Sweden’s forest roads are neither adapted for heavier vehicles nor for climate change. That’s the bad news. The good news is that there are several cost-effective ways to improve and reinforce the roads in the future. This is shown by a large research project that was recently completed.
The project “Solutions for faster development of forest roads” (Lösningar för snabbare utveckling av skogsbilvägar) is one of the biggest research initiatives ever carried out in the forest industry in Sweden. This VTI-led project has been funded by Vinnova and involved a total of eleven partners, including several of the major forestry companies.
The background to the project is that current forest roads have been designed according to old guidelines and are not adapted to the demands of today. This applies both to climate change, with heavy rainfall over short periods, and to heavy vehicles as the maximum permissible gross weight has increased from 64 to 74 tonnes. As a result, roads break down and vehicles get stuck.
The project is testing five different ways of improving the load-bearing capacity of forest roads:
- Geocells. Geocell grids are buried in the roadway and packed with gravel and aggregate. (Stora Enso)
- Crowning/camber. The slope from the middle of the roadway varies from 0 to 10 per cent, which affects drainage. (SCA)
- Additives with low environmental impact. Various stabilising enzymes are added to the roadway. (Holmen)
- Various compaction methods. Increased compaction was carried out on both sandy and clay-rich road materials. (Sveaskog and Holmen)
- Stone mattresses. Stone mattresses, as they are known, packed with stone and covered with geotextile, are buried in the road to improve drainage. (Kopparfors Skogar)
The tests on the trial sections are clearly positive. With one exception, all methods showed improvements in the load-bearing capacity of between 10 and just over 60 per cent. The only exception was the sandy road material, where greater compaction had no impact on the load-bearing capacity.
The biggest improvement was achieved with the geocells, where the outcome is described as “remarkably positive”. Despite a relatively high moisture ratio, load-bearing capacity was improved by between 52 and 64 per cent compared to a reference section. Geocells are also the method considered most economically advantageous in terms of the percentage increase in load-bearing capacity per metre of road.
“The results are clearer and more positive than I’d expected. I believed that technical solutions were available, but I didn’t expect some of them to be so economically advantageous,” says project manager Dina Kuttah, a senior researcher at VTI.
The project has been funded as part of InfraSweden, one of Sweden’s 17 strategic innovation programmes (SIPs) funded by Vinnova, the Swedish Energy Agency and Formas.
Project partners: Skogforsk, Sveaskog, Stora Enso Skog, SCA Skog, Holmen Skog, Kopparfors Skogar, the Swedish National Association for Private Road Owners (Riksförbundet Enskilda Vägar), the Swedish Forest Agency, the Södra Skogsägarna Economic Association and the Swedish Transport Administration
Text: Mikael Sönne
Translation: CBG
The report: Lösningar för snabbare utveckling av skogsbilvägar i SverigeExternal link. (Diva)
The project’s website: Swedish forest roadsExternal link.
Film: Developing forest roads in SwedenExternal link. (Youtube)
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