The largest infrastructure project in Norway, called Follo Line, includes the country’s longest railway tunnel at over 20 kilometers, mostly passing through solid granite. The challenging heterogeneous soil conditions in the sections of tunnel before and after entering into solid granite were tackled by Keller, which executed the main foundation and retaining works using various geotechnical methods.   

Steel core piles were used for the foundation of the tunnel in the open sections, while stabilization of the sensitive clay and quick clay areas required a combination of dry deep soil mixing and jet grouting with ground anchors, using techniques successfully applied for the first time in Norway.

Keller says it mobilized three of its business units and equipment and manpower from all over Europe, including specialists from nine countries, to keep the project on track. The company organized cultural events to allow for team building in a more relaxed environment among the workers from various countries.

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