Bucharest launches second major tunnelling phase of airport metro project

Tunnelling has started on the northern section of Bucharest Metro Line 6, marking the next major phase of the 14.2 km metro extension that will eventually connect central Bucharest with Henri Coanda International Airport.

The first Earth Pressure Balance TBM, named Saint Parascheva, began excavation on 21 October from the launch shaft at the future Bruxelles station, where Metrorex marked the start of works with a launch ceremony. The machine will drive the first tunnel on Line 1, while a second TBM, Saint Catherine, will follow on Line 2. Following tradition, both are named after female saints: Parascheva as the protector of travellers, and Catherine as the patron saint of engineers, whose wheel symbol recalls the cutterhead. Together, the two machines will construct the twin tunnels forming the northern section between Tokyo station and Aeroport Otopeni.

The tunnelling programme is divided into two main drives. During the first, both machines will advance from Bruxelles towards Tokyo station, where the new tunnels will connect with the southern section of Line 6. After completing this drive, the TBMs will be relaunched from Bruxelles in the opposite direction towards Aeroport Otopeni.

Each machine is approximately 103 m long including the back-up train and weighs 602 tonnes, comprising a 380-tonne shield and 222 tonnes of back-up equipment. The cutterheads have an excavation diameter of 6.57 m and are adapted to the ground conditions expected along the alignment, which include sandy clay, Colentina gravels and silty sand, with the water table at a depth of 2 m to 7 m.

The use of EPB technology is particularly suited to these conditions because pressure can be maintained at the tunnel face while excavation proceeds, helping to control ground movement and groundwater inflow. As material is removed, precast concrete segments are installed immediately behind the shield to form the permanent tunnel lining.

Average advance is expected to reach around 14 m per day for each TBM, equivalent to 10 rings of 1.4 m each. Maintaining consistent face pressure, controlling excavation volumes and monitoring settlement will be particularly important where tunnelling passes beneath developed urban areas and through variable granular and cohesive deposits.

The northern section will serve six stations: Washington, Paris, Bruxelles, Otopeni, Ion I.C. Bratianu and Aeroport Otopeni. Once completed, it will connect directly with the southern section, where tunnelling has already been under way since April 2025.

Metro Line 6 will ultimately extend through twin tunnels and 12 new stations, linking Gara de Nord with Bucharest's main international airport. Mariana Miclaus, Director General of Metrorex, said the start of excavation on the northern section means the tunnels towards Henri Coanda are beginning to take shape. With excavation now advancing from both the southern and northern sections, the project is moving into a stage where the underground alignment is progressively taking shape from multiple fronts.

The start of northern tunnelling is therefore more than a ceremonial milestone. It marks the transition from station and shaft construction into continuous underground excavation on the final major section needed to complete Bucharest's direct metro connection to the airport.