HBAN Research Unit
HBAN Research Unit
Barral C.,HBAN Research Unit |
Touze-Foltz N.,HBAN Research Unit
Geosynthetics International | Year: 2012
The objective of the paper is the presentation of a test method to quantify advective flow rates through multicomponent geosynthetic clay liners (GCLs). A procedure was developed, combining measuring devices from EN 14150 for flow rate measurement through geomembranes and a rigid wall permeameter from NF P 84-705 aiming at measuring the flow rates through GCLs. Multicomponent GCLs by structure fall between geomembranes and GCLs. The resulting testing device allows measurement of very small variations of volume with time while applying constant hydraulic pressures. The pressure difference applied on both sides of the multicomponent GCL specimens varied between 25 kPa and 100 kPa, the latter value being equal to that applied across geomembranes in EN 14150, except in one case where the multicomponent liner had a light coating. In this case hydraulic heads of 0.3 and 0.6 m were applied. Four different multicomponent GCLs were tested, from three different manufacturers, in order to determine the ability of the testing equipment to quantify the flow rate through multicomponent GCLs. The flow rate measurement was performed after a hydration phase under a very low hydraulic head and a 10 kPa normal load on the specimens in accordance with NF P 84-705. Details are given of the experimental conditions that might lead to the development of a standard for the measurement of flow rates through multicomponent GCLs. Results obtained tend to show that flow rates are one order of magnitude larger than those usually measured for virgin geomembranes, that is 10-5 m3/(m2d), except for one of the multicomponent GCLs for which the light coating resulted in larger flow rates, measured with hydraulic heads of 0.3 and 0.6 m. In this case values consistent with previous values from the literature in the range 1.4 3 10-11m/s to 2.2 3 10-11m/s were obtained.
Ahari M.,HBAN Research Unit |
Touze-Foltz N.,HBAN Research Unit |
Mazeas L.,HBAN Research Unit |
Guenne A.,HBAN Research Unit
Geosynthetics International | Year: 2011
The aim of this paper is to present the experimental results obtained regarding the adsorption on various constitutive geotextiles and bentonites of geosynthetic clay liners of phenol, o-cresol, p-cresol, 2-chlorophenol, 4-chlorophenol, 2,4-dimethylphenol, 3,4-dimethylphenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol, 2,3,5,6-tetrachlorophenol, pentachlorophenol, and bisphenol A. These contaminants, including certain derivatives of halogenated phenols, are known to be toxic even at very low concentrations. Geotextiles and bentonites were sampled from four geosynthetic clay liners (GCLs) representative of the GCLs commonly used in bottom liner systems in France. Adsorption was studied through batch adsorption tests. The effect of the nature of the bentonite (sodium versus calcium activated) was studied. Results obtained in this study show that, contrary to what has been observed for volatile organic compounds (VOCs), the adsorption isotherms are non-linear. For VOCs, linear adsorption isotherms are obtained both for geotextiles and for bentonites. The contrast between the adsorption on geotextiles and bentonites is smaller than for VOCs. Up to two orders of magnitude difference can be obtained between the low adsorption coefficient for bentonite as compared with the large adsorption coefficient for geotextiles when adsorption of VOCs is considered. For phenolic compounds, the adsorption coefficients are of the same order of magnitude for bentonite and geotextiles. Two different trends were observed for woven and nonwoven needle-punched geotextiles as regards the adsorption parameters measured. For chlorophenols, polarity appears to affect adsorption: the adsorption coefficients increased with increasing number of chlorine atoms. © 2011 Thomas Telford Ltd.