A4 Porto - Amarante Highway. New Águas Santas North Tunnel

— Project Description:

The 4 lane + 1 emergency lane road tunnel is approx. 20 m wide with a cross section of about 200 m². The excavation was predominantly carried out with D&B method (top-heading-and-bench), except at the east portal where, due to poor geological conditions, the excavation was performed with a sequential excavation method (multi-drift). The tunnel primary support was accomplished with steel fibre reinforced shotcrete, rock bolts and lattice girders (or steel sets). Pipe roof umbrellas were also installed at the entrances to minimize settlements of the ground surface and the effects on existing buildings. The tunnel final lining was realized with reinforced cast-in-place concrete with invert at the East entrance stretch only.

The project included the design of approach stretches (120 m westbound and 170 m eastbound) and portal areas; MOT (to be restored through the "Restabelecimento 2A"); retaining structures (huge piles-retaining wallat the East and 8m high gabion walls at est portal) and a massive temporary bridge for the existing rail line (which runs only 5m above the tunnel entrance at West portal). The project location was between km. 8+675 and km. 9+475 of the A4 Highway, known as "Via Descendente".

— Description of Services:

Detailed Engineering Design and Design Supervision during construction of the new tunnel north of Águas Santas, including excavation and support structures, drainage system, road pavement, signalling, ventilation, illumination and other E&M installations, monitoring system, retaining structures and slope protection systems at portals.