Project: 580-metre-long outer wall for the cut-and-cover Katzensee tunnel on the northern bypass in Zurich, Switzerland
Principal: Swiss Federal Roads Office (FEDRO), Winterthur infrastructure office
Contractor: Northern ring road construction consortium consisting of the construction companies AG Zurich, Eberhard Tiefbau, STUTZ AG, Specogna, and Hagedorn
MEVA systems: Mammut 350 wall formwork
Engineering and support: MEVA Schalungs-Systeme AG, Seon, Switzerland
In Zurich the motorways cross each other from all directions. Every morning and evening in this densely populated region the heavy through and long-distance traffic is joined by commuter traffic. And then the traffic simply comes to a standstill on the northern ring road in Zurich, which, with over 100,000 vehicles a day, is one of the busiest stretches of road in Switzerland.
The Swiss Federal Roads Office has planned a series of construction projects to relieve this bottleneck by 2025: The Gubrist Tunnel will be getting a third parallel tube to take up the traffic on the A1 motorway coming from St. Gallen and heading towards Bern and Basel, and the two existing tubes will be renovated. In addition, the entire section of motorway between the Limmattal and the Zurich North junctions will be widened to three lanes in both directions and roofed over for a length of 580 metres where it passes the Katzensee nature reserve.
Outer walls for the cut-and-cover Katzensee tunnel
Large-size Mammut 350 industrial formwork units are being used for the outer walls. The 6-metre-high and 80-centimetre-thick outer wall has already been poured in the St. Gallen direction. 12.5-metre-long and 6-metre-high units made up of largesize panels were used. It was possible to move the large-size units, each weighing 9.5 tons, using a crawler crane.
The work is being performed using five initial and three final formwork units with quick pouring cycles:
Pouring time of 2.5 hours for each cycle
The Mammut 350 with its freshconcrete pressure load of 100 kN/m² allows concrete to be poured up to a height of 4 metres without restricting the rate of placing, a significant advantage for high walls that is exploited to the full here. Load gauges attached to the formwork ensured that the capacity of the formwork was utilised to its full potential but not exceeded.
“We have been able to pour up to six cycles a week and are actually ahead of plan. The quality is also first-class”, says head foreman Giuseppe Petrolofrom Marti, who is clearly proud of the speed of placing and the concrete surface quality which he has achieved using Mammut 350.
Besides rerouting the traffic, this year the central and outer walls in the Bern direction and the tunnel slab will be poured. This work will be performed using twice the quantity of formwork equipment.
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