Civil Engineering Reference
In-Depth Information
4.4.5 Geothermal
Geothermal methods use temperature measurements on the surface, underground and in
boreholes to describe the temperature distribution with place and time. It includes the
study of natural and artificial sources of heat, heat transfer processes inside the Earth and
geothermal parameters of rocks and rock mass to enable the consideration of mineral de-
posit processes and structural features.
4.4.6 Examples and experience
There now follow two practical examples of the scope of application of geophysical meth-
ods.
4.4.6.1 Probing with SSP (Sonic Softground Probing)
Despite intensive geological investigations before the start of tunnelling, unexpected ob-
structions along the tunnel alignment cannot be fully ruled out before starting. Since these
obstructions are a particular problem for a shield tunnelling machine, systems have been
developed to probe the ground in front of the cutting wheel. The SSP advance probing
system (Fig. 4-39) developed by Herrenknecht can display contrasts of density in the
ground up to 40 m ahead of the machine, which enables the detection of any obstructions
in the ground. Ultrasound transmitters mounted on the cutting wheel send signals, which
are differently reflected according to the properties of the ground.
1 Transmitter
2 Boulder
3 Strata boundary
4 Receiver
5 Display
Figure 4-39
Diagram
of the SSP system from
Herrenknecht and display
on the monitor [91].
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