DAUB recommendations for the selection of tunnelling machines - Tunnel Engineering: Basics and Additional Services for Design and Construction - page 370

The core of the recommendations can be found in Sections 11.5 and 11.6. In Section 11.5,
the technical features of the tunnelling machines are explained and the various processes
are categorised into types (Appendix 1). Section 11.6 explains the system behaviour of
each machine type and includes details of the interaction between the machine and the
surrounding ground. Then the significant ground/soil parameters used in the production
and analysis of the geotechnical report (Step 1) are defined in relation to the processes
(Appendix 2). Environmental aspects are dealt with in Section 11.7 and other significant
constraints in Section 11.8. Finally, recommended applications are formulated in Section
11.9 for each type of machine based on the key parameters in the form of an application
matrix (Appendix 3) for the selection of the tunnelling machine (Step 2).

11.5 Categorisation of tunnelling machines

11.5.1 Types of tunnelling machine (TVM)
Tunnelling machines either excavate the entire tunnel cross-section with a cutterhead or
cutting wheel or excavate partial sections using appropriate excavation equipment.
Tunnelling machines can be differentiated into tunnel boring machines (TBM), double
shield machines (DSM), shield machines (SM) and combination machines (KSM).
The machine is either continuously or intermittently driven forward as it excavates.
A systematic categorisation of tunnelling machines is shown in Fig. 11-2 (see also Appen-
dix 1 “Overview of tunnelling machines”).

11.5.2 Tunnel boring machines (TBM)
Tunnel boring machines are used for the excavation of tunnels in stable hard rock. Active
support of the face is not necessary and is not technically feasible. These machines can
generally only bore circular cross-sections.
TBMs are differentiated into machines without shield skin (gripper TBM), enlargement
tunnel boring machines or reamers (ETBM) and tunnel boring machines with shield skin
(TBM-S).

11.5.2.1 Tunnel boring machines without shield (Gripper TBM)
Tunnel boring machines without shield are used in hard rock with medium to long standup
time. They have no completely surrounding shield skin. The scope of economic applica-
tion can be greatly influenced and limited by elaborate conventional support measures and
the cost of wear to the excavation tools.
In order to be able to apply the contact force to the cutterhead, the machine is braced radially
by plates (grippers) hydraulically driven against the sides of the tunnel. Rock is excavated,
with little damage to the surrounding rock and to an exact profile, by disc cutters mounted on a
cutterhead. The machine fills most of the cross-section. Systematic support of the inner surface
of the tunnel is normally only carried out behind the machine (10 to 15 m and more behind the
face). In less stable rock, particularly when there is a danger of rockfall, it must be possible
to install steel arches, poling plates and rock bolts as close as possible behind the cutterhead.