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Experimental study on the influence of preliminary desiccation on the swelling pressure and hydraulic conductivity of compacted bentonite

Lang, Lin Zhi, Baille, Wiebke, Tripathy, Snehasis and Schanz, Tom 2018. Experimental study on the influence of preliminary desiccation on the swelling pressure and hydraulic conductivity of compacted bentonite. Clay Minerals 53 (4) , pp. 733-744. 10.1180/clm.2018.53

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Abstract

In deep geological repositories, compacted bentonites have been proposed for use as barrier materials for isolating nuclear waste. The prevailing thermo-hydro-mechanical boundary conditions in the repositories may affect the swelling capacity and permeability of the compacted bentonites. In this study, the effect of preliminary desiccation on the subsequent hydro-mechanical behaviour (swelling pressure and hydraulic conductivity) of compacted Calcigel bentonite was investigated experimentally at 22°C and 80°C. In the first stage of the test, the compacted specimens were subjected to suction-controlled desiccation at 22°C and 80°C using the vapour-equilibrium technique. After the water content reached equilibrium at a given suction, the axial, radial and volumetric shrinkage strains were measured. Afterwards, constant-volume swelling-pressure tests were performed on the desiccated specimens (second test stage) by saturating the dried specimens with deionized water at 22°C and 80°C. At the end of the swelling-pressure test, the hydraulic conductivities of four saturated specimens were measured at each temperature. The volumetric shrinkage strain of the compacted bentonite during desiccation is controlled by suction instead of temperature. In addition, the preliminary desiccation increases both the swelling pressure and hydraulic conductivity of compacted bentonite, particularly if compacted bentonite undergoes extreme desiccation at an applied suction of >700 MPa.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Engineering
Publisher: Mineralogical Society
ISSN: 0009-8558
Date of First Compliant Deposit: 8 April 2019
Last Modified: 24 Jul 2019 10:54
URI: http://orca.cf.ac.uk/id/eprint/120944

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