Erosion control in France

bontec nonwoven under rock armour

The French electricity producer EDF constructed an LNG-terminal in Dunkirk. The LNG terminal in Dunkirk represents an additional capacity of 13 billion m³ of natural gas per year and thus makes an important contribution to the strengthening of the reliability of supply and the functioning of the natural gas market in northwest Europe.

Challenge

In order to protect the inner port from erosion by waves, rock armour was installed to provide the protection. The design called for a geotextile filter underneath the rock armour that would withstand the harsh conditions and placement of rock armour.
Also, there was a need to keep the stand-in time of the pontoon as low as possible during the installation.

Solution

During the project, Jan De Nul cooperated with BontexGeo to supply and install the nonwoven geotextile filter. In total, BontexGeo supplied 250.000 m² of nonwoven geotextile.
The nonwoven geotextiles selected for this project were SNW type nonwovens as these products offer, next to excellent hydraulic characteristics, an optimal combination of strength and elongation. This results in a high energy index, allowing absorption of possible installation damage.
The geotextile filter provides the long term stability of the rock armour layer in the long term, as it avoids fine sand particles to be washed away from behind/underneath the rock armour layer. As such, the stability is maintained as shifts or subsidence are prevented.

In order to lower the stand-in time of the pontoon during the installation, BontexGeo produced large panels of 15m wide. This was done by stitching together 5m wide rolls in the finishing department of BontexGeo.
By doing this, installation on the water could take place a lot quicker compared to standard 5m wide nonwoven product and a big cost saving was realized.

Products used

  • Bontec SNW 50
  • Bontec SNW 55
  • Bontec SNW 62
  • Bontec SNW 80

Different types of SNW nonwoven were used depending on the class of rock armour used.

Get in touch

Would you like to know more how we can help you in your project? Get in touch with us through the form below.