During flooding of the River Aude, there is a significant risk of dyke failure due to overflow. The purpose of the operation was to go on the repair work that had already been carried out and to make the whole of the study perimeter permanent so that it could withstand the flow in the event of an overflow, while maintaining the existing altimetric height. Indeed, when the flood passes over the dike, there is a regressive erosion of the slope which can lead to a total failure of the dike depending on the duration and the height of the overflow. It was therefore necessary to define a surface protection solution that could withstand overtopping heights of up to 15cm.
THE ENKA SOLUTION
EnkaMat A20, used as a surface erosion control layer, is a three-dimensional polyamide 6 mat consisting of looped filaments, welded where they cross. It is especially designed with a flatback to allow the product to be prefilled in factory with a bitumen bound mineral filter of stone chippings of 2-6 mm. The three-dimensional filamentary structure is designed to achieve optimum interlocking of the mineral filter and its binder. EnkaMat A20 allows the area to become fully vegetated.
INSTALLATION BENEFITS & RESULTS
In addition to the performance tests carried out by independent institutes or internally, EnkaMat A20 has many references in vegetated bank protection over the last 40 years. This application of downstream dyke lining extends the Enka-solutions scope in dyke restoration, see the case study EnkaDrain : “Rebuilding of the Grand-Rhône dyke”.
The EnkaMat A20 offers many advantages:
• A high water permeability which prevents under-pressure underneath the product,
• A ballast weight of 20 kg/m² provided by the mineral filter and its bituminous binder, the resulting stress limits the displacement of soil particles from the substrate or the spillway.
• The high roughness of the bituminous binder reduces the water velocity over the protected surface in case of river overflow,
• The high porosity of the product allows vegetation to grow through.
• Polyamide 6 is highly resistant to temperature with a melting point at 220°C.
• U.V-field and laboratory tests confirmed the extremely high resistance of EnkaMat to weathering.