Numerical Prediction of the Large‑Scale in Situ PRACLAY Heater Test in the Boom Clay

The large-scale PRACLAY heater test has been running since November 2014 in the HADES URF (Belgium) to examine the
combined impact on the host Boom Clay of the thermo-hydro-mechanical (THM) perturbations due to gallery construction
and a large-scale thermal load which simulates the heat dissipation of radioactive waste. To get an insight into the expected
evolution of the test, which will be helpful to guide the test, numerical prediction of the PRACLAY heater test had been
performed before the heater was switched on. The numerical prediction, based on the existing related knowledge before
the switch-on of the heater test, took into account the complex coupled THM processes and interactions in all the involved
materials of the experimental set-up (Boom Clay, bentonite, concrete lining, backfill sand, etc.) and the test phases from the
gallery excavation till the end of heating which is planned in 2025. A large number of constitutive models and associated
parameters required to define the numerical problem had been identified and calibrated on the basis of literature review,
results of extensive laboratory tests and back analysis of many relevant in situ measurements from the HADES URF. The
results of the numerical prediction are constantly and extensively compared with the in situ measured data obtained since the
switch-on of the heater till 4-year stationary heating. Overall, it can be stated that the general Boom Clay THM responses in
the PRACLAY heater test are in good agreement with the numerical prediction, which gives good indications on the model
capacity and confirms the existing knowledge of the Boom Clay THM behaviour.