By rosebell
The 178 m long, approximately 700 tonne Mixshield TBM has a cutterhead diameter of around 5 m and was manufactured by Herrenknecht for DB InfraGO and ARGE Tunnel Hauptbahnhof. Following factory acceptance at Herrenknecht’s Schwanau works in May, the machine was dismantled, transported to Munich and reassembled at the western tunnel portal near Donnersbergerbrücke. Mechanised excavation is currently scheduled to begin on 17 September 2026.
Although Donna Maria is the first TBM to start work on this major railway project, passengers will never travel through the tunnel she is about to excavate. Her initial assignment is the approximately 3 km long exploratory and rescue tunnel running between Donnersbergerbrücke and Marienhof, positioned between the two future S-Bahn running tunnels.
During construction the bore will act as an exploratory tunnel, providing valuable information about ground conditions ahead of excavation of the substantially larger passenger tunnels. Once the Second S-Bahn Trunk Line enters service, the tunnel will become part of the emergency and rescue infrastructure serving the railway tunnels. Deutsche Bahn has consequently described the first machine as a pathfinder for the tunnelling programme.
Donna Maria has been developed specifically to tackle the challenging conditions beneath Munich. The Mixshield system uses supporting fluid within the excavation chamber to control pressure at the tunnel face while excavating below groundwater and beneath densely developed areas of the city. Controlling face pressure is particularly important in reducing settlement and protecting buildings and infrastructure above the alignment.
As excavation progresses, precast concrete segments will be installed immediately behind the shield to form the permanent tunnel lining. Up to eight people can work aboard the machine, with Deutsche Bahn expecting an average advance of approximately 8 m/day during the drive. Parts of the tunnelling operation will take place at depths of up to around 40 m beneath Munich.
Donna Maria was developed jointly by Herrenknecht and ARGE Tunnel Hauptbahnhof. The consortium comprises Wayss & Freytag Ingenieurbau AG, Max Bögl, Ed. Züblin AG and Bauer Spezialtiefbau, bringing together several of Germany’s leading tunnelling and specialist civil engineering contractors.
The machine’s name was chosen following a public competition that attracted more than 1,000 suggestions. Around 2,300 people subsequently participated in the final vote, with Donna Maria receiving approximately 59% of the votes. The name links the two ends of the machine’s first journey: “Donna” represents Donnersbergerbrücke, where excavation starts, while “Maria” represents Marienhof, where the machine is heading.
Donna Maria represents only the beginning of the mechanised excavation programme beneath Munich. Six TBMs are planned to work on the Second S-Bahn Trunk Line, constructing running tunnels approaching central Munich from the east and west together with the exploratory and rescue tunnels. Around 6.4 km of the project will be excavated using TBMs, with Deutsche Bahn estimating that the six machines will remove approximately two million tonnes of material.
The scale of the next tunnelling phase will also increase significantly. While Donna Maria has a diameter of approximately 5 m, the TBMs intended to excavate the main railway tunnels will have diameters of around 8.5 m. Excavation of the first passenger running tunnel is currently expected to begin in 2028.
The Second S-Bahn Trunk Line is being constructed to provide additional capacity and greater operational resilience for Munich’s S-Bahn network. The project will create another high-capacity east-west rail connection beneath the city, supplementing the existing trunk line that has carried S-Bahn services through central Munich since 1972.
The scheme includes major underground works at Hauptbahnhof, Marienhof and Ostbahnhof as well as the new tunnels beneath the city. DB InfraGO says the additional infrastructure will increase S-Bahn capacity, improve operational stability and provide capacity for future growth. Current planning anticipates commissioning of the new route between 2035 and 2037.
Before Donna Maria disappears beneath Munich, Deutsche Bahn is planning an open construction-site weekend at Tunnelportal West on 12 and 13 September. Visitors will have the unusual opportunity to see the assembled 178 m long TBM only days before its scheduled launch towards Marienhof.
With the first mechanised drive due to begin in September, Donna Maria will provide the first real test of TBM excavation conditions along the western section of the Second S-Bahn Trunk Line. The information gathered during her 3 km journey should help prepare the way for the much larger machines that will follow from 2028 and excavate the tunnels that will eventually carry Munich’s S-Bahn trains beneath the city.
