Employer
Canton of Zurich, Department of Construction,
Amt für Abfall, Wasser, Energie und Luft
Walcheplatz 2
CH-8090 Zurich
Designer
IG Sihl Entlastungsstollen
c/o IUB Engineering AG
Belpstrasse 48
CH-3000 Berne
Time of Completion
03.2022 – 11.2025
Execution of the Work
ARGE Marti Entlastungsstollen Thalwil
Consortium Partners
Marti AG, Zurich Construction Company, CH-8050 Zurich
Marti Tunnel AG, CH-3302 Moosseedorf
Marti AG Solothurn, CH-4500 Solothurn
Grund- und Tiefbau AG Solothurn, CH-4500 Solothurn
Stump-BTE Bautechnik AG, CH-4503 Solothurn
Alwatec AG, CH-4512 Bellach
Lead Company and Commercial Lead
Marti AG, Zurich Construction Company, CH-8050 Zurich
Technical Lead
Above ground: Marti AG, Zurich Construction Company, CH-8050 Zurich
Underground: Marti Tunnel AG, CH-3302 Moosseedorf
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Scope of the Works
HWS Sihl, spillway Thalwil
Master builder works and underground construction
- Inlet structure Sihl
- spillway Ø = 6.60m, L=2014.15m, TBM excavation falling with tubbing lining
- Lake Zurich outlet structure
Activities
Sihl intake structure:
The intake structure in the tailwater of the already realized alluvial rake is designed to collect a discharge of up to 330 m³/s (design case) or 400 m³/s (overload case) and to discharge it into the spillway. The water intake is located along the right bank of the Shil River with a curved side spillway.
Relief gallery:
Excavation of the 1,994.46 m long mining gallery with an excavation diameter of 7.55 m and an inside diameter of 6.68 m (Di = 6.60 plus room for deviations of 2 x 4 cm) will be carried out with a TBM (shield machine).
Excavation will be on a downward gradient from the inlet structure to the outlet structure with a longitudinal gradient of 1.259 to 3.330 %.
The excavation support and final lining (single-shell tubbing segment lining) is carried out with reinforced concrete segments grouted over the entire circumference with annular gap grout.
The TBM starts from a 20 m launch tube, which is created from the intake structure.
Shortly before the outlet structure, the relief tunnel crosses under the Zurich - Zug and Zurich - Chur railroad lines of the SBB in Thalwil. In order to reduce the driving risk under the Zurich - Chur railroad line, around 36 m of the relief gallery will be constructed by counter heading (from the outlet structure). The tunnel will be secured with a pipe shield as well as support bends and mesh reinforcement.
Discharge structure:
The outlet structure consists of the following elements_.
- Access from the level of the cantonal road (Sees- trasse)
- Lift shaft (private side project)
- Tos chamber with rake construction
- Ventilation shaft above the stilling chamber
- Rectangular channel under the Seestrasse and the Bürger 1 lake resort
- Dam beam closure
- Rectangular canal in the lake with estuary structure
- Valve gate (procurement later if required)
From the spillway, water flows into the Toskammer as a free level discharge. In the stilling chamber the energy conversion and the change to pressure discharge takes place. Under pressure, the water flows through the rectangular channel or the outlet structure into Lake Zurich.
Geology
Upper fresh water molasse
Contact
Marti Tunnel AG
Seedorffeldstrasse 21
CH-3302 Moosseedorf
Tel. +41 31 388 75 10
tunnel@martiag.ch