Underground transportation systems

A modern, efficient transport infrastructure is vital for any country’s successful economic, cultural and social development. This applies to both inner-city and regional, national and international traffic.

Public rail transport systems play an important part here, alongside an efficient local and trunk-road network. Particularly in inner-city areas, the volume of traffic and the degree of development is constantly rising, increasing the need to construct underground traffic arteries.

In many industrialised countries, high-speed railway lines now form an environmentally compatible alternative to cars and aircraft for the movement of people and goods. The construction of numerous tunnel structures is just one of the requirements of these straight-line routes.

Inner-city tunnelling – Underground railways, road tunnels and service tunnels

The first underground railways were built at the end of the 19th century, mostly in the main capitals of central Europe. since the 1970s, most major cities in the leading industrial nations – the USA, Japan and the countries of Europe – have had underground railway networks. At the start of the third millennium, the construction of underground railways is booming, particularly in the high-growth countries of Asia, South America and southern and eastern Europe. On top of this, existing underground railway networks worldwide are being extended.

Just as important as the construction of underground railways is the construction of inner-city road and service tunnels, for which the planning procedures, construction methods and risks are practically identical.

Long railway tunnels - High-speed tracks and trans-Alpine rail routes

It began with France’s TGV high-speed trains and Japan’s Shinkansen bullet trains in the 1970s. Some European countries, like Germany with its ICE (InterCity Express), then took the development of high-speed railway technology further. These high-speed lines are now among the fastest, most efficient and environmentally-friendly means of transport in the medium-distance sector. The ideal location of railway stations in city centres, high average speed and straight-line routing of these trains guarantee a very high standard as far as speed and comfort are concerned.

However, many existing routes no longer satisfy presentday requirements.The transport system as a whole is not very efficient and is too slow. New tunnel projects of unprecedented size are set to change this situation. The desire to switch more goods traffic from road to rail, higher speeds and special geographical conditions are the reasons behind what are certainly the most demanding and longest tunnel projects ever being undertaken.

Under the project name AlpTransit, two base tunnels are being driven under the Lötschberg and Gotthard mountains in Switzerland, with lengths of 35 km and 57 km respectively. Once the two railway tunnels have been completed, in 2014, the train journey between Zurich and Milan will be cut by over an hour. A similarly efficient trans-Alpine route is planned with the Brenner base tunnel linking Austria and Italy.

New lines are also under construction in many European countries, as well as in Taiwan. An equally demanding project is also coming up in the People’s Republic of China, with the plan to link the two major cities of Beijing and Shanghai.

The realisation of such projects requires the construction of many tunnels, often in very congested conditions in innercity areas, or in some cases under extremely difficult topographical and geological conditions high in the mountains. This generally results in the entire range of construction techniques available being used.

Uniform code worldwide creates uniform safety and quality standards

Past experience shows that the occurrence of spectacular loss events during the construction of tunnels cannot be avoided. Although the insurance industry has suffered disastrous results over the years through providing CAR (contractors’ all risks) insurance for tunnel risks, it will continue to be one of the main risk carriers for such projects in the future.

However, this can only happen if risk management is radically improved in all the stages of a tunnelling project – starting with the planning, through the award procedure, and all the way up to execution of the works. With the Joint Code of Practice for Risk Management of Tunnel Works, the construction and insurance industries in the UK have succeeded in creating a code that has been accepted by all those involved in projects. The worldwide introduction and implementation of its requirements should in future make a decisive contribution to achieving the highest possible safety and quality standards at tunnel sites, and thus to minimising loss events.