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PORTUGAL - “ÁGUAS SANTAS” TUNNEL ON THE A4 MOTORWAY

The “Águas Santas” Tunnel, currently in operation, is integrated in the subsection Águas Santas – Ermesinde of the A4 Motorway, which connects the cities of Oporto and Amarante, and is included in the BRISA concession network. The design for widening the A4 underground works was developed by COBA in association with SENER-Engivia, and the Technical Assistance to the construction works is currently underway. The design envisages the construction of a new gallery with four traffic lanes and located north of the existing ones intended for traffic in the Amarante-Oporto direction, as well as upgrading of existing galleries, which will accommodate traffic in the Oporto-Amarante direction.

These are urban tunnels with important geotechnical risks, with shallow overburdens and areas of completely weathered granitic rock. The main constraints are on the Eastern portal of the New Gallery the constructions on Dom Afonso Henriques Street / National Road NR 105; and on the Western portal, the presence of the railway line that connects Leixões to Ermesinde. In this zone, the overburden between the railway line and the top heading of the new North gallery amounts to about 5 m. The cross-section accommodates a clearance of 16.65 x 5.25 m (lxh), and the roadbed comprises a 2,0 m left shoulder, a carriageway with four 3,5 m wide-lanes and a 0,65 m right shoulder. Construction works are in progress, by the group of contractors Ramalho Rosa / Cobetar, Conduril and Amandio Carvalho.

Upgrading of the existing “Águas Santas” Tunnel will begin upon completion of construction of the new gallery. This tunnel has two twin unidirectional galleries with about 360 m each and is composed of 0,20 m left and right shoulders and a carriageway with two 3,5 m wide lanes. Its construction dates back to 1989 and the design was prepared in 1988.

Improvements will be made to: pavements and sidewalks; the drainage system; the coating structure in areas with detected pathologies; treatment of the fire protection and renewal of soffit finishings; cables; signalling; fire-fighting network; SOS facilities inside the tunnel; replacement of the existing lighting; CCTV facilities; power supply and installation of sockets.

With regard to equipment, a combined approach to both tunnels was taken into consideration, an equipment structure similar to the New North tunnel was designed, with infrastructures, such as the firefighting network reservoirs and the transformer stations, being common for both tunnels.

 

 

 

Lx, 30 Nov 2015