Final breakthrough at the Albabstieg tunnel

06.04.2017

The new ICE line has arrived in Ulm

One last rumble under the Michelsberg was heard when the two excavator milling machines were eating their way through the last piece of rock in mid-November 2016. Dust fountains whirled up, then it was done. To the applause of about 450 guests from politics and business, a seven-minute laser show finally announced the light at the end of the tunnel. The Albabstiegstunnel has officially been breached.

Final breakthrough at the Albabstieg tunnel

 

 

Just under a month later, the miners and tunnel builders from Max Bögl, who are working together to build the 5,940 metre long railway tunnel in shotcrete construction, were once again delighted. After the breakthrough of the east tunnel a month earlier, the parallel west tunnel also reached the north head of Ulm main station in mid-December. In about two and a half years since the official tunnel stop at the north portal in Dornstadt, the entire driving performance was achieved in both individual tubes. As a result of outstanding engineering and construction skills, the breakthrough after more than twelve kilometres of tunnel driving symbolises an important milestone in the history of the NBS Wendlingen-Ulm railway project and is thus a prime example of the speedy construction of major transport projects in Germany.

Untiring commitment underground

More than three million tons of excavated material were moved by the miners on their way through the underground of the Swabian Alb. For geological reasons, the client, Deutsche Bahn AG, decided not to use a tunnel boring machine for this final construction phase of the nearly 60-kilometer-long new ICE line. Instead, the tunnel builders drew and blasted their way through the predominantly limestone face of the White Jurassic with numerous karst formations seven days a week in continuous operation - on average 4.50 metres a day. Around the clock, up to 500 workers as well as 30 excavators and wheel loaders, nine drill rigs and a total of 80 dump trucks and round dump trucks were in continuous use, sometimes under difficult conditions.

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Safety first

For example, in addition to the more than 20-metre-high "Rappenbad" valley filling, the Rommel barracks also had to be crossed under with additional measures. With just six metres of cover, the teacher had to pass under the valley. Elaborate measures, including computer-assisted drilling of the blast holes, multiple ignitions, minimisation of the excavated cubatures and extensive monitoring, had to be implemented precisely and carefully. For the safety of all those involved, all structures in the immediate vicinity were documented in advance of the excavation work by means of preservation of evidence reports. Most of the blasting took place during the day. Due to the expected vibrations, it was therefore important to permanently monitor compliance with the applicable standards. As the working group could not, as is usually the case, make use of the local fire brigade for any underground rescue operations, a comprehensive concept had to be developed for the formation of its own rescue brigade. As a result, the construction site personnel received additional training, which made it possible to set up an organisation similar to a works fire brigade.

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Several driving attacks

With the north portal near Dornstadt and the south portal in Ulm, the Albabstiegstunnel overcomes an altitude difference of around 95 metres from the Alb plateau down to the railway tracks at Ulm main station. In addition to the construction site at the north portal near Dornstadt, another attack on the mountain took place in parallel from an additional tunnel in the Lehrer Tal. From the approximately 390 metre long access tunnel, the tunnel was driven both in the direction of Dornstadt and in the direction of Ulm. No driving was possible from the south portal in Ulm central station due to the inner-city location and the limited space available.

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Maiden voyage in 2021

The Alb descent tunnel consists of two single-track tubes, which are connected by eleven cross passages at intervals of 500 metres each. As part of the European railway project "Magistrale für Europa", high-speed trains, including the ICE, TGV and Orientexpress, are to travel through the modern double tunnel at speeds of up to 250 kilometers per hour. Together with the major Stuttgart 21 project, the tunnel and the new Wendlingen-Ulm line will go into operation at the end of 2021 according to current planning. The travel time between Stuttgart and Ulm will then be reduced from around 60 to less than 45 minutes for regional traffic and from around 55 to 30 minutes for long-distance traffic.

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Complex earthworks

Connected to the tunnel and also included on behalf of the joint venture are various earthworks and about 900 meters of the open section. At the border to the Stuttgart-Munich 8 motorway, not only a side deposit with several hundred thousand cubic metres of paving material is being built. The northern, above-ground railway line also had to be constructed in accordance with the guidelines by means of extensive soil improvement and replacement measures after the exploration measures had been carried out. At a later date, the new line will be given a "ballastless track" as permanent way as the subject of a separate tender.

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Interior finishing at full speed

The structural work for the 250 million Euro project of the Albabstieg Tunnel is expected to be completed by 2018. Currently, the interior shell is being completed under high pressure, more than 50 percent of the in-situ concrete inner shell has already been completed. To date, more than 200,000 cubic metres of shotcrete, 90,000 cubic metres of structural concrete, 10,000 tonnes of reinforcement steel and 200,000 square metres of sealing foil have been used. The supply of a total of around 580,000 cubic metres of concrete is ensured on site by two stationary mixing plants, one of which is operated by Max Bögl Roh- und Baustoffe.

 

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