A premiere in the Frisian Hurdegaryp, where Haskoning, Boskalis Netherlands, and Swietelsky, commissioned by ProRail, are using Vibroflot technology to install geotextile-encased gravel columns to strengthen the railway and embankment. It is a well-known headache for ProRail: the railway embankment is slowly sinking, and trains are running on the soft subsoil of clay and peat.
The development involves driving enormous gravel-filled sleeves (columns) vertically into the ground; like a foundation that makes the soil more stable and solid. The result is a sustainable innovation that improves the entire railway and track structure without breaking open the track. This is now taking place in existing tracks, with hardly any disruption, which is remarkable.
Champions League of geotechnics
ProRail contracted a knowledge combination including the companies Haskoning, Swietelsky Rail Benelux, and Boskalis Netherlands to drastically increase track stability in a sustainable manner. The gravel columns form a new foundation for the railway embankment and are driven vertically into the ground between and next to the sleepers of the track.
In Friesland, such gravel columns have now been installed under the track. In the first week of August, the last column was installed. “After that, you lay the ballast back, and the trains can safely run over it again. The intervention has minimal impact on train traffic, and we have equipped the soil with sensors so that we can precisely understand what happens in the subsoil when a train passes over it. With that knowledge, we improve ourselves again. You could say that this entire design and execution is the Champions League of geotechnics,” says Jelle van der Zon, geotechnical engineer at Haskoning.
Sustainable alternative
“The solution with gravel columns as foundations in the railway embankment is significantly more sustainable than the steel sheet piles currently used. And socially more attractive than a solution based on support berms,” says Arjan Dirven, project leader at Swietelsky. The ballast material used (gravel) increases the stability of the railway. The combination of companies sees the use of recycled ballast material as an opportunity to become more sustainable. “Combined knowledge of design, execution, and monitoring forms the basis for this further development,” adds André de Lange, involved in soil improvement COFRA at Boskalis Netherlands.
The next twelve months will see a monitoring phase. If the results are positive, this technique can be applied more broadly to make sinking railway embankments and tracks in the Netherlands future-proof.
For questions, more information, or an interview request: please contact nicoline.mezger@haskoning.com and 06-33002133.
