Italy is enclosed in the north along the entire length of its border with Europe by the Alps. The peninsula stretches southward and is traversed for the whole length by the Apennines. From a geological point of view, the situation is an ever changing and challenging one, since the Italian subsoil includes sedimentary rocks as well as plutonic and metamorphic rocks.

In the northern alpine region there are different kinds of rock which are generally subject to metamorphic phenomena, contributing to the formation of competent lithologies. In central and southern Italy, most rocks are of the sedimentary and volcanic kind. There are outcrops of sedimentary rocks along the Apennine chain which include clays and argillaceous rocks, sandstones, calcilutites, marls, deep peat and evaporite layers. The complexity of the rock types is often found in association with structural complexity as a result of deformation of the various layers during extensive folding.

From a geotechnical point of view, the rocks that make up the Italian Apennines are often classified as ‘complex’ and ‘weak’; rock bursts and plasticisation phenomena are commonplace in tunnels, and major inflows of water or natural gas are a major hazard.

On one hand, mountains create a great demand for tunnels. On the other, the difficult geology which often accompanies a high overburden makes the construction of tunnels difficult, complicated and expensive. Moreover, some of the large urban areas are located in the plains on detrital soil, including: sand and gravel alluvia – Milan, Turin, Bologna and Florence; and volcanic ash and tuff – Rome and Naples. Therefore, urban tunnel construction generally requires major preventative consolidation to control settlements.

Despite the fact that construction costs are high, tunnels of every kind are widespread because of the substantial advantages they provide for protecting the environment and optimising land management. In this context, Italy must fulfill four basic objectives in the next 20 years that will require intense activity in design as well as construction. The main objectives are as follows:

  • To update the railway network to adapt it to faster speeds and wider trains, as well as to transfer long sections of the coastal railway further inland to protect the beautiful Italian coastline

  • To build the new high-speed railway network, including the underground railway crossings of large urban areas like Bologna, Florence and Rome

  • To update a great part of the country’s motorway network, which is sometimes 30-40 years old, by adjusting the routes and enlarging the roads from two to three lanes

  • To improve environmental and living conditions in rural and urban areas through a new political approach that will at last promote a more extensive use of underground construction integrated with the provision of metropolitan light railways
  • Improvement of the existing rail network

    There are many large and small projects to be included in this activity. The major ones are:

  • Changing the last remaining single-track section of the Genoa-Ventimiglia (west Liguria) railway line into double tracks and taking it inland. The project under completion will include about 11 tunnels covering a total length of 16km with an estimated cost of US$144m.

  • Modernisation of the Orte-Falconara railway line, an important west-east link in central Italy. The project, which is under development, will have eight new tunnels totalling 13km.

  • Other projects for the Pontremolese (La Spezia-Parma line); the Palermo-Messina line, the Matera-Bari lines and the Milan railroad node are in planning
  • New high-speed rail network

    Construction of the high-speed rail link is the most demanding of all the financial and technological investment undertaken in Italy over the past few years. The new high-capacity rail network is divided into five sections. Two of them are in an advanced phase of construction:

  • Bologna-Florence section (78km). The project as a whole involves construction of 83km of tunnels, 71km of which are actual mainline tunnels with an average length of 10km, the longest being the Vaglia Tunnel, which is 18.5km in length. The remaining 12km (15 access tunnels) are necessary to keep construction time down and will be used for maintenance and emergency access when the tunnel is in operation.

  • Rome-Naples section (220km); underground length: 37km. The remaining three sections are in an advanced design phase or are awaiting the approval of the relevant authorities. They include:

  • Milan-Bologna section (180km). Main tunnels: Somaglia (1100m) and Fontanellato (1600m); main technology: cut+cover.

  • Turin-Venice section (352km). Main tunnels: Lonato (4.8km); Monte Guaino (8.1km).

  • Milan-Genoa section (136km). Underground length:over 50km, of which 30km will be the main tunnel.
  • Underground rail crossings of large urban areas

    The development of these underground crossings is mainly linked to construction of the new high-speed railway lines. The works undertaken for construction or transformation of the existing railway lines into underground lines in Milan and Turin are almost completed.

    For the major railway junctions of Bologna, Florence, Rome, Palermo and Genoa, projects are under development to permit a rapid start of the construction works:

    Bologna. Some of the work has already been assigned thanks to international calls for tender for a total value of $900m, of which about $225m covers construction of about 20km of double- or single-track tunnels; pedestrian tunnels; and hydraulic tunnels. All have to be excavated in alluvial soil.

    Florence. Planning is complete and includes works to a total value of $450m, $144m for the construction of 21km of tunnels for various purposes, excavated in alluvial soil.

    Rome. Planning of the project is finished and comprises 2.2km of tunnels, including a bifurcation chamber excavated in alluvial soil with low overburden, having a total cost of $27m.

    Planning for Palermo and Genoa are still in progress. Genoa will require about 30km of new single- or double-track tunnels to be excavated in rock.

    Modernisation of the old motorway system

    The first major Italian motorways, which were built in the ’50s and ’60s after the Second World War, contributed to the Italian industrial and economic boom but are now highly inadequate to absorb the increase in industrial and commercial traffic. The increase in road traffic is due to the fact that the railway system has not been able to satisfy the freight transportation needs of the country as a whole.

    The main project is concerned with the Autostrada del Sole that links Milan to Reggio Calabria. There will be improvements to this road, including a vertical and horizontal adjustment, and many sections of the road will be widened to three lanes each way.

    Two of these comprise the sections where the main modernisation works will be undertaken:

  • The Apennine mountain range between Bologna and Florence, where construction of a new motorway approximately 40km long is planned with numerous tunnels for a total of 2 x 24km. Planning is in progress and some of the works have already been assigned through international calls for tender. The main work consists of the base twin tunnel (length 2 x 8.5km), and in order to carry out the design of this tunnel, preliminary survey tunnels have been excavated throughout its whole length using TBM technology;

  • The Salerno-Reggio Calabria section, with a total length of 443km, 80km of which cross hills and mountains, with 276 viaducts and 77 tunnels totalling 2 x 26km. Design activities under way are influenced by the delicate geological, geomorphological and hydrogeological conditions. They require an assessment of different technical solutions to comply with the client’s aims of increasing safety and reducing intervention and maintenance costs, and the impact on the operating highway. Some works have already been assigned, but the main effort is being spent on the design. The sections requiring modernisation are divided into 70 lots, total value of $4.5bn.
  • Underground works in urban areas

    In the near future, Italy will have to face a progressive increase in underground construction to improve urban traffic conditions. Among these are: the extension or construction of underground transport systems, underground crossings and underground car parking. In large metropolitan areas such as Milan, Rome, Naples and Genoa, construction works for the extension of the existing metro networks are already in the planning stage or are under way.

    In Brescia and Turin, the first metro line is under construction and extensions to them are already being studied. In Turin, the 9.6km Line 1 will be designed to use the VAL automated metro system for connecting the Collegno Depot with Porta Nuova, Turin’s main railway station. Excavation for the track will be carried out by EPB machines at a depth of 10-25m.

    In addition, 15 stations will be excavated by cut+cover. The design of the metro Line 1 is in progress. The expected date for start of construction is the end of 2000 or the beginning of 2001 so that the line will be in use by November 2005 in anticipation of the 2006 Winter Olympic Games.

    The estimated cost of the project is $293m and the design+construct management contract is valued at $12m.

    Other kinds of underground works are being studied with the aim of improving better safety and quality of life in urban areas. Among them is the underground floodway channel for the Bisagno stream in Genoa. The preliminary design has to be completed within four months.

    In the 1930s, the last section of the Bisagno stream was covered by concrete slabs; in the 1960s, increased urbanisation affected the stream’s outlet. In the last 30 years, bad floods have occurred in the area and it has been decided that the only solution for avoiding further flooding has been identified as an underground channel (about 5km long) to be excavated by TBM.

    Large transalpine railway and road tunnels

    New tunnels of major interest are:

  • The Mont Cenis base tunnel on the 52km long high-speed railway line link connecting Turin (Italy) to Lyons (France), for a total of $4.2bn

  • The Brenner base tunnel, 50-60km long, on the railway line link connecting Munich (Germany) to Verona (Italy)

  • The Mercantour 18km long road tunnel between Cuneo (Italy) and Nice (France).

  • Related Files
    Turin’s first metro line