Design of Inclined Covers with Capillary Barrier Effect |
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| Authors: | Serge-Étienne Parent Alexandre Cabral |
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| Institution: | (1) Department of Civil Engineering, Faculty of Applied Science, University of Sherbrooke, 2500, University Boulevard, Sherbrooke, Quebec, J1K 2R1, Canada |
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| Abstract: | A design procedure is proposed to minimize water infiltration into landfills by optimizing the water diversion length of inclined
covers with capillary barrier effect (CCBE). This design procedure is based on a conceptual, mathematical and numerical approach
and aims at selecting materials and optimizing layer thickness. Selection among candidate materials is made based on their
hydraulic conductivity functions and on a threshold infiltration rate imposed on the designer. The capillary break layer (CBL;
bottom layer) is characterized by a weak capillarity, while the moisture retention layer (MRL; upper layer) is characterized
by a compromise between strong capillarity and high hydraulic conductivity. The thickness of the CBL corresponds to the height
where suction reaches its maximum value for a given infiltration rate. This height can be calculated using the Kisch Géotechnique 9 (1959)] model. The optimal thickness of the MRL is determined by applying an adaptation of the Ross Water Resources Research 26 (1990)] model. The results obtained using the proposed design procedure were compared to those obtained from numerical simulations
performed using a finite element unsaturated seepage software. The procedure was applied for two cover systems; one where
deinking by-products (DBP) were used as MRL and sand as CBL and another where sand was used as MRL and gravel as CBL. Using
this procedure, it has been shown that an infiltration control system composed of thin layers of sand over gravel is highly
efficient in terms of diversion length and that its efficiency can be enhanced by placing a hydraulic barrier – such as a
layer of DBP – above the MRL. |
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| Keywords: | capillary barrier landfill cover lateral diversion unsaturated flow |
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