M-111 Underground Tunnel

The M-111 Highway Underpass was constructed as part of the Madrid-Barajas Airport expansion programme and represented a strategic infrastructure project designed to maintain road traffic continuity beneath the new airport runways and the future Satellite Terminal Building. The project consisted primarily of the construction of a 1,770 m long reinforced concrete cut-and-cover tunnel, incorporating a four-cell cross-section. Two of the internal cells accommodate the M-111 highway carriageways, while the remaining two are dedicated to airport service traffic and utility infrastructure

From the perspective of fabricated reinforcing steel, the project presented significant technical challenges due to the unique geometry of the structure and the exceptionally high loading conditions generated by airport operations. The tunnel structure was formed by a system of vaults, invert slabs and reinforced concrete side walls, all constructed with 60 cm thick heavily reinforced concrete sections designed to withstand the demanding loads associated with heavy road traffic as well as aircraft taxiing, take-off and landing operations on the runways located directly above the tunnel

ERSIGROUP participated in the supply, fabrication and installation of reinforcement for the tunnel walls, vaults, invert slabs, foundation slabs and transition structures. Meeting the demanding construction schedule required the implementation of advanced reinforcement industrialization and optimization techniques. To achieve the required production rates, a system based on the prefabrication of standardized reinforcement units for walls and vaults was developed in a dedicated off-line fabrication yard and subsequently lifted into position by crane. Some of these prefabricated reinforcement assemblies exceeded 5 tonnes in weight, significantly reducing installation times while improving site safety conditions

The industrialized reinforcement solutions developed by ERSIGROUP enabled the project team to maintain 48-hour concreting cycles per formwork carriage, using self-supporting formwork systems measuring 12 m in length, a key requirement for achieving the planned construction programme. In addition, industrialized unidirectional reinforcement panels incorporating bars up to Ø25 mm were used for foundation slabs and retaining walls, ensuring accurate bar spacing and optimized installation procedures. In areas with particularly complex geometry, including tunnel transitions, section changes and airport access ramps, reinforcement was assembled using specialized installation teams due to the high reinforcement densities and demanding geometric requirements involved

The combination of detailed engineering, reinforcement prefabrication, specialized logistics and industrialized installation methods enabled construction rates of up to 24 linear metres of fully completed tunnel per week, contributing significantly to the successful delivery of one of the most technically demanding underground structures associated with the Madrid-Barajas Airport expansion project

KEY MILESTONES

• Construction of a 1,770 m long reinforced concrete cut-and-cover tunnel
• Strategic infrastructure forming part of the Madrid-Barajas Airport expansion programme
• Four-cell tunnel section accommodating highway traffic, airport service roads and utility infrastructure
• Vaults, invert slabs and side walls constructed with 60 cm thick reinforced concrete sections
• Use of 12 m long self-supporting formwork carriages for rapid construction cycles
• 48-hour concreting cycles achieved for each formwork carriage
• Industrialized prefabrication of reinforcement assemblies for walls and vaults developed by ERSIGROUP
• Fabrication and installation of prefabricated reinforcement units weighing more than 5 tonnes
• Use of industrialized unidirectional reinforcement panels incorporating bars up to Ø25 mm
• Construction productivity reaching 24 linear metres of fully completed tunnel per week
• Implementation of dedicated reinforcement prefabrication yards and specialized logistics systems for large-format reinforcement assemblies
• Development of reinforcement solutions for complex tunnel transitions, section changes and airport access structures
• Application of advanced reinforcement industrialization processes developed by ERSIGROUP to optimize construction schedules, quality control and site safety