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2.2 “In situ” experiment
The disposal tunnel model was built in a short driven, former mining adit. The lining was made up
of segments obtained from the PRACLAY project (SCK-CEN Mol, Belgium). The outside radius of
the lining measures 250cm with a segment thickness of 30cm and a width of 50cm. The model itself
is composed of 4 rings and the space between the lining and the rock consists of concrete (Fig. 3).
The longitudinal deformation of the lining is prevented on the one side by solid rock and on the
other by a steel frame.
Figure 3: Construction of the “in situ” experiment
The “in-situ” experiment environment models the case in which the lining deformation (displacement
of the segments) is prevented and maximum stress arises as a consequence of thermal loading.
The thermal loading of the inside surface of the lining is performed by means of the REVEL heating
system. The heating medium employed is water which is heated to a temperature of 90 o C by
electric boilers. The heating system is fitted with thermal insulation to eliminate heat loss. The experiment
is fully instrumented in order to measure temperature, stress, deformation and displacement.
Measurement is performed by means of a data logger with a data reading interval of once
every 10 minutes. The experiment was launched in October 2008 (Fig. 4).
Figure 4: The “in situ” experiment under operation
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