Coupled thermo-hydro-mechanical behaviour of a deep clay

¹ Universitat Politècnica de Catalunya, Barcelona, Spain
² Centre Internacional de Mètodes Numèrics en Enginyeria, Barcelona, Spain
³ ONDRAF/NIRAS, Brussels, Belgium

^* Corresponding author: enrique.romero-morales@upc.edu

Abstract

An experimental study on Ypresian clays –one of the potential deep formations in Belgium for the geological disposal of heat-emitting radioactive waste– was undertaken to systematically study its thermal properties and coupled hydro-mechanical response during fast heating pulse tests. An accurate characterisation of the thermal properties is required for assessing the near-field perturbations around disposal galleries that the sedimentary host rock formation will undergo. A new experimental cell adapted to apply the high in situ stresses and with thermal flux sensors was used to directly measure the thermal conductivity at different sample orientations (heat flux orthogonal and parallel to bedding planes). A clear influence of the degree of saturation – despite being close to saturation – and anisotropic features on thermal conductivity have been detected. The study was complemented by performing fast heating pulse tests under constant volume on a new and fully-instrumented axisymmetric cell. The cell allowed recording the pore pressure build-up and dissipation along a heating pulse and under water-undrained conditions.