1 Laurent BROCHARD May 2 nd , 2019 Clays: New Perspectives, Challenges & Opportunities Role of water adsorption in the thermo- mechanical behavior of clays Laurent BROCHARD Laboratoire Navier, UMR 8205, École des Ponts, IFSTTAR, CNRS, UPE, Champs-sur-Marne, France May 2 nd , 2019 Workshop “Clays: New Perspectives, Challenges & Opportunities”
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1 Laurent BROCHARD May 2nd, 2019 Clays: New Perspectives, Challenges & Opportunities
Role of water adsorption in the thermo-mechanical behavior of clays
Laurent BROCHARD
Laboratoire Navier, UMR 8205, École des Ponts, IFSTTAR, CNRS, UPE, Champs-sur-Marne, France
May 2nd, 2019
Workshop “Clays: New Perspectives, Challenges & Opportunities”
2 Laurent BROCHARD Clays: New Perspectives, Challenges & Opportunities May 2nd, 2019
1st anomaly: undrained heating experiment
• Excessive water pressurization
Monfared, M., Sulem, J., Delage, P., & Mohajerani, M. (2011). A Laboratory Investigation on Thermal Properties of the Opalinus Claystone. Rock Mechanics and Rock Engineering, 44(6), 735–747. http://doi.org/10.1007/s00603-011-0171-4
Poromechanics
Interpretation: confined water thermal expansion higher than bulk water th. exp.
3 Laurent BROCHARD Clays: New Perspectives, Challenges & Opportunities May 2nd, 2019
αirreversible ~ -10-3 K-1 Interpretation: drainage of confined water
αreversible ~ 10-4 K-1
αminerals ~ 10-5 K-1 Interpretation: confined water is not drained
Sultan, N., Delage, P., & Cui, Y. J. (2002). Temperature effects on the volume change behaviour of Boom clay. Engineering Geology, 64(2-3), 135–145. http://doi.org/10.1016/S0013-7952(01)00143-0
4 Laurent BROCHARD Clays: New Perspectives, Challenges & Opportunities May 2nd, 2019
Objective: poromechanics capturing confinement
• Anomalies attributed to the effects of confinement • Usual poromechanics assumes bulk properties
Clay matrix and inclusions (10 – 100 µm)
Stacks of layers (0.1 – 1 µm)
Clay layers (~ 10 nm)
Confined water = bound water = adsorbed water
Bulk water = free water = normal water
5 Laurent BROCHARD Clays: New Perspectives, Challenges & Opportunities May 2nd, 2019
Usual interpretations are non-obvious
• In adsorption community : confined th. exp. usually lower (e.g. Lennard-Jones in a slit pore)
solid walls
Periodic boundaries
rfs
rff e
6 Laurent BROCHARD Clays: New Perspectives, Challenges & Opportunities May 2nd, 2019
Usual interpretations are non-obvious
• In adsorption community : confined th. exp. usually lower (e.g. Lennard-Jones in a slit pore)
• But water is not any liquid
7 Laurent BROCHARD Clays: New Perspectives, Challenges & Opportunities May 2nd, 2019
Usual interpretations are non-obvious
• In adsorption community : confined th. exp. usually lower (e.g. Lennard-Jones in a slit pore)
• But water is not any liquid • Thermal expansion is not the only fluid property
15 Laurent BROCHARD Clays: New Perspectives, Challenges & Opportunities May 2nd, 2019
Confrontation with experiment
• New poromechanics captures experiment if the confined water is 2W water
• The main origin of the anomalous pressurization is the less intuitive contribution (difference between thermal expansion at constant Pb and at constant Pc)
16 Laurent BROCHARD Clays: New Perspectives, Challenges & Opportunities May 2nd, 2019
Drained heating • Reversible expansion: also captured by new poromechanics • Irreversible contraction: model based on transition between
hydration states inspired by shape memory alloys (qualitative)
Brochard et al. (2017). Acta Geotechnica, 12(6), 1261. Honorio et al. (2017). Langmuir, 33(44), 12766.
17 Laurent BROCHARD Clays: New Perspectives, Challenges & Opportunities May 2nd, 2019
Conclusions • Revisit the poromechanics of clays starting from
confined water • Successfully reproduce THM anomalies • Main messages
• Confinement = more thermo-mechanical properties • Fluid transfers between free and bound water are essential