The Europaviertel is a new district being developed on the former site of Frankfurt's freight yard, where about 30,000 people will work and 10,000 will live. The extension of the U5 light rail line will create an efficient connection to link the growing district to the city's public transport network. One of the most important infrastructure projects in Frankfurt, from 2024 the expansion of the U5 will provide people with a modern means of public transport.
The U5 line will be extended about 2.7 km to the west, past the former terminus "Hauptbahnhof" to the new Europaviertel quarter and will have four new stations, one of them underground. The client, Verkehrsgesellschaft Frankfurt am Main (VGF), set up the Stadtbahn Europaviertel Projektbaugesellschaft GmbH (SBEV) in cooperation with the city of Frankfurt specifically for the "Extension of the light rail line U5 Europaviertel” project.
Construction of the underground part of the line and the shell of the "Güterplatz" station located in this section is being carried out by the joint venture U5 Europaviertel, a consortium consisting of the two companies PORR Germany GmbH and the PORR subsidiary Stump-Franki Spezialtiefbau GmbH.
The two almost parallel tunnel tubes, 837 and 860 meters long, are being bored one after the other by a 7.15 meter excavation diameter Herrenknecht Earth Pressure Shield and lined with concrete segments. The tunnel boring machine S-1127 was christened "Eva" at a launching ceremony on August 26. The name was chosen in a competition and stands for the German acronym for "connecting Europaviertel".
"Eva" is specially adapted to the circumstances of the project. The Frankfurt underground is characterized by cohesive soils with a high clay and silt content and low water permeability. Due to the inner-city tunnelling, however, very high demands are being placed on settlement minimization.
The cutting wheel of the EPB Shield, which is equipped with around 100 scrapers and 29 disc cutters as tools to excavate the soil, is pressed against the tunnel face as it moves forward and loosens the soil ahead. The excavated material, the soil paste, is used directly as a support medium. This allows the necessary pressure balance at the tunnel face and thus prevents an uncontrolled collapse of the soil. As a result, the risk of settlement or heave on the surface is minimized and consequent damage to structures prevented.
"Eva" began tunnelling in early September 2019. Initially the tunnel boring machine is excavating the southern tunnel tube and digging from the launch pit to about 3 meters away from the existing structure at the Platz der Republik square. In doing so, it passes through the retaining walls of the future underground station "Güterplatz". The machine will then be disassembled and pulled back through the previously built tunnel to its starting point. After reassembly the machine will set off again to bore the second tunnel tube as well.
During excavation, eight miners per shift will work seven days a week and 24 hours a day on the machine at depths of up to 25 meters in the Frankfurt underground. In total the team consists of 60 miners.
Individual photos courtesy of SBEV GmbH/Klaus Helbig.