The Follo Line project is the largest infrastructure project in Norway. It includes 22 km of new high speed railway from Oslo to Ski.
The project
The main part of the project consists of a 20 km long tunnel representing the longest railway tunnel in Norway. On the project in SKI, Keller has performed Steel core piles in various dimensions, grouting works, the installation of permanent and temporary strand anchors as well as rock bolts in steel and fibre glass.
The challenge
The tight time schedule for the drilling works in combination with the difficult soil and the big differences in the bed rock level were the main challenges at site. The soil in the area mainly consisted of clay. In some parts the clay was soft, but in other parts the clay was medium stiff and low to medium sensitivity. Above the clay there was a layer of dry crust and fill that mostly varied between 1 and 5m in thickness. Beneath the clay there iwas a moraine layer with a thickness that varied between 1 and 3m. Due to changing soil conditions at site Keller used its Double head drilling system to install the anchors. This techniques allows the retrieval of the casing after the anchor is installed in a safe way, which has a positive impact on the environmental footprint of the works.
The solution
With its large foundation portfolio, Keller asissted the client with several different technologies. Keller installed around 20,000m of permanent anchors for retaining walls with up to 15 strands for permanent use of up to 100 years. Keller executed this project with up to two rigs simultaneously using several in-house drilling techniques. Keller also provided a large machine park, consisting of more then 130 drilling machines which created flexibility and security for the client.