The milan-genoa railway line, also known as Terzo Valico dei Giovi, is one of 30 European priority projects. It links the port of Genoa with Milan and Turin in Italy up to Rotterdam/Antwerp through Switzerland. Started in April 2012, the project is about 53km long and involves the construction of two single-track, parallel tunnels with a total length of 37km, connected by cross-passages every 500m. The general contractor is the COCIV consortium comprising Salini-Impregilo (64 per cent), Società Italiana Condotte d’Acqua (31 per cent) and CIV (5 per cent). Milan-based engineering company Rocksoil is the COCIV’s design consultant for underground works and is responsible for job site technical assistance.
The Interministerial Committee for Economic Planning (CIPE) approved the final project in April 2006. In 2011 COCIV and RFI – the owner of Italy’s railway network – signed the contract for detailed engineering design, construction and construction management. The project cost is EUR 6.6bn (USD 7.1bn) and is funded by RFI.
According to the contract, 60 per cent of the civil and permanent works have to be performed by third-party companies chosen by means of international tenders. This is for risk reduction reasons. The project is scheduled to be completed by the end of 2021.
Bridge Between seas
The high-speed line will work as a “bridge between two seas,” connecting the port of Genoa with Rotterdam via a 200-250km/h rail link. The new line focuses on sustainable transport modes, transferring large amounts of freight traffic from road to rail, with benefits for environmental, safety and social issues.
The 53km-long Terzo Valico tunnels are located in the complex Apennines range between Piedmont and Liguria. The new line is connected to the existing line:
¦ to the north side to Milan through the existing line at Tortona;
¦ to the north side to Turin through the Novi Ligure Shunt that connects to the new line with the existing Genoa-Turin line;
¦ to the south side to Genoa and to the Port of Genoa through “Bivio Fegino”;
¦ to the south side to Voltri and the Port of Savona through the interconnection of Voltri.
Starting at the Genoa hub, the new line will run along the Genoa-Milan route, as far as Tortona, and along the Alessandria-Turin route, and will then connect with the existing lines in Milan and Turin.
In terms of tunnel construction, the main works include: Campasso Tunnel of 716m (single-tube, dual-track); two Voltri Interconnecting Tunnels of 2,000m and 2,5000m (both single-tube, single-track); Valico Tunnel of 27,110m (dual-tube, single-track); Serravalle Tunnel of 7,094m (dual-tube, single-track); access adits of 7,200m; and a tunnel made from precast segmental rings for 8,000m. Four intermediate access adits (Polcevera, Cravasco, Castagnola and Vallemme) are required for the Valico Tunnel, both for construction and safety purposes. From the Serravalle Tunnel’s exit, the main line is mainly above ground or in an segmentally lined tunnel, until it joins the existing line in Tortona (en route to Milan), while a diverging branch line establishes the underground connection to and from Turin on the existing Genoa-Turin line.
COCIV director Pierpaolo Tommasini explained that the name “Terzo Valico” is refers to it being the third span and references the existing lines.
“The first line, the Passo dei Giovi, was built around 1850, followed by its branch, the Succursale dei Giovi, with smaller inclines and larger radius of curvatures than the previous line,” Tommasini says.
“We are currently working on the third line, which features a limited incline and really large radius of curvature to allow the transport of goods by train according to the more modern European standards.”
Work in progress
Tommasini talks about the construction progress, starting from the northern entrance of Serravalle tunnel. “Excavation work for the segmentally-lined tunnel section is ongoing, which is through alluvial formations near the Scrivia stream’s plain and its tributaries,” he says.
“We have already completed two of the adits, with the remaining two by March 2017. Now we are ready to start digging four faces of the Valico Tunnel.” Near the southern entrance, excavation of the 30km base tunnel has begun.
“We have already completed the Campasso tunnel, which is located shortly after Giovi’s branch,” Tommasini says. The tunnel is 608m long with double tracks up to the Valico tunnel and then two single tracks with cross-passages.
During T&T’s visit to the intersection tunnel between Voltri and Valico inside the GN 13 chamber, Rocksoil’s geologist, Ilario Larosa, showed that each tunnel is equipped with formwork for inverted arches and sidings (kickers). “Before spraying concrete we need to waterproof the cavity to prevent any damage to the groundwater,” Larosa says. “It’s also important to analyse the face, to determine how best to advance.
“When the face suggests good geological conditions and minimal deformation there is no need to reinforce it. If the face evidences particularly strong material, we can proceed quickly and safely using non mechanised excavation. When the rock is highly deformed and the face shows significant extrusion, we insert fibreglass tubes to reinforce and stabilise the core ahead of the advancing tunnel. After excavation the fibreglass tubes can be dumped with the rest of the spoil. Spoil on this project is used in the environmental restoration of abandoned quarries.”
Safety measures In an emergency, train passengers will be evacuated to a safe area inside the Valico tunnel, near one of the adits, called the ‘Lemme Valley’ adit.
According to the safety plan, two pedestrian tunnels will be ready to receive evacuees. The tunnels are 750m-long and are both linked via a “transect” that overpasses these tracks, reaching the adit, which works as an emergency exit and vehicle access point.
This flyover also connects two nearby platforms with the two evacuation tunnels. Passengers can either escape to the clear tunnel and then board another train or go to the emergency exit at the Lemme Valley adit. A vehicular tunnel will also be built to connect the adit with the down track evacuation tunnel.
The safety facilities include emergency escape lighting along the tunnels and, a surveillance system in addition to the fire suppression and smoke control system. The safety plan also involves the presence of emergency vehicles on the new line. They will be equipped with special devices to safeguard passengers.
Geological conditions
The final design of the Terzo Valico project required a geological survey to analyse the complexity of the Apennine ground. This cost EUR 84M (USD 90M) – 2 per cent of the total cost of the project. The survey revealed different types of ground ranging from clayey schists to limestone, argillites and even loose soil, sometimes with extensive water content.
Overburdens reached 600m. During the survey the route was divided into sections with similar geological and geomechanical features.
It was also discovered that 30 per cent of the Valico Tunnel crosses an area with exceptional geological complexity. This is the Sestri Voltaggio area, which has an overburden of 600m and consists of a sub-vertical surface, roughly oriented from north to south. According to the most recent interpretations, this area is “a channel of preferential concentration of the tectonic deformation”.
Some formations also show gas and occurrence of asbestos. “To prevent any fire or explosion risks, appropriate ventilation and the use of explosion-proof equipment was required for sensitive areas such as the Lemme Valley,” Tommasini says. The rock samples collected during geotechnical investigation were analysed by the Institute of Environmental Geology and Geoengineering (CNR) at the Polytechnic of Turin. The final study says: ”In general the amount of asbestos minerals was modest. The specific procedure for determining the hazard in regard to the release of fibres has highlighted their harmlessness.”
Excavation methods
Both non-mechanised and mechanised excavation will be used for the Terzo Valico tunnels. The 7,000m Serravalle Tunnel will be completed entirely with TBM excavation, using two 9.73m-diameter Herrenknecht EPBMs. Conversely, the Valico Tunnel will be excavated using both technologies: nonmechanised from the southern entrances and from the four access adits, and mechanised excavation, using two 9.77m-diameter Herrenknecht EPBMs, from the northern entrances.
The excavated diameters of the tunnels and the access adits, completed using non mechanised excavation, are approximately 9m. Rocksoil project manager Andrea Bellocchio says that excavation was advanced full-face at all times, even under the most difficult stress-strain conditions, after reinforcing the core-face with suitable stabilisation tools.
Reinforcing the core face with suitable technologies (fibreglass structural elements, horizontal jet-grouting, mechanical pre-cutting), it’s possible to control ground extrusion during the excavation. It is important to have the invert and kickers close to the excavation face, particularly in difficult conditions.
As Tunnels and Tunnelling goes to print approximately 10,000m of main tunnels and adits have been excavated. Also the large intersection chamber (GN13, cross-section 400sqm) at the southern entrance of the Valico Tunnel is almost completed. The average rates of advancement have been in the order of 40m/month/face for non-mechanised excavation in full-face, reflecting the degree of stabilisation required, whereas the average advance rates for the mechanised excavation have been around the 165m mark per month, with peaks of up to 300m per month.
Logistics and site preparation
The tunnel entrances and adits have been positioned near disused industrial lands to avoid impacts on the environment. Site preparation for the entire project includes: the construction of base camps and villages to accommodate personnel; the construction of new roads and the adjustment of the existing ones for the trucks; the construction of operational sites; concrete mixing facilities; equipment for the excavation and construction of the tunnels; installations to build the railway superstructure (ballast and tracks); installations for the construction of railway technological systems; installations for the crushing and production of the aggregates needed for the concrete; extraction sites for quarrying the aggregates needed for carrying out the earthworks or for concrete; mitigation of environmental impacts that are inevitably created with construction sites as extensive and complex as those necessary to complete this project.
