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Rentable formwork shapes Wienerwald cavern Dec 2009
Rentable formwork shapes Wienerwald cavern Dec 2009
Doka news release
- A comprehensive formwork from Doka has been used to construct the reinforced-concrete final lining for the emergency ventilation cavern on the Wienerwald railway tunnel project in Austria. The 10m high x 35m long cavern lies at the junction between the 11km long twin TBM-excavated tunnels for the western section of the Westbahn widening project between Vienna and St Pölten and the shorter 2.3km single-tube, double track NATM eastern section. Set at 90° to the tunnel alignment, the cavern, with its many geometrically challenging intersections, transition zones and headings, is one of the most difficult casting operations on the project.
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Doka tunnel formwork traveller
- To construct the cavern's reinforced-concrete inner lining, the cavern, management of the Arge Wienerwaldtunnel JV (consisting of Porr Tunnelbau , Porr Technobau und Umwelt AG, Bilfinger Berger, Swietelsky, Jäger, Hochtief Construction AG and Züblin Tunnelbau) selected the Doka system. Alongside the technical formwork concept, the key factors behind this decision were the high proportion of rentable components (more than 90%), and the high degree of pre-assembly of the formwork equipment.
- The cavern itself is intended to provide rapid ventilation of the tunnel in the event of a fire. Following the primary shotcrete lining, the cavern's finish is a reinforced-concrete lining of about 50cm thick. For the first, 6m high lifts, casting step, the site crew of the Wienerwald Tunnel JV formed the 10m high end-walls using a combination of Doka supporting construction frames and rented standard panels from the Framax Xlife framed formwork system. Above this, the high-load Doka dam formwork D 15K, also fitted with Framax Xlife panels, formed the 4m high upper lifts. To facilitate concrete placement, the formwork panels are equipped with filler necks. Both these systems are fully rentable, are built from pre-assembled system components, and come with extensive safety features such as generously sized working platforms and integrated vertical access facilities. "With this formwork, we were able to pour the end walls in a safe, fast and cost-effective way, "explained Site Engineer Robert Uschan.
- Dimensionally accurate formwork for complex intersections
The 35m long sidewalls were formed with large-area elements of Doka Top 50 formwork on 6m high Doka supporting construction frames Universal F. For the geometrically difficult intersections with the tunnel tubes, -
Geometrical intersections formed with precision
- the Doka project technicians planned intersection elements designed specially to the complex geometry of the structure. Based on Large-area formwork Top 50, these elements were prefabricated with complete dimensional accuracy by the Doka Ready-to-Use service and supplied to the site ready-assembled. "By using these pre-assembled intersection elements, we have saved a huge amount of time and achieved a first-rate result", said Uschan, neatly summing up the benefits of working with the Doka Ready-to-Use service.
- A Doka tunnel-formwork traveller consisting of three sections in the longitudinal, was in action for pouring the cavern vault. The traveller is built from rentable standard components of the heavy-duty supporting system SL-1 and fitted with large-area formwork Top 50. Thanks to the system's high proportion of rentable system components, and its pre-assembled parallel truss segments, it can be finally assembled very quickly on the site, ensuring fast and efficient construction progress. In addition, experienced Doka field service technicians were on hand to help the site crew assemble the tunnel formwork traveller correctly. Using custom-built intersection elements, it was possible to form the transition zone between the vault, the sidewalls, and the tunnel tubes quickly and accurately. As well as the formwork solution for the emergency ventilation cavern, Doka also kept this major underground site supplied with just-in-time deliveries of formwork for transformer recesses, escape galleries and jet-vent tunnels. Detailed planning of the formwork operations, including verifiable static calculations, formwork pre-assembly and just-in-time site delivery, round off the extensive spectrum of Doka products and services provided to this challenging construction project.
- The Wienerwald Tunnel is the centrepiece of the project to widen the main Westbahn east-west railway between Vienna and St Pölten to four tracks. The new twin-tube tunnel runs for more than 13km beneath the Vienna Woods district between Hadersdorf and Klein Staasdorf and is one of the largest infrastructure projects currently underway in Austria.
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