Herrenknecht TBMs Cut Through the Pyrenees

The Herrenknecht tunnel boring machines “Canigou” and “Alberas” are compact powerhouses: Equipped with an installed power of 1,250 kW, they have a torque of 2,000 kNm with a cutterhead diameter of 4.3 m. The tunnel boring machines have a length of 301 and 253 m, respectively, and weigh 620 tonnes. The double-shield TBMs started at their launch portals in March and October 2012 to pre-drill and construct the 8.2-km long tunnel through the hard rock of the Catalan Pyrenees. “Alberas” begun its mission in La Jonquera, Spain. “Canigou” advanced toward its sister machine from Montesquieu-des-Albères, France.

The two double-shields from Herrenknecht were ordered by the Franco-Spanish joint venture, consisting of tunneling specialists Eiffage and Dragados. The challenge was to create an ambitious tunnel project within a demanding timeframe.

After 1.23 km of tunneling, “Canigou” reached the end of the lot, coming from France beneath the Massif des Albères, in March 2013. “Canigou” was immediately dismantled in the protection of a tunnel section in stable rock without any lining under the supervision Herrenknecht specialists. After 7.01 km of tunneling, “Alberas,” coming from Spain, drove into the tunnel drilled by “Canigou” on April 22, 2013.

The best drilling performance of the overall project was achieved by “Alberas” on the Spanish side: 53.5 m per day with up to 1,040 m drilled and built tunnel per month. “Alberas” was also dismantled in the drilled tunnel, and the components were removed through the north portal. The physical connection for the exchange of electricity is thus completed.

The cross-border power lines that connect Spain with France and the rest of Europe need to be extended urgently. The four existing connections do not have sufficient capacity to cope with bottlenecks or to compensate for fluctuations resulting from the use of renewable energy sources. As part of the bi-national project, “INELFE” (INterconexión ELéctrica Francia-España), a 64.5-km long, ultra-modern high-voltage direct current transmission link (HVDC), is being installed from Baixas, near Perpignan in France, to Santa Llogaia, near Figueras in Spain. In the tunnel drilled by the two Herrenknecht tunneling machines, the route passes under the Pyrenees on the Catalan Mediterranean coast.

Double-shield TBMs combine the functional principles of the gripper TBM and the single-shield TBM in one machine. This combination of methods allows the installation of concrete segments in stable geological conditions parallel to the excavation work, thus achieving very high advance rates.

For the “INELFE,” project Herrenknecht prepared the back-up systems of the two machines for double storage: Logistics and storage facilities were designed in such a way that segments and grout could always be stored on the machine for two ring-building sequences. Thus, the machine operators were able to exploit the potential of the double-shield principle, without being limited by possible shortages in the material logistics. Due to the design of the machine components it was possible to dismantle them within the excavated drilling diameter without having to break out an additional cavern.