Community Research and Development Information Service - CORDIS

Granular backfill material

Compacted expansive clays are proposed as engineered barriers in reference concepts for the disposal of heat-emitting nuclear waste in granite and clay.The backfill material of the BACCHUS 2 test consists of a mixture of high density pellets and powder. This granular backfill material was characterized. The hydraulic conductivity and swelling pressure was measured as a function of the dry density. X-ray tomography has been applied successfully to measure the evolution of the density distribution during hydartion.

The installation procedure, materials and techniques used in the BACCHUS 2 were close to realistic industrial processes and capabilities. To gain more confidence in the hydromechanical model for unsaturated clay-based materials, BACCHUS 2 was instrumented so that it can be used as a validation experiment.

The instrumentation (including total stress, pore-water pressure and water content measurements) of the backfill material and of the surrounding clay massif has allowed observation of the hydration process. The measured parameters in the backfill show clearly the hydration effect (ie a strong increase in water content, pore-water pressure and a redistribution of the mechanical stresses). Results of the natural hydration modelling are in good agreement with the in situ measurements.

Reported by

Centre d'Etudes de l'Energie Nucleaire, Studiecentrum voor Kernenergie
Boeretang 200
2400 Mol
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