Abstract:
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The understanding of the thermo-hydro-mechanical behaviour of a clay barrier is needed for the prediction of its
final in situ properties after the hydration and thermal transient in a radioactive waste repository.
As part of the CEC 1990-1994 R&D programme on radioactive waste management and storage, the CEA (Fr),
CIEMAT (Sp). ENRESA (Sp). SCK CEN (B). UPC (Sp) and UWCC (UK) have carried out a joint project on
unsaturated clay behaviour (Volckaert et al.. 1996). The aim of the study is to analyse and model the behaviour of a
clay-based engineered barrier during its hydration phase under real repository conditions. The hydro-mechanical and
thermo-hydraulic models developed in this project have been coupled to describe stress/strain behaviour, moisture
migration and heat transfer. A thermo-hydraulic model has also been coupled to a geochemical code to describe the
migration and formation of chemical species.
In this project. suction-controlled experiments have been performed on Boom clay (B), FoCa clay (Fr) and Almeria
bentonite (Sp). The aim of these experiments is to test the validity of the interpretive model developed by Alonso and
Gens (Alonso et al., 1990). and to build a database of unsaturated clay thermo-hydro-mechanical parameters. Such
a database can then be used for validation exercises in which in situ experiments are simulated.
The Boom clay is a moderately swelling clay of Rupellian age. It is studied at the SCK. CEN in Belgium as a
potential host rock for a radioactive waste repository. In this paper, suction-controlled experiments carried out on
Boom clay by SCK CEN are described. SCK CEN has performed experiments to measure the relation between
suction, water content and temperature and the relation between suction, stress and deformation. The applied suctioncontrol
techniques and experimental setups are detailed. The results of these experiments are discussed in the
perspective of the model of Alonso and Gens. The influence of temperature on water uptake was rather small. The
measured swelling-collapse behaviour can be explained by the Alonso and Gens model. |