Construction of Poland’s flagship high-speed rail tunnel beneath Łódź has reached a significant milestone, with the launch chamber in Retkinia now ready for the installation of the tunnel boring machine (TBM) that will drive one of the country's most ambitious rail infrastructure projects.
Work at the Retkinia launch shaft has advanced rapidly in recent weeks, with engineers completing the construction of a specialist concrete foundation known as the cradle, while the first components of the TBM are already being assembled at the bottom of the chamber. The machine is expected to begin excavation during the first quarter of 2027.
The cradle plays a critical role in tunnel construction. Designed as a precisely engineered semi-circular concrete structure, it supports the TBM shield and ensures the machine is correctly aligned before entering the launch opening. Engineers say even the smallest geometric deviation at this stage could affect the TBM's trajectory during the early stages of tunnel excavation, making accuracy essential.
International Expertise Behind Critical Construction Phase
Completing the cradle required a major engineering effort. Construction took almost three weeks and was carried out around the clock, with teams working 24 hours a day, seven days a week.
Four specialist tunnelling teams were deployed for the works, bringing together expertise from across Europe, including Poland, Austria, Germany, Slovakia, Romania, Croatia and Italy. The international workforce ensured continuous progress on one of the most technically demanding phases ahead of the TBM launch.
Excavation Set for Early 2027
Once assembly of the TBM has been completed and all operational testing has been successfully carried out, the machine will be guided into the prepared launch opening before commencing excavation.
According to the programme established by the scheme's main contractor, PORR S.A., tunnelling operations are scheduled to start in Q1 2027. The project forms a key section of Poland's future high-speed rail corridor, which will ultimately connect Warsaw, Łódź, Wrocław and Poznań.
“The use of TBM technology will enable the works to be carried out beneath the city while limiting their impact on existing buildings and urban infrastructure. This method is now standard for major tunnelling projects in densely urbanised areas, providing a high level of safety and precision.” – says Mateusz Kura, Project Manager at the Łódź–Sieradz Portfolio Department, Port Polska.
The finished tunnel will stretch approximately 4.6km beneath Łódź and, at around 14m in diameter, will become the longest and widest railway tunnel excavated in a single drive in Poland. Designed to accommodate two tracks, it will allow trains to operate in both directions at speeds of up to 160km/h through the underground section.
Progress Continues on Ventilation and Emergency Shafts
Elsewhere on the project, construction activity continues on the intermediate shafts that will provide ventilation and emergency evacuation facilities once the railway enters service.
Preparatory works are currently under way at the K5 shaft near Atlas Arena, while the K6 shaft has entered its main construction phase. Works there include the installation of excavation support structures using diaphragm wall technology.
The wider high-speed rail scheme is a central element of Poland’s future transport strategy and is expected to play a major role in improving connectivity between the country’s largest cities over the coming decade.
Image credits: Port Polska
