Project Description

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 project consists of two parallel tubes, each about 4.4 km long, which both increase in slope by approx. 1.6 % between the east and the west portals. Stations with equipment and installation rooms will be built at both the west and east portals.
The underground central ventilation station is located in the Reppisch Valley (Landikon).

West portal today The Tunnel are lined with a double layer and a full sealing
Standard cross-section

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.

Standard cross-section of 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.

Standard cross section in the Eichhoz molasse section and the soft ground sections

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.