The idea of the Brenner Base Tunnel (BBT) is to reduce the amount of heavy-load traffic on roads by shifting some to rail. To be constructed between Innsbruck Hauptbahnh, Austria and Franzensfeste (Fortezza), Italy, BBT will become the second-longest tunnel in the world with a planned length of 56km (35 miles).

Gotthard Base Tunnel, being built between Italy and Switzerland is just a kilometre longer than BBT.

The total length of the railway line from Innsbruck bypass to Fortezza will be 62.7km, making it the world’s longest underground railway line. The life span of BBT is expected to be 14.5 years.

The EU has been coordinating between the Austrian and Italian authorities to start the project. It has also granted €1bn towards the project, stating it as high priority. Construction on BBT was originally scheduled to begin in Austria in 2010, however this has been postponed to 2011 due to opposition from Austrian citizens forum Tyroleans. The Tyroleans termed the project as “unnecessary” due to the high investment involved.

The project is expected to be completed by 2025. Once operative, the tunnel will reduce the travel time between Innsbruck and Bolzano in Italy by 70 minutes, as trains will be able to pass through the Alps much faster.

On 10 July 2007 Austria and Italy signed a memorandum of understanding to support the BBT project for shifting the traffic from road to rail. The tunnel project was submitted for authorisation in spring 2008 and the government approved it in 2009.

Project

The tunnel was first planned in 1955. The initial plan was to build a 12km-long double-decker tunnel with three railway tracks on the lower level and two highway lanes for each direction on the upper level.

“The project is expected to be completed by 2025 and will reduce travel time between Innsbruck and Bolzano in Italy by 70 minutes.”

However, the project was not found to be feasible in terms of cost and usage. The second plan was to build a 40km tunnel covering the Innsbruck and Vipiteno route with a slope of 9.6%.

In April 2004, a 55km Brenner base tunnel that connects Munich-Verona was approved by the EU.

The Brenner base tunnel in Austria will be primarily used by goods trains. The Innsbruck bypass and the base tunnel’s slope will be 6.7%. The low slope Brenner Base tunnel comprises two tubes interconnected at every 333m. Goods train in the tunnel will travel only in one direction as each tube consists of a single track.

The train will come out of the mountain before reaching Innsbruck and Fortezze stations.

Construction

The Brenner tunnel lies at 794m below the lowest alpine pass at 1,371m. About two-third’s of the tunnel construction will be completed using tunnel boring machines and the remaining one-third through cyclical and conventional methods.

An exploratory tunnel worth €430m will be built at about 12m below the two tunnel tubes to test the rock. The test results will be considered during main tunnel construction, as it reduces construction risk and saves costs and time.

“An exploratory tunnel worth €430m will be built at about 12m below the two tunnel tubes for testing the rock.”

According to the final configuration estimates Brenner section will have the capacity to withstand a weight of 400 trains (222 goods trains and 42 passenger trains in the base tunnel). Initially, 22 goods trains will use the existing lines and about 182 will pass through the tunnel. Within five years, the number of goods trains travelling through the tunnel is expected to increase to 201.

Approximately 32.3 million tons will be carried through rail in 2025, an increase of 67%. The estimated total goods traffic over the Brenner in 2025 will be 63 million tons.

The work on the tunnel construction will include digging and blasting. Equipment used at the digging stage will comprise tunnel-boring machines, explosives, mechanical diggers with hydraulic hammers and drilling equipment.

Excavations

Mechanical excavations or continuous excavations at the tunnel site are being carried out using gripper tunnel shielded boring machines.

Normal rocks are drilled by equipping the boring machine with precast cement parts, while cutters are installed for hard rock drilling.

Shotcrete, steel arches, cement-steel reinforcement mats and flexible anchors improve the cavity during mechanical excavations. Glass fibres, deformable steel arches and highly deformable concrete strengthen the stressed or hard rocks.

Mechanical excavations such as the loosening of rock or spoil material, muck removal and strengthening will be adapted if the required conditions for explosive excavations are not present.

Rolling stock

Equipment to be installed in the tunnel will include rails and vibration/shock absorbers, ventilation and air conditioning, telecommunications and surveillance systems, command and control systems, electrical traction systems, energy supply systems, machinery and emergency systems.

About 320 goods trains and 80 passenger trains will pass through the tunnel after its completion in 2025. The goods trains will run at a speed of 160km/h, and the freight trains at 250 km/h.

Signalling and communication rail systems

The Brenner base tunnel uses ERTMS/ETCS Level 2, 5kV 50 Hz and GSM-R systems.

ERTMS (European rail traffic management systems) comprise two components, the European Train Control System (ETCS) and Global System for Mobile Communications-Railway (GSM-R).

UNIFE members Alstom, Thales, Invensys Rail Group, Ansaldo STS, Siemens Mobility and Bombardier Transportation develop ERTMS systems that can be divided into track gear and train gear.

“GSM-R is an international wireless communication device that can provide effective communication between rail and railway regulation control centres.”

GSM-R system

GSM-R is an international wireless communication device that can provide effective communication between rail and railway regulation control centres at speeds of 500km/h (310mph) without any breakage in the signal.

GSM-R is part of ERTMS and will operate at frequency bands of 876MHz-880MHz for uplink for data transmission, while the 921MHz- 925MHz frequency band will be used for downlink data reception. GSM-R has a channel spacing of 200KHz.

GSM-R features include ASCI (Advanced Speech Call Items) and VGCS (Voice Group Call Service) for multiple users, VBS (Voice Broadcast Service) for single speakers and multiple listeners, and REC (Railway Emergency Call), principally for high-priority matters.

Structural protection

Derailments, collisions and fires are the main causes of accidents in railway tunnels. There is a fire extinguisher installed within the tunnel. The tunnel has the capacity to withstand up to 1,300°C.

Environmental safety

Construction work causes disturbances to residents living across the construction site due to dust, noise and isolated instances of vibrations. Various measures have been taken to mitigate the effect of construction on mountain groundwater, surface water, landscape, vegetation, fauna and public health.

Surveys will be conducted during the construction of tunnel to determine flow rate, electrical conductivity and temperature. Chemical analysis of water levels and tests on drinking water for the presence of bacteria will also be taken up.