The project stems from the Municipality of Arezzo’s desire to modify the road junction connected to the railway underpass, which links the Baldaccio area with the Pescaiola area, in order to improve vehicular flow in the city center. Another current critical issue is the limited height of the existing underpass, which, with its 4.50m clear height, does not allow the passage of large emergency vehicles.
Road Network
The restructuring of the junction involves the construction of a new road section extending from North to South relative to the railway axis for just under 200 m (40 of which are in an underpass, with gradients reaching a maximum of 10%). The northern intersection between the converging road axes on the current mini-roundabout of Via Baldaccio d’Anghiari will be regulated by the construction of a new roundabout. The southern road network, near the new underpass, will be modified by configuring Via A. dal Borro into two lanes, allowing a left turn towards the Baldaccio area or continuation towards Viale Cittadini without intersecting other traffic flows (and thus without conflict points), while only a turn towards Viale Cittadini is permitted from the exit of the old underpass. The issue of vehicle turn radius was graphically approached using Transoft Solutions’ Autoturn online calculation software, simulating the turning clearance generated by the transit of 12-meter long buses. Finally, the project includes the creation of a new shared pedestrian and cycle path towards Pescaiola (through the new underpass) and towards the city center (Via Baldaccio D’Anghiari – Via Petrarca) to connect with existing paths at the edges of the junction.
Structures
The main structural element of the intervention is the newly constructed underpass. It is a monolithic structure with the following geometric and weight characteristics: 39 meters long (top slab), 12.20m wide, 8m high, with an approximate weight of about 4,200 tons. The construction took place on-site on a launching and sliding platform positioned 8.95m below the rail level: this position is dictated by the need for a 95cm clearance between the rail level and the extrados of the structure, accompanied by the bulk of the upper (1.10m) and lower (1.20m) slabs, and an internal clear passage height of 5.70m. At the end of the launching slab, a thrust wall is positioned, against which the hydraulic jacks responsible for launching the monolith are braced. At the front end, the structure is equipped with inclined cutting edges that support reinforced concrete beams, necessary to ensure the correct functioning of the Essen support system. To ensure the stability of the slopes during the monolith’s jacking operations, two diaphragms were constructed downstream of the thrust, which, once properly finished, will form the boundary walls of the road path on Via L. Cittadini.
Accessibility Barriers
The road network along the underpass is accompanied on the right (for those traveling from West to East) by a sidewalk which, as it descends into the underpass, consists of multiple ramps with a maximum gradient of 8%, interspersed every 10.00 m with level platforms. The path does not descend as deeply as the road, as it only needs to guarantee a clear passage height of 2.50m, compared to the 5.00m required for vehicular traffic. It therefore remains elevated, above the roadway, with a usable height of 2.70m, slightly higher than the minimum.
Safety Coordination
The project, with its related works and provisions, is integrated into the urban and infrastructural fabric of the city of Arezzo, at a junction that experiences significant traffic entering and exiting the city during certain hours of the day. The design involved managing two distinct phases: the first concerned the site setup of the northern area of the intervention (towards the Baldaccio garage) and the general excavation works (following ordnance clearance of the area) preparatory to the construction of the launching slab, the thrust wall, and the subsequent construction of the box culvert. The second phase saw numerous modifications to the construction site area and the work schedule to account for the progress of the works, coupled with the need to never interrupt road traffic through this important city junction. The simultaneous presence of two significant risk factors (vehicular and railway traffic) necessitates maximum attention to maintaining the site fencing and using appropriate signage in relation to the location of site access/exit points. The proximity to the railway line also required utmost attention to potential interferences with infrastructure, in terms of separating work phases closest to the lines themselves. In this regard, the separation systems had to ensure stability in the event of wind and/or air displacement generated by passing vehicles. Maximum attention was paid to the movement of construction vehicles and their arms, always respecting the safety distance within which it is forbidden to approach with people, vehicles, or equipment.
