Anisotropic thermal conductivity of natural Boom Clay

Abstract

The thermal conductivity of host rocks is an important parameter in the design of deep geological disposal of heat-emitting radioactive waste. Due to bedding, heat transfer in sedimentary rocks is affected by their transversally isotropic structure. In this work, an experimental program is run to measure the thermal conductivities of Boom Clay along various orientations with respect to the bedding plane by using the needle thermal probe technique. Measurements were performed on specimens obtained from cores drilled from the HADES Underground Research Laboratory (URL) at Mol, Belgium, at a depth of 223 m. The thermal conductivity values obtained are in good agreement with those previously published, confirming the thermal anisotropy of Boom Clay. Moreover, the observed changes in thermal conductivity with respect to the distance to the gallery provide further evidence on the extent of the Excavation Damaged Zone around the gallery.

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

“…The small-strain shear modulus (G 0 ) in different orientations of natural Boom Clay was determined by performing bender elements tests under unconfined conditions (Dao et al 2014b). In a bender element test, the velocity of shear wave (V S ) is determined allowing calculation of the small-strain shear modulus (G 0 ).…”

Studying the thermal conductivity of a deep Eocene clay formation: Direct measurements vs back-analysis results

“…Recently, Refs. [8,9] studied the thermal conductivity of Boom Clay (retrieved from HADES Underground Research Laboratory at Mol, Belgium, at a depth of 223 m) with a needle thermal probe technique at different orientations with respect to the bedding planes. Despite the apparent simplicity and standardisation of the experimental setup used, it is important to highlight that exploring thermal conductivity features on this type of sedimentary rocks with bedding planes is not straightforward.…”

A multiphysics and multiscale approach for modeling microcracked thermo-elastic materials

“…We compare the results with a bar without microcracks, whose governing equation reduces to the classical wave equation .€ u À Cu 00 ¼ 0, that we numerically solve for different ratios a u =a d and with the initial and boundary conditions (19) 1À4 . As already shown in [79,70], due to the dispersion properties in wave propagation, related to the presence of the term d -that is neither a time nor a space second derivative -the shape of the resulting wave is altered by the presence of the microcracks.…”

“…Here we extend the microstructure to the thermomechanical framework, stemming from the ideas exposed in [24], where a simple and paradigmatic example of continua with (micro-)structure is exposed within the beams theory framework. The effects of cracks on the thermal conductivity have been investigated on various materials such as fiber-reinforced composites [41], optical coatings [58], graphite materials [52], thermal barrier coatings [49,16,65], clay [19] and others. The results of these studies can be roughly summarized in the fact that the thermal conductivity of materials decreases when they are affected by microcracks, due to the very low thermal conductivity of air void induced by cracks.…”