Understanding the heat transfer, water flow, and swelling pressure development in engineered clay barrier and the evaluation of the influence of these phenomena on the barrier performance are important issues in constructing nuclear waste repositories. The thermal, hydraulic and mechanical processes that take place within the clay barrier during its functioning lifetime are strongly coupled and therefore difficult for experimental and numerical modelling. In order to collect valuable experimental data for predicting the long term barrier functionality it is necessary to carry out tests with known and controlled initial and boundary conditions as well as to measure temperature, water content and mechanical stress along the specimen in a reliable and robust way. For this reason a new apparatus has been developed for laboratory testing of coupled thermo-hydro-mechanical behaviour of clay-buffer material under conditions close to the situation in the field. The main objectives of this paper are: (1) to describe the experimental device; (2) to introduce the sensors implemented and their calibration, and (3) to present the first experimental results obtained with the new equipment.
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