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Single and double oedometer tests to estimate osmotic compression of clays


Authors: Rao, S.M., Thyagaraj, T.
Key words: Clays, osmotic compression, osmotic suction, oedometer
Source: The International Journal of Geotechnical Engineering
Volume: 4
Issue: 3
Pages: 11
Date: 2010-07-01
DOI: 10.3328/IJGE.2010.04.03.325-335

Abstract
Estimation of osmotic compression strain magnitudes is important in certain geoenvironmental engineering applications. Typically, clay barriers exposed to chemical concentration gradients in waste disposal facilities are susceptible to osmotic compression strains. The chemical concentration gradient between pore water of clay and external chemical reservoir induces osmotic compression strains. The current laboratory method is based on consolidating the saturated clay specimen to the desired consolidation pressure and replacing the distilled water in the oedometer reservoir with preferred salt solution. As dissipation of osmotic suction difference is diffusion controlled, establishing the time-osmotic compression curve at each consolidation pressure may extend over weeks. Designing oedometer experiments that facilitate rapid estimation of osmotic compression strains forms the focus of this study. A double oedometer test based on an earlier concept of Barbour and Fredlund is developed to rapidly estimate the osmotic compression strains of saturated clays at multiple consolidation pressures. The proposed double oedometer method relies on establishing volumetric strain (ε)-log pressure curves of clay samples saturated with distilled water and salt solution respectively and reading the difference in volumetric strains of the two clay samples at constant consolidation pressure. The predicted osmotic compression strains from double oedometer method are compared with experimental osmotic compression strains obtained using single oedometer test.

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This paper was added to our catalog on Tuesday 24 August, 2010.

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