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ULMA Solutions for the Widest Tunnel on the Iberian Peninsula

Oct 04, 2017
Measuring 63 feet in width, this mine tunnel is to become the widest on the entire Iberian Peninsula.

As part of the first phase in the expansion of the A-4 Motorway, this project includes both the construction of a new tube 1,200 feet in length and the renovation of existing tubes. The new tube, located just north of the original tunnel, will have four separate lanes for traffic travelling from Amarante to Porto; the original tubes will provide passage for traffic in the opposite direction. The project is designed to significantly improve travel conditions for traffic going in and out of the city of Porto.

One of the complexities posed by the project was its location in an urban center with significant geotechnical risk, characterized by thin soil cover and areas of extremely weathered granite.

 Three carriages for a tailor-madsolution

ULMA’s technical team developed three separate structures in partnership with the client, in order to make work as efficient as possible.  First, a BRIO-MK scaffolding carriage was used to waterproof the entire tunnelA similar carriage was then used to install the rebar. In both cases, ULMA’s most versatile systems were combined to create carriages adjusted and optimized to meet the demands of the project without any need for additional space.  Next, the MK formwork carriage was used to pour the tunnel structure itself. With a single carriage it is possible to create all of the dimensions needed for a tunnel, a feature that proved ideal for this tube design with four distinct sections, each varied at the bottom. As an additional benefit, the carriage allowed for the passage of vehicles during construction, which is a necessity in such projects. 

The MK Carriage is a high-performance, versatile solution. It offers high load-bearing capacity without compromising the ability to adapt to different sections.

The carriage features hydraulic equipment to facilitate formwork installation and stripping, as well as lowering, levelling, and advancing the entire assembly.

Using a single MK formwork carriage 40 feet long, 33 feet tall, and 63 feet wide, the tunnel was completed in three months.

The pace of work exceeded client expectations. Work cycles were approximately a day and a half, with 10 to 11 hours of pouring and 3 hours for advance and adjustments. Thus four cycles were completed on a weekly basis

 The project in figures

Project data
Tunnel length 1200 ft.
Longitudinal slope 0.9876%
Floor plan radius 3539 ft


Formwork data
Formwork length 40 ft.
Thickness 19.5-45.3 mm
Width 63 ft.
Height 33 ft.
m² of formwork 4,175 f²
Section/pour volume 2475-2690 f³