Flow rate in composite liners including GCLs and a bituminous geomembrane

Some studies were performed in the past years regarding the behaviour of geosynthetic clay liners (GCLs) as part of a composite liner, focused on the situation where a GCL is located under a hole in a high density polyethylene (HDPE) geomembrane (GM). In this case, the contact between the GM and the GCL was quantified in terms of flow rate through the composite liner and in terms of interface transmissivity. Various situations were tested in the past in order to evaluate the situation where a smooth GM is used in contact with the GCL. The situation where a textured GM is used in contact with the GCL was also evaluated. More recently, the effect of the nature of the bentonite in the GCL, sodium or calcium bentonite, leading to different flow rates in the GCL was evaluated. In all cases an HDPE GM was used. This choice is linked to the fact that it is the most commonly GM used in composite liners including GCLs for chemical compatibility reasons. However one could imagine that the use of other GMs, like bituminous geomembranes (B-GMs) associated to a GCL, could be adapted for hydraulic applications. A quantification of flow rates was thus performed in laboratory tests at the decimetric scale for the case of a damaged B-GM located on top of sodium or calcium GCLs. This corresponds to an alternative design for a canal projected in France at the moment. Results obtained will be presented in the paper and evaluated depending on the B-GM side (polymeric film or sand layer) in contact with the GCL, the type of GCL tested (sodium or calcium bentonite in the GCL) and also compared to test results obtained from the literature carried out with a HDPE GM associated to a GCL.