Bank protection for a temporary water-carrying channel

Task

In 2008, the Spanish engineering firm INPROESA planned the bank protection of the Entrín Verde, a watercourse that temporarily carries water in the village of Entrín Bajo in Extremadura. Flow velocities of up to 6 m/s were endangering the 1:2-sloped embankments of the trapezoidal channel. In collaboration with the Department of Hydraulic Engineering and Waterways of the Government of Extremadura, it was decided to install a concrete mat along the riverbanks to provide erosion protection.

Solution

To prevent the groundwater table from becoming decoupled from the river’s water balance, a permeable concrete mat was installed. This consists of two high-strength, interconnected fabric layers filled with flowable concrete. Water permeability is ensured by the filter points arranged at regular intervals. The fabric layers serve as permanent formwork for the fresh concrete, which significantly simplifies installation compared to conventional construction methods and noticeably shortens the construction time. The formwork fabric was supplied in the form of pre-assembled panels, consisting of 8 to 10 sewn-together strips, each being 5 m wide. The embankment, having been levelled, was first lined with a filter fleece to permanently ensure the functionality and hydraulic effectiveness of the filter points. The panels were then laid over this and temporarily fixed to the top edge of the embankment.

Advantages

• Quick and easy installation
• Environmentally friendly solution 
• Perfect connection between the groundwater in the hoses and the sewer
• Savings on concrete and guaranteed thickness 
• Time and cost savings