Civil Engineering Reference
In-Depth Information
11.5.5 Adaptable shield machines with convertible process
technology (KSM)
Numerous tunnels run through very changeable ground conditions, which can range from
rock to loosely consolidated soil. The process technology therefore has to be adapted to
suit the geological conditions and appropriate adaptable shield machines have to be used.
The various types are:
a) Shield machines, which can be operated with a different process without rebuilding:
- earth pressure balance shield SM-V5 ↔ compressed air shield SM-V3
b) Shield machines, which can be operated with a different process but have to be rebuilt.
The following combinations have been tried:
- slurry shield SM-V4 ↔ shield without support SM-V1
- slurry shield SM-V4 ↔ earth pressure balance shield SM-V5
- earth pressure balance shield SM-V5 ↔ shield without support SM-V1
The rebuilding work normally lasts several shifts.
11.5.6 Special types
11.5.6.1 Blade shields
In blade shields, the shield skin is split into blades, which can be advanced independently.
The ground is excavated by partial face machinery, cutting wheel or excavator. An advan-
tage of blade shields is that they do not have to be circular and can, for example, drive
a horseshoe-shaped section, in which case the invert is normally open. This is described
as blade tunnelling. Because of various negative experiences in the past, however, blade
shields are seldom used today.
11.5.6.2 Shields with multiple circular cross-sections
These shields are characterised by overlapping and non-concentric cutting wheels. The
type of machine is currently only offered by Japanese manufacturers and mostly used to
drive underground station cross-sections. The machines are difficult to steer and have not
yet been used in Europe.
11.5.6.3 Articulated shields
Practically all types of shields can be equipped with an articulated joint to divide their
length. This is provided particularly when the length of the shield skin is longer than the
shield diameter in order to make the tunnelling machine easier to steer. The layout can also
be necessary to drive very tight radius curves.
The description of the tunnelling machines is then according to one of the categories de-
scribed above. A separate category of “articulated shields” is no longer usual.
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