Final breakthrough of Swedish tunnel achieved
7 October 2014SWEDEN - The final breakthrough of tunnelling work at the Hallandsås Tunnel, Sweden, has been achieved. The project used a Herrenknecht TBM to cut through the last meters of rock to the target shaft after eight years of tunnelling.
The projects aim was to expand the railway route along the Swedish west coast from Malmö to Göteborg, Sweden.
Due to its geology, the project occupies a top position on the list of tunnel projects with extremely complex ground conditions. Large sections of the abrasive rock formations, mainly gneiss and amphibolite, with high rock strengths of up to 250MPa are extremely fissured. In addition, the tunnel is exposed to extreme groundwater pressures of more than 10bar on large parts of the route.
For the mechanised tunnelling Herrenknecht developed and delivered a specially adapted TBM for the two remaining 5.5km sections of the 8.7km long Hallandsås Tunnels.
The machine was designed to work in both the closed slurry mode with hydraulic removal of excavated material and the open hard rock mode with belt conveyor removal. Permanently installed drilling and injection tools ensured water inflow could be controlled by grout injection when needed. As part of comprehensive test series, the sealing system of the machine was designed to withstand a groundwater pressure of up to 13bar.
Werner Burger, head of design department traffic tunnelling at Herrenknecht said: "The machine design for Hallandsås was both a response to the extreme project requirements and a large technological advance: the concept aimed to provide a hard rock machine with the potential to work safely and efficiently in loose rock and even under high groundwater pressure if needed. Hallandsås has set the right course for later projects."
The Swedish-French joint venture of Skanska and Vinci started tunnelling on the first Eastern tunnel in September 2005.
