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Experimental study of swelling in unsaturated compacted clays

¹ Institut de Recherche en Génie CiviletMécanique, CNRS UMR 6183, EcoleCentrale de Nantes– Université de Nantes, 44321 Nantes Cedex 3, and ² INRA, Station de Science du Sol, Route de Saint Cyr, 78026 Versailles Cedex, France

^* E-mail: nadia.saiyouri{at}ec-nantes.frdg

(Received 25 July 2002; revised 6 May 2004)

This paper describes the swelling properties of two highly compacted clays, natural, untreated Wyoming montmorillonite (MX80) and Fourges smectite (FoCa7), saturated with Na and Ca, respectively.

The initially compacted samples were hydrated by subjecting them to different suction pressures in a range between 100 MPa and 1 kPa. For each equilibrium state, the volume change (swelling) and water content (hydration) were measured. The samples were then studied by X-ray diffraction using a transmission device to determine interlayer distance and particle size, in order to clarify both the swelling and hydration mechanisms. The distances between clay layers ranged between 10 and 21.6 Å, i.e. corresponding to between 0 and 4 water layers. Upon hydration, the particle size decreased from 350 and 100 clay layers per particle to 10 layers per particle when the suction pressure decreased from 100 MPa to 1 kPa for MX80 and FoCa7, respectively. The first swelling stage is described as being an insertion of water molecules between the layers. Then a division of the initial particles into particles of smaller size with increasingly large inter-particle distances was observed. Observations by transmission electronic microscopy confirmed these results.

KEYWORDS: clays, swelling, suction pressure, microstructure, X-ray diffraction, hydration, Ca-smectite, Na-Wyoming montmorillonite, MX80, FoCa7

This article has been cited by other articles:

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