Measurement for monitoring, probing and recording evidence - Tunnel Engineering: Basics and Additional Services for Design and Construction - page 153

Figure 4-17 “Rex” multiple extensometer
from Interfels GmbH.
Figure 4-18 Example of
extensometer measure-
ment.
In shallow tunnelling, extensometers set at ground level can be used to record the settle-
ment behaviour of various soil strata and also the particularly interesting course of settle-
ment above the crown at each phase of construction (Fig. 4-19). The surface settlement
itself must, as already explained in Section 4.3.1.4, be measured by levelling.