The first construction milestone has been achieved on the $687.5M Uetliberg Tunnel project near Zurich, Switzerland, with the breakthrough on the 20 September of the 545m long $3.5M Fideren-Repischtal muck transport tunnel.
The 11.2m2 tunnel is essential for transporting spoil under a hill that forms a barrier between the construction site of the main Uetliberg twin 4.4km long highway tunnels and the Fildern rail facility. The Uetli hoint venture of Zschokke Locher/Murer/Prader/CSC Bauunternehmung/Wayss & Freytag/Alpine Mayreder Bau/Spaltenstein Hock + Tiefbau, began construction of the transport tunnel in October 2000 from two faces.
Soft ground methods were used for the first 20m on the Reppisch side and 40m on the Fildren side. The 485m long molasses section between the sot ground was then driven by a 3.2m diameter TBM.
The tunnel passed under the existing Landikon railway tunnel by only 7m, requiring reinforcement before and strict monitoring during construction. A spokesman for the consultant, Amberg Consulting Engineers, told T&TI that settlement measured as trains passed through the tunnel exceeded that measured during TBM excavation.
The invert is currently being constructed containing power supply cables for the TBM on the main drive. This is scheduled for completion at the end of this month when a conveyor system will be installed to connect the main heading via the tunnel to the railway loading installation.
Uetli, which was awarded the contract in September 2000 by the Canton of Zurich Engineering Department, will also construct the Uetliberg twin tunnels with a vairety of techniques to suit the geology.
The largest section of the tunnel is the 2.8km long molasses central section. This will initially be driven as a 5m diameter TBM pilot tunnel; the first tube (northern) will start in February 2002 for completion in October that year followed by the second tube (Chur) in November for completion in July 2003.
The tunnels will then be widened by a tunnel bore extender (TBE) to a finished diameter of around 14.4m. The north tube will be widened from October 2002 to March 2004 and the Chur tunnel between May 2004 and September 2005.
Other lengths of the tunnel will be driven by drill and blast with core boring. Technical commissioning of the tunnel is expected in 2008.
The tunnels form a integral part of the 11km long Zurich western bypass. The tunnel links the Birmensdorf bypass (N20.1.4) in the west with the Zurich-Chur highway in the east (N3) thereby closing a substantial gap in the Swiss national road network.
