Spring 2014


Geosynthetics for dyke reinforcement

Factors such as piping and global warming have caused sea levels to rise, which in turn has led to greater pressure on flood defences. Geosynthetics are well suited to raising and reinforcing dykes and dams. A new development is a vertical sand-tight geotextile based on geotextiles from TenCate.

This vertical sand-tight geotextile (VSG) is a preventive measure against piping - one of the possible causes of the subsidence or even breaching of dykes. The geotextile, which is incorporated as a filter into the dyke body, will allow water to pass through, but not sand. As a result no sand boils will occur, so there will be no seepage. The use of TenCate GeoDetect® in the geotextile also makes it possible to monitor the stability of the dyke. A geotextile is a sustainable material that is suitable for use in dyke improvement. Geotextiles for the erosion protection of flood defences have been used across the world for decades and this vertical sand-tight geotextile will also be able to find a new application worldwide. Before that point is reached, however, extensive field tests will take place, which may lead to modifications and further development.

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Vertical sand-tight geotextile (photo Deltares/A.R. Koelewijn)

Global warming has led to a rise in sea levels and to greater pressure on dykes and dams on coastlines and along lakes and rivers. This calls for the raising and/or reinforcing of these structures. A large part of the Netherlands may become flooded following a breach in a dyke. Every five years therefore a test of the flood defences in our country is conducted to ensure that they still meet legal standards. The last time this happened was in 2011. The new Flood Protection Programme (nHWBP) has the aim of reinforcing the primary water-retaining structures that failed to reach the required standard at that time. This has consequences for 731 kilometres of primary flood defences (dykes) and 238 water-retaining structures (locks and dams). In addition, three surveys will be carried out in 2014 that exceed the remit of the project, including piping. Implementation of the project includes several innovative techniques.

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Vertical sand-tight geotextile (photo Deltares/A.R. Koelewijn)

What applies to the improvement and reinforcement of the 7,000 km of primary dykes in the Netherlands also holds true for flood defences on coastlines and along lakes and rivers elsewhere in the world: there are often insufficient funds available for this work and innovative solutions are thus needed. As it so happens, VSG is an innovative and environment-friendly preventive measure. This solution requires little space and it saves money. Methods and equipment exist to install the geotextile at great depths, as piping can occur down to a depth of some six to seven metres.

VSG is a good addition to the portfolio of anti-erosion products of the Water & Environment business unit within TenCate Geosynthetics. The importance of this business unit within TenCate Geosynthetics is growing. A global sales and marketing organization has been established to strengthen the position of the Geosynthetics group in infrastructure and environmental markets, which has led to revenue growth in this segment. End-user marketing has been strengthened through cooperation with engineering firms and the group is now also setting its sights on areas that are less traditional for TenCate.

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