Underground works begin on major Madrid Metro extension

Tunnelling works have commenced for the extension of Metro Line 11 in Madrid, marking a key milestone in the city’s underground infrastructure expansion, according to project announcements and industry reports. The launch of the tunnel boring machine (TBM) “Mayrit” initiates excavation of a major section between Comillas and Conde de Casal, forming part of a broader underground development of approximately 6–7 km.

The Herrenknecht-built Earth Pressure Balance (EPB) TBM, measuring approximately 9.4 m in diameter and nearly 100 m in length, will carry out the majority of the excavation works. Operating at depths of around 20 to 30 meters, the machine is designed to advance under controlled pressure conditions, helping to limit ground movement and surface settlement in dense urban environments.

The tunnelling process includes the installation of precast segmental linings that provide immediate structural support to the excavation. These linings are designed to maintain tunnel stability and ensure long-term performance. A smaller portion of the alignment is expected to be constructed using conventional excavation methods, particularly in sections where TBM use is less practical due to geometric or logistical constraints.

The Line 11 extension предусматривает the construction of several new stations, including Comillas, Madrid Río, Palos de la Frontera, Atocha, and Conde de Casal, along with additional ventilation and emergency infrastructure. Slab track systems are planned throughout the tunnel to enhance operational efficiency and reduce maintenance compared to traditional ballast track.

The deployment of TBM “Mayrit” required a complex logistical operation, with components transported from Germany to Spain through multiple transport modes and assembled on site, as reported by project stakeholders. This reflects the scale and complexity of modern mechanised tunnelling projects.

The extension represents the first phase of a larger planned corridor that will significantly expand Madrid’s metro network. Once completed, the line is expected to improve cross-city connectivity and reduce congestion on existing routes, particularly those passing through central interchange stations.

The use of EPB technology is well suited to Madrid’s ground conditions, which include cohesive soils and mixed geology. By balancing earth and groundwater pressures at the tunnel face, the method helps reduce the risk of ground loss and settlement, a critical factor in urban tunnelling projects with existing surface and subsurface infrastructure.

The project is scheduled for completion later in the decade and forms part of broader infrastructure investment initiatives aimed at enhancing sustainable urban mobility and connectivity.