Winter 2015

Strengthening and monitoring embankments in France

Geosynthetics from TenCate were recently used in France to strengthen a dyke section on the Donzère-Mondragon canal and for a warning system under a railway line in an area with potential sinkholes near Sauzé-Vaussais. TenCate GeoDetect® is a system based on geotextiles with embedded fibre optic cables. 

The Tricastin nuclear power plant is located in south-eastern France on the Donzère-Mondragon canal. This diversion canal of the Rhône is used to provide cooling water. 

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The French electricity company EDF and the Compagnie Nationale du Rhône have improved the level of protection of the Tricastin nuclear power plant against the risk of water shortages occurring in the event of flooding by strengthening a weaker part of the protective dyke along the Rhône.  

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This one-kilometre-long dyke section on the left bank of the river protects not only the nuclear site but also the city of Donzère and the towns and villages in the vicinity. The dyke consists of several layers of soil, the body is moisture permeable and at high water the dyke is vulnerable to erosion. By installing a filtration and drainage system that incorporates TenCate Bidim® S72, permeability and vulnerability to erosion have been halted. In order to increase the safety of this critical dyke section, a monitoring system was installed at the request of EDF to warn of both unexpected water flow and changes in the dyke. This system was designed with the TenCate GeoDetect® S-BR sensor embedding four optical cables and measuring in total some 15 kilometres of optical fibres. 

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The 302-kilometre-long South Europe Atlantic (SEA) high-speed Tours-Bordeaux railway line forms a new link in the future trans-European route from Northern Europe to the Iberian Peninsula. The stretch between Tours and Bordeaux is being laid by a consortium (COSEA). 

The line will be connected to the high-speed rail link to Paris. Trains reach a speed of 320 km/hr between Tours and Bordeaux, so for safety reasons the railway must be as flat and as stable as possible. However, near Sauzé-Vaussais, 60 km south of Poitiers, the line crosses an area (approximately 200 metres long and 60 metres wide) with potential sinkholes. COSEA decided to complement the ballast bed under the rails in this area with TenCate GeoDetect®. At Sauzé-Vaussais measurements are carried out at two levels in the new railway body: at about 7 metres and 2 metres below the rails. There are approximately 6,000 measuring points, enabling a total of 14 kilometres of fibre optic to be measured in a monitor room.
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TenCate GeoDetect® is a patented system for monitoring deformations in earth structures such as embankments and dykes. This sensing solution consists of a geotextile with embedded fibre optic cables, together with special measuring equipment and software. This enables the smallest soil deformations and changes in temperature and tension to be registered at an early stage, for example indications of incipient sinkholes.

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