Modelling coupled behaviour of a clay barrier at high temperatures

The design of repositories for the isolation of radioactive waste generally contemplates the use of expansive clays as a buffer material. In field conditions the clay barrier will be hydrated under confined conditions and will also undergo processes of heating, up to maximum of 100 ° C ( this is according to the Spanish concept for the isolation of high level radioactive waste). Based on experimental data, models have been developed to explain and reproduce the observed thermo-hydro-mechanical (THM) behaviour of expansive clays. However, unplanned overheating in a large scale test has provided the opportunity to analyze the clay barrier under conditions quite different from the design ones. A THM formulation and constitutive model have been used to describe and reproduce the main aspects of the observed response of the clay barrier. The analysis provides a unique opportunity to test our current understanding of compacted expansive clay behaviour at temperatures not previously reached.