Swell index, oedopermeametric, filter press and rheometric tests for identifying the qualification of bentonites used in GCLs
ABSTRACT Geosynthetic clay liners (GCLs) are used in landfill liner applications and there is a need for a better control of the properties of the bentonite in the GCL received on site, particularly in the European context where a wide variety of bentonites can be encountered. This paper presents the results of a project aimed at a rapid identification of the nature of the bentonite in a given GCL. The interaction between the bentonite and the fluid was increased by producing dispersions then testing its structure within a few hours with filter press tests and flow curves. The results of those tests were compared with swell index tests, electrical conductivity values and oedopermeametric tests. Eight GCLs were studied. Two of these GCLs contained natural calcium bentonites; they presented poor swelling properties and high permittivities. The dispersions had a low viscosity and their filtration under pressure led to large amounts of filtrate. A further two GCLs contained natural sodium bentonites and the remaining four contained sodium-activated calcium bentonites. Their permittivities, swell indices and filtrate masses were similar; however, their rheometrical behaviours were different due to a difference in the values of electrical conductivity. Thus it seems that electrical conductivity measurements and rheological tests can provide a good and fast way of identifying the nature of the bentonite contained in GCLs.
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ABSTRACT: A fully coupled model is used to simulate the results of large-scale laboratory tests that investigated the non-isothermal behaviour of geosynthetic clay liners in landfill basal liner applications. Results of numerical simulations of the laboratory tests in terms of water content, capillary pressure, temperature and stress distributions are presented, and encouraging agreement between the numerical and experimental results is achieved. Under the conditions examined, a 258C/m temperature gradient led to the development of tensile stresses within the GCL, increasing the resultant likelihood of cracking. A Poisson's ratio of 0.25 resulted in predicted horizontal tensile stresses supporting qualitative observation of desiccation cracking in the GCLs. One important implication of the work reported herein is that elevated temperatures need not occur for extended periods to create the risk of desiccation.Geosynthetics International 10/2011; 18(5). DOI:10.1680/gein.2011.18.5.289 · 1.17 Impact Factor