The 4.4 km long Uetliberg Tunnel, connecting the Birmensdorf bypass (N20.1.4) in the west with the existing Zurich-Chur highway (A3 motorway) in the east, is the key structure of the new Zurich western bypass.
The underground central ventilation station is located in the Reppisch Valley (Landikon).
Each tunnel tube has two lanes and a hard shoulder with a total carriageway width of 10.5 m. The tunnels are lined with a double layered full sealing in between. The primary support consists of steel-fiber or mesh-reinforced shotcrete, bolts and partly of steel segments. The seal is pressure-maintaining in the Gjuch, Diebis and Juchegg soft ground and Eichholz molasse sections and drained (unpressurized) in the Uetliberg molasse section.
The standard cross-section of the Uetliberg molasse section
is 14.40 m wide and 14.20 m high.
The excavated area is approx. 160 m2.
The horseshoe cross-section, which is used in all the soft
ground sections and in the Eichholz molasse section, is about 14.70 m
wide and about 12.70 m high.
The excavated area is approx.
148 m2.
Ventilation / safety
The tunnel is normally ventilated in both directions
by the natural longitudinal ventilation / piston effect. A system of environmental
ventilation is installed for the tube Basle which permits the air flowing
out of the tunnel to be extracted before reaching the portal Wannenboden.
In the event of backups of fires, air can be with drawn through the intermediate
ceiling at stragegic points and fed back along a network of ducts to the
central ventilation station in the Reppisch Valley, where it is discharged
outside via the exhaust air tunnel and Eichholz shaft/flue.
There are three road crossings for traffic diversion in the event of a
disturbance in operations (accident, fire etc.) and for maintenance work.
A crossing is located at each of the two portals and the third is underground
in the Reppisch Valley ventilation station area. The tunnel itself also
has cross-cuts every 300 m to connect the two motorway tubes. Every third
cross-cut can be used by vehicles. Both tunnel tubes also have SOS and
hydrant niches at 150 m intervals.
Material handling / Environment
Construction of the Uetliberg Tunnel will produce a
total of 1.7 million solid m3 of muck and spoil material. Most of the
excavated material that cannot be reused in the project area will be transported
by rail to gravel pits in the northern part of Canton Zurich to be deposited
in accordance with current regulations. Suitable rail loading facilities
for the spoil material are located on the west and south sides.
About 70% of the total spoil, representing 1.2 million solid m3, is generated by the Reppisch Valley cut-and-cover works and the tunnelling which begins at that point. For this reason the tunnelling site in Landikon is connected by a conveyor belt to the railway loading facility in the Filderen area, upon which the muck and spoil material is to transported. On the return trip, the same conveyor belt transports the aggregate used for concrete production in Landikon. The cement is supplied by the railway near the construction site (by night) and blown to the concrete production plan through a pipe with air pressure.
