Impact of excavation damage on the thermo-hydro-mechanical properties of natural Boom Clay

Boom Clay has been considered as a potential host-rock for the geological radioactive waste disposal in Belgium. In this context, it is important to well understand the thermo-hydro-mechanical behaviour of this clay around the disposal galleries. This study aimed at investigating the influence of EDZ around the connecting gallery on the thermal conductivity, small-strain shear modulus and hydraulic conductivity. Several samples of natural Boom Clay at different distances from the gallery were taken from the borecore drilled in July 2012, and thermal conductivity and bender element tests were carried out on these samples. As Boom Clay is a crossanisotropic material, the anisotropy of its properties was investigated by considering different directions with respect to the bedding plane. Microstructural observations were also made using MIP and SEM methods on the samples located at different distances from the gallery. The identified macro-pores were related to the effect of excavation damage, and a damage variable was thus defined, allowing the properties of Boom Clay to be estimated.