Characterization of textural and hydric heterogeneities in clayey geomaterials with Induced Polarization method: a case study at the experimental Underground Research Laboratory of Tournemire

Tez Türü: Doktora

Tezin Yürütüldüğü Kurum: Université Pierre-et-Marie-Curie: Paris VI, GEOSCIENCES ET RESSOURCES NATURELLES, GEOSCIENCES ET RESSOURCES NATURELLES, Fransa

Tez Danışmanı: Phılıppe Cosenza, Andre Revıl, Nıcolas Florsch

Tezin Onay Tarihi: 2011

Tezin Dili: Fransızca

Açık Arşiv Koleksiyonu: AVESİS Açık Erişim Koleksiyonu

Desteklendiği Program: Diğer

Özet:

This Ph-D thesis investigates the potential of clay rocks for deep geological disposal of

radioactive waste. Underground excavations are responsible in their vicinity a region, where

the clay-rock is damaged or disturbed. This region must to be characterized to ensure the

safety of repositories. The extension of the excavation damaged zone (EDZ) and its evolution

over time have been investigated thought electrical resistivity and induced polarization

methods from three galleries belonging to the French Institute of Radioprotection and Nuclear

Safety (IRSN)’s experimental underground research laboratory of Tournemire (Aveyron,

France). Time domain induced polarisation indicates the presence of mineralization (e.g.,

especially pyrite) located in the structural discontinuities such as tectonic fractures (mm-cm),

tectonic fault (m) and calcareous nodules (cm). Combined electrical resistivity and Induced

Polarization methods show the possibility to delineate textural changes associated to

desaturation of the clay-rock induced by the ventilation of galleries. The impact of the

desaturation is particularly observed on the gallery’s walls. In addition, Spectral Induced

Polarization (SIP) tomography results can be used to discriminate the responses of the

desaturated zones from the fractured zones.

We have performed laboratory experiments (in the range 1.4 mHz - 12 kHz) using saturated

unconsolidated sand-clay mixtures. The results illustrate that the amplitude of polarization is

strongly affected by the surface properties of these mixtures (e.g., cation exchange capacity,

specific surface area) and by the volumetric clay content. However, the amplitude of

polarization is independent of the concentration of electrolyte. The SIP response is also

strongly sensitive to the mineralogy of the clays.