Frankfurt a. M.

Extension of the U5 Europaviertel metro line

Entire value chain for a complex infrastructure project from a single source

A project driven by a pioneering spirit
Initial work involved preparatory activities for the tunnel, which was constructed using the cut-and-cover method. Two tunnel tubes, 827 m and 842 m long, were constructed using shield tunneling - a first for Frankfurt am Main. The 580-ton tunnel boring machine EVA (“Europaviertel anbinden”) was specially adapted to the geological conditions and installed a total of 8,358 segments during tunneling to form the future inner tunnel lining. Advancement of the south tube began in September 2019 and was completed in September 2020, followed by the advancement of the north tube between January and May 2021.

Ground freezing work in the connection area to the existing tunnel

In the area adjacent to the existing tunnel at Platz der Republik, ground freezing was necessary to safely pass beneath the highly sensitive and densely built-up downtown area without endangering neighboring existing buildings or disrupting surface traffic. Based on technical and economic analyses, it was decided to use a brine freezing unit with a cooling capacity of 140 kW. The cold was introduced into the ground via precisely drilled freezing holes, creating a frozen soil mass with a specially shaped, collar-like arrangement of freezing pipes. The tunnel boring machine entered this pre-frozen funnel in a controlled manner. An additional active cooling system installed on the stop wall utilized the residual cold from the returning, already warmed brine and accelerated the freezing process. The successfully executed ground freezing sealed and consolidated the construction ground so reliably that the mining-style tunnel excavation could subsequently be carried out safely under compressed air.

Challenging Work Under Compressed Air

The final meters to the existing subway tunnel at Platz der Republik were completed using the mining method by July 2022. Technically complex compressed-air airlocks equalized the air pressure at/in the construction site with the pressure of the surrounding groundwater to prevent water ingress. Working in 24/7 shifts, PORR Tunnelbau excavated 11 meters of tunnel in the south tube and 3 meters in the north tube. Health and safety were the top priority, so all personnel underwent occupational health examinations as a precaution. Work was carried out in three 6-hour shifts. Additionally, approximately 1.5 hours were required for entry and exit in the pressure chamber.

Ramp structure and open-cut tunnel construction along Europa-Allee

Parallel to the mechanized tunnel construction, PORR Ingenieurbau began above-ground work on the construction site along Europa-Allee in early 2022. Here, the U-shaped trough structure of the future ramp and the adjoining tunnel were constructed using the cut-and-cover method. In sections, the floor, walls, and ceiling elements were concreted and connected to the already driven tubes. The approximately 137-meter-long ramp structure, including the striking, three-dimensionally curved ramp collar, was completed in 2023.

Excavation work for one of Frankfurt’s deepest construction pits

Parallel to this progress, the construction pit for the Güterplatz underground station developed into one of Frankfurt’s deepest: approximately 180 meters long, 25 to 30 meters wide, and up to 24 meters deep. Excavation took place in multiple stages beneath a total of three large reinforced concrete support levels, which had to withstand the considerable earth and water pressure. Excavation began in 2022 beneath the first support level, followed later by work beneath the second and third support levels. As part of the excavation, the segment linings of the previously constructed tunnel tubes in the area of the future station also had to be selectively dismantled. This dismantling posed a significant logistical challenge, as the demolition material had to be removed under cramped inner-city conditions.

Final excavation phase and construction of the station floor at Güterplatz

By the end of 2023, the third and deepest bracing level was completed, clearing the way for the final excavation down to the final depth. After reaching the target floor level, the 0.5-meter-thick sub-concrete floor was constructed, followed by the pouring of the 2-meter-thick structural floor of the Güterplatz station. This will later take over the structural bracing function of the previously constructed lowest bracing layer. In the following months, the station walls were successively raised and concreted up to the lower edge of the middle bracing layer.

Tunnel shell construction along Europa-Allee successfully completed

At the same time, the final sections of the tunnel were completed using the cut-and-cover method along Europa-Allee. At the end of October 2023, the final ceiling section was concreted, officially marking the completion of all tunnel work - both in open and closed construction methods. With the completion of the ramp structure, the tunnel portal, and the tunnel shell sections, a key milestone on the path to commissioning was reached. The successful acceptance of the tunnel constructed using the cut-and-cover method by the client took place in February 2026.

Structural work on the Güterplatz station is taking shape

The project’s focus is currently on the structural work for the underground Güterplatz station, which will form a major transportation hub in the Europaviertel in the future. Here, not only are the platform and access structures being built, but also all load-bearing structures that will later accommodate the technical finishing work. Architecturally sophisticated light domes and smoke extraction shafts made of cast-in-place concrete in special formwork are currently being constructed on the station ceiling. With these advances, the station is moving step by step closer to the completion of its structural shell. Completion of the station - initially without access points - is scheduled for late 2026.

With the extension of the U5, PORR, as part of the ARGE-Struktur consortium, is creating an efficient, future-oriented transportation link for one of Frankfurt’s most dynamic development areas. The combination of mechanical tunneling, specialized civil engineering, structural engineering, and sophisticated logistics demonstrates the full range of PORR’s expertise - and underscores its commitment to efficiently and safely executing complex infrastructure projects from a single source, meeting the highest quality standards.

See more pictures and videos about the project:

• Media library: Extension of the U5 Europaviertel

See more photos and videos of the project: