Two of the four tunnel boring machines (TBMs) customised for the rock conditions in the Follo Line Project are now ready from the factory. The second TBM for this Norwegian large scale project has now been accepted by Jernbaneverket at Herrenknechts factory in Germany.
Another two tunnel borers are still in production, and the four will be operational by the end of this year. The TBMs will work their way through Norwegian granite and produce the whole 18,5 km TBM-tunnel by the end of 2018 according to plan. Starting from the installation site in Åsland, two will head northwards to the capital of Oslo, the other two will head south towards the regional transport hub at Ski.
“The excavation method for the main part of the long tunnel in the Follo Line Project was decided at the end of 2012, after careful consideration. For this project in particular, TBM was considered the best solution due to the environment and the fact that we have access to one large rig area for the total TBM tunnel construction work. We are impressed by the TBM production, and are pleased to see two TBMs now finished one year after the contract was signed. We are looking forward to our further cooperation”, said Mrs Anne Kathrine Kalager, Project Manager TBM for the client Norwegian National Rail Administration (Jernbaneverket).
Largest Norwegian tunnelling contract to date
The joint venture between the Spanish company Acciona and Italian Ghella was awarded the 1 billion euro contract by Jernbaneverket in the spring of 2015 for the TBM tunnelling.
Fernando Vara, Project Director at Acciona Ghella Joint Venture, said, “The cooperation between Herrenknecht, Jernbaneverket and AGJV has been very good, which is reflected in a delivery ahead of schedule, with good quality.”
Start in September
The now completed TBMs will arrive at the construction site in pieces and be assembled in an underground cavern at the construction site. According to plan, the first TBM will start boring towards Oslo in September 2016, the second one month later.
Double Shield TBMs are among the most technically sophisticated tunnel boring machines. They combine the functional principles of Gripper and Single Shield TBMs in one machine. In stable geological conditions, combining these methods permits the installation of concrete segments parallel to the drive, resulting in very high performance rates. This powerful technology is ideal for the construction of the future longest tunnel in Scandinavia.
TBMs excavate rock using cutter disks in the cutter head at the front of the machine. Inside the TBM, there are a number of installations, including a conveyor for the transport of rocks and the lining of concrete segments.
The twin railway tunnels made by the TBMs will be 8.75 metres in internal diameter, and 18.5 km long. In total, the tunnel will have a length of 20 km. The four TBMs will each have a length of 150 m and weigh 2400 tonnes.