The Port of Brest is expanding with EU and Brittany Region funding. New industrial areas will support marine renewable energy. A 10-hectare polder made from dredged materials will provide storage and handling space for ongoing port development.
Naue Combigrid® is a geogrid with integrated nonwoven geotextile that combines stabilisation, reinforcement, separation and filtration in a single installation step.
Naue Secugrid® geogrid stabilises and reinforces roads, embankments, working platforms, slopes and walls.
The project’s main goal was to construct a quay, breakwater, and a platform with sufficient bearing capacity for storage of heavy offshore wind turbine foundations. However, the soft marine sediments in the area posed a significant challenge, as they lacked the shear resistance to support the required loads.
Around 1 million m3 of soft marine sediment was dredged from the port of Brest and used to backfill the new polder. This ecological approach ensured minimal waste and supported the development of the region’s renewable energy projects.
To stabilise and reinforce the soft ground, the consultant proposed using Naue Combigrid® and Secugrid®. Combigrid®, a geocomposite made of stretched monolithic flat bars with welded junctions and a mechanically bonded and calendered geotextile welded within the geogrid structure, was used as the first layer. A second layer of Secugrid® was installed at the centre of the base course. The geogrids provided the necessary tensile strength and stability to support the platform, preventing deformation and ensuring long-term performance.
Naue Combigrid® provided separation between the fill material and the in-situ fine grained subgrade soil, while its geogrid component enhanced the shear resistance of the unbound base course material. This ensured improved load distribution, reducing the risk of differential settlement. Combigrid® was installed at seabed level and covered with 40cm of sand fill material. Secugrid® was installed on top of the compacted sand layer to achieve the necessary factor of safety for the bund’s stability.
With approximately 150,000 m2 of Combigrid® and Secugrid® supplied, Naue’s products played a crucial role in ensuring the successful completion of this innovative project. The use of advanced geosynthetics allowed the construction team to stabilise the challenging soft ground conditions, paving the way for future renewable energy infrastructure at the port.
Combigrid® and Secugrid® provided the tensile strength needed to create a load-bearing platform for heavy port operations.
Combigrid® prevented mixing between the fine subsoil and fill, while reducing deformation and differential settlement.
The reinforced system enabled around one million cubic metres of dredged sediment to be reused in the new polder construction.
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