Forty years of investigation into the thermo-hydromechanical behaviour of Boom Clay in the HADES URL

The heat generated by high level waste or spent fuel will create disturbances around a deep geological repository (DGR) containing these wastes. Since the 1990s, SCK CEN, EIG EURIDICE and ONDRAF/NIRAS have been characterizing the thermo-hydromechanical (THM) behaviour of Boom Clay and assessing the impact of the thermal disturbances. This research included laboratory tests as well as in situ experiments in the HADES Underground Research Laboratory (URL). Both types of tests have been complementary. Laboratory tests have allowed understanding the THM behaviour and determining associated values of the THM parameters of the clay under well controlled boundary conditions and loading paths. This knowledge and parameters were then validated and even improved by in situ tests which allowed investigating the effects of temperature on the Boom Clay behaviour at large scales. This paper gives an overview of this research and presents the main findings. It also explains how the knowledge gained supports the design of a possible future DGR and contributes to assessing the extent and impact of the THM disturbances in the Boom Clay around a DGR.