A4 Motorway Widening (Italy)

The project concerns the enlargement of the motorway’s cross-section from 2+2 road lanes to 3+3 driving lanes of 3,75m and of the emergency lanes of 3,00 m. It develops between the historical points of the A4 Motorway Km 63+300 (Tagliamento River) and Km 89+000 (Gonars). The design speed is 140 km/h, while the speed limit is between 90 km/h - 130 km/h. The cross-section’s enlargement has required a detailed study of the construction phases and the setting-up of the construction site to ensure that vehicles can travel along the 2+2 lanes motorway during the construction. Concerning the works related to the reconstruction of the hydraulic and road crossing’s works, the bridge on the Tagliamento river (L=1,520m) is one of the most significant constructions. It is made up of a double prestressed reinforced concrete deck and it has 20 spans (84.4 m maximum span) in order to reduce the piles number in the river area. Two other main items along the motorway axis are the 110 m long bridge on the Stella River and the 90 m long bridge on the Cormor canal. Both of them have a mixed steel-concrete deck structure. The project consists of no. 3 multi span bridges and no. 4 single span bridges. According to the project, all the crossing flyovers will be redesigned so that their spans will be compatible with the new motorway section. There will be 9 flyovers and all of them will have a mixed steel-concrete deck structure, and they will have three spans. The main central span will be between 45 and 51 m. The project also envisages that the motorway S. Giorgio Nogaro interchange and its related plants will be updated. Special works for draining the platform’s water are envisaged in order to obtain a closed system and to avoid dangerous spills in the natural recipients’ network. The project provides for 47 gathering basins (lagooning) and water treatment basins. In fact, waters are canalised through a system of waterproof ditches. As regards the Earthworks, the Excavated material is 2,100,227,989.82 m3, of which 1,116,137.52 m3 is from existing excavation and demolition surveys, while 494,286.18 m3 is from topsoil removal and reclamation (vegetable soil). The design is completed by the updating of all the motorway plants with the laying of a new optical fiber network and new electronic variable-message signs. Important interventions of landscaping engineering are planned. Amongst others, trees and plants, bridges’ decks and noise protection barriers have been studied. Noise barriers are provided with a height of 3.00 m, 3.50 m, and 4.00 m. Moreover, multipurpose safety and acoustic barriers with a height between 3.00 m and 3.50 m are also foreseen. In addition to the intervention on the motorway axis, the contract also provides for the design of compensative works such as the variant of the No 352 Regional Road (overall length of approximately 2.5 km). Along the road, there will be a cut-and-cover tunnel and the relevant entrance works. As the works concern the ground-water level, they are made up of a road section entirely below the water table and built in a long waterproof tank. There will also be a flyover and an elevated pedestrian bridge so that the cycle and pedestrian path will not be interrupted. This design complies with existing EU standards.