The works were carried out largely with entrance from the shaft, and were completed in 2009. The De Ferrari - Brignole section is between point 6400.00, in correspondence with the final section using the existing “Le Grazie” tunnels; from these, through a cavern, one passes to section of the double-tube tunnel at point 7206.23, in correspondence with the open-air excavation for the Brignole station. At Piazza Corvetto we come across the maximum coverings in crown equal to about 25 m, while at Piazza Brignole we find the minimum ones, equal to about 8 metres. The entire section has the characteristics of an urban excavation with low covering, mainly centred under the road network, historic buildings, and monuments of considerable importance to the city of Genoa. The advance of the tunnel was made possible by guaranteeing a full-section excavation by A.DE.CO. system, using different cross-sections according to the convergences observed during work in progress and to the strain behaviour of the soils that were crossed. Each typical cross section of the tunnel is defined by consolidations at the crown, at the face, and at the foot of the rib with different intensities.  

Corvetto station Between points 6636.94 and 6716.94 is the Corvetto station, consisting of a dropshaft 36 metres deep, from which the cavern called “Camerone di Attacco,” which leads to the station tunnels, begins. Camerone di Attacco was built with an excavation in three phases of bench. It is 21 metres high in total, with an average cross-section of 170 m2, and is 32 metres in length. A consolidation of the excavation with cemented VTR at the face, on the subhorizontal and subvertical boundaries from the excavation level, was made. The excavation proceeded in current section, covering the partial section with reinforced concrete before the start of the subsequent bench phases. The station tunnels are double-tracked, and start from Camerone di Attacco for a length of 80 metres each and an excavation cross-section of 152 m2. For the final lining, curved precast concrete slabs were used, containing the casting of concrete that includes them. The slabs, known as “curved predalles,” have the design reinforcement already placed on their back, and specially design equipment has been made to move and position them.

Corvetto station - De Ferrari section From the Corvetto station tunnel towards De Ferrari, we made the sequence of tunnels that follow one after the other as follows: line tunnel section 2, of a length equal to 167 metres, with an excavation cross-section of 66 m2, connection cavern type 2 of a length equal to 70 metres and excavation cross-section of 99 m2, and cavern type 1 of a length equal to 50 metres and an excavation cross-section of 145 m2. Inside the latter is the realignment of the two existing “Le Grazie” tunnels, restored by us for a total of 180 metres, which, through a 300 metre path, will join the layout under construction with the one in operation that at present ends at the De Ferrari station. Both caverns were covered with curved precast reinforced concrete slabs containing the casting of concrete that includes them. Delicate situations were encountered during the excavation activity for the cavern type 1, first of all because the curvature of the layout brought the tunnel beneath the buildings in Via Roma, and secondly because from the first metres of excavation of this second widening, the two existing Le Grazie tunnels were intercepted, thus causing, during advancement, an environmental impact in terms of noise and vibrations, forcing us to suspend excavation at night.

Corvetto shaft - Piazza Brignole ventilation shaft section From the Corvetto station tunnel, the layout continues with the section 4 line tunnel for a total length equal to 334 metres, and passes beneath Via Serra until reaching the ventilation chamber at Piazza Brignole. This section was excavated from two heading faces, entering from the two shafts: Corvetto and Brignole. The two faces met in December 2008, while the final linings were completed in the month of January 2009. 

Brignole station - Piazza Brignole ventilation shaft section The only line tunnel in the layout with grade-level access is section 5, from the Brignole station to the Brignole shaft, having a length of 377 metres. It proceeds in slope, passing the cluster of limestone at Corso Monte Grappa, taking a position perpendicular to the group of rails of the Brignole station railway yard and then crossing beneath them and finally reaching the Piazza Brignole ventilation chamber. Surely the most critical working phase of the entire layout was this section, in correspondence with the undercrossing of the group of rails at the Brignole station, which had to be done without interrupting or limiting railway operation. There were many reasons for the criticalities of the undercrossing in operating conditions, including the low coverings, ranging from 4 to 7 metres, and the inconsistent material, consisting mainly of filling material. After identifying a section of about 65 metres beneath the complete group of rails, the designer prescribed using a series of highly conservative geomechanical sections, in which the consolidation activities were of primary importance for the success of the undercrossing. The undercrossing’s first consolidations began at 280 metres in April 2008, and were completed at 345 metres in October 2008. Just as important was the preparation of a continuous, real-time monitoring that made it possible to determine the deformations induced onto the rail by the underground construction activities. The prompt and continuous monitoring of these deformations made it possible to accurately verify the soundness of the already restrictive design specifications, and to modulate the frequency and intensity of the working activities. The arrival at the Brignole shaft took place in the month of November 2008. Once the ventilation chamber was reached, all the machinery passed the shaft and continued the advance on section 4 until the meeting with the heading face from Corvetto, which took place in December 2008. 

Connection of Largo Lanfranco shaft with the line tunnel This was a small excavation and covering of the connection adit.