ABSTRACT
For the Folloline Project in Norway, running from Oslo to Ski, a double track railway tunnel is under construction. The sections of the project where the tunnels are entering from clay and quick clay into hard Norwegian rock are the geotechnical challenges due to the sensibility of such soils during construction. Keller is executing the main foundation and retaining works in Oslo and Ski using various geotechnical methods to find the best solution for the heterogeneous soil conditions. Especially in the Oslo Area a combination of Lime Cement Columns with Jet Grouting Columns ensured the flexibility and the required safety during execution to avoid movements and landslides in the Oslo City Centre. The dry soil mixing procedure is a standard process for soil improvement in the Scandinavian Countries. Jet grouting so far was not used as a standard method for the treatment of Clay and Quick Clay in relation to retaining structures, soil improvement and underpinning works. The combination of the above stated techniques with Keller´s leading position in the development of those methods were the key to the successful execution at site. To reduce the environmental impact of the ground improvement works, Keller used its own Water and Sludge Treatment plant and was able to decrease the Volume to 40%. A large number of Vibrating Wire Sensors were installed for a live time monitoring of the pore pressure and movements during the Jet Grouting works.
