classification - Tunnel Engineering: Basics and Additional Services for Design and Construction - page 65

Table 2-27 Valid ranges for the 2 nd ordinal [172].

Round length
of top hea-
ding up to

Maximum scope of validity
for the 2 nd ordinal (support
measures) in top heading

Round length
of bench up
to

Maximum scope of validity
for the 2 nd ordinal (support
measures) in bench

not given ± 0.35 not given ± 0.45

4.0.m ± 0.35

3.0 m ± 0.45 3.0 m ± 0.70

2.2 m ± 0.60

1.7 m ± 0.80 2.0 m ± 1.20

1.3 m ± 1.00

1.0 m ± 1.30 1.0 m ± 2.10

0.8 m ± 1.60

0.6 m ± 2.10

Figure 2-12 Diagram of rating areas [172].