Engineering geology aspects for design and classification - Tunnel Engineering: Basics and Additional Services for Design and Construction - page 68

2.4.4 Example of a project-related classification according to DIN 18312
for the shotcrete process
The project-related classification according to DIN 18312 [62] is now illustrated through
the example of the drill and blast driving of the Oerlinghausen road tunnel (construction
period 9/1994 to 3/1996) on the route of the L 751.

2.4.4.1 Procedure at the Oerlinghausen Tunnel
Working from the geotechnical investigations and the intended construction process, a
project-related tunnelling classification with support types according to DIN 18312 was
developed for the excavation and support works. Rock mass behaviour, excavation and
support were each defined through one tunnelling class (Fig. 2-16).
The excavation of the entire cross-section was generally divided into top heading, bench
and invert, not only for reasons of stability but also for construction process reasons (Fig.
2-17 and 2.18).
In the areas of the top heading, bench and invert, the same tunnelling class applies within
one cross-section. Within a tunnelling class, round lengths and support are laid down dif-
ferently for the areas of the top heading, bench and invert. The geological and rock me-
chanics documentation and the interpretation of the geotechnical measurements are used
in order to determine the tunnelling classes as the tunnel advances.

The individual support measures are laid down according to the behaviour of the rock
mass for tunnelling at the location.
The support measures are agreed according to local conditions within the range given in
the plans (Fig 2.17 and 2.18). It is not possible to derive any change of the tunnelling class
from this, however, as long as the classification criteria for the excavation remain constant.
The round lengths given in the tunnelling classes are maximum values.

Table 2-28 Shares of the forecast tunnelling classes for the Oerlinghausen Tunnel.

Section Length Expected tunnelling class

4.1 4.2 4.3 4.4 6 7

[m] [m] [m] [m] [m] [m] [m]

1 32 - - - - 16 16

2 224 - 90 74 45 15 -

3 85 55 30 - - - -

4 51 - 15 20 13 3 -

5 50 - - - - 25 25

Sum 442 55 135 94 58 59 41

Sum % 100 12 31 21 13 13 10