Last Tuesday, July 30th, the breakthrough on O Serro Tunnel was carried out in the works to link the N-120 and N-536 between Sobradelo and O Barco de Valdeorras (Ourense).
Supported by the Ministry of Transport and Sustainable Mobility, and with the Esteyco-Tecyp joint venture providing technical assistance to the works management, the project involves an investment of €57 million (including VAT), of which €11.6 million is for the tunnel.
This is a single-tube tunnel with a length of 490 m. It has a longitudinal gradient of 3% with a radius of 2,500 m. The useful cross-section will be at least 11.8 m wide, accommodating two 3.50 m lanes, shoulders, median and pavements.
Excavation and support were carried out in several phases, with up to three different types of support being used in the tunnel, depending on the quality of the material being passed through. Of the total length of 490 m, 465 m were excavated in the mine, while the remaining 25 m were cut-and-cover: 15 m in the south portal and 10 m in the north portal. The maximum depth (thickness of earth) above the tunnel keystone is 80 metres.
In addition to the aforementioned tunnel, the link includes a 405-metre-long viaduct over the River Sil and a 258-metre-long viaduct over the River Cigüeño.