Day after day, the Sihltal Zürich Uetliberg Bahn SZU transports around 25,000 people through the city - and almost unnoticed right through the center. This is because the S-Bahn lines S4 and S10 run from the main station to the Zurich Selnau stop through the two-lane Sihl Tunnel. This lies partly under the Sihl, partly next to the riverbed under the Gessnerallee. The 1,400-meter tunnel was put into operation by SZU in 1990 - before that, the line ended in Zurich Selnau.
Now the roadway had to be renewed, because after 30 years its useful life had been reached.
Since the Sihl Tunnel is located in the inner-city area, this complicated the general conditions during execution.
The renewal of the carriageway of the first lot took place during the summer vacations in a 7-week total closure (from July 13 to September 1, 2019).
Between the Zurich HB SZU station and the Zurich Selnau stop, services were suspended during this period. From the stop Zurich Selnau, however, the operation ran regularly. Rail operations up to and at the Zurich Selnau stop were not to be affected by the construction site.
The track of the existing double-track tunnel had to be renewed, including adaptation of the track geometry and drainage situation, during a total closure of 6 weeks. The new track was constructed using the LVT-Low Profile (LP) system and the new turnouts with concrete monoblock sleepers with elastic inlay and rubber shoe (ATG system).
All logistics were rail-bound to the installation site in Sihlwald. The entire material handling (removal of old material - rails, sleepers, demolition material, etc.) and delivery of new material was carried out by construction trains operated by the company's own rail transport company (RU), including transport drivers and transport escorts. Only the concrete was pumped into the tunnel via the surge opening (max. pumping length 250 m).
The renewal was carried out in 3-shift operation. After track demolition, a 2.70 m wide trough was cut into the existing grouted concrete using a large milling machine. In stages of 108 m, the new track was installed, roughly and finely aligned and finally concreted underneath. The four switches were installed during the Sunday/Monday night. Great attention was paid to the SA and FL inserts, which were all laid in the new concrete and connected to the existing cable duct. Following the welding, the entire new track was ground. After various finishing works and a tunnel cleaning, the installation was handed over to the SA and FL railroad engineering trades for recommissioning for the 7th week of the total closure.
Walo Bertschinger AG
8953 Dietikon 1
Trackwork & Rail Engineering
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