Marti announced on Thursday that it had been awarded the CHF 25M (USD 28.22M) contract to build the safety gallery of the Milchbuck road tunnel, near the University of Zurich in Switzerland, with work set to begin this month. Construction should take nearly three years, finishing in 2013.
The project is part of works in progress since 2003 to make the heavily used tunnel comply with modern safety standards. The safety gallery will run for 1,380m, parallel to the main tunnel and lie between 6 and 40m below the surface.
“Due to the differing geological conditions, the tunnel is to be excavated by two different methods,” said a Marti spokesperson. “A tunnel boring machine (TBM) with a diameter of 4.15 m will make its way from the North through a solid rock section of approx. 1 km.
“From the South, the about approximately 400m-long, loose rock section is being excavated beneath a jet grouted umbrella. The jet grouting method is a high-pressure jet injection that breaks up the ground material and mixes it with cement suspension to create solid ‘soil-cement-pillars’. Beneath the reinforced crown, the working face is being mined metre by metre with a tunnel excavator and the resulting roof supported with steel arches and shotcrete.”
Five cross connections to the main tunnel will be excavated after the primary works.
