Analysis of hydro-mechanical behaviour of compacted bentonite/sand mixture using a double structure formulation
- 252 Downloads
In this paper, a double structure formulation is used to describe the behaviour of compacted bentonite/sand mixtures intended as sealing material in underground repositories for nuclear waste. The formulation accounts for the presence of two distinct porosity levels in the material as revealed in the pore size distributions determined by mercury intrusion porosimetry technique. Non-equilibrium hydraulic conditions are assumed between micro and macroporosities. A water exchange term between the two porosities is determined. Experimental data obtained in the laboratory were analysed allowing determination of the hydro-mechanical (HM) parameters used in the modelling. These parameters were then used in modelling a 1:10 scale mock-up representative of the large-scale SEALEX performance experiments. It was observed that the model reproduced well the main features related to the swelling pressure development during hydration under confined conditions. Moreover, it allowed analysing interesting information not available from direct laboratory measurements (micro and macroporosities and suctions). The analysis is then up-scaled to the description of large-scale SEAling EXperiment (SEALEX). A challenging task consisted in predictions of field observations using the same hydraulic and mechanical parameters employed in the modelling of the small-scale laboratory tests. The model was able to predict correctly the global HM behaviour of the bentonite-based seal considering the uncertainties and heterogeneities associated with the fabrication and installation processes of the bentonite-based blocks.
KeywordsSwelling pressure MX80 bentonite/sand mixture In situ tests Microstructure Double structure Technological gap
The author would like to thank AITEMIN (SPAIN) and ENPC-CERMES (France) our partners in this project.
- Alonso EE (1998) Modelling expansive soil behaviour. In: Proceedings of the second international conference on unsaturated soil, Beijing, China, 27–30 August 1998Google Scholar
- Barnichon JD, Deleruyelle F (2009) Sealing experiments at the Tournemire URL. EUROSAFEGoogle Scholar
- Gatabin C, Touze G, Imbert C, Guillot W, Billaud P (2008) ESDRED Project, Module 1-Selection and THM characterisation of the buffer material. In: International conference underground disposal unit design and emplacement processes for deep geological repository, Prague, 16–18 June 2008Google Scholar
- Hassanizadeh SM (1986) Derivation of basic equations of mass transport in porous media, part 2. Macroscopic balance laws. Transp Porous Media 9:196–206Google Scholar
- Hassanizadeh SM (1988) Modelling species transport by concentrated brine in aggregated porous media. Transp Porous Media 3:299–318Google Scholar
- Kozeny J (1927) Ueber kapillare leitung des wassers im boden. Sitzungsber Akad. Wiss. Wien 136(2a):271–306Google Scholar
- Pusch R (1979) Highly compacted sodium bentonite for isolating rock-deposited radio-active waste products. Nucl Technol 45(2):153–157Google Scholar
- Saba S (2013) Hydro-mechanical behaviour of bentonite-sand mixture used as sealing material in radioactive waste disposal galleries. Ph.D. Thesis, Paris-Est University, FranceGoogle Scholar
- Van Genuchten R (1978) Calculating the unsaturated hydraulic conductivity with a new, closed-form analytical model. Research Report 78-WR-08, Water Resources Program, Department of Civil Engineering, Princeton Univ., Princeton, NJGoogle Scholar
- Wang Q (2012) Hydro-mechanical behaviour of bentonite-based materials used for high-level radioactive waste disposal. Ph.D. Thesis, Paris-Est University, FranceGoogle Scholar
- Yang DQ, Alonso EE, Rahardjo H (1998) Modelling volumetric behavior of an unsaturated expansive soil. In: 2nd international conference on unsaturated soils, Beijing, China, vol 2, pp 249–254Google Scholar