Zurich is the largest city in Switzerland, though Berne is the capital – a fact that many people don't know. Zurich is located in north-central Switzerland at the northwestern tip of Lake Zurich. The lake, the surrounding hills and woods, the nearby mountains and the old traditional houses are what make the city so charming and unique.

The municipality has approximately 400,028 inhabitants, and the Zurich metropolitan area 1.83 million. Zurich is a hub for railways, roads, and air traffic. Zurich's airport and railway station are the largest and busiest in the country. The city is also home to many of the employees in Sika's corporate team.

Over half a million passengers per day

The surge in population seen in recent years has to be addressed by expanding urban infrastructure. Over half a million passengers per day will pass through Zurich main station in 2020. It is the central hub for rail traffic in Switzerland. With trains pulling in and out virtually every minute, some 400,000 passengers arrive, depart or change services here every day. Commuter volumes are constantly on the rise. A new cross-city link was designed to ease the bottlenecks and provide more trains for Zurich.

Cross-city link with four-track underground station

The "once-in-a-lifetime" cross-city link project was launched in 2007 in response to the growing passenger numbers. The multi-billion project comprises a 9.6 km rail section including the new Löwenstrasse through-station, Letzigraben bridge, Kohlendreieck bridge and Weinberg tunnel. The four-track underground station, located some 16 m below two existing tracks, forms the heart of the new link.

Severe difficulties because of groundwater system

The site of the through-station posed severe difficulties given that it occupies part of the canton's largest groundwater system and crosses below the River Sihl as well as all three existing station malls. The new station was designed with wide platforms, numerous spacious access stairways and state-of-the-art security installations.

Concrete services partly without interruption of the train services

The challenging concreting operations – partly carried out without interruption of the train services in the overlying main station – placed high demands on the entire project team. During excavation, Sika® ViscoCrete® technology was used for the approx. 2,000 m3 of special self-compacting concrete placed for the umbrella seal. The admixtures were used for the 130,000 m3 of structural and fair-faced concrete.

That bridge will be Switzerland's longest railroad viaduct

To make way for the construction of new bridges, some sections of existing track had to be altered or lifted. The formwork erection and concreting works for the bridges are performed high above ground level while the normal train services continue to run. When finished, the Letzigraben bridge will be Switzerland's longest railroad viaduct. The works are progressing to plan and look set for completion in 2015.

Top-quality concrete in a variety of forms

The construction of the cross-city link involved the excavation of a million m3 of rock and soft ground. The Weinberg tunnel required top-quality concrete in a variety of forms: concrete with a stripping time of only 4.5 hours for the tubbings, in-situ concrete for the tunnel arch and shotcrete for stabilization.

The sheer volume of concrete placed testifies to the imposing size of the tunnel structure: 45,000 m3 of arch concrete, 25,000 m3 of shotcrete, and 45,000 m3 of tubbing concrete. The main 4,200 m section of the Weinberg tunnel was driven by an 11.3 m diameter tunnel boring machine and lined with 30 cm thick reinforced-concrete tubbings. Overall, some 14,000 concrete tubbings were cast for this one tunnel alone.

Sleep longer and get faster to work

The entire tunnel was waterproofed by approximately 140,000 m2 of 3 mm Sikaplan® FPO membranes as well as 6,000 m of Sika® AR-40/6 waterbars for the compartmentation. A lot of the people working in Sika's corporate team are looking forward to the inauguration because it marks the beginning of a new era of sleeping longer on weekday mornings, safe in the knowledge that they can get to their offices fast thanks to the new public transportation infrastructure.

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