PROJECT DATA

New Metro Line M4: 7.4 km long

Project: Metro Line M4

Developer: BVP-Metro4

Contractor (and Architects): Mahíd 2000 AG Konsortium Bilfinger-Vegyépszer-Porr

MEVA Systems: wall formwork system Mammut & StarTec, support frame STB 300/450, climbing scaffold KLK, folding scaffold KAB, slab formwork MevaFlex, circular formwork Rundfix

Formwork Engineering: MEVA Zsalurendszerek Rt., Hungary

 
 
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Project

Subway Under the Danube

Opened with line M1 in 1896 when the Hungarian capital celebrated its millenium, the Budapest Metro is the second oldest underground system in Europe – after the London Underground. Since then, the Budapest Metro network has been extended by adding lines M2 and M3 to line M1 and now a fourth line – M4 – is under construction. It will be 7.4 km long and connect the Kelenföld (south Buda) und Rákospalota (eastern Pest) quarters by subcrossing the Danube. Once M4 is in operation, the Budapest Metro network will have 42 stations and a total length of 33 km. Planned and equipped for a fully automated operation, M4 will be the first driverless underground line in Hungary. It will run every 90 seconds and travel as fast as 80 km per hour. The new line is expected to ease the chaotic traffic in Budapest, especially for those who enter Budapest from the west.

Planning, Formwork and Site Management: All Done and Delivered by MEVA
Since 80% of the concreted area will not be covered or plastered, a top concrete surface finish is an important requirement. A major forming challenge were the elliptical escalator openings that are embedded in a girder system of reinforced concrete. By using standard StarTec wall formwork panels together with radius panels and 4 mm forming faces, the MEVA formwork specialists were able to master this challenge without time-consuming special constructions. Using MEVA’s wall formwork Mammut and conventional girder formwork MevaFlex, the walls and top slab were simultaneously added to the girder system’s slab whereas the inside walls were poured using one-sided formwork.

Little Space and Many Forced Breaks - Make Pouring Another Challenge
The Metro stations are built with the cut-and-cover method. First, a diaphragm wall that is 0.25 to 1 m thick is erected on either side of the future structure, then the cover is poured. Following this, the earth beneath the cover is excavated 21 m deep. Then the 2.50 m thick foundation slab and the inside tunnel walls are poured. This top-to-bottom construction approach is also known as the Milano method.

At the same time and without interruption, two heading and cutting machines – one for each tube of the Metro line – keep on excavating their ways forwards and the excavated material is transported to the outside with trains that pass through the Metro stations that are behind them – and still under construction. This means that pouring and all related work is frequently interrupted to let the trains pass through, requiring agility and planning flexibility.

One-Sided Formwork to Pour the Inside Tunnel Walls With a Top Concrete Surface Finish
Project spefications demand the inside tunnel walls – 9.50 m high and approx. 60 cm thick – to have a top concrete surface finish. This was accomplished with a one-sided wall formwork solution made of wooden girders covered with a 4 mm plastic facing. An even joint pattern was achieved with trapezoidal strips that were attached to the facing every 2.50 m and covered the joints.

The formwork was attached at cones concreted in the beam of the top slab. Work was carried out under restricted, very narrow conditions since the entire formwork unit had to fit on the 70 cm concrete slab on which the Metro trains will later run. The one-sided formwork was anchored with much care and fine-tuning because the client’s rigorous deflection specifications would permit a maximum deflection of 10 mm along the 9.50 m wall. This was achieved by using Triplex alignment rails at two different levels. With the second rail level restricting the anchor force to 70 % of the predicted value, the rigorous specifications were easily met.

Internal and External Vibrators
The 13.50 m long formwork was placed on a support construction 9.50 m long, thus creating a mobile unit. Pouring was done with a hose and in 24 cycles, each with a maximum length of 12 ½ m. The pouring rate was 0.7 to 0.8 m per hour. Special attention had to be paid to the concrete consistency and the narrow conditions asked for a careful handling of the internal and external vibrators.

The 13.50 m long formwork was placed on a support construction 9.50 m long, thus creating a mobile unit. Pouring was done with a hose and in 24 cycles, each with a maximum length of 12 ½ m. The pouring rate was 0.7 to 0.8 m per hour. Special attention had to be paid to the concrete consistency and the narrow conditions asked for a careful handling of the internal and external vibrators.

he new Metro line is planned to be finished in 2009 and start service in May 2010.

 
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